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

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.

Effects of High-Concentrate-Induced SARA on Antioxidant Capacity, Immune Levels and Rumen Microbiota and Function in Goats

This study aims to explore the antioxidant, immune, and enzyme metabolism aspects in goats experiencing subacute ruminal acidosis (SARA). Furthermore, we seek to elucidate the relationship between the symbiotic microbiota of goats and their metabolic function. Sixteen goats were equally divided into two groups and fed a normal-concentrate diet (NC, 55% concentrate) or a high-concentrate diet (HC, 90% concentrate) for five weeks. We found that the HC diet reduced the total antioxidant capacity (T-AOC) (p = 0.022) and increased interleukin-1β (IL-1β) (p = 0.015), interleukin-4 (IL-4) (p = 0.008) and interleukin-6 (IL-6) (p = 0.002) concentration of goats. Simultaneously, the HC diet significantly increased the concentrations of alkaline phosphatase (ALP) and amylase (AMY) in the blood and rumen fluid of goats (p < 0.05). Microbial analysis in the rumen of goats revealed that the HC diet decreased bacterial richness and diversity, as evidenced by the changed observed species, Chao 1, PD whole tree and Shannon when compared to the NC diet (p < 0.01). The proportion of Proteobacteria increased while that of Spirochaetes and Fibrobacteres significantly decreased with the HC diet (p < 0.05). The Christensenellaceae_R-7_group and Ruminococcaceae_UCG-010 in rumen was notably decreased when a diet was switched from 55% concentrate diet to 90% concentrate diet (p < 0.05). Additionally, microbial functional potentials deduced that the HC diet significantly increased the abundance of the citrate cycle (TCA cycle) (ko00020) associated with carbohydrate metabolism (p = 0.028). Furthermore, the HC diet significantly increased the glutathione metabolism (ko00480) associated with the metabolism of other amino acids (p = 0.008). Our findings suggested that SARA reduced the total antioxidant capacity and increased levels of inflammatory factors in goats, as well as decreased rumen bacterial species and abundance.

Effect of olive cake supplementation on faecal microbiota profile of Holstein and Modicana dairy cattle

The present study aimed to investigate the effect of olive cake supplementation on faecal microbiota of Holstein (n = 16) and Modicana (n = 16) dairy cows. Although no difference in richness was detected, within breeds and between the two dietary treatment, the PERMANOVA analysis applied to the beta diversity allowed to discriminate samples according to breeds (p < 0.001) and treatment (p < 0.001). In Holstein cows, the olive cake supplementation led to the increase of Pseudobutyrivibrio and Christensenellaceae_R7-group genera (p < 0.05) recognized as health-promoting or associated with feed efficiency. Differently, no difference was detected between control and treated groups for Modicana suggesting a high adaptive capacity to diet changes. In addition, the higher prevalence of Firmicutes phyla in the Modicana microbiota reflected its better capacity to digest the fibrous sources. Our study supports the suitability of olive cake as a feed supplement for cows and could help validating a sustainable livestock system in the Mediterranean area, characterized by a relevant oil production and by a native breeds reared with extensive systems.

Development of a spore-based mucosal vaccine against the bovine respiratory pathogen Mannheimia haemolytica

Bovine respiratory disease (BRD) is a significant health issue in the North American feedlot industry, causing substantial financial losses due to morbidity and mortality. A lack of effective vaccines against BRD pathogens has resulted in antibiotics primarily being used for BRD prevention. The aim of this study was to develop a mucosal vaccine against the BRD pathogen, Mannheimia haemolytica, using Bacillus subtilis spores as an adjuvant. A chimeric protein (MhCP) containing a tandem repeat of neutralizing epitopes from M. haemolytica leukotoxin A (NLKT) and outer membrane protein PlpE was expressed to produce antigen for adsorption to B. subtilis spores. Adsorption was optimized by comparing varying amounts of antigen and spores, as well as different buffer pH and reaction temperatures. Using the optimal adsorption parameters, spore-bound antigen (Spore-MhCP) was prepared and administered to mice via two mucosal routes (intranasal and intragastric), while intramuscular administration of free MhCP and unvaccinated mice were used as positive and negative control treatments, respectively. Intramuscular administration of MhCP elicited the strongest serum IgG response. However, intranasal immunization of Spore-MhCP generated the best secretory IgA-specific response against both PlpE and NLKT in all samples evaluated (bronchoalveolar lavage, saliva, and feces). Since proliferation of M. haemolytica in the respiratory tract is a prerequisite to lung infection, this spore-based vaccine may offer protection in cattle by limiting colonization and subsequent infection, and Spore-MhCP warrants further evaluation in cattle as a mucosal vaccine against M. haemolytica.

