Board Invited Review: The hepatic oxidation theory of the control of feed intake and its application to ruminants

Effects of Chitosan-Based Additive on Rumen Fermentation and Microbial Community, Nutrients Digestibility and Lactation Performance in Goats

Recently, the potential of using chitosan (CHI) as a feed additive to enhance ruminal fermentation and improve animal performance has gained increasing attention in ruminant nutrition. This study was undertaken to investigate the effect of dietary supplementation with increasing doses of CHI on rumen fermentation attributes and microbial composition, digestibility and milk performance in Dhofari goats. Twenty-four lactating goats (27 ± 1.8 kg of initial live body weight) were fed a control diet comprising of Rhodes grass hay plus a concentrate feed mixture. Goats were assigned to one of three experimental treatments (n = 8 per treatment) as: (1) control diet with no supplement (CTRL), (2) control diet with 0.300 g/day CHI (CHI0.3) and (3) control diet supplemented with 0.600 g/day CHI (CHI0.6) for a 45-day experimental period. Dietary supplementation with increasing doses of CHI decreased (p < 0.05) linearly ruminal pH (p = 0.023), total short chain fatty acids concentrations (p = 0.011), acetate (p = 0.013) and butyrate (p = 0.042) proportions, acetate to propionate ratio (p < 0.001), estimated methane (CH4) production (p < 0.001), ammonia nitrogen concentrations (p = 0.003) and protozoa abundance (p = 0.003). However, the ruminal propionate proportion augmented (p = 0.002) linearly with increasing doses of CHI in the diet. Increasing doses of CHI linearly increased the abundance of the ruminal propionate-producing bacteria, while diminished acetate and CH4-producing bacteria (p < 0.05). Serum total protein (p = 0.037) and glucose (p = 0.042) levels linearly increased as CHI doses increased in the diet. However, serum UREA levels decreased linearly (p = 0.002) by 21% with increasing CHI amounts in the diet. The digestibility of organic matter, crude protein and neutral detergent fibre increased linearly with the increasing CHI doses (p < 0.05). Neither linear nor quadratic responses (p > 0.05) were observed in daily milk yield and feed efficiency by supplementing the diet with CHI. In conclusion, supplementing the diet with CHI at a dose of 0.600 g/day as a feed additive for dairy goats reduced estimated CH4 generation and improved fibre and protein digestion, with no influence on feed intake, milk yield or composition.

Impact of endophyte-infected tall fescue seed consumption on endocrine changes associated with intake regulation and post-absorptive metabolism in growing steers

Fescue toxicosis is a syndrome occurring from the consumption of endophyte-infected tall fescue and results in substantial economic losses to the beef industry primarily from reduced growth accompanied by decreased dry matter intake (DMI); however, the associations characterizing this reduction in DMI have yet to be elucidated. The objective of this experiment was to identify endocrine changes associated with intake regulation post-consumption of endophyte-infected tall fescue seed (E+). Twelve Holstein steers were stratified by body weight and assigned to 1 of 3 treatments (n=4): 0 ppm ergovaline (ERV), 1.8 ppm ERV, or 2.7 ppm ERV. Treatments were achieved by combining differing proportions of ground E+ and non-endophyte-infected tall fescue seed. Steers were adapted to their diets for 7 d followed by a 7 d DMI collection period. Within treatment, steers were assigned to a sampling day (d 16 or d 17). Blood samples were collected every 20 min for 8 h, beginning 1 h before feeding. Intake data was analyzed using the MIXED procedure of SAS 9.4 (SAS Inst. Inc., Cary, NC) with treatment, day, and the interaction as fixed effects. Hormone and metabolite data were analyzed with the fixed effect of treatment, time, and the interaction including time as a repeated measure and orthogonal contrasts. Dry matter intake was linearly decreased with increasing ERV in the diet (P < 0.001). Insulin and leptin concentrations exhibited a quadratic effect (P = 0.018 and P = 0.005) with insulin concentrations highest for the 2.7 ppm treatment and leptin concentrations highest for the 1.8 ppm treatment. No differences were detected for active ghrelin or β-hydroxybuytrate concentrations among treatment groups. Further, steers consuming both the 1.8 and 2.7 ppm ERV treatments had lower prolactin concentrations compared to the 0 ppm treatment (quadratic, P= 0.019). Glucose concentrations had a tendency for a linear increase as ERV concentrations increased (P = 0.091). A treatment × time interaction (P = 0.002) was noted in NEFA concentrations, with the 1.8 ppm ERV treatment showing increased pre-feeding concentrations, and the 2.7 ppm ERV treatment exhibiting elevated NEFA concentrations as time post-feeding progressed. The results suggest that E+ consumption reduces intake likely through alterations in intake-related hormones and post-absorptive metabolism and contributes to our current understanding of E+ effects on intake reduction while providing avenues for future research.

Relationship between rumen microbiota and pregnancy toxemia in ewes

Introduction

Pregnancy toxemia (PT) is a nutritional metabolic disease of ewes in late pregnancy. This study aimed to reveal the relationship between rumen microbiota and PT.

Methods

We selected 10 healthy ewes (CON) and 10 pregnancy toxemia ewes (PT) at 135 days of gestation according to the blood β-hydroxybutyrate (BHBA), glucose (Glu) concentrations and clinical symptoms. Blood and rumen fluid were collected before morning feeding to determine serum biochemical indices and rumen fermentation parameters. Total DNA of rumen fluid was extracted and the V3-V4 regions of 16S rRNA were amplified by PCR for high-throughput sequencing.

Results

The results showed that the serum concentrations of Glu, total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), uric acid (UA), creatinine (Cr), acetate, propionate, butyrate, and microbial crude protein (MCP) were decreased (p < 0.05) and the concentrations of BHBA, aspartate aminotransferase (AST), acetate to propionate ratio (A/P), and ammonia nitrogen (NH3-N)were higher (p < 0.05) in PT ewes than those in CON ewes. 16S rRNA analysis showed the differences of β-diversity were observed in rumen microbiota between CON and PT ewes. At the phylum level, the relative abundance of Bacteroidota and Proteobacteria were higher (p < 0.01), while Firmicutes was lower (p < 0.01) in PT ewes. At the genus level, the relative Prevotella, Butyrivibrio, Ruminococcus, Lachnospiraceae_AC2044_group, Lachnospiraceae_XPB1014_group, Lachnospiraceae_ND3007_group, and Oribacterium were lower (p < 0.01) in PT ewes. Meanwhile, the relative abundance of Oribacterium, Butyrivibrio, Ruminococcus, and Lachnospiraceae_AC2044_group were positively correlated (p < 0.01) with Glu, INS, acetate, propionate, and butyrate, and negatively correlated (p < 0.01) with BHBA, P, GC, AST, and A/P.

Discussion

In conclusion, the decrease of Oribacterium, Butyrivibrio, Ruminococcus, and Lachnospiraceae_AC2044_group in the rumen of PT ewes reduced the concentrations of volatile fatty acids (acetate, propionate, and butyrate) and serum Glu, and increased BHBA concentration, indicating that the differences in rumen bacteria genera were related to pregnancy toxemia of ewes.

Soybean oil, linoleic acid source, in lamb diets: carcass traits and meat quality

We developed a study to determine the ideal level of inclusion of soybean oil (SBOil) in the diet without affecting the quantitative and qualitative parameters of the carcass and meat of lambs in a feedlot system; therefore, determining the ideal level of inclusion. Forty male lambs (Santa Inês breed) were used. The initial body weight and age averaged 34.88 ± 3.19 kg and 5 months, respectively. Experimental units (lambs) were randomly distributed in 5 different diets: inclusion levels of SBOil: 0, 30, 60, 90, and 120 g/kg of dry matter (DM). The SOil inclusion reduced the DM intake (P < 0.001), Total digestible nutrients (P = 0.004), and crude protein (P < 0.001). Total weight gain (P < 0.001) decreased with the SBOil inclusion and subcutaneous fat thickness (P = 0.017) showed the same behaviour. The final body weight decreased by 42.9 g/kgDM until the inclusion level of 30 g/kgDM; from this level it was reduced by 145 g/kgDM. The hot and cold carcass weights (P = 0.013) decreased by 36.6 g/kgDM after including 30 g/kgDM of SBOil. Meat physicochemical composition was not altered (P > 0.05). Lower meat tenderness values ​​were obtained at the levels of 60 and 90 g/kgDM. The inclusion above 30 g/kgDM decreased meat tenderness. It is concluded that soybean oil should be included up to 30 g/kgDM in diets. It is important to note that with diets with 60% concentrate, SBOil levels greater than 30 g/kgDM promote yield losses.

Ruminal microbial metagenomes and host transcriptomes shed light on individual variability in the growth rate of lambs before weaning: the regulated mechanism and potential long-term effect on the host

Weaning weight is a reflection of management during the breastfeeding phase and will influence animal performance in subsequent phases, considered important indicators within production systems. The aims of this study were as follows: (i) to investigate variability in the growth rate among individual lambs from ewes rearing single or twin lambs fed with two different diets and (ii) to explore the molecular mechanisms regulating the growth rate and the potential long-term effects on the host. No significant change in lamb average daily gain (ADG) was observed in litter size and diet treatment, and there were large variations among individual lambs (ranging from 0.13 to 0.41 kg/day). Further analysis was conducted on serum amino acids, rumen fermentation characteristics, rumen metagenomics and transcriptome, and hepatic transcriptome of lambs with extremely high (HA; n = 6) and low (LA; n = 6) ADG. We observed significant increases in serum lysine, leucine, alanine, and phenylalanine in the HA group. The metagenome revealed that the HA group presented a higher rumen propionate molar proportion via increasing gene abundance in the succinate pathway for propionate synthesis. For the rumen transcriptome, higher expressed gene sets in the HA group were mainly related to rumen epithelial growth, including cytokine-cytokine receptor interaction, Jak-STAT signaling pathway, and adherens junction. For the liver transcriptome, the upregulated KEGG pathways in the HA group were primarily associated with fatty acid degradation, glyoxylate and dicarboxylate metabolism, cholesterol metabolism, and the immune system. This research suggests that preweaning lambs with high ADG may benefit from rumen development and enhanced liver metabolic and immune function.

IMPORTANCE

There is accumulating evidence indicating that the early-life rumen microbiome plays vital roles in rumen development and microbial fermentation, which subsequently affects the growth of young ruminants. The liver is also vital to regulate the metabolism and distribution of nutrients. Our results demonstrate that lambs with high average daily gain (ADG) enhanced microbial volatile fatty acid (VFA) metabolism toward rumen propionate and serum amino acid (AA) production to support host growth. The study highlights that high ADG in the preweaning period is beneficial for the rumen development and liver energy metabolism, leading to better growth later in life. Overall, this study explores the molecular mechanisms regulating the growth rate and the potential long-term effects of increased growth rate on the host metabolism, providing fundamental knowledge about nutrient manipulation in pre-weaning.

