Balancing diets for physically effective fibre and ruminally degradable starch: A key to lower the risk of sub-acute rumen acidosis and improve productivity of dairy cattle

Treatment of corn with lactic acid delayed in vitro ruminal degradation without compromising fermentation: a biological and morphological monitoring study

Grain processed by lactic acid (LA) is known to improve ruminant growth and health. However, the exact mechanism regarding rumen hydrolysis of LA-treated grain is still ambiguous. This experiment was designed to compare the effects of 5% LA treatment on the trophic and morphological variations in corn and to discover the alternations in ruminal hydrolysis between LA-treated and untreated corn macroscopically and microscopically using in vitro fermentation method. The results showed that, compared with untreated corn (CN), corn treated with 5% LA for 48 h (CNLA) experienced a decrease in the dry matter, albumin fraction, aNDFom, and water-soluble carbohydrate content but an increase in the resistant starch content. The in vitro fermentation showed that the pH of CNLA was higher, but dry matter disappearance was lower than that of CN. Most of the fermentation indices were unaffected, except for decreased iso-butyrate and iso-valerate. The abundances of total bacteria, Prevotella spp., Streptococcus bovis, and Selenomonas ruminantium were higher, but those of Ruminococcus flavefaciens and Ruminococcus albus were lower in CNLA than in CN. There were differences in the scanning electron micrographs between CNLA and CN after 3 h of fermentation. This study suggests that treating corn with LA for 48 h can induce changes in its nutrient composition and alter the bacterial flora during subsequent in vitro fermentation. These changes appeared to be crucial contributors to the beneficial effects observed in rumen fermentation.

Effects of dietary forage neutral detergent fiber and rumen degradable starch ratios on chewing activity, ruminal fermentation, ruminal microbes and nutrient digestibility of Hu sheep fed a pelleted total mixed ration

Pelleted total mixed ration (P-TMR) feeding, which has become a common practice in providing nutrition for fattening sheep, requires careful consideration of the balance between forage neutral detergent fiber (FNDF) and rumen degradable starch (RDS) to maintain proper rumen functions. The present study aimed to investigate the effects of the dietary FNDF/RDS ratio (FRR) on chewing activity, ruminal fermentation, ruminal microbes, and nutrient digestibility in Hu sheep fed a P-TMR diet. This study utilized eight ruminally cannulated male Hu sheep, following a 4 × 4 Latin square design with 31 d each period. Diets consisted of four FRR levels: 1.0 (high FNDF/RDS ratio, HFRR), 0.8 (middle high FNDF/RDS ratio, MHFRR), 0.6 (middle low FNDF/RDS ratio, MLFRR), and 0.4 (low FNDF/RDS ratio, LFRR). Reducing the dietary FRR levels resulted in a linear decrease in ruminal minimum pH and mean pH, while linearly increasing the duration and area of pH below 5.8 and 5.6, as well as the acidosis index. Sheep in the HFRR and MHFRR groups did not experience subacute ruminal acidosis (SARA), whereas sheep in another two groups did. The concentration of total volatile fatty acid and the molar ratios of propionate and valerate, as well as the concentrate of lactate in the rumen linearly increased with reducing dietary FRR, while the molar ratio of acetate and acetate to propionate ratio linearly decreased. The degradability of NDF and ADF for alfalfa hay has a quadratic response with reducing the dietary FRR. The apparent digestibility of dry matter, organic matter, neutral detergent fiber, and acid detergent fiber linearly decreased when the dietary FRR was reduced. In addition, reducing the dietary FRR caused a linear decrease in OTUs, Chao1, and Ace index of ruminal microflora. Reducing FRR in the diet increased the percentage of reads assigned as Firmicutes, but it decreased the percentage of reads assigned as Bacteroidetes in the rumen. At genus level, the percentage of reads assigned as Prevotella, Ruminococcus, Succinivibrio, and Butyrivibrio linearly decreased when the dietary FRR was reduced. The results of this study demonstrate that the dietary FRR of 0.8 is crucial in preventing the onset of SARA and promotes an enhanced richness of ruminal microbes and also improves fiber digestibility, which is a recommended dietary FRR reference when formulating P-TMR diets for sheep.

High rumen degradable starch diet induced blood bile acids profile changes and hepatic inflammatory response in dairy goats

The objective of this study was to reveal the effect of rumen degradable starch (RDS) on bile acid metabolism and liver transcription in dairy goats using metabolomics and transcriptomics. Eighteen Guanzhong dairy goats of a similar weight and production level (body weight = 45.8 ± 1.54 kg, milk yield = 1.75 ± 0.08 kg, and second parity) were randomly assigned to 3 treatment groups where they were fed a low RDS (LRDS, RDS = 20.52% DM) diet, medium RDS (MRDS, RDS = 22.15% DM) diet, or high RDS (HRDS, RDS = 24.88% DM) diet, respectively. The goats were fed with the experimental diets for 5 weeks. On the last day of the experiment, all goats were anesthetized, and peripheral blood and liver tissue samples were collected. The peripheral blood samples were used in metabolomic analysis and white blood cell (WBC) count, whereas the liver tissue samples were used in transcriptomic analysis. Based on the metabolomics results, the relative abundances of primary bile acids in the peripheral blood were significantly reduced in the group that was fed the HRDS diet (P < 0.05). The WBC count was significantly increased in the HRDS group compared with that in the LRDS and MRDS groups (P < 0.01), indicating that there was inflammation in the HRDS group. Transcriptomic analysis showed that 4 genes related to bile acid secretion (genes: MDR1, RXRα, AE2, SULT2A1) were significantly downregulated in the HRDS group. In addition, genes related to the immune response were upregulated in the HRDS group, suggesting the HRDS diet induced a hepatic inflammatory response mediated by lipopolysaccharides (LPS) (gene: LBP), activated the Toll-like receptor 4 binding (genes: S100A8, S100A9) and the NF-kappa B signaling pathway (genes: LOC106503980, LOC108638497, CD40, LOC102180880, LOC102170970, LOC102175177, LBP, LOC102168903, LOC102185461, LY96 and CXCL8), triggered inflammation and complement responses (genes: C1QB, C1QC, and CFD). The HRDS diet induced a hepatic inflammatory response may be mediated by activating the Toll-like receptor 4 binding and NF-kappa B signaling pathway after free LPS entered the liver. The changes of bile acids profile in blood and the down-regulation of 4 key genes (MDR1, RXRα, AE2, SULT2A1) involved in bile secretion in liver are probably related to liver inflammation.

Acid-Base, Gas, Ions, and Glucose Analysis in Follicular Fluid in Holstein-Friesian Dairy Cows Is Associated with the Follicle Size in Poland

The lack of fertilization and early pregnancy loss is seen in the quality and maturation of the oocytes. The environment of the first divisions and maturation of the oogonia, which is also a reflection of the quality of the oocyte, is the follicular fluid (FF). Thus, the purpose of this study was to investigate the variations in parameters such as pH, pCO₂, pO₂, standard HCO₃^-, actual HCO₃^-, base excess (BE), base excess of extracellular fluid (BE ecf), ctCO₂, ions: Na⁺, K⁺, actual ionized calcium Ca²⁺, adjusted ionized calcium (at pH 7.4) Ca²⁺ (7.4), Cl^-, anion gap (AnGap), and glucose in FF collected from different size follicles in dairy cattle. The most apparent differences were related to pH, K⁺, and Ca²⁺ 7.4 concentration in comparison to changes in follicle size (p < 0.05). Several trends were also evaluated as an increase in follicular size was followed by an increase in pH, BE, and Ca²⁺ 7.4 value and a decrease in the K⁺ concentration (p < 0.05). In conclusion, there are changes in FF formularies associated with the size of follicles. However, more research is necessary to establish the reference value, which then could be one of the factors describing the quality of the follicle and the developmental potential of the associated oocyte.