The effects of feeding α-amylase-enhanced corn silage with different dietary starch concentrations to lactating dairy cows on milk production, nutrient digestibility, and blood metabolites

Corn silage is one of the most common ingredients fed to dairy cattle. Advancement of corn silage genetics has improved nutrient digestibility and dairy cow lactation performance in the past. A corn silage hybrid with enhanced endogenous α-amylase activity (Enogen, Syngenta Seeds LLC) may improve milk production efficiency and nutrient digestibility when fed to lactating dairy cows. Furthermore, evaluating how Enogen silage interacts with different dietary starch content is important because the ruminal environment is influenced by the amount of rumen fermentable organic matter consumed. To evaluate the effects of Enogen corn silage and dietary starch content, we conducted an 8-wk randomized complete block experiment (2-wk covariate period, 6-wk experimental period) with a 2 × 2 factorial treatment arrangement using 44 cows (n = 11/treatment; 28 multiparous, 16 primiparous; 151 ± 42 d in milk; 668 ± 63.6 kg of body weight). Treatment factors were Enogen corn silage (ENO) or control (CON) corn silage included at 40% of diet dry matter and 25% (LO) or 30% (HI) dietary starch. Corn silage used in CON treatment was a similar hybrid as in ENO but without enhanced α-amylase activity. The experimental period began 41 d after silage harvest. Feed intake and milk yield data were collected daily, plasma metabolites and fecal pH were measured weekly, and digestibility was measured during the first and final weeks of the experimental period. Data were analyzed using a linear mixed model approach with repeated measures for all variables except for body condition score change and body weight change. Corn silage, starch, week, and their interactions were included as fixed effects; baseline covariates and their interactions with corn silage and starch were also tested. Block and cow served as the random effects. Plasma glucose, insulin, haptoglobin, and serum amyloid A concentrations were unaffected by treatment. Fecal pH was greater for cows fed ENO versus CON. Dry matter, crude protein, neutral detergent fiber, and starch digestibility were all greater for ENO than CON during wk 1, but differences were less by wk 6. The HI treatments depressed neutral detergent fiber digestibility compared with LO. Dry matter intake (DMI) was not affected by corn silage but was affected by the interaction of starch and week; in wk 1, DMI was similar but by wk 6, cows fed HI had 1.8 ± 0.93 kg/d less DMI than LO cows. Milk, energy-corrected milk, and milk protein yields were 1.7 ± 0.94 kg/d, 1.3 ± 0.70 kg/d, and 65 ± 27 g/d greater for HI than LO, respectively. In conclusion, ENO increased digestibility but it did not affect milk yield, component yields, or DMI. Increasing dietary starch content improved milk production and feed efficiency without affecting markers of inflammation or metabolism.

Physicochemical characterisation of barley straw treated with sodium hydroxide or urea and its digestibility and in vitro fermentability in ruminants