Effects of monensin and a blend of magnesium oxide on performance, feeding behavior, and rumen morphometrics of Zebu beef cattle fed high-starch diets

This study aimed to evaluate the effects of a blend of different sources of magnesium oxide associated or not with monensin, on productive, ruminal, and nutritional parameters of steers. Eighty-four Nellore steers with an initial body weight (BW) of 367.3 ± 37.9 kg were allocated to one of 28 pens, with three steers per pen. Each pen was considered an experimental unit. Using a completely randomized design with a 2 × 2 factorial arrangement, the following treatments were assigned to each pen: 1) Control (CON)-a basal diet without additive inclusion; 2) Magnesium oxide blend (MG)-basal diet plus a magnesium-based product (pHix-up, Timab Magnesium, Dinard, France) provided at 0.50% of dry matter (DM); 3) Monensin (MON)-basal diet plus 25 mg/ kg of DM of sodium monensin (Rumensin, Elanco Animal Health, Greenfield, IN); and 4) MG association with MON-basal diet plus MG + MON, at the same doses of the individual treatments. The experimental period lasted 100 d. Blood samples were collected on days 0, 13, and 70 to determine d-lactate levels. Daily feed intake was recorded, and animal ingestive behavior was visually observed on days 66 and 67. On day 70, skeletal muscle tissue samples were obtained through biopsy for gene expression analysis. At the end of the experimental period, carcass ultrasonography was conducted. Subsequently, the steers were slaughtered, and rumen epithelium samples were collected for morphometric analysis. The use of monensin, of magnesium oxide blend, and their interactions, were treated as fixed effects, while the pens were considered as a random effect. Statistical differences were considered when P < 0.05. Steers-fed MG-containing diets consumed approximately 0.6 kg more DM per day than those fed diets without this additive (P = 0.01; 11.3 vs. 11.9 kg/d). The inclusion of MG in the diet increased (P = 0.02) the average daily gain. There was a greater Longissimus muscle area (LMA) and LMA per 100 kg of BW (P ≤ 0.03) for steers-fed diets with MG. Steers-fed MON exhibited reduced mRNA expression of the Atrogin-1 and mTOR compared to steers-fed MG + MON diets (MON × MG: P ≤ 0.04). Steers-fed MON had 6.9% greater feed efficiency (P = 0.02). Papillae width was lesser for CON than other treatments (MON × MG: P = 0.02). In conclusion, the magnesium oxide blend improved performance and carcass traits in high-energy feedlot diets, while monensin enhanced feed efficiency, suggesting potential for their use as alternatives or complements in beef cattle nutrition.

Responses of dairy cows to weekly individualized feeding strategies for dairy cows regarding their metabolic status

In dairy farms, cows are commonly fed a mixture of forages and concentrates ad libitum. To improve the energetic status and productivity of dairy cows, individualized feeding strategies have been proposed. One of this strategy is providing supplemental concentrates to adjust the forage-to-concentrate ratio based on factors like individual milk yield or calculated energy balance. This strategy can affect milk production and cow health, though consistent rules for adjustment are lacking. The objectives of this study were to evaluate the effects of an individualized feeding strategy, adjusted weekly based on the body weight gain of dairy cows, on production performance; and to determine if the metabolic status of the cows could be predicted early in lactation to take it into account into the decisions rules of the strategy. A total of 40 multiparous Holstein cows were involved in a 4-mo trial. The cows entered the experiment individually after calving and were initially fed a standard ration with a fixed 3 kg of extra concentrate per day for the first 8 d (on average). The cows were then paired based on calving date, parity (2 or 3), and body weight gain over the initial week. One cow from each pair was assigned to the Standard Feeding (SF) strategy, which continued receiving the fixed ration, while the other was assigned to the Precision Feeding (PF) strategy, which received a variable amount of extra concentrate adjusted weekly based on body weight gain. Measurements included weekly body weight, daily milk yield, and daily intakes of concentrates and forages. Blood samples were collected to measure metabolites (glucose, BHB, NEFA) for metabolic profiling. The results showed no significant differences in overall body weight gain, milk yield, or intakes (concentrates and/or forages). Two metabolic clusters were identified based on blood metabolites (glucose, BHB, NEFA), predicting cows' metabolic status with 90% accuracy. The balanced cluster had higher milk production, feed intake, and lost more body weight than the imbalanced cluster. Alternative variables like body weight gain and total feed intake can be used to predict metabolic clusters, achieving up to 70% accuracy. To conclude, cows fed this precision feeding strategy had similar performances than those fed the standard feeding strategy. Long-term effect of this strategy should be studied. Metabolic profiling predicted cows' metabolic status suggesting its potential for enhancing individualized feeding decisions.

Impact of dairy cow personality traits and concentrate allowance on their response to training and adaptation to an automated milking system

The objectives of this study were to determine: 1) if dairy cow personality traits and concentrate allowance are associated with the behavior and performance of cows during training to use an automated milking system (AMS); and 2) if these factors were associated with the behavior and performance of cows after AMS training. Twenty-nine mid- to late-lactation Holstein cows (218 ± 49 DIM), who were milking on a rotary parlor and had never previously been milked in an AMS, were enrolled in this study. Cows were assigned to 1 of 2 dietary treatments, consisting of a basal partial mixed ration (PMR) common to both treatment groups, with a concentrate allowance (on dry matter basis) of: 1) 2.0 kg/d in the AMS (L-Tx); or 2) 6.0 kg/d in the AMS (H-Tx). Cows were trained to use the free-traffic AMS, with supervised milkings, over 72 h and were milked in this system for 63 d after training was complete. Variables relating to feeding behavior, milking activity, and production were measured from the start of AMS training until the end of the study. Between 42 and 63 d after AMS introduction, each cow was assessed for personality traits using a combined arena test consisting of exposure to a novel environment, novel object, and novel human. Principal components analysis of behaviors observed during the personality assessment revealed 2 factors (interpreted as boldness and activeness traits) that together explained 85% of the variance; each cow received a score for each trait. Associations between dietary treatment and personality traits with feeding behavior, milking activity, and production were analyzed using mixed-effect linear and logistic regression models. Cows with greater scores for the active trait produced less milk during the 3 d of AMS training compared with cows with lower scores. Within the H-Tx, more active cows had a 3.92 times greater risk of kicking off teat cups during AMS training than less active cows. However, during the 8 wk after training, more active cows had a 1.37 times lesser risk of teat cup kickoffs than those that were less active. Cows on the H-Tx produced 4.4 kg/d more energy-corrected milk compared with cows on the L-Tx in the 8 wk after training. During the 8 wk after AMS training the cows on the H-Tx consumed an average of 21.4 kg/d of PMR and were delivered 4.6 kg/d of AMS concentrate, while the L-Tx cows consumed 23.4 kg/d PMR and were delivered 2.0 kg/d of AMS concentrate. The results indicate that both dairy cow personality traits and AMS concentrate allocation influence their response to AMS training and subsequent feeding and milking behavior and production.

Enzymic Activity, Metabolites, and Hematological Responses in High-Risk Newly Received Calves for "Clinical Health" Reference Intervals

Enzymic activity, metabolites, and hematological responses for reference intervals (RIs) establish ranges of physiological normality, which are useful for diagnosing diseases and physiological alterations. Within the same species, RIs vary according to age, gender, productive and physiological states, and environmental factors including health management and nutrition. RIs have been extensively studied in dairy calves during a critical stage of life (from birth up to first 90 days of age). A critical stage for feedlot calves is their arrival at the feedlot, but no reports determine RIs for different enzymic activity, metabolites, and hematological responses during their initial period at the feedlot. Consequently, a total of 461 high-risk crossbreed beef calves, received on three different dates, were examined upon arrival at the feedlot. Of these, 320 calves (148.3 ± 1.3 kg body weight) whose "clinical health" was evaluated were included in the study. Blood samples were taken upon arrival and on days 14, 28, 42, and 56 to determine the following parameters: enzymic activity, metabolites, electrolytes, white blood cells, platelets, and red blood cells. Enzymic activity, metabolites, and complete blood count were determined by automated analyzers. The freeware Reference Value Advisor Software was used to calculate the non-parametric values of RIs. This study is the first to establish RIs for different enzymic activity, metabolites, and hematological responses in high-risk newly received calves during their initial period at the feedlot. This information will be useful for veterinary clinical practice and research related to the health and welfare of high-risk newly received calves during their initial period at the feedlot.

Effects of partial or full replacement of soybean meal with urea or coated urea on intake, performance, and plasma urea concentrations in lactating dairy cows

We expected mitigation of the hypophagic effects of urea (U) with a coated urea (CU) product that aimed to partially shift urea supply to the post-ruminal gastrointestinal tract. Ruminal release and post-ruminal digestibility of CU was evaluated in vitro, followed by a randomised complete block experiment (54 Holstein-Friesian cows; 177 ± 72 days in milk). Soybean meal (SBM) was partially (PR) or fully (FR) replaced on an isonitrogenous basis by beet pulp and U or CU. Urea sources were included at 12 (U-PR, CU-PR) and 19 (U-FR, CU-FR) g/kg dietary dry matter (DM). Hypophagic effects were similar for U-PR and CU-PR (-11% vs. -7%), and for U-FR and CU-FR (-13% vs. -12%) compared with SBM (average 25.8 kg DM intake/d). Compared with SBM, U-PR and CU-PR reduced yields of milk (-8%) and protein (-12%), U-PR reduced yield of fat (-9%) and fat- and protein-corrected-milk (FPCM; -9%), and CU-PR tended to reduce FPCM yield (-5%). Compared with SBM, U-FR and CU-FR respectively reduced yields of milk (-21%, -22%), protein (-25%, -26%), fat (both -14%), lactose (-20%, -21%), and FPCM (-17%, -19%), and lowered N (-15%, -12%) and feed (-8%, trend, -9%) efficiency. Human-edible protein efficiency approximately doubled with U-PR and CU-PR and approximately tripled with U-FR and CU-FR compared with SBM. Milk composition and plasma urea concentration were similar between U and CU, except for a trend for a greater plasma urea concentration with U-PR compared with CU-PR. Dry matter intake patterns differed for CU-PR compared with U-PR and for CU-FR compared with U-FR, suggesting effects of urea release rate or location on feeding behaviour. Overall, replacing SBM with U or CU reduced DM intake and milk production and affected nutrient efficiencies. Coated urea influenced DM intake pattern but did not affect total DM intake or milk production compared with U.

Magnitude of change in prepartum feed intake: estimations using multiple classes of predictors and associations with transition metabolism, health, and milk production

The objectives of this study were to identify factors associated with the relative change in prepartum dry matter intake (RCDMI) of 273 cows fed individually, evaluate the performance of linear models to estimate RCDMI using different classes of predictors, and characterize the implications of RCDMI to transition metabolism, health, and subsequent milk production. Two periods of interest were established. Period 1 comprised d -21 to -12 relative to calving, when DMI was stable. Period 2 comprised d -4 to -1, when average DMI was distinctly declined. The RCDMI from period 1 to 2 was calculated as a percentage value, which ranged from -75 to 15% and averaged -18.1% (±15.0). Season, parity, body fatness, body weight, milk production in the previous lactation and at dry-off, and length of dry period were associated with RCDMI and explained 11% of the variation in all cows, and 19% when only parous cows were considered. Performance of linear models to predict RCDMI was improved when data on rumination and physical activities and target blood metabolites were added. The adjusted R2 increased to values between 0.45 and 0.55, and selected models performed consistently in cross-validation analyses. To evaluate the implications of RCDMI, cows were ranked within parity according to RCDMI and classified into terciles as large decline (LD), moderate decline (MD), or small decline (SD). By design, DMI did not differ between tercile groups in period 1 (13.3 ± 0.2 kg/d), but differed substantially in period 2 (LD = 8.8; MD = 11.2; SD = 12.7 ± 0.2 kg/d), creating important differences in RCDMI among groups (LD = -33.8; MD = -16.2; SD = -3.4% ± 0.8%). At enrollment, cows in the LD and MD groups were heavier (LD = 788; MD = 775; SD = 750 ± 7 kg), and the proportion of cows with BCS >3.5 was higher in LD (LD = 63; MD = 47; SD = 38%). An interaction of group and time was observed for postpartum DMI, which started lower in LD than in SD cows, but equaled by the end of transition, and inverted at wk 13 and 14 after calving. Yields of energy-corrected milk were greater in LD than in SD cows, and both groups did not differ from MD (LD = 41.0; MD = 40.3; SD = 39.0 ± 0.5 kg/d). LD cows had decreased energy balance and greater concentrations of nonesterified fatty acids, β-hydroxybutyrate, and aspartate aminotransferase in serum, and greater glutathione peroxidase activity in plasma than SD cows. Larger declines in prepartum DMI were also associated with increased risk for postpartum disease, although the associations were only weak to moderate. In conclusion, a large decline in prepartum DMI was associated with important adjustments in the energy metabolism and antioxidants activities, and greater milk production in the subsequent lactation. These findings indicate that feed intake decline close to parturition is likely a normal response to physiological adaptations at the onset of lactation when cows are fed at libitum.