Replacement of corn silage with shredded beet pulp and dietary starch concentration: Effects on performance, milk fat output, and body reserves of mid-lactation dairy cows

We aimed to evaluate the interaction between dietary starch concentration, varied by replacing wheat bran with dry ground corn, and replacement of corn silage (CS) with shredded beet pulp (BP) on production, milk fat output, milk fatty acid profile, and body reserves in dairy cows. Sixty-four Holstein dairy cows (140 ± 26 d in milk) were randomly assigned to 8 pens (8 animals per pen). Treatments were arranged in a 2 × 2 factorial arrangement with 2 concentrations of starch and 2 sources of fiber and were allotted to 8 pens (2 pens per treatment). Treatments were (1) 15% dry ground corn and 24% CS, (2) 15% dry ground corn and 24% BP replacing CS, (3) 30% dry ground corn and 24% CS, and (4) 30% dry ground corn and 24% BP replacing CS. The trial lasted for 47 d and final 7 d of experimental period was used for data and sample collection. Cows fed the BP-based diets had greater dry matter intake than those offered the CS-based diets, whereas no effects were observed with starch concentration. Milk yield increased by 1.8 kg/d with BP-based diets compared with CS-based diets and by 2.5 kg/d when cows received the high-starch compared with low-starch diets. Interactions between dietary starch concentration and forage substitution were detected for milk fat concentration and yield as BP inclusion lowered milk fat output with high-starch diet. Milk trans-18:1 concentration was lower with 15% dry ground corn and 24% CS compared with other diets. In conclusion, the effects of dietary starch concentration (22 and 32% dry matter) and forage substitution on production responses were independent except for milk fat output and milk trans 18:1 isomers. Substituting CS with BP is effective at increasing milk yield regardless of starch concentration; however, milk fat yield is lower when BP is used with high-starch concentration.

Comparison of blood gas parameters, ions, and glucose concentration in polish Holstein-Friesian Dairy cows at different milk production levels

Genetic selection for increased milk yield has been a key driver of dairy intensification. The modern dairy cow produces much higher amounts of milk than the cattle of several years ago, and this may have an influence on hematologic values at different stages of lactation and on cows with different levels of milk production. The purpose of the study was to investigate the variations in blood parameters such as Ht, tHb, sO₂, FO₂Hb, FCOHb, FMetHb, FHHb, pH, pCO₂, pO₂, standard HCO₃-, actual HCO₃-, BE, BE ecf, ctCO₂, BO₂, p50, and ctO₂ in cows at different milk production levels. In addition, ions such as Na+, K+ , Ca++, Ca++ (7.4), and Cl-, and AnGap and glucose were examined. Our findings indicated that differences in the examined blood parameters between low and high-production dairy cattle do exist. The most apparent differences were connected with blood pH (p < 0.01), oxygen metabolism (Ht, tHb, sO2, FO2Hb; p < 0.01), and glucose utilization (p < 0.01) The results confirm that the parameters connected with blood oxygen metabolism and glucose metabolism increase significantly in high-production animals. In conclusion, reference values should be considered in light of the lactation stage and level of milk production, because these might influence how changes should be interpreted. The main limitation of the study is the delay to analysis. However, the blood was properly stored (4C), thus changes were delayed. Anyway, it is very hard in the field practice to perform it within 5 min after the blood collection and according to studies it has low impact on clinical outcomes.

Evaluation of fecal sampling time points to estimate apparent nutrient digestibility in lactating Holstein dairy cows

Introduction

The aim of this study was the evaluation of nutrient excretion patterns in samples of feces collected every 2 h to define the best sampling protocol for estimation of apparent digestibility.

Methods

Four multiparous mid-lactation Holstein cows, housed in a tie stall barn and milked twice a day (0800; 1900 h), were enrolled. Dry total mixed ration (TMR) without silages was fed once (0800 h) per day. Feces were sampled every 2 h for 72 h. Each sample was divided in 3 portions: hourly sample sample (8, 10, 12, 14, 16, 18, 20, 22, 00, 2, 4, 6), 8-h composite sample (00-06, 08-14 and 16-22), and a 24-h composite sample. Complete chemical analyses were performed and total tract nutrient digestibility was calculated using undegraded neutral detergent fiber at 240 h of in vitro fermentation (uNDF240h) as a marker. Feeding and rumination patterns were also recorded during the trial.

Results and discussion

For some parameters, excretion was not constant throughout the day: neutral detergent fiber (aNDFom), undegraded neutral detergent fiber at 24 h of in vitro fermentation (uNDF24h), uDNF240h, total tract crude protein digestibility (TTCPD), total tract neutral detergent fiber digestibility (TTaNDFomD), total tract potentially degraded neutral detergent fiber at 240 h of in vitro fermentation digestibility (TTpdNDF240hD) with minimal values after new TMR delivery and maximal values 12 h after feed delivery. Feeding and ruminating behavior seemed to have an important role in the excretion pattern, due to the pushing and evacuating effect they have. Considering our results, two fecal samples at 12 and 24 h after the TMR delivery are suggested. For one daily sample, 12 h post time of most stable and constant rumination 0000-0600 h, which is also 8 h post feed delivery is suggested.

Subacute ruminal acidosis in dairy herds: Microbiological and nutritional causes, consequences, and prevention strategies

Dairy cattle are frequently fed high-concentrate (HC) diets in modern intensive feeding systems, especially in the transition period. During this period, cows face many alterations that include hormonal changes and shifting to a lactating state. Switching to a HC diet that may disrupt the ruminal microbiota balance can lead to subacute ruminal acidosis (SARA). Moreover, the main factor shaping the rumen microbiota is dietary composition, especially the ratio of starch to fibrous carbohydrates. Feeding highly fermentable carbohydrate diets after adaptation to forage diets leads to a rumen fermentation rate that exceeds rumen absorption and buffering rates, resulting in a reduction in ruminal pH. As a result of Gram-negative bacterial cell lysis, an increase in harmful ruminal bacterial metabolites, including lipopolysaccharide, lactic acid, and histamine, is observed. The interactions between the host immune system and the ruminal microbiota play an essential role in many physiological processes and the development of the disorder. Progress in DNA sequencing and bioinformatics platforms provides new opportunities to investigate the composition of ruminal microbes and yields unique advances in understanding ecology of the rumen. Subacute ruminal acidosis is linked with a change in the ruminal microbiota structure and richness and with other metabolic disorders; such as rumenitis, milk fat depression, laminitis, and liver abscesses. Therefore, this review aims to explore a better understanding of the crosstalk between diet and microbiota in the prevalence of rumen acidosis and its consequences, which is crucial for control strategies such as feeding management, and supplementation with thiamine, prebiotics, and probiotics.

