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Diets rich in readily fermentable carbohydrates primarily impact microbial composition and activity, but can also impair the ruminal epithelium barrier function. By combining microbiota, metabolome, and gene expression analysis, we evaluated the impact of feeding a 65% concentrate diet for 4 weeks, with or without a phytogenic feed additive (PFA), on the rumen ecosystem of cattle. The breaking point for rumen health seemed to be the second week of high grain (HG) diet, with a dysbiosis characterized by reduced alpha diversity. While we did not find changes in histological evaluations, genes related with epithelial proliferation (IGF-1, IGF-1R, EGFR , and TBP) and ZO-1 were affected by the HG feeding. Integrative analyses allowed us to define the main drivers of difference for the rumen ecosystem in response to a HG diet, identified as ZO-1, MyD88 , and genus Prevotella 1. PFA supplementation reduced the concentration of potentially harmful compounds in the rumen (e.g. dopamine and 5-aminovaleric acid) and increased the tolerance of the epithelium toward the microbiota by altering the expression of TLR-2, IL-6 , and IL-10. The particle-associated rumen liquid microbiota showed a quicker adaptation potential to prolonged HG feeding compared to the other microenvironments investigated, especially by the end of the experiment. [ABSTRACT FROM AUTHOR]

In neonate calves, the association between gut microbial colonization and passive immunity acquisition remains largely unknown. We evaluated the effect of transition from colostrum to milk on the hindgut microbiota, and the correlations between acquired passive immunity and this microbiome. In 14 Holstein calves, colostrum quality and host passive immunity were measured, feces were sampled when feeding colostrum and after transition to milk. Then, in eight calves displaying a wide range of passive immunity, the hindgut microbiota was evaluated with DNA sequencing; differential abundance was analyzed with Maaslin2. With transition from colostrum to milk, many initial bacterial colonizers did not survive; genus Ralstonia decreased, but Lactobacillus and Bacteroides increased. When feeding colostrum, the amount of immunoglobulins consumed positively correlated with abundance of Lactobacillaceae and Lachnospiraceae , but Escherichia –S higella and Clostridium sensu stricto 1 correlated negatively with host passive immunity. After transition to milk, acquired passive immunity negatively correlated with Clostridium sensu stricto 1, Ralstonia , and Veillonella. Overall, many initial hindgut colonizers did not thrive during transition from colostrum to milk, homogenizing the bacterial profile with prevalence of milk digesters. Several bacterial taxa showed strong correlation with host passive immunity, suggesting an interplay between calf passive immunity acquisition and the colonizing microbiota. [ABSTRACT FROM AUTHOR]

Microbial protein synthesized in the rumen is a major contributor of metabolizable protein. Thus, accurate estimation of microbial protein is essential in ruminant nutrition. The objective of this review is to describe the microbial composition, major factors affecting its yield and methods to estimate microbial protein flow to the intestine. The use of novel molecular techniques to elucidate the ruminal microbiome and improve methods for estimating microbial protein are discussed. Bacteria, protozoa, fungi and archaea compose the ruminal microbiome. Main factors affecting microbial protein synthesis are availability of carbohydrates, ruminally degradable protein, dietary fat, and ruminal pH. Major microbial markers used to estimate microbial protein synthesis are total purines, diaminopimelic acid and labeled nitrogen; in addition, DNA through real-time PCR is being tested for the estimation of bacterial, protozoal and yeast protein separately. The main difficulty in the estimation of microbial protein flow is obtaining representative microbial pellets from the rumen, which are used as reference to establish the ratio of marker/nitrogen. Detailed phylogenetic analysis using High-throughput DNA sequencing has recently revealed drastic taxonomic differences between fluid-associated bacteria and bacteria from whole intestinal digesta contents. For example, ruminal fluid contains less Fibrobacteres and Proteobacteria, but more Firmicutes compared to whole intestinal digesta. This demonstrates the need of developing effective bacterial collection procedures for obtaining representative ruminal microbial reference pellets to prevent bias on the estimation of the contribution of microbial protein to the intestinal supply of metabolizable protein. [ABSTRACT FROM AUTHOR]