Effects of Replacing Soybean Meal with Cottonseed Meal, Peanut Meal, Rapeseed Meal, or Distillers' Dried Grains with Solubles on the Growth Performance, Nutrient Digestibility, Serum Parameters, and Rumen Fermentation in Growing Lambs

Considering the frequently large price fluctuations for soybean meal, an alternative is the increased use of locally produced high-protein ingredients. The objective of this study was to evaluate the effects of the total replacement of soybean meal with different sources of protein on the growth performance, nutrient digestibility, serum parameters, rumen fermentation parameters, and bacterial communities in growing lambs. Sixty sheep with similar body weights (38.46 ± 0.71 kg) were distributed to one of five treatments: soybean meal (SBM); cottonseed meal (COM); peanut meal (PEM); rapeseed meal (RAM); and distillers' dried grains with solubles (DDGS). The experiment lasted 62 days with a 10-day adaptation period and a 52-day growing period. The results indicated that the body weight and average daily gain were not affected by different protein sources (p > 0.05), but the dry matter intake of the SBM group was lower than that of the other groups (p < 0.05); otherwise, the feed efficiency was higher (p < 0.05). The digestion of dry matter was higher in the SBM, COM, and RAM groups than in the DDGS and PEM groups (p < 0.05). Meanwhile, compared to the other groups, the SBM group had the highest digestion of gross energy and crude protein (p < 0.05). In addition, the concentration of glutathione peroxidase was highest in the SBM group (p < 0.05). Regarding the rumen fermentation, the SBM group had the highest concentration of NH3-N (p < 0.05). The rumen bacterial community was not affected by treatments (p > 0.05). In conclusion, the total replacement of soybean meal with cottonseed, peanut, rapeseed, or DDGS reduced digestibility but did not impact the body weight or average daily gain of growing lambs and had no effect on the immune function and rumen bacterial community; thus, they can be used to substitute the soybean meal.

Soybean Oil, Linoleic Acid Source, in Lamb Diets: Intake, Digestibility, Performance, Ingestive Behaviour, and Blood Metabolites

The objective of the current study was to evaluate the effects of soybean oil inclusion in diets on feeding behaviour, digestibility, performance, and blood metabolites of feedlot lambs. Forty non-castrated Santa Inês lambs with a mean age of 5 months and initial body weight of 34.88 ± 3.19 kg were used in a 40-day feeding trial. The lambs were distributed in five experimental diets with the inclusion of increasing soybean oil (SO) levels: 0, 30, 60, 90, and 120 g/kg DM. The SO inclusion promoted a linear reduction in DM intake (p < 0.001), crude protein (CP, p < 0.001), non-fibrous carbohydrates (NFC, p < 0.001), and total digestible nutrients (TDN, p = 0.004). There was an increasing quadratic effect on the intake of ether extract (EE; p = 0.002) and decreasing for neutral detergent fiber (p = 0.005). The soybean oil inclusion promoted the greater apparent digestibility of CP (p = 0.016), EE (p = 0.005), NDFom (p < 0.001), and TDN (p < 0.001); on the other hand, the apparent digestibility of NFC (p = 0.005) was decreased. The average daily gain decreased (p < 0.001) with SO inclusion. The SO inclusion increased feeding time (p = 0.004), reduced the efficiency of DM rumination (p = 0.001), and reduced the concentration of blood N-ureic (p < 0.001). Considering the productive parameters, SO can be included in diets and it is recommended that we include SO of up to 41 g/kg DM in diets for fattening lambs as the ideal maximum level. The strategy implemented to adapt lambs to increasing levels of high-fat diet mitigated the detrimental effects of lipids on the rumen, with high-density energy intake being the constraining factor on performance.

Index Development to Comprehensive Assess Liver Function during the Dairy Cows' Transition Period in Low-Tropic Conditions

The aim of this work was to develop a liver tissue function index during the transition period of dairy cows managed in low-tropic conditions. In two farms, twenty crossbred and synthetic native cows during the peripartum period were selected, and blood samples were taken on days -30 and -15 prepartum, the calving day, and 7, 20, 35, 50, 65, 80 and 105 days postpartum for serum metabolic tests. On each measurement day, body condition scores (BCS) and parameters on nitrogen metabolism (total protein-TP, albumin-ALB, globulin-GLOB, urea), adipose tissue metabolism (cholesterol-COL, non-esterified fatty acids-NEFA) and two transaminases (alanine aminotransferase-ALT and aspartate aminotransferase-AST) were evaluated. Data analysis included the Spearman correlation, principal components, multiple linear regression and cluster analysis. Results showed that regarding the days after calving and BCS, a liver tissue function index can be constructed using the TP, urea, COL, ALT and NEFA. The estimated index generated three groupings, both by days after calving and BCS. In the former, the index discriminated the metabolic behavior in the prepartum, parturition and postpartum periods, while in the latter, the index discriminated between extreme (2.25, 2.50 and 4.25), slightly low (2.75 and 3.0) and slightly high (3.25 to 4) conditions. The results allow us to conclude that it is feasible to construct mathematical function indexes for liver function to monitor metabolic changes during highly demanding productive phases in dairy cows under tropical conditions.

Effects of altering diet carbohydrate profile and physical form on zoo-housed giraffe Giraffa camelopardalis reticulata

Unlike wild giraffe that primarily consume low starch browse, the preference of zoo-housed giraffe for consuming supplemental feeds over forage could increase the risk of digestive disorders such as ruminal acidosis. Our objective was to evaluate the effects of modifying a supplemental feed's non-fibre carbohydrate profile and physical form on nutritional, behavioural, and blood measures of giraffe in a zoological setting. Six non-lactating, adult, female reticulated giraffes were used in a two-pen modified reversal study using two dietary treatments in seven 21-day periods with data collected on days 15-21. Dietary treatments were a control feed comprised of commercially available products used at the time as the giraffe feed (GF) and an unpelleted experimental feed (EF). On a dry matter basis, GF and EF, respectively, contained 17.0% and 17.4% crude protein, 14.2% and 1.5% starch, 14.9% and 21.3% ethanol-soluble carbohydrates, 22.9% and 26.0% acid detergent fibre (ADF) and 9.50% and 14.9% ND-soluble fibre (NDSF), with modulus of fineness values of 3.62 and 4.82. Supplemental feeds, alfalfa hay, salt, and water were available for ad libitum consumption. Significance was declared at p ≤ 0.05. Intakes of hay, supplemental feeds, and total feed did not differ by diet (p > 0.28), though intakes of starch (0.93 and 0.12 kg; p = 0.05) and ADF (1.83 and 2.23 kg; p = 0.04) differed between GF and EF respectively. Giraffe behaviour values (min/48 h) were greater with EF for total eating (p = 0.04); diets were not detected as different for engagement in oral stereotypes (GF = 433, EF = 318 min/48 h; p = 0.22). Blood glucose was higher on GF than EF (99.0 and 82.3 mg/dL; p = 0.03). The lower EF blood glucose value is more similar to ranges reported for domesticated ruminants. No differences were detected for changes in body weight or body condition score in the 21-day periods (p > 0.32). Modification of supplemental feed carbohydrate profile and physical form can influence behaviour and blood glucose values of zoo-housed giraffe.

Lactational performance, ruminal fermentation, and enteric gas emission of dairy cows fed an amylase-enabled corn silage in diets with different starch concentrations

This study investigated the effects of feeding an amylase-enabled corn silage (ACS) on the performance and enteric gas emissions in lactating dairy cows. Following a 2-wk covariate period, 48 mid-lactation Holstein cows were assigned to 1 of 3 treatments in a 10-wk randomized complete block design experiment. Treatments were diets containing the same proportion of corn silage (40% of dietary DM) as follows: (1) a conventional hybrid corn silage control (CON), (2) ACS replacing the control silage (ADR), and (3) the ADR diet replacing soybean hulls with ground corn grain to achieve the same dietary starch concentration as CON (ASR). Control corn silage and ACS were harvested on the same day and contained 40.3% and 37.1% DM and (% of DM): 37.2% and 41.0% NDF and 37.1% and 30.0% starch, respectively. Enteric gas emissions were measured using the GreenFeed system. Two cows were culled due to health-related issues during the covariate period. Ruminal fluid was collected from 24 cows (8 per treatment) using the orogastric ruminal sampling technique. When compared with CON, cows fed ADR had increased DMI during experimental wk 3, 4, and 9, but treatment did not affect milk or ECM milk yields (39.0 kg/d on average; SEM = 0.89). Compared with CON, feed efficiency (per unit of milk, but not ECM) tended to be lower for ADR, whereas milk true protein concentration (a tendency) and yield were lower for ASR. Milk urea N was decreased by both ADR and ASR diets relative to CON. Compared with CON, daily CH4 emission and emission intensity were increased by ADR but not ASR. Total protozoal count tended to be increased by both diets formulated with ACS when compared with control corn silage. Total-tract digestibility of dietary NDF was greater for ASR, and that of ADF was greater for both ADR and ASR versus CON. The molar proportion of acetate (a tendency) and acetate-to-propionate ratio were increased by ADR, but not ASR, when compared with CON. Replacement of CON with ACS (having lower starch concentration) in the diet of dairy cows increased DMI during the initial weeks of the experiment, maintained ECM, tended to decrease feed efficiency, and increased enteric CH4 emissions, likely due to increased intake of digestible fiber, compared with CON.

Protein Lactylation Profiles Provide Insights into Molecular Mechanisms Underlying Metabolism in Yak

Protein lysine lactylation, a recently discovered post-translational modification (PTM), is prevalent across tissues and cells of diverse species, serving as a regulator of glycolytic flux and biological metabolism. The yak (Bos grunniens), a species that has inhabited the Qinghai-Tibetan Plateau for millennia, has evolved intricate adaptive mechanisms to cope with the region's unique geographical and climatic conditions, exhibiting remarkable energy utilization and metabolic efficiency. Nonetheless, the specific landscape of lysine lactylation in yaks remains poorly understood. Herein, we present the first comprehensive lactylome profile of the yak, effectively identifying 421, 308, and 650 lactylated proteins in the heart, muscles, and liver, respectively. These lactylated proteins are involved in glycolysis/gluconeogenesis, the tricarboxylic acid cycle, oxidative phosphorylation, and metabolic process encompassing carbohydrates, lipids, and proteins during both anaerobic and aerobic glucose bio-oxidation, implying their crucial role in material and energy metabolism, as well as in maintaining homeostasis in yaks.

Invited review: Ketone biology-The shifting paradigm of ketones and ketosis in the dairy cow

Ketosis is currently regarded as a major metabolic disorder of dairy cows, reflective of the animal's efforts to adapt to energy deficit while transitioning into lactation. Currently viewed as a pathology by some, ketosis is associatively implicated in milk production losses and peripartal health complications that increase the risk of early removal of cows from the herd, thus carrying economic losses for dairy farmers and jeopardizing the sustainability of the dairy industry. Despite decades of intense research in the mitigation of ketosis and its sequelae, our ability to lessen its purported effects remains limited. Moreover, the association of ketosis to reduced milk production and peripartal disease is often erratic and likely mired by concurrent potential confounders. In this review, we discuss the potential reasons for these apparent paradoxes in the light of currently available evidence, with a focus on the limitations of observational research and the necessary steps to unambiguously identify the effects of ketosis on cow health and performance via controlled randomized experimentation. A nuanced perspective is proposed that considers the dissociation of ketosis-as a disease-from healthy hyperketonemia. Furthermore, in consideration of a growing body of evidence that highlights positive roles of ketones in the mitigation of metabolic dysfunction and chronic diseases, we consider the hypothetical functions of ketones as health-promoting metabolites and ponder on their potential usefulness to enhance dairy cow health and productivity.