Phytonutrients in Red Amaranth (Amaranthus cruentus, L.) and Feed Ratios Enhanced Rumen Fermentation Dynamics, Suppress Protozoal Population, and Methane Production

The search for alternative modifiers of rumen fermentation to improve the production efficiency of livestock production is highly essential. This in vitro fermentation experiment was conducted using a factorial arrangement of two ratios of roughage to concentrate and seven levels of red amaranth (Amaranthus cruentus L.) leaf powder (RALP) as a percentage of total substrate in a completely randomized design (CRD). There were two factors: factor A was two ratios of roughage (R) to concentrate (C) at 60:40 and 40:60 and factor B was levels of RALP supplementation at 0, 2, 4, 6, 8, 10, and 12% dry matter (DM) of total dietary substrate. The results revealed that a R:C ratio at 40:60 increased rumen fermentation and reduced methane production (p &lt; 0.05). The RALP incorporation as a feed additive was highly promising in enhancing propionate (C3) concentration, reducing acetate (C2) to (C3) ratio, and the protozoal population, while mitigating methane (CH4) production. Furthermore, DM degradation percentages were remarkably enhanced by increasing the RALP levels and R:C ratio at 40:60. In conclusion, plants rich in phytonutrients and minerals such as RALP and the lower R:C ratio showed a promising role in modulating rumen fermentation, mitigating methane production, as well as increasing substrate DM degradability.

Microbiome network traits in the rumen predict average daily gain in beef cattle under different backgrounding systems

Background

Backgrounding (BKG), the stage between weaning and finishing, significantly impacts feedlot performance in beef cattle; however, the contributions of the rumen microbiome to this growth stage remain unexplored. A longitudinal study was designed to assess how BKG affects rumen bacterial communities and average daily gain (ADG) in beef cattle. At weaning, 38 calves were randomly assigned to three BKG systems for 55 days (d): a high roughage diet within a dry lot (DL, n = 13); annual cover crop within a strip plot (CC, n = 13); and perennial pasture vegetation within rotational paddocks (PP, n = 12), as before weaning. After BKG, all calves were placed in a feedlot for 142 d and finished with a high energy ration. Calves were weighed periodically from weaning to finishing to determine ADG. Rumen bacterial communities were profiled by collecting fluid samples via oral probe and sequencing the V4 region of the 16S rRNA bacterial gene, at weaning, during BKG and finishing.

Results

Rumen bacterial communities diverged drastically among calves once they were placed in each BKG system, including sharp decreases in alpha diversity for CC and DL calves only (P < 0.001). During BKG, DL calves showed a substantial increase of Proteobacteria (Succinivibrionaceae family) (P < 0.001), which also corresponded with greater ADG (P < 0.05). At the finishing stage, Proteobacteria bloomed for all calves, with no previous alpha or beta diversity differences being retained between groups. However, at finishing, PP calves showed a compensatory ADG, particularly greater than that in calves coming from DL BKG (P = 0.02). Microbiome network traits such as lower average shortest path length, and increased neighbor connectivity, degree, number and strength of bacterial interactions between rumen bacteria better predicted ADG during BKG and finishing than variation in specific taxonomic profiles.

Conclusions

Bacterial co-abundance interactions, as measured by network theory approaches, better predicted growth performance in beef cattle during BKG and finishing, than the abundance of specific taxa. These findings underscore the importance of early post weaning stages as potential targets for feeding interventions that can enhance metabolic interactions between rumen bacteria, to increase productive performance in beef cattle.

Supplementary Information

The online version contains supplementary material available at 10.1186/s42523-022-00175-y.

Effect of soybean grain (Glycine max L.) supplementation on the production and fatty acid profile in milk of grazing cows in the dry tropics of Mexico

Improving the lipid profile in milk of cows with the use of soybean grain (Glycine max L.) can be favored in the grazing systems in the dry tropics of Mexico. The objective was to evaluate the milk production, the chemical composition, and the fatty acids profile (FAs) of the milk of cows in continuous grazing and supplemented with and without ground roasted soybean in the dry tropics of Mexico. Ten cows randomly distributed in two equal groups were used. Daily during confinement for milking, the cows individually received the treatments on dry basis T0: supplement with 4.6 kg commercial concentrate® without soybean, T1: supplement with 3.7 kg commercial concentrate® with 380 g of soybean. During the 78 days of the experiment, milk production was measured in all cows, and samples were collected to determine the chemical composition and FAs profile. Milk production, protein, milk total fat, lactose, and non-fat solids did not vary with treatment (p >0.05). Linoleic acid content (C18: 2, cis, cis-∆9, ∆12) increased by 22% in milk fat of cows of the T1 (p ˂0.05). The sum of the mono- and polyunsaturated FAs 29.1%, the ratio of saturated-unsaturated FAs (1.65), and the atherogenicity index (1.71) also improved in the milk of cows supplemented with T1 (p ˂0.05). It was concluded that ground roasted soybean supplement in the diet of grazing dairy cows did not affect production and did improve the lipid profile in milk fat with favorable index to promote human health.

A novel ammoniation treatment of barley as a strategy to optimize rumen pH, feed degradability and microbial protein synthesis in sheep

BACKGROUND

Meeting the energy and nitrogen (N) requirements of high-performing ruminants at the same time as avoiding digestive disturbances (i.e. rumen acidosis) is a key priority in ruminant nutrition. The present study evaluated the effect of a cereal ammoniation treatment, in which barley grains are combined with urea and enzymes that catalyze the conversion of urea to ammonia to optimize rumen function. Twelve rumen cannulated sheep were randomly divided into two groups and fed a diet containing 60% of ammoniated barley (AMM) or untreated barley supplemented with urea (CTL) to investigate the impact on rumen fermentation and feed utilization.

RESULTS

AMM had higher total N content and effective rumen degradable N than untreated barely. AMM sheep had a consistently higher rumen pH throughout the day (6.31 versus 6.03) and tended to have a lower post-prandial ammonia peak and higher acetate molar proportion (+5.1%) than CTL sheep. The rumen environment in AMM sheep favored the colonization and utilization of agro-industrial by-products (i.e. orange pulp) by the rumen microbes leading to a higher feed degradability. AMM sheep also had higher total tract apparent N digestibility (+21.7%) and urinary excretion of purine derivatives (+34%), suggesting a higher N uptake and microbial protein synthesis than CTL sheep.

CONCLUSION

The inclusion of AMM in the diet of ruminants represents a valid strategy for maintaining rumen pH within a physiological range and improving N utilization by the rumen microbes, which could have positive effects on the health and productivity of animals in intensive production systems. These findings warrant further studies under conventional farm conditions. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Effects of Calving Body Condition Score on Blood Acid-Base Balance of Primiparous Holstein-Friesian Dairy Cows in a Commercial Dairy Farm: A Case Study

Simple Summary

This study assesses the effect of the body condition score (BCS) on productive variables and the acid–base balance in Holstein heifers. For this purpose, two groups were established according to the BCS: a group of 12 animals with an optimal BCS (range 3.25–3.5) and a group of 15 heifers with a BCS higher than 3.5. The study period started one month before calving (BC) and ran until one month after calving (AC). The results showed that the BCS of heifers does not affect milk production in terms of quantity and quality. In addition, the study of acid–base balance variables provides information that contributes additional insights into metabolic changes that can sometimes go unnoticed.