The aim was to evaluate the effect of changing from forage to a high grain diet on chewing, feed sorting and lying behavior of cows supplemented with or without a phytogenic feed additive. Nine cows were blocked in two groups and used in a change-over design. Each experimental run consisted of one week of forage feeding, one week of diet transition, and four weeks of high grain feeding (65% concentrate). During the washout period of 10 weeks between the two runs, cows grazed on pasture. Cows were fed either a control diet (CON) or a diet with a phytogenic additive (PHY) based on menthol, thymol and eugenol. Data on chewing, feed sorting and lying behavior were analyzed using SAS with week of feeding and supplementation as fixed effects, and cow as random effect. Data across weeks from the same cow were processed using a first order variance-covariance structure matrix taking into account that the covariance decays with time. We found a reduction (P < 0.01) in rumination time by 53% with diet change. Within the high grain feeding, rumination reached lowest value in the second week (160 min/d). The high grain diet increased (P < 0.01) selection for long size particles by 20%. Although lying time was not affected immediately after diet change, it increased (P < 0.01) by 8% from the second week of high grain consumption. In the fourth week of grain feeding, there was a tendency for PHY to increase rumination (P = 0.07) and total chewing time (P = 0.10), but with no effect on sorting for fiber or lying time. The high grain diet decreased chewing and standing time, and increased sorting for fibrous ingredients especially after one week of feeding. The phytogenic feed additive may contribute to stimulate chewing in long term supplementation. [ABSTRACT FROM AUTHOR]

Modern dairy production systems require larger inputs of energy in diets to increase milk yield. Therefore, dairy cows are at risk of experiencing subacute ruminal acidosis (SARA). The objective of this study was to evaluate grains and forage rumen degradability in cows fed different diets supplemented with a phytogenic (PHY) feed additive. The experiment was conducted with nine rumen-cannulated non-lactating Holstein cows blocked in two groups of four and five animals, and were part of a cross-over design. This study consisted in 2 runs separated by a 12-week washout period, in which cows grazed on pasture. Each experimental run had one week of forage (F) feeding, one week of transition to a high grain (HG) diet, and four weeks of HG (65:35 concentrate to forage ratio in dry matter basis). Cows were supplemented with PHY (a blend of menthol and thymol) or a control carrier (CON) from week F. Corn and wheat grain were ground through a 4 mm screen, while grass silage was ground through a 6 mm screen. Sampling for in situ degradability was performed in F and in week four of HG diet. Data were analyzed with SAS with week of feeding and supplementation as fixed effects and cow as random effect. Corn and wheat 24-h dry matter (DM) and organic matter (OM) degradability increased during HG diet compared with F (P < 0.05), grass silage DM and OM 48-h degradability was reduced by HG diet compared to F (P < 0.01). Additionally, wheat grain 24-h OM degradability was higher for PHY compared to CON under F and HG diet conditions (P = 0.05). Overall, diet composition and SARA conditions can influence grains and fiber degradability in the rumen. [ABSTRACT FROM AUTHOR]

This study evaluated the effect of the media and pre-incubation time for reactivating preserved ruminal inoculum, assessed through in vitro fermentation kinetics and dry matter digestibility (IVDMD). In the first experiment, treatments were 1) CONTROL, fresh ruminal fluid, 2) LOW24, inoculum reactivated by 24 h pre-incubation in a basal culture solution, 3) MODE24, inoculum reactivated by 24 h pre-incubation in basal culture solution, yeast extract and peptone from casein; and 4) HIGH24, inoculum reactivated by 24 h pre-incubation in basal culture solution, yeast extract, peptone from casein and carbohydrates. In the second experiment, treatments evaluated were 1) CONTROL, fresh ruminal fluid, and 2) HIGH12, similar to HIGH24 but inoculum was pre-incubated for 12 h. Each experiment included three replicates. Maximum gas volume (Vm), lag phase (L), gas production rate (S) and IVDMD were measured using four fermentation substrates. Main effects of inoculum and fermentation substrate, and interactions, were analyzed. Compared to CONTROL, Vm, L and S were negatively affected (P<0.01) by preservation of inoculum. However, HIGH24 displayed an improvement (P<0.01) in fermentation kinetics and IVDMD compared to MODE24 or LOW24. In the second experiment, HIGH12 displayed lower (P<0.01) IVDMD at 72 h compared to CONTROL. Alfalfa and orchardgrass had higher (P<0.01) Vm and IVDMD compared to cocuite and guinea grass. Overall, reactivation of preserved ruminal inoculum by pre-incubation for 24 h in a medium containing yeast extract, peptone from casein and carbohydrates performed better compared to reactivation by pre-incubation for 12 h; however, fermentation kinetics and IVDMD were still depressed compared to fresh ruminal fluid. [ABSTRACT FROM AUTHOR]