Evaluation of different ratios of neutral detergent-soluble carbohydrate fractions on performance, ingestive behavior, and nitrogen balance in dairy goats

Cell components soluble in neutral detergent are a diverse group, both compositionally and nutritionally. The present study aimed to evaluate production responses, behavior (eating, ruminating, and idling), and nitrogen balance of dairy goats fed different ratios of neutral detergent-soluble carbohydrate fractions. Five multiparous Alpine does with mean ± SD initial body mass of 49.5 ± 7.9 kg and 60 days of lactation were randomly assigned in a 5 × 5 Latin square design. The treatments were the ratios of starch (starch associated with soluble sugar [StSS]) to neutral detergent-soluble fiber (NDSF) (StSS:NDSF): 0.89, 1.05, 1.24, 1.73, and 2.92. No effect was observed (P > 0.05) of StSS:NDSF on the intakes of neutral detergent fiber (NDF) and NDSC. However, DM intake showed a quadratic behavior (P = 0.049). The ingestive behavior was affected by StSS:NDSF linearly increased (P = 0.002) the feeding efficiency. The increase in StSS:NDSF caused a linear increase in fecal (P = 0.011), urinary (P < 0.001), and milk nitrogen excretion (P = 0.024). The increase in StSS:NDSF affected (P = 0.048) milk yield and net energy lactation (P = 0.036). In conclusion, dairy goats experience reduced dry matter intake and milk yield when subjected to high-NDSC diets, specifically those above 1.24 StSS:NDSF ratio. Elevated NDSC levels in the diets lead to decreased feeding time, whereas rumination remains unaffected. Nitrogen losses in goats increase linearly with high-NDSC diets, and a significant impact on nitrogen balance.

Impact of the Oral Administration of Polystyrene Microplastics on Hepatic Lipid, Glucose, and Amino Acid Metabolism in C57BL/6Korl and C57BL/6-Lepem1hwl/Korl Mice

The impact of microplastics (MPs) on the metabolic functions of the liver is currently unclear and not completely understood. To investigate the effects of the administration of MPs on the hepatic metabolism of normal and obese mice, alterations in the lipid, glucose (Glu), and amino acid regulation pathways were analyzed in the liver and adipose tissues of C57BL/6Korl (wild type, WT) or C57BL/6-Lepem1hwl/Korl mice (leptin knockout, Lep KO) orally administered polystyrene (PS) MPs for 9 weeks. Significant alterations in the lipid accumulation, adipogenesis, lipogenesis, and lipolysis pathways were detected in the liver tissue of MP-treated WT and Lep KO mice compared to the vehicle-treated group. These alterations in their liver tissues were accompanied by an upregulation of the serum lipid profile, as well as alterations in the adipogenesis, lipogenesis, and lipolysis pathways in the adipose tissues of MP-treated WT and Lep KO mice. Specifically, the level of leptin was increased in the adipose tissues of MP-treated WT mice without any change in their food intake. Also, MP-induced disruptions in the glycogenolysis, Glu transporter type 4 (GLUT4)-5' AMP-activated protein kinase (AMPK) signaling pathway, levels of lipid intermediates, and the insulin resistance of the liver tissues of WT and Lep KO mice were observed. Furthermore, the levels of seven endogenous metabolites were remarkably changed in the serum of WT and Lep KO mice after MP administrations. Finally, the impact of the MP administration observed in both types of mice was further verified in differentiated 3T3-L1 adipocytes and HepG2 cells. Thus, these results suggest that the oral administration of MPs for 9 weeks may be associated with the disruption of lipid, Glu, and amino acid metabolism in the liver tissue of obese WT and Lep KO mice.

New biochemical pathways for forming short-chain fatty acids during fermentation in rumen bacteria

Short-chain fatty acids (SCFA) are essential to cattle as a source of energy and for other roles in metabolism. These molecules are formed during fermentation by microbes in the rumen, but even after decades of study, the biochemical pathways responsible for forming them are not always clear. Here we review recent advances in this area and their importance for improving animal productivity. Studies of bacterial genomes have pointed to unusual biochemical pathways in rumen organisms. One study found that 8% of rumen organisms forming acetate, a major SCFA, had genes for a pathway previously unknown in bacteria. The existence of this pathway was subsequently confirmed biochemically in propionibacteria. The pathway was shown to involve 2 enzymes that convert acetyl-coenzyme A to acetate. Similar studies have revealed new enzymatic steps for forming propionate and butyrate, other major SCFA. These new steps and pathways are significant for controlling fermentation. With more precise control over SCFA, cows can be fed more precisely and potentially reach higher productivity.

Flexible feeding: Dairy cow personality affects changes in feeding behavior and milk production under feed competition conditions

The objective of this study was to determine the effect of individual cow personality traits on feeding behavior and production under low levels of feeding competition, and to determine whether personality traits influence how feeding behavior changes in response to greater feeding competition. Forty-two Holstein cows were assigned to 1 automated feed bin per cow (low competition condition) from 15 to 28 d in milk (DIM; period 1, P1), and 2 feed bins per 3 cows (higher competition condition) from 63 to 76 DIM (period 2, P2). A total mixed ration (TMR) was fed into the automated feed bins which recorded each feed bin visit time, duration, and intake. Cow personality traits were assessed at 21 DIM during P1 and at 70 DIM during P2 using a combined arena test, measuring behavioral responses to a novel environment, novel object, and novel human. Principal components analysis of behaviors observed during the P1 combined arena test revealed 1 factor (interpreted as active-explorative) from the novel environment test explaining 51% of the variance, and 3 factors (interpreted as fearfulness, active-explorative, and sociability toward conspecifics) from each of the novel object (76% cumulative variance) and human (75% cumulative variance) tests. The principal components analysis of behaviors observed during the P2 combined arena test revealed 2 factors jointly from the environment, object, and human tests (interpreted as fearfulness and active-explorative) that together explained 68% of the variance. Fearfulness and active-explorative trait scores were correlated across P1 and P2, indicating stability of personality over a challenging period and advancing DIM. In P2 when competition for feed was increased at greater stage of lactation, the more active-explorative cows appeared to make few alterations to their feeding behavior, yet still maintained their milk yield, compared with lower competition in P1. In contrast, cows who were more fearful increased their feed bin visits from P1 to P2, and less fearful cows increased their eating rate, without increased milk production, despite advanced lactation. Overall, the results indicate that cows of different personalities adopt different feeding strategies in response to a change in their environment, and may benefit from tailored management during challenging periods.

Impact of combined management strategies of monensin and virginiamycin in high energy diets on ruminal fermentation and nutrients utilization

Feed additives such as monensin (MON) and virginiamycin (VM) are commonly utilized in feedlot diets to enhance rumen fermentation. Nevertheless, the precise effects of combining MON and VM during specific feedlot periods and the advantages of this combination remain unclear. This study was designed to investigate the effects of withdrawal of MON when associated with VM during the adaptation and finishing periods on ruminal metabolism, feeding behavior, and nutrient digestibility in Nellore cattle. The experimental design was a 5 × 5 Latin square, where each period lasted 28 days. Five rumen-cannulated Nellore yearling bulls were used (414,86 ± 21,71 kg of body weight), which were assigned to five treatments: (1) MON during the entire feeding period; (2) VM during the entire feeding period; (3) MON + VM during the adaptation period and only VM during the finishing period 1 and 2; (4) MON + VM during the entire feeding period; (5) MON + VM during the adaptation and finishing period 1 and only VM during the finishing period 2. For the finishing period 1, animals fed T3 had improved potential degradability of dry matter (p = 0.02). Cattle fed T3 and T5 had the highest crude protein degradability when compared to animals receiving T2 (p = 0.01). Animals fed T2 and T3 had reduced the time (p < 0.01) and area under pH 6.2 (p = 0.02). Moreover, animals fed T4 had greater population of protozoa from the genus Diplodinium (p = 0.04) when compared to those from animals fed T2, T3 and T5. For the finishing period 2, animals fed T3 had greater starch degradability when compared to animals receiving T4 and T5 (p = 0.04). Animals fed T3, T4 and T5 had increased the duration of time in which pH was below 5.6 (p = 0.03). The area under the curve for ruminal pH 5.2 and pH 5.6 was higher for the animals fed T3 (p = 0.01), and the area under pH 6.2 was higher for the animals fed T3 and T5 (p < 0.01) when compared to animals receiving T2. There is no substantial improvement on the rumen fermentation parameters by the concurrent utilization of MON and VM molecules, where the higher starch and protein degradability did not improve the rumen fermentation.

Effects of low-quality forage and starter protein content in starter diet of young calves on growth performance, rumen fermentation, and urinary purine derivatives

Feeding low-quality forage (LQF) has been evaluated in mature ruminants and results show that it has been improved nitrogen utilization efficiency. The present study evaluated the interaction effect of feeding wheat straw as LQF (0 and 7.5%, DM basis) and starter protein level (20 vs. 24%, DM basis) on growth performance, ruminal fermentation, and microbial protein synthesis in Holstein dairy calves raised under moderate heat stress condition. Forty-eight 3-day old dairy calves (averaging 40.6 kg) were assigned in four experimental treatments as follow; 1) no LQF with 20% CP (NLQF-20CP), 2) no LQF with 24% CP (NLQF-24CP), 3) 7.5% LQF with 20% CP (LQF-20CP) and 4) 7.5% LQF and 24% CP (LQF-24CP). The calves were weaned on d 53 of age but the experiment extended until d 73 of age. Feeding LQF increased starter intake, average daily gain (tendency), ruminal acetate concentration, and improved fecal score of calves. The average daily gains before and after weaning were positively influenced with greater starter protein content. Hence, weaning and final BWs were improved when calves received greater CP content. In addition, greater starter CP content increased total ruminal volatile fatty acid concentration. With respect to the interaction effect between LQF feeding and starter protein content, the lower nitrogen excretion through urine was obtained for LQF-20CP diet among experimental treatments. The results of the current study showed that feeding LQF improved ruminal fermentation pattern and improved growth performance through increased starter intake. In addition, greater starter protein content is advisable during pre-weaning period for calves raised under mild heat stress condition. In conclusion, based on the results found in the current study, it can be suggested that feeding LQF for calves under heat stress condition can improve nitrogen utilization when dietary protein content is low. This can be opportunity to formulate starter diets with greater nitrogen utilization efficiency which is critical for accelerated growth programs at early stages of growth for young calves while calves raised under hot season condition.

Effect of monensin on milk production efficiency and milk composition in lactating dairy cows fed modern diets

Since the US Food and Drug Administration's approval of monensin in 2004, significant nutritional advances have been made to increase feed efficiency and milk fat production. Recent evidence suggests monensin's adverse effect on milk fat percentage may be absent when diets are formulated to address known diet-induced milk fat depression risk factors. Thus, study objectives were to evaluate effects of monensin level on dry matter intake (DMI), milk production and composition, and efficiency of high-producing cows fed diets formulated to optimize milk fat. Ninety-six lactating Holstein cows (36 primiparous, 60 multiparous; 106 ± 17 d in milk [DIM]) were balanced by parity, DIM, and milk production and were randomly assigned to 1 of 12 pens with 8 cows per pen. All cows received 11 g/t monensin for 5 wk after which pens received 1 of 4 dietary treatments (n = 3) formulated to provide 0 (CON), 11 (R11), 14.5 (R14.5), or 18 (R18) g/t monensin for 9 wk. The basal diet was 54% forage, 27% NDF, 29% starch, and 2.3% rumen unsaturated fatty acid load. Pen was the experimental unit and data were analyzed using the Fit Model Procedure of JMP. Effects of treatment, time, and treatment × time interaction were included as fixed effects and pen as a random effect. Least squares means were determined and linear and quadratic contrasts were tested. Dry matter intake tended to decrease linearly with increasing monensin dose. Milk yield, fat percentage, and protein percentage and yield were unaffected by treatment while fat yield was quadratically increased. Milk de novo and mixed fatty acid (FA) yields (g/d) increased quadratically with monensin whereas preformed FA linearly decreased during the experimental period. Energy-corrected milk (ECM) was quadratically increased by monensin. Milk urea nitrogen concentrations increased linearly with increasing monensin dose. Monensin linearly increased feed efficiency (ECM/DMI, 3.5% fat-corrected milk/DMI, and solids-corrected milk/DMI). Body weight gain did not differ between treatments. Estimated dietary energy tended to increase linearly with increasing monensin level. These data suggest monensin improves component-corrected milk production efficiency, estimated dietary energy, and does not negatively affect milk fat percentage or FA profile.