Abstract

The study was carried out on 27 healthy primiparous Holstein heifers (620 ± 50 kg) kept in a commercial dairy herd. The animals were divided into two groups taking into account the body condition score (BCS) index: BCS < 3.5, n = 12; BCS > 3.5 n = 15. The study period started one month before calving (BC), and ran until one month after calving (AC). Venous blood samples were collected 1 month and 1 week BC, and 1 week and 1 month AC. This study had two objectives: (i) to assess whether a higher or lower BCS affected total milk production and its quality; (ii) to assess changes in the internal fluid (venous pH; partial pressure of CO₂, ppCO₂; bicarbonate; total CO₂, TCO₂; base excess, BE; electrolytes Na⁺, K⁺, Cl⁻; and anion gap, AG) that occur during this phase depending on the BCS. We can conclude that the BCS at calving does not affect the productive status during lactation, both in terms of the quantity and quality of milk produced. The excess of crude protein (CP) added through the ration in the lactation phase can trigger a tendency to an alkalotic state, in this case compensated by respiratory buffering mechanisms, as reflected by the TCO₂. The changes in electrolytes are a reflection of the movement of free water for milk production, where a balance between measurable anions and cations is observed.

Models to predict the risk of subacute ruminal acidosis in dairy cows based on dietary and cow factors: A meta-analysis

The present research aimed at developing practical and feasible models to optimize feeding adequacy to maintain desired rumen pH conditions and prevent subacute ruminal acidosis (SARA) in dairy cows. We conducted 2 meta-analyses, one using data from recent published literatures (study 1) to investigate the prediction of SARA based on nutrient components and dietary physical and chemical characteristics, and another using internal data of our 5 different published experiments (study 2) to obtain adjustments based on cow status. The results of study 1 revealed that physically effective neutral detergent fiber inclusive of particles >8 mm (peNDF >8) and dietary starch [% of dry matter (DM)] were sufficient for predicting daily mean ruminal pH {y = 5.960 - (0.00781 × starch) + (0.03743 × peNDF >8) - [0.00061 × (peNDF >8 × peNDF >8)]}. The model for time of pH suppression (<5.8 for ruminal pH or <6.0 for reticular pH, min/d) can be predicted with additionally including DMI (kg/d): 124.7 + (1.7007 × DMI) + (20.9270 × starch) + (0.2959 × peNDF >8) - [0.0437 × (DMI × starch × peNDF >8)]. As a rule of thumb, when taken separately, we propose 15 to 18% peNDF >8 as a safe range for diet formulation to prevent SARA, when starch or NFC levels are within 20 to 25% and 35 to 40% ranges, respectively. At dietary starch content below 20% of DM, grain type was insignificant in affecting ruminal pH. However, increasing dietary starch contents by using corn as the sole grain source could lead to more severe drops of pH compared with using grain mix based on barley and wheat, as underlined by an interaction between starch content and grain type. Data from study 2 emphasized an increased risk of SARA for cows in the first and second lactation with lower mean pH (0.2 units) and double amounts of time at pH <5.8 compared with the cows with ≥3 parities. Given that a lower ruminal pH is expected in these high-risk cows, it is advisable to keep the lower end of recommended starch (20%) and higher peNDF >8 (18%) contents in the diet of these cows. Overall, the present study underlines the possibility of predicting SARA based on dietary factors including peNDF >8 and starch contents, as well as DMI of the cows, which can be practically implemented for optimal diet formulation for dairy cows. With more data available, future studies should attempt to improve the predictions by including additional key dietary and cow factors in the models.

Effects of supplementation of nonforage fiber source in diets with different starch levels on growth performance, rumen fermentation, nutrient digestion, and microbial flora of Hu lambs

The objectives were to evaluate the effects of fiber source and dietary starch level on growth performance, nutrient digestion, rumen parameters, and rumen bacteria in fattening Hu lambs. A total of 360 Hu lambs (BW = 24.72 ± 0.14 kg, 2 months old) were subjected to a 2 × 3 factorial arrangement. Lambs randomly assigned 6 treatments with 6 repetitions (10 lambs per repetition) of each treatment. Six treatments were formulated to include the fiber sources with three starch levels. The experiment lasted a 63 d. The amount of feed, orts, and total feces were sampled on the 42nd day of the experiment. Rumen fluid samples were collected after 2 h of morning feeding on day 56. Rumen contents were collected last day after the selected lambs were slaughtered. Increasing the starch content decreased the digestibility of neutral detergent fiber (NDF, P = 0.005). Increasing the starch level increased the proportions of propionate (P = 0.002) and valerate (P = 0.001) and decreased the proportion of acetate (P < 0.001) and the ratio of acetate to propionate (P = 0.005). The abundance of Fibrobacter succinogenes was affected by an interaction between the fiber source and the starch level (P < 0.001). Fibrobacter succinogenes tended to be greater in lambs fed SH than in lambs fed BP (P = 0.091), which was greater in lambs fed high starch levels than in lambs fed low starch levels (P = 0.014). Increasing the starch level increased Streptococcus bovis abundance (P = 0.029) and decreased total bacteria (P = 0.025). At the genus level, increasing the starch level reduced the abundance of Butyrivibrio_2 (P = 0.020). Nevertheless, the final body weight (BW) and acid detergent fiber (ADF) digestibility were greater (P < 0.01) in lambs fed soybean hull (SH) than in lambs fed BP. The proportion of butyrate was greater (P = 0.005), while the rumen pH was lower (P = 0.001) in lambs fed beet pulp (BP) than in those fed SH. The abundances of Succiniclasticum, Candidatus_Saccharimonas, Ruminococcus_1, and Christensenellaceae_R-7 were greater in lambs fed SH than in those fed BP (P < 0.050), whereas the abundance of Fibrobacter was lower (P = 0.011). The predominant microbial phyla in all of the groups were Firmicutes, Bacteroidetes, and Fibrobacteres. Changing the starch level for fiber sources mainly changed the rumen community in terms of the phylum and genus abundances. Lambs fed SH with low starch level increased the final BW without affecting total volatile fatty acids (TVFA) concentrations.

High Rumen-Degradable Starch Diet Promotes Hepatic Lipolysis and Disrupts Enterohepatic Circulation of Bile Acids in Dairy Goats

BACKGROUND

High rumen-degradable starch (RDS) diets decrease milk fat. The increase of LPS in plasma associated with increased RDS impairs liver function, immune response and lipid metabolism, which depress the precursors for milk fat.

OBJECTIVE

This study investigated the mechanism of depression of milk fat precursors in the liver and small intestine of dairy goats fed different RDS diets.