The development of strategies to overcome the shortage of forage due to persistently low rainfall is becoming a central task for animal nutrition in research and practice. In this study, it was investigated how the treatment of straw with NaOH or feed urea in a practicable procedure for modern farms affects rumen fermentation (gas production and greenhouse gas concentration) as well as the digestibility of feed energy and nutrients. For this purpose, the treatments were tested individually and in different proportions in a total mixed ration (TMR) in ruminal batch cultures in vitro and in a digestibility trial with sheep. In order to explain the observed effects at the molecular level, descriptive data from ¹³C solid state nuclear magnetic resonance (NMR) and Fourier-transform infrared (FTIR) spectroscopy were obtained. NaOH treatment of straw increased crude ash (CA), non-fibrous carbohydrates, digestible energy (DE), and metabolizable energy (ME) concentration, whereas the proportion of neutral detergent fibre (aNDFom) and hemicellulose decreased. In urea treated straw, NH₃-N and crude protein increased, whereas acid detergent lignin (ADL), DE, and ME decreased. The physically effective fibre (peNDF₈) concentration increased in TMR containing 18% of NaOH or urea treated straw (p < 0.01). The application of straw treatments as pure substrates (not as part of a TMR) increased gas production and decelerated ruminal fermentation (p < 0.05). In vitro organic matter digestibility (IVOMD) of the straw (0.31) increased after NaOH (0.51; p < 0.05) and urea treatment (0.41; p > 0.05). As part of a TMR, straw treatments had no distinct effect on gas production or IVOMD. Concentrations of CH₄ and CO₂ were likewise not affected. Apparent total tract digestibility of aNDFom, acid detergent fibre (ADFom), hemicellulose, and cellulose increased in the TMR by approximately 10% points following NaOH treatment (p < 0.05). The inclusion of urea treated straw did not affect apparent digestibility. Calculated true digestibility of aNDFom was 0.68, 0.74, and 0.79, of ADFom 0.58, 0.57, and 0.65, and of ADL 0.02, 0.13, and 0.08 in TMR including untreated, NaOH treated, and urea treated straw, respectively. ¹³C NMR and FTIR analyses consistently revealed that the global structure and crystallinity of the carbohydrates (cellulose and hemicellulose) was not altered by treatment and the concentration of lignin was likewise not affected. Depolymerisation of lignin did not occur. However, NMR signals assigned to acetyl groups were significantly altered indicating that straw treatments disrupted linkages between hemicelluloses and lignin. Moreover, the acetates signal was affected. This signal can be assigned to linkages between ferulic acids and hemicelluloses (arabinoxylans). FTIR spectra of straw treatments mainly differed at a wavelength of 1730 cm^-1 and 1240 cm^-1. Disappearance of the 1730 cm^-1 peak suggests removal of hemicelluloses or lignin related compounds by treatment. The disappearance of the lignin peak at 1240 cm^-1 could be due to conjugated ketone (phenyl-carbonyl) removal or the removal of ferulic and p-coumaric acid acetyl groups. Both treatments are supposed to release fermentable cell wall components (hemicelluloses) from lignin-associated bonds and as a result, straw fibre can be better fermented in the rumen. This contributes to energy supply and increased fibre digestibility at least in the TMR that contained NaOH treated straw. The alkaline straw treatments probably induced a release of phenolics such as ferulic acid and p-coumaric acid, which can be metabolised in the gut and the liver and metabolites might be excreted with the urine. This could notably contribute to metabolic energy losses.

Producing natural functional and low-carbon milk by regulating the diet of the cattle-The fatty acid associated rumen fermentation, biohydrogenation, and microorganism response

Conjugated linoleic acid (CLA) has drawn significant attention in the last two decades for its various potent beneficial effects on human health, such as anticarcinogenic and antidiabetic properties. CLA could be generally found in ruminant products, such as milk. The amount of CLA in ruminant products mainly depends on the diet of the animals. In general, the fat content in the ruminant diet is low, and dietary fat supplementation can be provided to improve rumen activity and the fatty acid (FA) profile of meat and milk. Especially, dietary 18-carbon polyunsaturated FA (C18 PUFA), the dominant fat source for ruminants, can modify the milk FA profile and other components by regulating the ruminal microbial ecosystem. In particular, it can improve the CLA in milk, intensify the competition for metabolic hydrogen for propionate producing pathways and decrease methane formation in the rumen. Therefore, lipid supplementation appears to be a promising strategy to naturally increase the additional nutritional value of milk and contribute to lower methane emissions. Meanwhile, it is equally important to reveal the effects of dietary fat supplementation on rumen fermentation, biohydrogenation (BH) process, feed digestion, and microorganisms. Moreover, several bacterial species and strains have been considered to be affected by C18 PUFA or being involved in the process of lipolysis, BH, CLA, or methane emissions. However, no review so far has thoroughly summarized the effects of C18 PUFA supplementation on milk CLA concentration and methane emission from dairy cows and meanwhile taken into consideration the processes such as the microorganisms, digestibility, rumen fermentation, and BH of dairy cattle. Therefore, this review aims to provide an overview of existing knowledge of how dietary fat affects rumen microbiota and several metabolic processes, such as fermentation and BH, and therefore contributes to functional and low-carbon milk production.