Optimizing dietary rumen-degradable starch to rumen-degradable protein ratio improves lactation performance and nitrogen utilization efficiency in mid-lactating Holstein dairy cows

The dietary rumen-degradable starch (RDS) to rumen-degradable protein (RDP) ratio, denoted as the RDS-to-RDP ratio (SPR), has been proven to enhance in vitro rumen fermentation. However, the effects of dietary SPR in vivo remain largely unexplored. This study was conducted to investigate the effect of dietary SPR on lactation performance, nutrient digestibility, rumen fermentation patterns, blood indicators, and nitrogen (N) partitioning in mid-lactating Holstein cows. Seventy-two Holstein dairy cows were randomly assigned to three groups (24 head/group), balanced for (mean ± standard deviation) days in milk (116 ± 21.5), parity (2.1 ± 0.8), milk production (42 ± 2.1 kg/d), and body weight (705 ± 52.5 kg). The cows were fed diets with low (2.1, control), medium (2.3), or high (2.5) SPR, formulated to be isoenergetic, isonitrogenous, and iso-starch. The study consisted of a one-week adaptation phase followed by an eight-week experimental period. The results indicated that the high SPR group had a lower dry matter intake compared to the other groups (p < 0.05). A quadratic increase in milk yield and feed efficiency was observed with increasing dietary SPR (p < 0.05), peaking in the medium SPR group. The medium SPR group exhibited a lower milk somatic cell count and a higher blood total antioxidant capacity compared to other groups (p < 0.05). With increasing dietary SPR, there was a quadratic improvement (p < 0.05) in the total tract apparent digestibility of crude protein, ether extract, starch, neutral detergent fiber, and acid detergent fiber. Although no treatment effect was observed in rumen pH, the rumen total volatile fatty acids concentration and microbial crude protein synthesis increased quadratically (p < 0.05) as dietary SPR increased. The molar proportion of propionate linearly increased (p = 0.01), while branched-chain volatile fatty acids linearly decreased (p = 0.01) with increasing dietary SPR. The low SPR group (control) exhibited higher concentration of milk urea N, rumen ammonia N, and blood urea N than other groups (p < 0.05). Despite a linear decrease (p < 0.05) in the proportion of urinary N to N intake, increasing dietary SPR led to a quadratic increase (p = 0.01) in N utilization efficiency and a quadratic decrease (p < 0.05) in the proportion of fecal N to N intake. In conclusion, optimizing dietary SPR has the potential to enhance lactation performance and N utilization efficiency. Based on our findings, a medium dietary SPR (with SPR = 2.3) is recommended for mid-lactating Holstein dairy cows. Nevertheless, further research on rumen microbial composition and metabolites is warranted to elucidate the underlying mechanisms of the observed effects.

Ration particle size has different effects on digestive but not production parameters in higher-yielding (Holstein) compared to lower-yielding (Girolando) cows

The aim of the study was to evaluate the effect of total mixed ration particle size (length) and breed of cow on intake dynamics, animal performance and CH4 emissions, comparing high yielding Holstein and low yielding Girolando cows. The experimental design was 2 × 2 Latin Square arranged as a crossover factorial scheme with two diets (short particle size, SPS and long particle size, LPS) and the two breed compositions. The design comprised two periods of 26 d each, where all data collection was performed at cow level. No influence of the particle size occurred for the passage rate, neutral detergent fiber digestibility, performance and milk composition, methane emissions or ruminal fermentation parameters. Girolando cows had greater dry matter intake (DMI) when fed SPS, while Holsteins had the same (P < 0.05). Girolando cows had lower dry matter digestibility when fed LPS compared to SPS, while Holsteins had the opposite effect (P < 0.05). Also, the digestibility of crude protein and non-fibrous carbohydrates decreased in Girolando cows fed LPS, but not in Holsteins (P < 0.05). Girolando cows reduced DMI by 10.6% when fed LPS diet (P < 0.05). Girolando had an increased eating rate (+24 g of DM/min; P < 0.05) compared to Holstein cows, but Holstein cows had a lower CH4 intensity (by 29.7%: P < 0.05). Girolando cows increased the dry matter intake when fed a diet with short particle size, while the same did not happen in Holsteins. Dry matter digestibility increased in Holsteins when fed long particle size, while the opposite was observed in Girolando cows. Nutrient digestibility was reduced in Girolando cows when fed short particle size. Particle size did not influence eating time, eating rate, feed trough visits, visits with intake, milk yield and composition regardless of the breed. Reducing particle size increased CH4 intensity in both breeds.

Starter protein content and supplemental soybean oil or hydrogenated palm fatty acids in Holstein dairy calves: growth performance, protozoa population, and nitrogen utilization efficiency

The study hypothesized that a 24% protein starter diet supplemented with inert fat (palm fatty acids; PLFs) instead of triglyceride-rich soybean oil (SBO) would promote the growth of dairy calves. The effects of different protein contents (20 vs 24% CP) and fat sources (SBO vs PLF at 2.5% DM) on growth, digestibility, blood metabolites, rumen protozoa and urinary nitrogen in dairy calves were investigated. A total of 52 female dairy calves (mean age 3 days and BW 40.7 kg) were allocated to the following treatments in a completely randomized design: (1) 20% CP starter diet supplemented with SBO (20CP-SBO), (2) 20% CP starter diet supplemented with PLF (20CP-PLF), (3) 24% CP starter diet supplemented with SBO (24CP-SBO), and (4) 24% CP starter diet supplemented with PLF (24CP-PLF). Calves were weaned on day 53, and the study ended on day 73. The 24CP diets enhanced starter feed intake, average daily gain (ADG), withers height, hip width, organic matter (OM) digestibility, and preweaning blood glucose compared to the 20CP diets. In contrast, SBO supplementation reduced feed intake, ADG, withers height, OM and CP digestibility, and pre- and postweaning blood glucose and beta-hydroxybutyrate levels, while increasing preweaning aspartate aminotransferase, compared to PLF. SBO supplementation led to lower urinary excretion of purine derivatives and microbial protein synthesis postweaning, and a reduction in protozoa population both pre- and postweaning. Calves fed PLF had higher starter intake than those fed SBO, regardless of the diet being 20CP or 24CP. Calves fed the 24CP-PLF diet had the highest ADG, while calves fed the 20CP-SBO diet had the lowest ADG. Calves fed the 20CP-SBO diet had lower feed efficiency than calves fed the other diets during the preweaning period and throughout the experimental period. Calves fed the 24CP-PLF diet had higher hip heights at weaning and on day 73 than calves fed the other diets. Calves fed the 20CP-SBO diet had lower neutral detergent fiber digestibility than calves fed the other diets. Calves fed the 24CP-SBO diet had higher postweaning blood urea nitrogen concentration than calves fed the other diets. Feeding the 20CP-SBO diet to dairy calves decreased urinary allantoin excretion and rumen microbial protein synthesis but increased urinary nitrogen excretion during the preweaning period. Our results suggest that PLF is more suitable than SBO in calf diets, especially when calves fed 24% CP, possibly due to improved nutrient digestibility.

- Invited Review - The role of rumen microbiota in enteric methane mitigation for sustainable ruminant production

Ruminal methane production functions as the main sink for metabolic hydrogen generated through rumen fermentation and is recognized as a considerable source of greenhouse gas emissions. Methane production is a complex trait affected by dry matter intake, feed composition, rumen microbiota and their fermentation, lactation stage, host genetics, and environmental factors. Various mitigation approaches have been proposed. Because individual ruminants exhibit different methane conversion efficiencies, the microbial characteristics of low-methane-emitting animals can be essential for successful rumen manipulation and environment-friendly methane mitigation. Several bacterial species, including Sharpea, uncharacterized Succinivibrionaceae, and certain Prevotella phylotypes have been listed as key players in low-methane-emitting sheep and cows. The functional characteristics of the unclassified bacteria remain unclear, as they are yet to be cultured. Here, we review ruminal methane production and mitigation strategies, focusing on rumen fermentation and the functional role of rumen microbiota, and describe the phylogenetic and physiological characteristics of a novel Prevotella species recently isolated from low methane-emitting and high propionate-producing cows. This review may help to provide a better understanding of the ruminal digestion process and rumen function to identify holistic and environmentally friendly methane mitigation approaches for sustainable ruminant production.

Effects of feeding an inoculated corn silage with or without a direct-fed microbial on dry matter intake, milk production, and nutrient digestibility of high-producing lactating Holstein cows

This study evaluated the effects of inoculating corn silage and/or feeding a direct-fed microbial (PRO) on performance and nutrient digestibility of lactating dairy cows. At harvesting, corn silage was treated either with water (culated or not [CON]) or Lactococcus lactis and Lentilactobacillus buchneri (INC; SiloSolve FC) at 1.5 × 105 cfu/g of corn silage. Ten mini silos and one farm-scale silo bunker per treatment were prepared for the laboratory and the lactating dairy cow trial, respectively. Five mini silos per treatment were opened on days 2 or 90 post-ensiling for pH measurement, as well as chemical analysis and aerobic stability, respectively. The farm-scale silo bunkers were opened 77 d post-ensiling for the beginning of the lactating cow trial. Eighty lactating Holstein cows were assigned in a 2 × 2 factorial design to: (1) CON silage without PRO (CON-CON; n = 20), (2) CON silage with PRO at 14 g/head/d (CON-PRO; n = 20), (3) INC silage without PRO (INC-CON; n = 20), and (4) INC silage with PRO at 14 g/head/d (INC-PRO; n = 20). Concurrently with the feeding trial, eight cows per treatment were chosen for nutrient digestibility. The pH of the corn silage was not affected by the silage inoculant (P ≥ 0.29), but INC yielded greater concentration of acetic acid and longer aerobic stability (P < 0.01). Dairy cows fed INC had a lower mean total dry matter intake (DMI), milk protein content, and somatic cell counts vs. CON (P ≤ 0.02). On the other hand, milk and fat- and protein-corrected milk (FPCM) production efficiency, milk urea-N, DM, crude protein, and starch digestibility were greater for INC-fed cows (P ≤ 0.03). Feeding direct-fed microbials (DFM) improved mean body weight, milk yield, and FPCM, as well as milk protein and lactose yield (P ≤ 0.05), but reduced milk fat and protein content (P = 0.02). A silage inoculant × DFM interaction was observed for milk production efficiency, milk protein and lactose content, and somatic cell count (P ≤ 0.05). Dairy cows fed INC-CON had a greater milk production efficiency and milk lactose content (P ≤ 0.04), but INC-PRO had lower milk protein content and SCC (P ≤ 0.03). In summary, inoculating L. lactis and L. buchneri increased acetic acid content and aerobic stability of corn silage, reduced DMI, but improved milk production efficiency and nutrient digestibility of lactating Holstein dairy cows. On the other hand, feeding PRO improved milk, protein, and lactose yield. Additionally, combining the feeding of an inoculated corn silage with PRO reduced milk somatic cell count.