METHOD

Eighteen Guanzhong lactating goats (second lactation, 45.8 ± 1.54 kg) and 6 ruminally cannulated dairy goats (aged 2-3 y, 54.0 ± 2.40 kg) were fed 3 different diets with low dietary RDS concentrations of 20.52% (LRDS), medium RDS of 22.15% (MRDS), and high RDS of 24.88% (HRDS) for 36 and 21 d, respectively, in experiments 1 and 2. The liver metabolites and jejunal microbiota in experiment 1 and LPS concentrations in rumen fluid and plasma in experiment 2 were measured. One-way ANOVA was used to analyze the biochemical parameters and mRNA or protein expression. The MIXED procedure was used to analyze LPS concentrations.

RESULTS

In experiment 1, the HRDS diet showed increased activity of alkaline phosphatase (27.4 to 41.4 U/L) in plasma (P < 0.05) compared with LRDS treatment. The HRDS diet significantly increased the hepatic concentrations of l-carnitine (129%), l-palmitoylcarnitine (306%), taurochenodeoxycholate (856%), and taurodeoxycholic acid (588%) in liver (variable importance in the projection > 1, P < 0.10) compared with the LRDS treatment. Goats fed the HRDS diet had 33.6% greater liver protein expression of carnitine palmitoyltransferase-1 (P < 0.05), and greater relative abundance of Firmicutes and Ruminococcus 2 in the jejunal content (linear discriminant analysis > 2.0, P < 0.05) than did goats fed LRDS diet. In experiment 2, goats fed the HRDS diet had greater LPS concentrations in rumen fluid (7.57 to 13.6 kEU/mL) and plasma (0.037 to 0.179 EU/mL) (P < 0.05) than did goats fed LRDS diet.

CONCLUSIONS

Feeding the HRDS diet promoted hepatic lipid β-oxidation and disrupted phospholipid and bile acids metabolisms in liver, thereby reducing the supply of lipogenic precursors to the mammary gland in dairy goats.

Rumen CO2 species equilibrium might influence performance and be a factor in the pathogenesis of subacute ruminal acidosis

This experiment was conducted to explore rumen carbon dioxide (CO₂) species equilibrium. Three lactating, fistulated cattle were consecutively exposed to three dietary treatments tailored to produce low rumen pH and increase the risk of subacute ruminal acidosis (SARA) by reducing physically effective neutral detergent fiber (Low _peNDF), increasing rumen degradable starch (High RDS) or both (Combined). Under these conditions, high and varied rumen concentrations of the CO₂ associated to water or dissolved CO₂ (dCO₂) were found. The results suggest that the activity of dCO₂ and bicarbonate (HCO₃⁻) represents an important component of the rumen environment. Rumen CO₂ holdup was associated with high dCO₂ and HCO₃⁻ activity as well as changes in the viscosity and surface tension of the rumen fluid. All dietary treatments produced low rumen pH, <5.5 for >3 h/d, a condition associated with SARA, but clinical SARA was observed only during CO₂ holdup. This pilot study highlights the possible role of CO₂ holdup and rumen CO₂ species in cattle performance and nutritional diseases. In the future, better estimations of CO₂ species might help clarify these findings.

Feeding diets varying in forage proportion and particle length to lactating dairy cows: I. Effects on ruminal pH and fermentation, microbial protein synthesis, digestibility, and milk production

Physically effective neutral detergent fiber (peNDF) content of dairy cow diets was modified by varying the theoretical chop length of alfalfa silage and forage:concentrate (F:C) ratio, and effects on nutrient intakes, ruminal fermentation, site and extent of digestion, microbial protein synthesis, and milk production were evaluated. Estimates of dietary peNDF contents were compared with recommendations, and predictions of ruminal pH from peNDF and the recently developed physically adjusted neutral detergent fiber (paNDF) system were compared with observed pH. The experiment was designed as a triple 4 × 4 Latin square using 12 mid-lactating dairy cows with 4 intact, 4 ruminally cannulated, and 4 ruminally and duodenally cannulated cows. Site and extent of digestion and microbial protein synthesis were measured in a single 4 × 4 Latin square. Treatments were a 2 × 2 factorial arrangement; 2 forage particle lengths (FPL) of alfalfa silage (short and long) were combined with low (35:65) and high (60:40) F:C ratios [dry matter (DM) basis]. The peNDF contents were determined by multiplying the proportion (DM basis) of total mixed ration retained on 2 (8 and 19 mm; peNDF_8.0) or 3 (1.18, 8, and 19 mm; peNDF_1.18) sieves of the Penn State Particle Separator by the neutral detergent fiber content of the diet. The dietary peNDF contents ranged from 10.7 to 17.5% for peNDF_8.0 or from 23.1 to 28.2% for peNDF_1.18. Interactions between F:C ratio and FPL content were few. Increasing peNDF content of diets by increasing F:C ratio decreased DM intake, milk yield, and milk protein yield, whereas apparent total-tract DM digestibility and milk efficiency improved. Increasing F:C ratio improved ruminal pH status but decreased total volatile fatty acid concentration and microbial protein synthesis. Increasing peNDF content of diets via dietary FPL increased mean ruminal pH, but did not affect DM intake, total-tract digestibility, or milk production. The results indicate that feeding dairy cows a low F:C diet helps increase DM intake, milk production, and microbial protein synthesis, but may adversely affect feed digestibility and milk efficiency due to increased risk of subacute ruminal acidosis. Increased FPL improved ruminal pH status, but had minimal effects on feed intake, ruminal fermentation, nutrient digestibility, and milk production. The results indicate a trade-off between reducing the risk of subacute ruminal acidosis and maximizing ruminal fermentation, feed digestibility, and milk production of dairy cows. The paNDF model showed improvement in the predictability of ruminal pH over the peNDF model, but the accuracy of predictions varied depending upon the diet and ruminal fermentation variables considered in the equations.

Effects of inclusion of corn gluten feed in dairy rations on dry matter intake, milk yield, milk components, and ruminal fermentation parameters: a meta-analysis

Corn gluten feed (CGF) is a co-product of wet milling that can replace energy or fiber ingredients in dairy cow rations. The present meta-analysis examines how inclusion of CGF can affect dry matter intake (DMI), milk yield (MY), milk components, and ruminal fermentation parameters. A literature search was conducted to identify papers published from 1990 to 2018. Effect size for all parameters was calculated as standardized mean difference with a 95% confidence interval. Heterogeneity was determined using Q test and I² statistic, while meta-regression was used to examine factors influencing heterogeneity. Results indicate that feeding CGF increased the effect size for DMI and MY. No differences were observed for effect size for percentage milk fat or protein; however, increases were observed in the effect size for milk fat yield, milk protein yield, milk lactose percentage, and milk lactose yield. Ruminal fermentation parameters revealed a decrease in the effect size for pH and acetate and an increase for propionate. No differences were observed in the effect size for total VFA or butyrate. The Q test demonstrated heterogeneity (P < 0.1) for MY, MFP, and pH. The results indicate differences in forage intake between groups receiving CGF and control as an important factor contributing to heterogeneity for DMI, MFP, and pH. It can be concluded from this meta-analysis that in addition to increased DMI, inclusion of CGF in cow diets increases MY and improves milk components. Furthermore, inclusion of CGF in the diet lowers ruminal pH while decreasing acetate and increasing propionate contents.