Palm Kernel Cake in Diets for Lactating Goats: Intake, Digestibility, Feeding Behavior, Milk Production, and Nitrogen Metabolism

This study was carried out to determine the optimal inclusion rate of palm kernel cake (PKC) in diets for lactating goats based on intake, digestibility, feeding behavior, milk production and nitrogen metabolism. Twelve goats were used, eight Saanen and four Anglo Nubian, with a body weight of 46.0 ± 9.4 kg and 105 ± 5 days of lactation, distributed in a 4 × 4 Latin square design in triplicate. The diets were composed of increasing levels of PKC; 0, 80, 160 and 240 g kg−1 of dry matter (DM). The DM, crude protein, neutral detergent fiber and non-fibrous carbohydrates intakes decreased (p < 0.01) with the PKC inclusion. Milk production and milk protein decreased (p = 0.001), and milk production efficiency was not affected (p > 0.05) by the PKC inclusion. The ether extract intake varied quadratically (p < 0.01). Feeding and rumination efficiencies of dry matter and NDF were reduced (p < 0.001). The fat and total solids contents of the milk were influenced quadratically (p < 0.05). Nitrogen excretion (feces and milk), and retained nitrogen decreased (p < 0.001). Moderate use of up to 80 g kg−1 DM of PKC in the diet of lactating goats is recommended since at these levels milk production or body weight are significantly affected.

Effect of dietary peNDF levels on digestibility and rumen fermentation, and microbial community in growing goats

Physically effective neutral detergent fiber (peNDF) is a concept that accounts for the particle length of NDF in diets, sustaining the normal chewing behavior and rumen fermentation of ruminants. Specifically, peNDF>1.18 is the commonest one that is calculated from NDF and the percentage of feed dry matter left on the 1.18, 8.00, and 19.00 mm sieves. This study aimed to investigate the effects of different levels of peNDF>1.18 on the rumen microbiome and its correlation with nutrient digestibility and rumen fermentation in goats. A total of 30 Lezhi black goats were randomized and blocked to five dietary treatments (n = 6). All the diets were identical in composition but varied in hay lengths, leading to the different peNDF>1.18 content of the diets: 32.97, 29.93, 28.14, 26.48, and 24.75%. The results revealed that the nutrient digestibility increased when dietary peNDF>1.18 levels decreased from 32.97% to 28.14%, with the highest digestibility at 28.14% peNDF>1.18 treatment, after which nutrient digestibility decreased with the decreasing of dietary peNDF levels. Ruminal NH3-N concentrations in the 29.93% and 28.14% groups were higher than that in the 24.75% group (p < 0.05). Ruminal microbial protein concentration was the highest in the 32.97% group (p < 0.05). Daily CH4 production in the 32.97% and 24.75% peNDF>1.18 treatments was lower than that in the 26.48% group (p < 0.05) and no differences were observed among other groups. The relative abundance of rumen fungi at the phylum and genus levels and archaea at the species were affected by dietary peNDF>1.18 content. In conclusion, decreasing dietary peNDF>1.18 levels within a certain range can improve nutrient digestibility and change the rumen microbial community structure of goats. Dietary peNDF>1.18 level should be 28.14% (roughage length around 1 cm) among the five levels for 4 months Lezhi black goats with the purpose of optimal nutrient digestibility.

Is greater milk production associated with dairy cows who have a greater probability of ruminating while lying down?

The objective of this study was to determine whether associations exist between position while ruminating (lying vs. standing) and milk and component production in dairy cows. Data from 30 lactating Holstein cows were assembled from 2 studies in which cows were milked by automated milking system (AMS) and fed a partial mixed ration (PMR) in feed bins that recorded intake behavior. Rumination and lying behavior were monitored using automated neck- and leg-based sensors, respectively. Each cow was monitored over 2 separate 2-wk treatment periods. To estimate position while ruminating for each 2-h period of the day for each cow, a conditional probability was calculated to determine the probability that any rumination time and lying time were occurring at the same time in any 2-h period. These probabilities (RwL), and all behavioral data, were summarized per cow per 2-h interval, and then averaged per day and per 2-wk period, along with milk yield and component data. Cows averaged (mean ± standard deviation) 1.9 ± 1.1 lactations and 85.5 ± 55.2 d in milk, and weighed 668.5 ± 96.0 kg. Data included rumination time (557.7 ± 41.1 min/d), lying time (703.9 ± 65.3 min/d), idle standing time (520.1 ± 83.2 min/d), PMR feeding time (204.7 ± 48.5 min/d), PMR dry matter intake (DMI; 21.8 ± 4.6 kg/d), AMS pellet provision (4.6 ± 1.6 kg/d), total DMI (26.4 ± 4.5 kg/d), milk yield (42.4 ± 7.2 kg/d), milk fat content (3.75 ± 0.51%), and milk protein content (3.21 ± 0.32%). Greater rumination time and lying time were associated with greater RwL probability (mean = 0.19 ± 0.02; range = 0.14 to 0.23). The RwL probability tended to be positively associated with total DMI and milk fat content, was associated with milk protein content, but was not associated with any measures of milk yield. The results indicate that in a free-traffic AMS, cows who have greater probability of ruminating while lying down spend more time ruminating and lying, and tend to consume more total dry matter and produce milk with greater components.