Objective: To determine the impact of a two-stage rumen cannulation on the health and rumen function of lactating dairy cows., Study Design: Experimental study., Animals: Six lactating Holstein cows., Methods: We performed a two-stage rumen cannulation in six Holstein cows that were 49 ± 11 days in milk. The following clinical health parameters and digestion-associated variables were analyzed on seven measurement days, from before the first surgery until 28 days after the second surgery: body temperature, heart rate, respiratory rate, pain score, rumen fill score, fecal score, wet sieving, auscultation and palpation of the rumen, bodyweight, body condition score, and activity., Results: The pain score of the cows was constantly zero. Similarly, the body temperature and respiratory rate remained within physiological ranges, whereas the heart rate was slightly higher immediately after the second surgery. No differences were observed in rumen fill (2.00-2.67; p = .10) and fecal consistency scores (2.17-2.67; p = .42). The fecal particle size distribution showed negligible differences. The cows lost approximately 43 kg of bodyweight during the experiment (p < .01), which was reflected in a 0.5-point body condition score loss (p < .01)., Conclusion: A temporary minimal negative effect of a two-stage rumenostomy on the health and body condition of early lactating Holstein cows was observed, whereas digestion was unaffected. Considering the limited sample size, further studies are required to substantiate these findings., Clinical Significance: Given that animals are appropriately medically managed, experimental rumenostomy of lactating dairy cows may not compromise their health or rumen function., (© 2024 The Author(s). Veterinary Surgery published by Wiley Periodicals LLC on behalf of American College of Veterinary Surgeons.)

This study explores the dynamics of immune gene expression, ruminal metabolome, and gut microbiota in cows due to the duration of high-grain feeding, shedding light on host response and microbial dynamics in parallel. Cows consumed forage for a week, then gradually transitioned to a high-grain diet, which they consumed for 4 weeks. Immune response was evaluated in ruminal papillae by expression of genes related to the nuclear factor-kappaB (NFkB) pathway and correlated with the microbiota. Rumen metabolome was evaluated with high-performance liquid chromatography coupled with mass spectrometry and anion-exchange chromatography. Rumen and fecal microbiota were evaluated with 16S rRNA gene amplicon sequencing. In the rumen, expression of inflammation-associated genes increased with the duration on high grain, indicating activation of pro-inflammatory cascades; microbial diversity decreased with a high-grain diet but stabilized after week 3 on high grain. Changes in microbial relative abundance and metabolite enrichment were observed throughout the 4 weeks on high grain, with increments in propionogenic taxa (i.e., Succinivibrionaceae ). Metabolite enrichment analysis showed that at the start of high-grain feeding, simple carbohydrates were enriched; then, these were substituted by their fermentation products. There were correlations between certain ruminal bacterial taxa (i.e., Ruminococcaceae UCG-005) and expression of genes of the NFkB pathway, suggesting the influence of these taxa on host immune response. In feces, microbial diversity and several Ruminococcaceae members initially declined but recovered by weeks 3 and 4. Overall, despite the stabilization of microbial diversity, changes in microbial relative abundance and proinflammatory genes were observed throughout high-grain feeding, suggesting that cows need more than 4 weeks to fully adjust once consuming a high-grain diet.IMPORTANCEDespite the stepwise diet transition typically assumed to serve for animal adaptation, expression of signaling receptors, mediators, and downstream targets of nuclear factor-kappaB pathway were found throughout the 4 weeks on high grain, which correlated with changes in the rumen microbial profile. In addition, although microbial diversity recovered in the feces and stabilized in the rumen in week 3 on high grain, we observed changes in microbial relative abundance throughout the 4 weeks on high grain, suggesting that cows need more than 4 weeks to adjust once consuming this diet. Findings are particularly important to consider when planning experiments involving dietary changes., Competing Interests: The authors declare no conflict of interest.