Effects of feeding hybrid rye grain as a replacement for barley grain on dry matter intake, ruminal fermentation, and the site and extent of nutrient digestion in finishing beef heifers

The objective of this study was to evaluate effects of increasing the inclusion of dry-rolled hybrid rye (HR) as a replacement for dry-rolled barley grain (DRB) on feed intake, ruminal fermentation, and the site and extent of nutrient digestion for finishing cattle. Eight ruminally and duodenally cannulated Hereford-cross heifers were used in a replicated 4 × 4 Latin square design with 21-d periods including 15 d of dietary adaptation and 6 d of data and sample collection. Dietary treatments included a control diet with 10.00% grass hay, 85.21% DRB, 4.51% of a vitamin and mineral supplement, and 0.28% of urea on a dry matter (DM) basis. Hybrid rye grain replaced 33%, 67%, or 100% of the DRB. Feed ingredients, feed refusals, ruminal pH, ruminal fluid, duodenal digesta, and fecal samples were collected from days 18 to 21 in each period. Data were analyzed using the Proc Glimmix procedure of SAS 9.4 (SAS Inst. Inc., Cary, NC) to evaluate the linear, quadratic, and cubic effects of increasing HR inclusion. Increasing HR inclusion as a substitute for DRB linearly decreased (P < 0.01) DM intake, linearly decreased mean ruminal pH (P < 0.01), and increased the duration (P < 0.01) and area (P = 0.02) that ruminal pH was < 5.5. There were no effects of HR inclusion on total short chain fatty acid and lactic acid concentrations in ruminal fluid. Likewise, the molar proportions of acetate and butyrate were not affected by HR inclusion. Propionate was cubically affected by HR inclusion (P = 0.02). Ruminal ash-free neutral detergent fiber (aNDFom) digestibility linearly increased (P = 0.03) with increasing HR, but there was no effect on ruminal starch digestibility averaging 71.1% (SEM = 3.611). Increasing HR inclusion linearly increased intestinal DM digestibility (% of flow to the duodenum; P = 0.03), tended to linearly increase intestinal digestibility of organic matter (P = 0.08), and tended to quadratically affect intestinal digestibility of aNDFom (P = 0.07). Increasing hybrid rye linearly increased apparent total tract DM, organic matter, crude protein, aNDFom, and starch digestibility (P ≤ 0.05). In addition, increasing HR inclusion linearly increased GE digestibility (P < 0.01) and the DE concentration (P < 0.01). Increasing the inclusion rate of HR grain as a substitute for DRB in finishing diets decreased DMI and increased risk for low ruminal pH, which may be influenced by greater digestible energy concentration arising from greater DM, OM, aNDFom, and starch digestibility.

Divergent planes of nutrition in mature rams influences body composition, hormone and metabolite concentrations, and offspring birth measurements, but not semen characteristics or offspring growth

Objectives of this experiment were to characterize the effects of ram plane of nutrition on body composition, concentrations of hormones and metabolites, sperm characteristics, and offspring outcomes. Mature Rambouillet rams (n = 24, BW = 82.9 ± 2.63 kg) were individually housed and randomly assigned to either a positive (POS; n = 8), maintenance (MAINT; n = 8), or negative (NEG; n = 8) plane of nutrition for an 84-day feeding period. Rams were fed a common diet, with daily feed allocations adjusted weekly based on body weight (BW) to achieve the targeted weight gain or loss (approximately 12% of initial BW). On 0, 28, 56, and 84-d, body condition score (BCS) and scrotal circumference (SC) were recorded, and blood and semen were collected. Following the feeding period, rams were placed in pens with 10 ewes each for a 28-d breeding period. Ewes were managed similarly throughout gestation and body weight and measurements were recorded at birth and weaning. Data were analyzed as repeated measures in time where appropriate with the mixed procedure of SAS, and individual ram was the experimental unit for all analysis. Ram BW was influenced by a treatment × day interaction (P < 0.001), with POS (0.12 ± 0.01 kg) having greater daily weight change than MAINT (0.1 ± 0.01 kg), which was greater than NEG (-0.12 ± 0.01 kg). Ram BCS and SC were influenced by treatment × day interactions (P ≤ 0.01), being similar on day 0 but POS being greater than NEG by day 56. Concentrations of triiodothyronine (T3) and T3:T4 ratio exhibited treatment × day interactions (P ≤ 0.02), as POS had greater values than NEG by day 84 (P ≤ 0.02). Concentration of insulin-like growth factor-1 was greater in POS than MAINT and NEG (P ≤ 0.02), and non-esterified fatty acids and thyroxine (T4) were influenced by a day effect (P ≤ 0.01), but testosterone was unaffected (P ≥ 0.09). Minimal differences in semen volume, sperm concentration, motility, or morphology were observed among treatments (P ≥ 0.31). A similar proportion of ewes bred by rams in the respective treatments lambed and weaned lambs (P ≥ 0.54). Birth weight, chest circumference, and shoulder-hip length were greater (P ≤ 0.05) in NEG lambs compared with POS and MAINT; however, no differences were detected in weaning weight and weaning body measurements (P ≥ 0.40). Findings suggest paternal nutrition during the period of sperm development may influence offspring outcomes, potentially as a result of in-utero programming of paternal origin.

Dose response to postruminal urea in lactating dairy cattle

Inclusion of urea in dairy cattle diets is often limited by negative effects of high levels of feed urea on dry matter intake (DMI) and efficiency of rumen N utilization. We hypothesized that supplying urea postruminally would mitigate these limitations and allow greater inclusion of urea in dairy cattle diets. Four rumen-fistulated Holstein-Friesian dairy cows (7 ± 2.1 lactations, 110 ± 30.8 d in milk; mean ± standard deviation) were randomly assigned to a 4 × 4 Latin square design to examine DMI, milk production and composition, digestibility, rumen fermentation, N balance, and plasma constituents in response to 4 levels of urea continuously infused into the abomasum (0, 163, 325, and 488 g/d). Urea doses were targeted to linearly increase the crude protein (CP) content of total DMI (diet plus infusion) by 0%, 2%, 4%, and 6% and equated to 0%, 0.7%, 1.4%, and 2.1% of expected DMI, respectively. Each 28-d infusion period consisted of a 7-d dose step-up period, 14 d of adaptation, and a 7-d measurement period. The diet was fed ad libitum as a total mixed ration [10.9% CP, 42.5% corn silage, 3.5% grass hay, 3.5% wheat straw, and 50.5% concentrate (dry matter basis)] and was formulated to meet 100%, 82%, and 53% of net energy, metabolizable protein, and rumen-degradable protein requirements, respectively. Linear, quadratic, and cubic effects of urea dose were assessed using polynomial regression assuming the fixed effect of treatment and random effects of period and cow. Dry matter intake and energy-corrected milk yield responded quadratically to urea dose, and milk urea content increased linearly with increasing urea dose. Apparent total-tract digestibility of CP increased linearly with increasing urea dose and ruminal NH3-N concentration responded quadratically to urea dose. Mean total VFA concentration was not affected by urea dose. The proportion of N intake excreted in feces decreased linearly and that excreted in urine increased linearly in response to increasing urea dose. The proportion of N intake excreted in milk increased linearly with increasing urea dose. Urinary urea excretion increased linearly with increasing urea dose. Microbial N flow responded cubically to urea dose, but the efficiency of microbial protein synthesis was not affected. Plasma urea concentration increased linearly with increasing urea dose. Regression analysis estimated that when supplemented on top of a low-CP diet, 179 g/d of postruminal urea would maximize DMI at 23.4 kg/d, corresponding to a dietary urea inclusion level of 0.8% of DMI, which is in line with the current recommendations for urea inclusion in dairy cattle diets. Overall, these results indicate that postruminal delivery of urea does not mitigate DMI depression as urea dose increases.

Effects of isoenergetic supplementation as water use mitigation strategy on water footprint and health of nursing bull calves

Sustainable livestock systems focus on mitigating natural resource use such as water. Dietary management strategies can significantly reduce the water footprint of livestock animals; however, animal health is of concern when animals reduce water intake due to subacute dehydration. To evaluate potential consequences of this nutritional management intervention, a total of 23, 60 ± 3 days old nursing Holstein bull calves, weighing 94.7 ± 12.07 kg, were distributed in a completely randomized design and received one of three diets. Control was a basal diet composed of a non-medicated milk replacer (milk replacer; n = 7), and the additional two diets, were composed of the same non-medicated milk replacer in addition to either lipid [n = 8; milk replacer + menhaden fish oil (3 %)] or soluble carbohydrate [n = 8; milk replacer + corn starch (7%) isoenergetic to fat group] supplements. Animals were offered ad libitum mineral mix and water, as well as 120 g/day of a composite mix of dried microbrewery's spent grains. Data were analyzed as linear and generalized linear mixed models with diet as a fixed effect and animal as random utilizing R studio (R Core Team, 2021, Vienna, Austria; SAS Inst., Cary, NC). Within supplementation groups, lipid supplemented calves had the highest lymphocyte (63.24 vs 57.69 counts/100 lymphocytes; P < 0.033), and lowest neutrophil counts (29.3 vs 35.3 counts/100 lymphocytes; P < 0.047). Supplementation significantly increased total serum protein (P = 0.001) and skin moisture (P < 0.011), with carbohydrate group having the highest skin moisture (5.30 vs 3.99; P < 0.047). Supplementation also decreased fecal fluidity scores (P < 0.001) with no significant change in serum electrolytes (P > 0.256). No significant differences were found amongst treatments for the ingestive behavior (P > 0.338). The carbohydrate-supplemented calves significantly decreased all daily water footprints compared to the control and fat-supplemented groups: blue a 47.55 L decrease, (P < 0.001), green a 265.62 L decrease (P = 0.005), and gray a 55.87 L decrease (P = 0.009) water footprint, as well as total water footprint (369.04 L, P = 0.004). Our results indicate the potential to maintain animal performance while increasing water use efficiency through diet supplementation tailored to mitigate water use, without adverse effects on animal health.

Short communication: Impact of corn grain particle size on production performance of lactating dairy cows

Corn grain particle size has the potential to influence the performance of lactating dairy cows and the overall profitability of a dairy farm. The objective of this study was to evaluate the productive performance of lactating cows fed diets containing finely or coarsely ground corn grain. Fifty lactating Holstein cows (n = 50; 10 primiparous and 40 multiparous), averaging (mean ± standard deviation, SD) 658 ± 64 kg of BW, 38.8 ± 7.3 kg of milk/d, and 155 ± 80 DIM, were fed diets with finely ground corn grain (FGC) or coarsely ground corn grain (CGC) in a randomized block design with a 28-d treatment period. Finely and coarsely ground corn grain had an average particle size of 660 and 915 µm, respectively. Dry matter intake (DMI) was reduced (p < 0.01) for cows fed FGC (22.1 vs. 21.2 kg d-1). Milk yield and efficiency were not affected by treatments (37.9 vs. 36.8 kg d-1; p = 0.12 and 1.78 vs. 1.79; p = 0.15). Concentrations of milk protein and fat, as well as other milk solids, were unaffected (p > 0.05) by treatments. Fecal starch (FS) concentrations were greater (p < 0.01) for cows fed CGC (7.0 vs. 4.9%), whereas plasma concentrations of D-lactate were greater (p < 0.05) for cows fed FGC (98.5 vs. 79.7 µM). Overall, feeding finely ground corn grain increased total-tract starch digestibility and reduced DMI while maintaining milk yield.

The Performance and Metabolism of Dairy Cows Receiving an Ultra-Diluted Complex in the Diet during the Transition Period and Early Lactation

This study evaluated the effects of feeding an ultra-diluted complex to dairy cows during the transition period and early lactation. Thirty multiparous pregnant dairy cows were blocked and randomly assigned to either a placebo control (CON) group or ultra-diluted complex (UD) group. The CON group received a placebo (basal diet + 40 g/cow/day of expanded silicate), while the UD group received the ultra-diluted complex (basal diet + 40 g/cow/day of PeriParto Transição-RealH, composed of ultra-diluted substances + vehicle: expanded silicate). Cows were evaluated from 30 days before the expected calving date until 60 days in milk (DIM) for sample and data collection. Post-partum dry matter intake (DMI) was not affected by the treatment. Cows fed UD had higher DMI relative to BW. Feeding UD increased milk lactose content and decreased milk protein content. Cows fed UD had lower somatic cell counts in the third and fourth week of lactation. Cows fed UD showed a tendency for higher liver health index. Using UD during the transition period and early lactation may benefit liver and udder health of dairy cows with no detrimental effect on milk performance.