Profiles of Odd- and Branched-Chain Fatty Acids and Their Correlations With Rumen Fermentation Parameters, Microbial Protein Synthesis, and Bacterial Populations Based on Pure Carbohydrate Incubation in vitro

The objectives of this study were to evaluate changes in profiles of odd- and branched-chain fatty acids (OBCFA), including pentadecanoic acid (C15:0), 13-methyltetradecanoic acid (iso-C15:0), 12-methyltetradecanoic acid (anteiso-C15:0), 14-methylpentadecanoic acid (iso-C16:0), heptadecanoic acid (C17:0), 15-methylhexadecanoic acid (iso-C17:0), and 14-methylhexadecanoic acid (anteiso-C17:0) during in vitro fermentation of pure carbohydrates mixtures in the buffer-rumen fluid. The second objective was to correlate the changes in the OBCFA profile to the corresponding changes in ruminal fermentation parameters, microbial crude protein (MCP) synthesis, and bacterial populations. Five pure carbohydrates mixtures containing different cellulose: starch (C:S) ratios, i.e., 0:100, 25:75, 50:50, 75:25, and 100:0, were incubated for 6, 12, 18, and 24 h in vitro. The results showed that there was significant interaction (P < 0.05) between C:S and incubation time for changes in all OBCFA profiles, except iso-C17:0. The highest concentration of total OBCFA (3.94 mg/g dry matter; DM) was observed in the residues after 24 h of fermentation when the C:S was 0:100, while the lowest concentration of OBCFA (1.65 mg/g DM) was produced after 6 h of incubation when the C:S was 50:50. The correlation analysis revealed that the concentration of iso-C16:0 might be a potential marker for the estimation of total volatile fatty acids (ρ = 0.78) and MCP synthesis (ρ = 0.82) in the rumen. Compared to starch degrading bacteria, cellulolytic bacteria had stronger correlations with OBCFA concentrations, and the strongest correlation was found between the population of Ruminococcus flavefaciens with C15:0 concentration (ρ = 0.70). Notably, this is the first paper reporting relationship between OBCFA with rumen fermentation products and microbial protein synthesis based on fermentation of pure carbohydrates mixtures in vitro, and thus avoid confounding interference from dietary protein and fat presence in the in vivo studies. However, more in-depth experiments are needed to substantiate the current findings.

Effects of dietary forage to concentrate ratio on nutrient digestibility, ruminal fermentation and rumen bacterial composition in Angus cows

This study evaluated effects of dietary forage to concentrate ratio (F:C) on the body weight, digestibility, ruminal fermentation and rumen bacterial composition in Angus cows. Three diets with different F:C (LCD: 65:35, MCD:50:50, and HCD: 35:65) were fed to ninety Angus cows (3.2 ± 0.18 years old, 387.2 ± 22.6 kg). The average daily gain (ADG) and ammonia nitrogen concentration increased (P = 0.039 and P = 0.026, respectively), whereas the acetate to propionate ratio (P = 0.027) and the neutral detergent fiber (NDF) digestibility decreased with increasing concentrate level. The acetate concentration and ruminal pH (P = 0.033 and P = 0.029, respectively) decreased by feeding HCD diet. Serum amyloid A (SAA), C-reactive protein (CRP), haptoglobin (Hp) and lipopolysaccharide binding protein (LBP) increased under the HCD. The relative abundances of Bacteroidetes, Fibrobacterota, Prevotella and Prevotellaceae UCG-003 decreased, whereas the relative abundances of Ruminococcaceae NK4A214 group, Saccharofermentans and Spirochaetota increased with increasing dietary concentrate level. Our study provides a better understanding of rumen fermentation parameters and microbiota under a wide range of dietary F:C ratios, supporting the potential dietary manipulation of microbes, which could enhance feed digestibility associated with cow rearing.