Effects of supplementing a Saccharomyces cerevisiae fermentation product during the periparturient period on the immune response of dairy cows fed fresh diets differing in starch content

The objective of this study was to evaluate the effects of supplementing a Saccharomyces cerevisiae fermentation product (SCFP; NutriTek, Diamond V, Cedar Rapids, IA) during the periparturient period (d -28 ± 3 to 44 ± 3 relative to calving) on mRNA abundance of genes in the rumen epithelium, inflammation indicators, oxidative status, and adaptive immunity of dairy cows fed diets with different starch content after calving. From d 28 ± 3 (± standard deviation) before the expected calving date to calving, Holstein cows (n = 38) received a common basal controlled-energy close-up diet (1.43 Mcal/kg, net energy for lactation; 13.8% starch) with (SCFP; n = 19) or without (CON; n = 19) SCFP, and cows within each treatment (CON or SCFP) were fed either a low- (LS; 22.1% starch) or high-starch (HS; 28.3% starch) diet from d 1 to 23 ± 3 after calving (fresh period). There were 4 treatment groups: LS + CON (n = 9), LS + SCFP (n = 10), HS + CON (n = 10), and HS + SCFP (n = 9). From d 24 ± 3 to 44 ± 3 after calving, all cows were fed the HS diets (post-fresh period). Animal assignment to treatments was balanced for parity, body condition score, and expected calving date. An interaction was observed between dietary starch content and SCFP on indices of oxidative stress; plasma concentrations of total antioxidant capacity tended to be reduced on d 21 after calving for SCFP compared with CON cows when a LS fresh diet was fed, but did not differ for cows fed HS fresh diets. Regardless of starch content, SCFP supplementation increased plasma concentrations of malondialdehyde at d 21 after calving compared with CON. Supplementing with SCFP reduced serum concentrations of haptoglobin on d 7 after calving, indicating reduced inflammation, and feeding LS fresh diets reduced mRNA abundance of IL receptor associated kinase-1 in rumen tissue at d 21 after calving, suggesting reduced immune activation in rumen tissue. Other than the anti-inflammatory effects indicated by lower serum haptoglobin concentration, no other effects of treatment on adaptive immunity were detectable. These results indicate that supplementing SCFP through the transition period and feeding low-starch diets during the fresh period may reduce inflammation.

Effects of fumaric acid supplementation on methane production and rumen fermentation in goats fed diets varying in forage and concentrate particle size

Background

In rumen fermentation, fumaric acid (FA) could competitively utilize hydrogen with methanogenesis to enhance propionate production and suppress methane emission, but both effects were diet-dependent. This study aimed to explore the effects of FA supplementation on methanogenesis and rumen fermentation in goats fed diets varying in forage and concentrate particle size.

Methods

Four rumen-cannulated goats were used in a 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments: low or high ratio of forage particle size: concentrate particle size (Fps:Cps), without or with FA supplementation (24 g/d). Fps:Cps was higher in the diet with chopped alfalfa hay plus ground corn than in that with ground alfalfa hay plus crushed corn.

Results

Both increasing dietary Fps:Cps and FA supplementation shifted ruminal volatile fatty acid (VFA) patterns toward more propionate and less acetate in goats. An interaction between dietary Fps:Cps and FA supplementation was observed for the ratio of acetate to propionate (A:P), which was more predominant when FA was supplemented in the low-Fps:Cps diet. Methane production was reduced by FA, and the reduction was larger in the low-Fps:Cps diet (31.72%) than in the high-Fps:Cps diet (17.91%). Fumaric acid decreased ruminal total VFA concentration and increased ruminal pH. No difference was found in ruminal DM degradation of concentrate or alfalfa hay by dietary Fps:Cps or FA. Goats presented a lower ruminal methanogen abundance with FA supplementation and a higher B. fibrisolvens abundance with high dietary Fps:Cps.

Conclusions

Adjusting dietary Fps:Cps is an alternative dietary model for studying diet-dependent effects without changing dietary chemical composition. Fumaric acid supplementation in the low-Fps:Cps diet showed greater responses in methane mitigation and propionate increase.

Impact of dietary carbohydrate balance on rumen fermentation, eating behaviour, growth and development of 8–10-month-old heifers

The present study was undertaken to determine an optimal balance between the amount of physically effective fibre and rumen readily fermentable carbohydrates in the diets of heifers. The dietary carbohydrate balance index (CBI) was expressed as the ratio of physically effective neutral detergent fibre (g/kg of DM) to rumen degradable starch (g/kg of DM). Twenty-four Chinese Holstein heifers aged ~8 months were randomly divided into four groups of six. The length and content of Chinese wild-rye hay and the content of rumen degradable starch in diets were used to adjust dietary CBI, and treatment diets consisted of the following four CBI levels: 1.21 (Treatment A), 1.53 (Treatment B), 1.86 (Treatment C) and 2.29 (Treatment D). The feeding trial lasted 75 days, with 15 days for adaptation. DM intake of heifers was not influenced by different treatments (P > 0.10). Average daily gain of heifers varied (0.86 ± 0.10, 1.03 ± 0.06, 1.12 ± 0.08 and 0.98 ± 0.04 (mean ± s.d.) kg/day among groups respectively), with significant (P < 0.05) differences among treatments, but the initial and final bodyweight of heifers were not different (P > 0.10). In addition, the abdominal girth of heifers in Treatments C and D was significantly (P < 0.05) greater than that in Treatment A. With the increment of CBI, eating and chewing time increased significantly (P < 0.05), while eating frequency decreased significantly (P < 0.05). Rumen fluid pH increased significantly (P < 0.05) with the increasing of CBI level, while there was little difference in total volatile fatty acid concentration, and propionate, butyrate and valerate concentrations. Acetate concentration was significantly (P < 0.05) higher in Treatments C and D than in Treatment A. Moreover, ammonia-nitrogen concentration of Treatments B and C was significantly (P < 0.05) higher than that of Treatment D. These results indicated that 1.86 is the optimal CBI in diets for 8–10-month-old heifers in the present study.

Long-term influence of feeding barley treated with lactic acid and heat on performance and energy balance in dairy cows

The study evaluated the long-term influence of feeding ground barley treated with lactic acid (LA) alone or with LA and heat on performance, energy and protein balance in dairy cows. Thirty cows were fed three diets differing in the treatment of barley grain, either unprocessed ground barley (Control), ground barley steeped in 1% LA at room temperature (LA-treated barley) or ground barley steeped in 1% LA with an additional heating at 55°C (LAH-treated barley). Cows were studied from week 3 to 17 post-partum. Dry matter intake (DMI), milk yield and composition and body weight (BW) were measured daily. Estimated energy and protein balances were calculated and blood samples were collected three times during the experiment and analysed for common metabolites of energy and lipid metabolism. Digestibility of different treated barley and other dietary ingredients was investigated in vivo using four wethers. The treatment of barley with LA and LAH increased the digestibility of organic matter (OM) by approximately 5% and the content of metabolisable energy by 0.5-0.6 MJ/kg DM. Data showed no effect of feeding diets containing LA- or LAH-treated barley at 39% of DM on overall DMI, BW, BW change, milk production and composition and on the blood variables studied. Diet influenced the estimated balances of net energy of lactation (p < 0.01) and the content of utilisable protein at the duodenum (p = 0.07) with cows fed the diet with LA-treated barley showing improved balances. In conclusion, feeding diets containing LA- or LAH-treated barley had no influence on performance, milk composition and blood metabolites, but LA treatment without heat seems to improve the energy balance of cows.