Effect of pre- and postpartum supplementation of a pure glycerol product to dairy cows on feed intake, metabolic markers, and milk yield and components

The objective of this study was to quantify the effects of supplementing transition dairy cows with a low inclusion dry glycerol product in the pre- and postpartum periods on feed intake, metabolic markers, and milk yield and components. Multiparous Holstein dairy cows (n = 60) were enrolled in a 2-by-2 factorial design study. Starting 21 d before expected parturition, cows individually received a dry cow diet with (1) 250 g/d glycerol product supplementation [66% pure glycerol (United States Pharmacopeia grade); GLY], or (2) no supplementation (CON) mixed to their total mixed ration. After parturition, cows, again, were individually assigned to either GLY, or (2) no supplementation (CON) to their partial mixed ration for the first 21 d in milk (DIM). Cows were milked by an automated milking system and offered a target of 5.4 kg DM/d pellet (23% of target total dry matter intake, DMI) in the automated milking system and followed for 42 d into lactation. Blood samples were collected 6.3 ± 3.47 d before calving for all blood measures and 3, 7, 10, and 14 DIM for analysis of glucose and β-hydroxybutyrate, as well as 3 and 7 DIM for nonesterified fatty acids (NEFA) and haptoglobin. Initial dry cow body weight (BW), calf birth weight, previous 305-d milk, and month of parturition were used as covariates in the statistical model. Cows supplemented with GLY prepartum lost less BW and consumed more DMI pre- and postpartum, as well as had lower postpartum blood β-hydroxybutyrate and NEFA concentrations compared with those fed the CON treatment prepartum. Cows supplemented with GLY postpartum had lesser DMI in the first 42 DIM than cows fed CON postpartum, but also had reduced blood NEFA concentrations, odds of a high haptoglobin test, odds of a low blood glucose test, and lesser preformed fatty acid concentrations and yields in their milk. Cows supplemented glycerol both pre- and postpartum lost the least total BW from -21 to 21 DIM. No treatment effects were detected for milk yield; however, cows receiving GLY postpartum had lower milk fat. Overall, glycerol supplementation during the transition period, particularly during the 21 d before calving, was associated with markers of improved metabolic status.

Physical effectiveness of corn silage fractions stratified with the Penn State Particle Separator for lactating dairy cows

This study evaluated the physical effectiveness of whole-plant corn silage (CS) particles stratified with the Penn State Particle Separator, composed of 19- and 8-mm-diameter sieves and a pan, for lactating dairy cows. Eight Holstein cows (27.6 ± 2.8 kg/d of milk, 611 ± 74 kg body weight; 152 ± 83 d in milk) were assigned to two 4 × 4 Latin squares (22-d periods, 16-d adaptation), where one square was formed with rumen-cannulated cows. Three CS particle fractions were manually isolated using the 8- and 19-mm diameter sieves and re-ensiled in 200-L drums. The 4 experimental diets were (% dry matter): (1) CON (control): 17% forage neutral detergent fiber (NDF) from CS (basal roughage), 31.5% starch, and 31.9% NDF; (2) PSPan: 17% forage NDF from CS + 9% NDF from CS particles <8 mm, 25.9% starch, and 37.9% NDF; (3) PS8: 17% forage NDF from CS + 9% NDF from CS particles 8 to 19 mm, 25.5% starch, and 38.3% NDF; and (4) PS19: 17% forage NDF from CS + 9% NDF from CS particles >19 mm, 24.9% starch, and 38.8% NDF. Cows fed PS8 had greater dry matter intake and energy-corrected milk yield (22.4 and 26.9 kg/d, respectively) than cows fed CON (20.8 and 24.7 kg/d) and PS19 (21.2 and 24.8 kg/d), but no difference was detected between PSPan (21.6 and 25.8 kg/d) and other treatments. Milk fat concentration was greater for PS8 than CON, with intermediate values for PSPan and PS19. Milk fat yield was greater for cows fed PS8 than CON and PS19, and cows fed PSPan secreted more fat than CON cows but were not different from cows fed the other 2 diets. Cows fed CON had a lower meal frequency than cows fed PSPan, shorter meal and rumination times than PS8, and greater meal size and lower rates of rumination and chewing than the other 3 diets. Total chewing per unit of NDF was higher for PS8 than PSPan, although neither treatment differed from CON or PS19. Cows fed PS19 had higher refusal of feed particles >19 mm than cows fed CON and PSPan. The refusal of dietary NDF and undigested NDF in favor of starch were all greater for PS19 than on the other treatments. Cows fed PS19 had a greater proportion of the swallowed bolus and rumen digesta with particles >19 mm than the other 3 diets. Cows fed CON had the lowest ruminal pH and greatest lactate concentration relative to the other 3 diets. Plasma lipopolysaccharide was higher for cows fed CON and PSPan than for cows fed PS8 and PS19, and serum d-lactate tended to be lower on PSPan than for CON and PS8. In summary, the inclusion of CS fractions in a low-forage fiber diet (CON) reduced signs of ruminal acidosis. Compared with CS NDF <8 and >19 mm, CS NDF with 8- to 19-mm length promoted better rumen health and performance of dairy cows. These results highlight the importance of adjusting CS harvest and formulating dairy diets based on the proportion of particles retained between the 8- and 19-mm sieves.

Transition Cow Nutrition and Management Strategies of Dairy Herds in the Northeastern United States: Associations of Nutritional Strategies with Analytes, Health, Milk Yield, and Reproduction

The objective was to identify relationships between transition cow nutritional strategies and the prevalence of elevated analytes (nonesterified fatty acids (NEFA), β-hydroxybutyrate (BHB), and haptoglobin (Hp)), disorder incidence (DI), milk yield, and reproductive performance. Multiparous and primiparous cows from 72 farms in the northeastern US were enrolled in a herd-level cohort study. Farms were dichotomized within parity into a nutritional strategy within each period; far-off: controlled energy (CE; <16.5% starch and ≥40% forage neutral detergent fiber (FNDF)) or not CE (NCE; ≥16.5% starch or <40% FNDF or both), close-up: high FNDF (HF; ≥40% FNDF) or low FNDF (LF; <40% FNDF), and fresh: low starch (LS; <25.5% starch) or high starch (HS; ≥25.5% starch). No evidence existed that transition cow nutritional strategies were associated with milk yield outcomes (p ≥ 0.20). In general, our results support feeding multiparous cows HF close-up and HS fresh to minimize excessive BHB and DI; however, multiparous cows fed LF close-up had a higher pregnancy rate, and lower prepartum NEFA and Hp. Similarly, our results support feeding primiparous cows CE far-off, HF close-up, and HS fresh to maximize reproductive performance, and minimize BHB and DI; however, herds fed HF close-up or HS fresh had higher Hp.

Dietary Ruminant Enteric Methane Mitigation Strategies: Current Findings, Potential Risks and Applicability

This review examines the current state of knowledge regarding the effectiveness of different dietary ruminant enteric methane mitigation strategies and their modes of action together with the issues discussed regarding the potential harms/risks and applicability of such strategies. By investigating these strategies, we can enhance our understanding of the mechanisms by which they influence methane production and identify promising approaches for sustainable mitigation of methane emissions. Out of all nutritional strategies, the use of 3-nitrooxypropanol, red seaweed, tannins, saponins, essential oils, nitrates, and sulfates demonstrates the potential to reduce emissions and receives a lot of attention from the scientific community. The use of certain additives as pure compounds is challenging under certain conditions, such as pasture-based systems, so the potential use of forages with sufficient amounts of plant secondary metabolites is also explored. Additionally, improved forage quality (maturity and nutrient composition) might help to further reduce emissions. Red seaweed, although proven to be very effective in reducing emissions, raises some questions regarding the volatility of the main active compound, bromoform, and challenges regarding the cultivation of the seaweed. Other relatively new methods of mitigation, such as the use of cyanogenic glycosides, are also discussed in this article. Together with nitrates, cyanogenic glycosides pose serious risks to animal health, but research has proven their efficacy and safety when control measures are taken. Furthermore, the risks of nitrate use can be minimized by using probiotics. Some of the discussed strategies, namely monensin or halogenated hydrocarbons (as pure compounds), demonstrate efficacy but are unlikely to be implemented widely because of legal restrictions.

Feed intake and milk yield and composition of lactating dairy goats in response to partial substitution of soybean meal for formaldehyde-treated sesame meal in the diet

This study was conducted to evaluate the effect of substitution of soybean meal (SBM) for formaldehyde-treated sesame meal (FTSM) on nutrient intake and digestibility, ruminal and blood parameters and milk production and composition in lactating Murciano-Granadina goats. Forty lactating goats were randomly assigned to one of the following four treatments: (1) diet with 16.5% CP, containing SBM (CON); (2) diet with 16.5% CP, containing untreated SM (USM); (3) diet with 16.5% CP, containing FTSM (FT); and (4) diet with 14.5% CP containing FTSM (LPFT). The results showed that nutrient intake was highest in the FT group (p < 0.001), while it was similar between the CON and LPFT groups, except for the intake of CP, which was higher in the CON group. The FT and LPFT had lower ruminal pH compared to CON and USM groups (p < 0.001), with goats in group FT having the highest volatile fatty acids (VFA) production (p < 0.001). The highest propionate concentration was observed in the LPFT treatment (p < 0.001), followed by the FT, CON, and USM treatments. Goats offered USM and LPFT treatments presented the highest and lowest acetate: propionate values, respectively, among the experimental groups (p < 0.001). The results also showed that LPFT goats had the lowest blood urea nitrogen (BUN) level (p = 0.004), while FT goats presented a lower non-esterified FA (NEFA) level compared with CON and LPFT goats (p = 0.01). Goats offered the FT diet had the highest milk yield (p = 0.002) and energy-corrected milk yield (p < 0.001) among all dietary groups. The highest milk fat (p < 0.001), protein (p = 0.001), lactose (p = 0.007), total solids (p = 0.003), and solids-not-fat (SNF) (p = 0.003) contents were observed in FT goats, which didn't differ from USM goats. The inclusion of formaldehyde-treated SM increased the percentage of C18:3 (p < 0.001) and C20:1 (p = 0.04) FAs compared with USM and CON treatments. Milk from USM, FT, and LPFT goats had lower levels of saturated (p < 0.001) and medium-chain FAs (p = 0.014) compared with CON goats, whereas milk from CON goats had lower levels of unsaturated, monounsaturated, and long-chain FAs compared to other groups (p < 0.001). The lowest and the highest concentrations of polyunsaturated FAs were observed in CON and LPFT goats, respectively (p = 0.001). It can be concluded that SBM can be advantageously replaced by formaldehyde-treated SM in the diet as a feasible alternative to improve feed intake and production performance of dairy goats.

Effects of Dietary Enrichment with Olive Cake on the Thyroid and Adrenocortical Responses in Growing Beef Calves

Agro-industrial by-products incorporated into livestock feed formulations can positively impact feed costs and promote a circular bio-economy. Italy produces significant amounts of olive cake (OC), a by-product of olive oil extraction, with the potential for incorporation into bovine diets. However, information on its effects on endocrine responses in growing beef calves is lacking. Forty-eight Limousines randomly allocated to dietary treatment (control or 10%-OC or 15%-OC inclusion) were segregated according to sex and body weight. Serum concentrations of TSH, thyroid hormones, and cortisol were measured on day 0, day 56, and at the end of the trial on day 147. Circulating TSH, total (T₃, T₄) and free (fT₃, fT₄) iodothyronines, and cortisol concentrations were all within the normal physiological ranges, with no significant effect imparted by diet. However, the diet × time interaction was significant for T₃. The cortisol, T₃, T₄, and fT₄ registered on day 147 were higher than those of day 56, and cortisol was higher in heifers than bulls. Final body weight was positively correlated with TSH and T₃ and negatively with cortisol concentration. These findings suggest that the inclusion of OC at levels up to 15% in growing/finishing beef diets had no adverse effects on the calves' thyroid and cortical status.