The potential and effects of saline-alkali alfalfa microbiota under salt stress on the fermentation quality and microbial

Background

The objective of this study was to evaluate the chemical compositions and microbial communities of salt-tolerant alfalfa silage. Salt-tolerant alfalfa was ensiled with no additive control, and cellulase for 30 and 60 to 90 days. In this study, the dry matter (DM) content of the raw material was 29.9% DM, and the crude protein (CP) content of the alfalfa was 21.9% CP.

Results

After 30 days of fermentation, the DM content with the cellulase treatment was reduced by 3.6%, and the CP content was reduced by 12.7%. After 60 days of fermentation, compared with alfalfa raw material, the DM content in the control group (CK) was reduced by 1%, the CP content was reduced by 9.5%, and the WSC (water-soluble carbohydrates) content was reduced by 22.6%. With the cellulase, the lactic acid content of the 30- and 60-day silages was 2.66% DM and 3.48% DM. The content of Firmicutes in salinized alfalfa raw material was less than 0.1% of the total bacterial content. Before and after ensiling, the microbes had similar composition at the phylum level, and were composed of Firmicutes, Actinobacteria, Bacteroidetes, and Proteobacteria. The abundance of Pantoea was dominant in fresh alfalfa. In the absence of additives, after 30 days and 60 days of silage, the dominant lactic acid bacteria species became Lactococcus and Enterococcus.

Conclusions

The results showed that LAB (Lactobacillus, Lactococcus, Enterococcus, and Pediococcus) played a major role in the fermentation of saline alfalfa silage. It also can better preserve the nutrients of saline alfalfa silage. The use of cellulase enhances the reproduction of Lactobacillus. The fermentation time would also change the microbial community of silage fermentation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-021-02213-2.

Predicting ruminally undegraded and microbial protein flows from the rumen

The objectives of the present work were (1) to identify the cause of the linear bias in predictions of rumen-undegradable protein (RUP) content of feeds, and devise methods to remove the bias from prediction equations, and (2) to further explore the impact of rumen-degradable protein (RDP) on microbial N (MiN) outflow from the rumen. The kinetic model used by NRC (2001), which is based on protein fractionation and rates of degradation (Kd) and passage (Kp), displays considerable slope bias (-0.30 kg/kg), indicating parameter or structural problems. Regressing Kp by feed class and a static adjustment factor for the in situ-derived Kd on observed RUP flows completely resolved the slope bias problem, and the model performed significantly better than models using unadjusted Kd and marker-based Kp. The Kd adjustment was 3.82%/h, which represents approximately a 50% increase in rates of degradation over the in situ values, indicating that in situ analyses severely underestimate true rates of protein degradation. The Kp for concentrate-derived protein was 5.83%/h, which was slightly less than the marker-predicted rate of 6.69%/h. However, the derived forage protein rate was 0.49%/h, which was considerably less than the marker-based rate of 5.07%/h. Compartmental analysis of data from a single study corroborated the regression analysis, indicating that a 25% reduction in the overall passage rate and an 87% increase in the rate of degradation were required to align ruminal N pool sizes and the extent of protein degradation with the observed data. Therefore, one must conclude that both the in situ-derived degradation rates and the marker-based particle passage rates are biased relative to protein passage and cannot be used directly to predict RUP outflow from the rumen. The effects of RDP supply on microbial nitrogen (MiN) flow were apparent when intakes of individual nutrients were offered but not when DM intake and individual nutrient concentrations were offered, due to collinearity problems. Microbial N flow from the rumen was found to be linearly related to ruminally degraded starch, ruminally degraded neutral detergent fiber (NDF), RDP, and forage NDF intakes; and quadratically related to residual OM intake. More complicated models containing 2- and 3-way interactions among nutrients were also supported by the data. Independent MiN responses to RDP, ruminally degraded starch, and ruminally degraded NDF aligned with the expected responses to each of those nutrients. Nonlinear representations of MiN were found to be inferior to the linear models. Despite using unbiased predictions of RUP and MiN as drivers of AA flows, predictions of Arg, His, Ile, and Lys flow exhibited linear slope bias relative to the observed data, indicating that representations of the AA composition of the proteins may be biased or the observed data are biased. This is an improvement over the NRC (2001) predictions, where bias adjustments were required for all of the essential AA. Despite the bias for 4 AA flows, the revised prediction system was a substantial improvement over the prior work.

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.