Prevalence and consequence of subacute ruminal acidosis in Polish dairy herds

The aim of this study was to estimate the prevalence of subacute ruminal acidosis (SARA) in Polish high-yielding dairy herds. Also, the relationships between the chemical composition of the diet and the feed particle size, ruminal pH and the occurrence of this metabolic disease and the fermentation profile were determined. Rumen fluid samples were obtained from a total of 213 cows from nine dairy herds (≥20 cows per herd) via rumenocentesis. Almost 14% (30/213) of cows as acidotic (pH<5.6) were found, which is indicative of SARA. Moreover, 44% of the herds were classified as SARA-positive and 56% as SARA-negative. Results of the current study suggested that the physically effective NDF (NDF_>1.18 mm) -to-starch ratio could be better indices than peNDF_>1.18 mm to preventing the occurrence of SARA, and their level should not be lower than 1.00. Also, linear negative relationships between rumen fluid pH and concentration of propionate, valerate and total VFA were determined. According to the herd's SARA status and rumen fluid biochemical indices, there were significant differences between the pH of rumen fluid (p ≤ 0.01), concentrations of acetate (p ≤ 0.05), propionate (p ≤ 0.05), n-butyrate (p ≤ 0.01), n-valerate (p ≤ 0.01), the sum of VFA (p ≤ 0.01) and ammonia (p ≤ 0.05) in SARA-positive herds compared to SARA-negative herds. The better understanding the strategy of ruminant nutrition to coordinate energy conversion and the role of the ruminal pH in regulating N-NH₃ production, absorption through rumen mucosa, urea secretion, the more successfully we can utilize these processes with due recognition of animal needs and welfare, as well as prevention of SARA occurrence.

Arginine Relieves the Inflammatory Response and Enhances the Casein Expression in Bovine Mammary Epithelial Cells Induced by Lipopolysaccharide

As one of functional active amino acids, L-arginine holds a key position in immunity. However, the mechanism that arginine modulates cow mammary inflammatory response in ruminant is unclear. Therefore, this study was conducted to investigate the effects of L-arginine on inflammatory response and casein expression after challenging the bovine mammary epithelial cells (BMECs) with lipopolysaccharide (LPS). The cells were divided into four groups, stimulated with or without LPS (10 μg/mL) and treated with or without arginine (100 μg/mL) for 12 h. The concentration of proinflammatory cytokines, inducible nitric oxide synthase (iNOS), mammalian target of rapamycin (mTOR), and Toll-like receptor 4 (TLR4) signaling pathways as well as the casein was determined. The results showed that arginine reduced the LPS-induced production like IL-1β, IL-6, TNF-α, and iNOS. Though the expression of NF-κB was attenuated and the mTOR signaling pathway was upregulated, arginine had no effect on TLR4 expression. In addition, our results show that the content of β-casein and the total casein were enhanced after arginine was supplemented in LPS-induced BMECs. In conclusion, arginine could relieve the inflammatory reaction induced by LPS and enhance the concentration of β-casein and the total casein in bovine mammary epithelial cells.

Growth performance and carcass characteristics of feedlot Thai native × Lowline Angus crossbred steer fed with fermented cassava starch residue

Ten Thai native × Lowline Angus crossbred (50:50) steers were used in a completely randomized design to receive two treatments including concentrate containing cassava chips (Control) and fermented cassava starch residue (FCSR) as major carbohydrate sources. FCSR was prepared as yeast (Saccharomyces cerevisiae) inoculates with exogenous enzyme addition. All steers received ad libitum rice straw and concentrate in equal proportions (1:1). Replacement of cassava chip with FCSR increased neutral detergent fiber and acid detergent fiber intakes but decreased non-protein nitrogen intake of steers. Digestibility of dry matter, organic matter, and crude protein were decreased with replacement of cassava chip by FCSR; however, digested nutrients were similar between groups. Replacement of cassava chip in the concentrate with FCSR resulted in comparable growth performance and feed efficiency of the feedlot steers. Moreover, carcass characteristics in terms of yield and meat quality of the steers were not affected by cassava chips replaced by FCSR as a major carbohydrate source in the concentrate. In conclusion, replacement of cassava chip in the concentrate with FCSR decreased feed digestibility; however, it did not impact negatively on growth performance and carcass traits of feedlot Thai native × Lowline Angus crossbred steers.

Nutrition, rumen health and inflammation in the transition period and their role on overall health and fertility in dairy cows

Transition is a stressful period and critical for the entire cow's productive lifespan and reproduction. Optimal feeding management during transition period enables smooth metabolic adaptation to the initiation of lactation. Major nutritional challenge during this period is the urgent need to counteract the drastic deficits in energy and nutrients of the early-lactating cow. This is primarily done by inclusion of large amounts of concentrates in the diet during early lactation, causing major dietary imbalances with utmost importance for rumen health. Proper feeding management targeting rumen health in the transition period improves nutrient degradation and the net supply with energy and key nutrients of the host while preventing systemic disturbances and inflammation, events which are instrumental for cow's overall health and reproductive performance. The review provides insights into the role of, and gives practical hints regarding diet balancing efforts and feeding management strategies targeting rumen health and systemic inflammation during the periparturient period with the aim to enhance cow health and fertility.

Effects of by-product feed-based silage on feeding, rumination, and excretion in growing Hanwoo heifers

This study investigated the effects of feeding by-product feed (BF)-based silage on the behavior of growing Hanwoo heifers. Twelve Hanwoo heifers (13.2 months-old, 315 kg body weight; four heifers per pen) were assigned to three diets: a rice straw (RS) diet (concentrate mix and free access to RS), a RS and BF-based silage (RSBFS) diet (concentrate mix and free access to RS and BF-based silage), and a BF-based silage (BFS) diet (concentrate mix and free access to BF-based silage). Behavior was recorded for 5 days using camcorders. Compared to the RS group, the BFS group showed 21.7% higher dry matter intake, shorter feeding, rumination, and chewing times, as well as longer resting time (p < 0.05). Although all groups exhibited similar drinking, urination, and defecation frequencies, the BFS group exhibited higher feeding rates, rumination efficiency, and chewing efficiency than the RS group (p < 0.05). Compared to the BFS group, the RSBFS group showed higher peNDF_8.0 intake (15.2% vs. 25.0% dry matter intake), longer feeding and sitting times, lower defecation frequency (p < 0.05), and similar rumination efficiency. In conclusion, complete replacement of conventional RS with BF-based silage reduced rumination and chewing activity in growing Hanwoo heifers, and BF-based silage feeding with large-particle straw is an effective approach in improving heifer behavior.