Intake, digestibility and ruminal parameters of lambs fed with increasing levels of wheat bulgur

The aim was to evaluate the effect of the inclusion of wheat bulgur in the diet on intake, digestibility, N balance and ruminal parameters in cannulated lambs. Four castrated Santa Ines×Dorper lambs, cannulated in the rumen, (45 ± 9 kg) were housed in metabolism crates. They were randomly distributed in a 4×4 Latin Square,10-day adaption, a 6-day sampling period. The base diet was composed by ryegrass hay and concentrate, in a 40:60 roughage:concentrate ratio and four inclusions of wheat bulgur on the total diet: 0, 190, 380 and 570 g/kg dry matter. The inclusion of wheat bulgur did not affect the intake of non-structural carbohydrates. The intake of dry matter, fiber, crude protein, organic matter and crude fat decreased linearly (P<0.05). The digestibility of neutral detergent fiber decreased linearly (P=0.001). The N retained and the excreted in urine were not affected by wheat bulgur inclusion. Fecal excretion, total excretion and absorbed N, decreased linearly (P<0.05). There was no change on pH, ammonia, soluble carbohydrates and protozoa population in rumen. Increasing of wheat bulgur in the diet of lambs decrease the nutrient intake and fiber digestibility without affecting the digestibility of other compounds, ruminal parameters, and the protozoa count.

Effect of Particle Size of Silage of Flint Corn Grain on Dairy Cows Fed Tropical Pasture: Performance, Intake, Ruminal Fermentation, and Digestibility

The particle size (PS) of reconstituted corn (REC) can affect the grinding rate and starch digestibility in dairy cows. We evaluated the effect of the PS of REC ensiled for 40 days on the pasture dry matter intake (DMI), lactation performance, total tract digestibility, and ruminal fermentation of grazing dairy cows. The treatments were coarse REC (CO, 1694 µm), fine REC (FI, 1364 µm), or finely ground (GC, 366 µm) flint corn (68% vitreousness) at 29.6 ± 1.4% of diet DM (mean ± SD). Eighteen dairy cows (mean milk yield 21.3 kg/d) were split into three groups by production level and were assigned within each group to a sequence of treatments in 3 × 3 Latin squares of 21-day periods. Cows were individually fed a constant amount of whole-plant corn silage 3 ×/d (2.7 kg DM/d) and corn treatments and soybean meal according to their group. There was no significant interaction between treatment and the production level. Cows fed FI had a lower DMI (16.7 vs. 18.1 kg/d) than those fed GC, and both did not differ from CO (17.7 kg/d). There was no treatment effect on milk yield (mean: 19.2 kg/d). Cows fed CO had the lowest total tract digestibility of starch (86.3 vs. 92.3% of intake) and the highest fecal starch concentration (7.0 vs. 4.0% of DM). The NDF digestibility was lower for GC-fed cows than CO- and FI-fed cows. Plasma glucose was higher in cows fed FI and CO (75.0 mg/dL) than those fed GC (70.8 mg/dL). Ruminal volatile fatty acids and the pH did not differ. Fine grinding of REC increased the feed efficiency relative to CO and GC. Coarse grinding of REC ensiled for 40 days reduced the total tract starch digestibility relative to FI and GC.

Effect of feeding a Saccharomyces cerevisiae fermentation product to Holstein cows exposed to high temperature and humidity conditions on milk production performance and efficiency-A pen-level trial

The objective of this study was to evaluate the effect of feeding a Saccharomyces cerevisiae fermentation product (SCFP) on milk production efficiency of Holstein cows naturally exposed to high temperature and humidity conditions. The study was conducted in 2 commercial farms in Mexico from July to October 2020 and included 1 wk covariate period, 3 wk adaptation, and 12 wk data collection. Cows [n = 1,843; ≥21 d in milk (DIM) and <100 d carried calf] were enrolled and assigned to the study pens (n = 10) balanced for parity, milk yield, and DIM. Pens were fed a total mixed ration diet either without (CTRL) or with SCFP (19 g/d, NutriTek, Diamond V). Milk yield, energy-corrected milk (ECM), milk components, linear somatic cell score, dry matter intake (DMI), feed efficiency (FE; Milk/DMI and ECM/DMI), body condition score, and the incidence of clinical mastitis, pneumonia, and culling were monitored. Statistical analyses included mixed linear and logistic models accounting for repeated measures (when applicable; multiple measurements per cow within treated pens) with pen as the experimental unit and treatment, time (week of study), parity (1 vs. 2+), and their interactions as fixed and pen nested within farm and treatment as random effect. Parity 2+ cows within pens fed SCFP produced more milk than cows within CTRL pens (42.1 vs. 41.2 kg/d); there were no production differences between groups of primiparous groups. Cows within SCFP pens had lower DMI (25.2 vs. 26.0 kg/d) and greater FE (1.59 vs. 1.53) and ECM FE (1.73 vs. 1.68) than cows within CTRL pens. Milk components, linear somatic cell score, health events, and culling were not different between groups. At the end of the study (245 ± 54 DIM), SCFP cows had greater body condition score than CTRL (3.33 vs. 3.23 in the first parity; 3.11 vs. 3.04 in 2+ parity cows). Feeding Saccharomyces cerevisiae fermentation products to lactating cows exposed to high temperature and humidity conditions improved FE.

Genetic Analysis of Methane Emission Traits in Holstein Dairy Cattle

Genetic selection can be a feasible method to help mitigate enteric methane emissions from dairy cattle, as methane emission-related traits are heritable and genetic gains are persistent and cumulative over time. The objective of this study was to estimate heritability of methane emission phenotypes and the genetic and phenotypic correlations between them in Holstein cattle. We used 1765 individual records of methane emission obtained from 330 Holstein cattle from two Canadian herds. Methane emissions were measured using the GreenFeed system, and three methane traits were analyzed: the amount of daily methane produced (g/d), methane yield (g methane/kg dry matter intake), and methane intensity (g methane/kg milk). Genetic parameters were estimated using univariate and bivariate repeatability animal models. Heritability estimates (±SE) of 0.16 (±0.10), 0.27 (±0.12), and 0.21 (±0.14) were obtained for daily methane production, methane yield, and methane intensity, respectively. A high genetic correlation (rg = 0.94 ± 0.23) between daily methane production and methane intensity indicates that selecting for daily methane production would result in lower methane per unit of milk produced. This study provides preliminary estimates of genetic parameters for methane emission traits, suggesting that there is potential to mitigate methane emission in Holstein cattle through genetic selection.

Early versus late body condition score loss in dairy cows: Reproductive performance

This study aimed to compare milk production and reproductive performance in high yield Holstein cows that lose BCS early and late in the postpartum period. Lactating dairy cows (n = 76) were received first timed AI at 60 to 75 DIM using the farm-managed estradiol-progesterone-GnRH-based timed AI protocol. The BCS of all cows was daily evaluated by automated BCS cameras. Aiming to evaluate the effect of the days in milk (DIM) in which a cow reached the nadir BCS on the reproductive parameters, cows were separated into two groups: early BCS loss (n = 42), cows that reached the nadir BCS ≤ 34 DIM, and late BCS loss (n = 34), cows that reached the nadir BCS > 34 DIM. The optimal cut-off point for determining the relationship between days to nadir BCS and pregnancy by 150 DIM (P150) was calculated using the receiver operating characteristic (ROC) curve. From the ROC analysis, the cut-off was 34 DIM (Se, 80.9%; Sp, 66.7%; AUC, 0.74; P < 0.01). No differences (P>0.05) were detected between groups on the BCS and milk production. The average of milk production in both groups was 46.65 ± 6.15 Kg/day. Cows that reached the nadir BCS early postpartum presented lower (P < 0.01) calving interval and greater (P < 0.01) pregnancy at first AI and P150. In summary, cows that lost BCS early had better reproductive performance and had similar milk yield compared with cows that lost BCS late in the postpartum period.

Effects of Soybean and Linseed Oils Calcium Salts and Starter Protein Content on Growth Performance, Immune Response, and Nitrogen Utilization Efficiency in Holstein Dairy Calves

This study aimed to investigate the interaction of fatty acid (FA) source [calcium salt of soybean oil (n-6 FA) vs. calcium salt of linseed oil (n-3 FA) both 3% DM basis] with protein content (18% vs. 22% CP, based on DM) on growth performance, blood metabolites, immune function, skeletal growth indices, urinary purine derivatives (PD), and microbial protein synthesis (MPS) in young dairy calves. Forty 3-day-old calves (20 females and 20 males) with a starting body weight (BW) of 40.2 kg were assigned in a completely randomized block design in a 2 × 2 factorial arrangement of treatments. Experimental diets were: (1) n-6 FA with 18% CP (n-6-18CP), (2) n-6 FA with 22% CP (n-6-22CP), (3) n-3 FA with 18% CP (n-3-18CP), and (4) n-3 FA with 22% CP (n-3-22CP). Starter feed intake and average daily gain (ADG) were not influenced by experimental diets (p > 0.05). However, before weaning and the entire period, feed efficiency (FE) was greater in calves fed n-3 FA compared to n-6 FA (p < 0.05). Heart girth (weaning, p < 0.05) and hip height (weaning, p < 0.05 and final, p < 0.01) were highest among experimental treatments in calves who received n-3-22CP diets. The greatest blood glucose (p < 0.05) and insulin (p < 0.01) concentrations in the pre-weaning period and the lowest serum concentration of tumor necrosis factor (before weaning, p < 0.05) were observed in calves fed the n-3-22CP diet. However, the greatest blood urea N (before weaning, p < 0.05; after weaning, p < 0.05) and urinary N excretion (p < 0.05) were found in calves fed n-6-22CP diets compared to other experimental arrangements. In conclusion, offering calves with Ca-salt of n-3 FA along with 22% CP content may be related to improved nitrogen efficiency and immune function.

Effects of linseed oil supplementation in Holstein dairy calves received starters based on either corn or barley grain on growth performance and immune response

This study evaluated the effects of linseed oil (LO) and two-grain sources on growth performance, microbial protein yield (MPY), blood metabolites, and inflammatory markers in Holstein dairy calves. Forty-eight 3-day-old dairy calves (24 males and 24 females) with starting BW of 40.3 ± 1.6 kg were allocated in a completely randomised block design with a 2 × 2 factorial arrangement as follows; (1) Corn grain (CG) with no LO supplementation (CG-NLO), (2) CG with 2.5% LO supplementation (CG-LO), (3) Barley grain (BG) with no LO supplementation (BG-NLO), and (4) BG with 2.5% LO supplementation (BG-LO). The calves were weaned on d 59 but the study lasted for 14 days after weaning (Day 73 of experiment). The results showed that starter feed intake was influenced neither by grain source nor linseed oil. However, average daily gain, BW, hip height, and MPY were improved in calves received BG compared to CG diets. Linseed oil supplementation had no significant effects on growth performance and MPY. During preweaning period, calves fed BG-LO had the greatest feed efficiency and the highest wither height. However, the greatest tumour necrosis factor and serum amyloid A were observed in BG-NLO. Despite, LO supplementation did not influence growth performance of animals per se; however, it reduced circulating inflammatory markers in calves during preweaning period. Based on this study condition, BG is more favourable than CG in dairy calves from the daily gain and microbial protein synthesis perspectives, and supplementing the starters with n-3 FA can be strategy to improve immune performance of calves fed barley-based starter diets.

Symposium review: Integrating the control of energy intake and partitioning into ration formulation

Energy intake and partitioning are determined by many interacting factors and their prediction is the Achilles' heel of ration formulation. Inadequate energy intake can limit milk yield and reproductive performance, whereas excessive energy intake will increase body condition, increasing the risk of health and reproductive issues in the subsequent lactation. Ration composition interacts with the physiological state of cows, making it difficult to predict DMI and the partitioning of energy accurately. However, understanding the factors controlling these allows us to devise grouping strategies and manipulate rations to optimize energy intake through lactation. Eating is controlled by the integration of signals in brain feeding centers. Ration composition affects DMI of cows via signals from ruminal distention and the hepatic oxidation of fuels. Dairy cow rations must contain a minimal concentration of relatively low-energy roughages for proper rumen function, but signals from ruminal distension can limit DMI when the drive to eat is high. Signals from the hepatic oxidation of fuels likely dominate the control of DMI in the peripartum period when cows are in a lipolytic state and later in lactation when signals from distension diminish. Therefore, the effects of the ration on DMI vary with the physiological state of the animal. Furthermore, they interact with environmental stressors such as social (e.g., overcrowding) and thermal stress. The objective of this article is to discuss the effects of ration composition on energy intake and partitioning in lactating cows and how they can be manipulated to optimize productive performance.