The effects of pelleted dried distillers grains and solubles fed with different forage concentrations on rumen fermentation, feeding behavior, and milk production of lactating dairy cows

The physical form of feeds can influence dairy cow chewing behavior, rumen characteristics, and ruminal passage rate. Changing particle size of feeds is usually done through grinding or chopping forages, but pelleting feed ingredients also changes particle size. Our objective was to determine if pelleted dried distillers grains and solubles (DDGS) affected the feeding value for lactating dairy cattle. Seven lactating Jersey cows that were each fitted with a ruminal cannula averaging (± standard deviation) 56 ± 10.3 d in milk and 462 ± 75.3 kg were used in a crossover design. The treatments contained 15% DDGS in either meal or pelleted form with 45% or 55% forage on a dry matter basis. The forages were alfalfa hay, corn silage, and wheat straw. The factorial treatment arrangement was meal DDGS and low forage (mDDGS-LF), pelleted DDGS and low forage (pDDGS-LF), meal DDGS and high forage (mDDGS-HF), and pelleted DDGS and high forage (pDDGS-HF). Dry matter intake and energy-corrected milk were both unaffected by treatment averaging 19.8 ± 2.10 kg/d and 33.9 ± 1.02 kg/d, respectively. Fat yield was unaffected averaging 1.7 ± 0.13 kg/d, but protein yield was affected by the interaction of forage and DDGS. Protein yield was similar for both low forage treatments but was increased by when pDDGS was fed in the high forage treatment (1.05 vs. 0.99 ± 0.035 kg/d). When forage concentration was increased, starch digestibility increased by 1.9 percentage units, crude protein digestibility tended to increase 1.1 percentage units, and residual organic matter digestibility decreased 3.4 percentage units. Pelleting DDGS increased digestibility of neutral detergent fiber (NDF) digestibility (49.2 vs. 47.5 ± 1.85%) and gross energy (68.2 vs. 67.1 ± 1.18%). Increasing forage increased ruminal pH (5.85 to 5.94 ± 0.052). Passage rate slowed from 2.84 to 2.65 ± 0.205 %/h when feeding HF compared with LF. Rumination time increased from 417 to 454 ± 49.4 min with increasing forage concentration but was unaffected by the form of DDGS or the interaction of forage and DDGS. Eating time increased with pDDGS (235 vs. 209 ± 19.8 min), which may be a result of increased feed sorting behavior. Pelleting DDGS increased preference for particles retained on the 8-mm sieve and decreased preference for particles on the 1.18-mm sieve and in the pan (<1.18 mm). Results confirm that increasing forage concentration increases ruminal pH, rumination time, and slows passage rate, but contrary to our hypothesis increasing forage concentration did not increase NDF digestibility. Results also suggest that pelleted DDGS do not appear to affect milk production, ruminal characteristics, or passage rate, but pelleted DDGS may increase sorting behavior of lactating Jersey cows and increase NDF and gross energy digestibility.

Refining Knowledge of Factors Affecting Vitamin B12 Concentration in Bovine Milk

Simple Summary

Milk is considered a staple and complete food that contains several essential nutrients for humans. For instance, it is an excellent natural source of vitamin B₁₂ (B12) due to the presence in the bovine rumen of a myriad of bacteria and archaea capable of producing the vitamin. This vitamin is only produced by prokaryotic microorganisms; vegetal products do not naturally contain it. A 250-mL glass of milk contains about 46% of the daily recommended dietary allowance of B12 for individuals over 13 years old. However, B12 concentration is variable in milk; therefore, identifying factors contributing to its variation is critical to ensure a stable B12 supply for consumers. The aims of these experiments are to gather more knowledge on possible sources of variation in B12 concentrations in milk in order to optimize and stabilize its levels and thereby improve the perception of milk in terms of its health benefits. We observed that B12 concentration increases when the conditions of the rumen are optimal, such as with elevated pH. We also studied if bedding type—e.g., recycled manure solid bedding or straw, which has been reported to impact milk microbiota—could have an impact on milk B12 concentration. In this study, no such correlation was detected. This paper is one of a series seeking to elucidate factors responsible for variations in milk B12 concentration.