Long-term reticuloruminal pH dynamics and markers of liver health in early-lactating cows of various parities fed diets differing in grain processing

The present study aimed to investigate the long-term effect of feeding barley grain steeped in lactic acid (La) with or without thermal treatment on reticuloruminal pH dynamics and metabolic activity of the liver in 12 primiparous and 18 multiparous early-lactating dairy cows. All cows were included on d 21 postpartum and sampled until d 90 postpartum. Cows were fed a diet based on differently processed ground barley grain: untreated grain (control diet, CON), or grain treated with 1% La alone for 24 h before feeding (La), or with an additional oven-heating at 55°C for 12 h (LaH). The reticuloruminal pH and temperature were measured via indwelling sensors that allowed for continuous (every 10min) and long-term measurement from d 21 to 80 postpartum. Blood samples were taken on d 21, 40, and 90 of lactation and analyzed for liver enzymes aspartate aminotransferase (AST), gamma-glutamyltransferase, and glutamate dehydrogenase, as well as bilirubin, bile acids, and serum amyloid A. Dry matter intake was higher in multiparous cows (20.7±0.27 kg/d) compared with primiparous cows (18.2±0.33 kg/d), but was not affected by dietary treatment. Overall, the relatively short duration (51±5min/d) of reticuloruminal pH <5.8 suggests low risk of subacute ruminal acidosis throughout the experiment. Results indicated that La treatment of barley, with or without heat, lowered the time duration of pH <5.8 compared with CON, but only in primiparous cows (from 118±13 to 46±11 and 25±11min/d for CON, La, and LaH, respectively). In multiparous cows, the opposite effect of feeding the La-treated barley on time duration of pH <5.8 (11±8 vs. 46±9 vs. 57±9min/d for CON, La, and LaH, respectively) was observed. Multiparous cows generally showed higher pH readings and shorter periods in which the ruminal pH dropped below the threshold of pH 5.8. The reticuloruminal temperature was not affected by dietary treatment, whereas parity affected the time duration of reticuloruminal temperature >39.5°C, being 60±19min/d shorter in primiparous cows. The measured activities of the liver enzymes AST, gamma-glutamyltransferase, and glutamate dehydrogenase, as well as bilirubin, bile acids, and the acute phase protein serum amyloid A, were not affected by grain feeding. Additionally, only one small effect of parity on investigated serum variables was noticed, showing slightly but significantly higher values of AST in multiparous (80.5±1.4 U/L) compared with primiparous cows (76.0±1.7 U/L). In conclusion, our results indicate greater risk for primiparous cows to develop subacute ruminal acidosis-like conditions during early lactation than multiparous cows. The study also suggests limited benefits of feeding processed barley grain with La with or without thermal treatment to modulate ruminal tolerance of grain feeding, whereby differing effects in primiparous cows were observed compared with multiparous cows.

Effects of supplementation with a phytobiotics-rich herbal mixture on performance, udder health, and metabolic status of Holstein cows with various levels of milk somatic cell counts

This study evaluated the effects of dietary supplementation of a novel phytobiotics-rich herbal mixture (PRHM) on feed intake, performance, udder health, ruminal fermentation, and plasma metabolites in cows with moderate or high somatic cell counts (SCC) in the milk. Twenty-four Holstein dairy cows (117 ± 26 d in milk and 46.3 ± 4.7 kg of milk/d at the start of the experiment) were blocked by parity and days in milk and split into 2 groups, based on SCC in the milk; 12 cows were with moderate SCC (260,000<SCC <500,000 cells/mL), whereas 12 other cows had high levels of SCC (>500,000 cells/mL) in the milk. Within each SCC group, cows were blocked by milk yield and parity, and were randomly assigned to 2 different feeding regimens. Half of the cows in each SCC group (n=6) were supplemented with PRHM (185 g/cow per day, providing 12.4 g of phenolic compounds per day), and the other half (n=6) were not supplemented in their diets. The experiment lasted 36 d, whereby the first 24 d were used for adaptation to the diets and the last 12 d for sampling. Data showed that supplementation of PRHM decreased somatic cell score in the milk, indicating improved udder health of cows with high initial SCC, but not in cows with moderate SCC. Also, cows supplemented with PRHM consumed more feed DM, produced greater amounts of milk, and showed an improvement of feed utilization efficiency. However, these cows also lost more back-fat thickness during the experiment. Supplementation of PRHM increased fat- and energy-corrected milk yields in cows with high initial SCC, but not in cows with moderate SCC. Supplementation of PRHM decreased milk fat content, whereas other milk components were not affected by PRHM feeding. The PRHM supplementation decreased the acetate-to-propionate ratio in the rumen fluid, but increased β-hydroxybutyrate and cholesterol concentration in the plasma, irrespective of the initial SCC level in the milk. Other plasma metabolites and liver enzymes were not affected by PRHM supplementation. Apparent nutrient digestibility did not differ among treatments. Overall, supplementation of PRHM seems to be an effective strategy to enhance performance and lower SCC, particularly in cows having high SCC levels in the milk. Further research is warranted to evaluate long-term effects of PRHM supplementation, especially with regard to metabolic health status and reproduction.

Peculiarities of enhancing resistant starch in ruminants using chemical methods: opportunities and challenges

High-producing ruminants are fed high amounts of cereal grains, at the expense of dietary fiber, to meet their high energy demands. Grains consist mainly of starch, which is easily degraded in the rumen by microbial glycosidases, providing energy for rapid growth of rumen microbes and short-chain fatty acids (SCFA) as the main energy source for the host. Yet, low dietary fiber contents and the rapid accumulation of SCFA lead to rumen disorders in cattle. The chemical processing of grains has become increasingly important to confer their starch resistances against rumen microbial glycosidases, hence generating ruminally resistant starch (RRS). In ruminants, unlike monogastric species, the strategy of enhancing resistant starch is useful, not only in lowering the amount of carbohydrate substrates available for digestion in the upper gut sections, but also in enhancing the net hepatic glucose supply, which can be utilized by the host more efficiently than the hepatic gluconeogenesis of SCFA. The use of chemical methods to enhance the RRS of grains and the feeding of RRS face challenges in the practice; therefore, the present article attempts to summarize the most important achievements in the chemical processing methods used to generate RRS, and review advantages and challenges of feeding RRS to ruminants.

Evaluation of associative effects of total mixed ration for dairy cattle using in vitro gas production and different rumen inocula

BACKGROUND

Current feed evaluation systems for dairy cattle assume that nutritive values of feed components can be added, but do not take into account possible interactions among feed components. The main objective of this study was to investigate associative effects on in vitro gas production from total mixed ration (TMR), based on grass silage and cereal concentrate, and separate TMR components. TMR was incubated with inocula of free rumen liquid (FRL) and particle-associated rumen liquid (PAL) for 48 h and donor cows were fed TMRs with three different particle sizes to evaluate their influence on associative effects.

RESULTS

Associative effects on gas production largely occurred at 2 and 4 h of incubation and dissipated with time of incubation. Incubation of TMR with PAL increased (P < 0.01) gas production compared to FRL at all incubation times; however, associative effects were not different between rumen inocula. Dietary particle size affected associative effects on gas production when TMR was incubated with FRL (P < 0.05) compared to PAL, particularly at early hours of incubation.

CONCLUSIONS

Associative effects at early incubation hours emphasise that summing the nutritive values of feedstuffs may underestimate fermentation intensity of TMR which may have implications for prediction of ruminal fermentation yield.