Abstract

Milk is an excellent source of vitamin B₁₂ (B12) for humans. Therefore, being able to guarantee a high and consistent concentration of this vitamin would enhance consumer perception of milk as a health food. The aim of the paper was to gather additional knowledge on factors that could explain B12 variation in cow milk through two observational studies: (1) to explore the relationship between milk B12 and ruminal conditions, such as pH and volatile fatty acid concentrations; and (2) to examine the impact of bedding on B12 concentrations in bulk tank milk. For study 1, a total of 72 milk and ruminal liquid samples were obtained from 45 Holstein cows fitted with ruminal cannula between 10 and 392 days of lactation. For study 2, bulk tank milk samples were obtained from 83 commercial herds; 26 herds used recycled manure solid bedding and 57 used straw bedding. Milk samples were analyzed for B12 using radioassay. Using principal component regression analysis, we observed that ruminal pH and the acetate:propionate ratio for cows receiving the early lactation ration were positively correlated with milk B12. Bedding did not influence milk B12 in bulk tanks, which averaged 4276 pg/mL. In conclusion, as B12 is synthesized by ruminal bacteria, optimizing ruminal conditions had a positive effect on milk B12, while bedding management had no influence.

Milk Potential of Pantaneira Cows, a Local Breed, at Organic System

Simple Summary

Pantaneira cattle are descendants of the genetic group of crossed European animals and are a breed locally adapted to the Brazilian Pantanal. The use of this breed in organic systems can have benefits for the conservation of the breed and because it is a genetically rustic breed. The aim of this study was to evaluate the performance of Pantaneira primiparous cows under systems with reduced use of concentrate, simulating organic production conditions. There was a reduction in milk yield, but the energy-corrected milk yield and efficiency were not affected. The Pantaneira breed has the genetic potential for the maintenance of competitive production and quality in organic systems.

Abstract

Pantaneiro cattle (Bos taurus taurus) is a breed locally adapted to the Brazilian Pantanal. Local breeds are essential for the quality production of organic systems based on planned grazing practices, because of their results in resilient and productive ecosystems, enhancing biodiversity. This study aimed to evaluate the performance of Pantaneira primiparous cows, and systems with reduced use of concentrate, simulating organic production conditions. Five animals, with an average body weight of 396.2 ± 43.5 kg, were kept in individual continuous grazing regimes and supplemented with different concentrate levels (1.2%, 0.9%, 0.6%, 0.3%, and 0.0% of body weight). The animals were allocated at random in a 5 × 5 Latin square design repeated twice during the study time. The cows had a low dry matter and nutrient intake with a reduction in concentrate level, with improvement in neutral detergent fiber digestibility and a reduction in total nutrient digestibility. No changes were observed in plasma glucose levels or urea excretion, but the plasma urea nitrogen decreased with reductions in concentrate levels. There was a reduction in milk yield, but the energy-corrected milk was not affected by the reduction in concentrate levels; furthermore, the milk yield efficiency was not affected. The milk fat content improved with the reduction in concentrate levels. The Pantaneira breed has the genetic potential for the maintenance of competitive production and quality in organic systems.

Feeding diets varying in forage proportion and particle length to lactating dairy cows: II. Effects on duodenal flows and intestinal digestibility of amino acids

A study was conducted to evaluate the effects of forage-to-concentrate (F:C) ratio and forage particle length (FPL) on intake, duodenal flow, and digestibility of individual AA in the intestine of lactating dairy cows. The experiment was designed as a 4 × 4 Latin square with a 2 × 2 factorial arrangement of treatments using 4 lactating dairy cows (parity 2) with ruminal and duodenal cannulas. Low (35:65) and high (60:40) F:C ratios (dry matter basis) were combined with 2 FPL of alfalfa silage (short vs. long; 7.9 vs. 19.1 mm). Few interactions between F:C and FPL for duodenal flow and intestinal digestibility of AA occurred, but interactions were detected for intakes of several AA. Intake of essential AA and nonessential AA decreased with increasing F:C, and the intake of several individual AA increased or decreased with increasing FPL. Increasing F:C decreased duodenal flows of essential AA, nonessential AA, and microbial AA due to consistent decreased flows of most individual AA (except Glu). Degradability of most individual AA in the rumen was not affected by F:C ratio or FPL except that the degradability of His was greater with high than low F:C diets, and the degradability of Ser was greater with long versus short FPL diets. However, the degradability of individual AA within diet varied considerably. Overall, F:C ratio and FPL did not affect intestinal digestibility of AA and rumen undegradable protein AA, whereas the digestibility of individual AA in the intestine varied considerably regardless of dietary treatment. These results indicate that increasing F:C ratio decreased AA supply due to decreased flow of AA to the duodenum but altering FPL did not affect AA supply. The results also revealed the necessity to consider both the flows and digestibility of individual AA when optimizing ration formulation to meet AA requirements of dairy cows.