Effects of an increased concentrate diet on rumen pH and the bacterial community in Japanese Black beef cattle at different fattening stages

Understanding the Diversity and Roles of the Ruminal Microbiome

The importance of ruminal microbiota in ruminants is emphasized, not only as a special symbiotic relationship with ruminants but also as an interactive and dynamic ecosystem established by the metabolites of various rumen microorganisms. Rumen microbial community is essential for life maintenance and production as they help decompose and utilize fiber that is difficult to digest, supplying about 70% of the energy needed by the host and 60-85% of the amino acids that reach the small intestine. Bacteria are the most abundant in the rumen, but protozoa, which are relatively large, account for 40-50% of the total microorganisms. However, the composition of these ruminal microbiota is not conserved or constant throughout life and is greatly influenced by the host. It is known that the initial colonization of calves immediately after birth is mainly influenced by the mother, and later changes depending on various factors such as diet, age, gender and breed. The initial rumen microbial community contains aerobic and facultative anaerobic bacteria due to the presence of oxygen, but as age increases, a hypoxic environment is created inside the rumen, and anaerobic bacteria become dominant in the rumen microbial community. As calves grow, taxonomic diversity increases, especially as they begin to consume solid food. Understanding the factors affecting the rumen microbial community and their effects and changes can lead to the early development and stabilization of the microbial community through the control of rumen microorganisms, and is expected to ultimately help improve host productivity and efficiency.

Strategies to Mitigate Enteric Methane Emissions from Ruminant Animals

Human activities account for approximately two-thirds of global methane emissions, wherein the livestock sector is the single massive methane emitter. Methane is a potent greenhouse gas of over 21 times the warming effect of carbon dioxide. In the rumen, methanogens produce methane as a by-product of anaerobic fermentation. Methane released from ruminants is considered as a loss of feed energy that could otherwise be used for productivity. Economic progress and growing population will inflate meat and milk product demands, causing elevated methane emissions from this sector. In this review, diverse approaches from feed manipulation to the supplementation of organic and inorganic feed additives and direct-fed microbial in mitigating enteric methane emissions from ruminant livestock are summarized. These approaches directly or indirectly alter the rumen microbial structure thereby reducing rumen methanogenesis. Though many inorganic feed additives have remarkably reduced methane emissions from ruminants, their usage as feed additives remains unappealing because of health and safety concerns. Hence, feed additives sourced from biological materials such as direct-fed microbials have emerged as a promising technique in mitigating enteric methane emissions.

The Effect of Yeast and Roughage Concentrate Ratio on Ruminal pH and Protozoal Population in Thai Native Beef Cattle

Simple Summary

As a result of the recent ban on antibiotics in feed, animal probiotics are becoming increasingly popular. Yeast is extensively used as both a probiotic and prebiotic in the gastrointestinal tracts of ruminants. The purpose of this study is to determine how adding yeast (Saccharomyces cerevisiae) to the diet and changing the roughage-to-concentrate ratio (R:C ratio) affects nutrient consumption, rumen fermentation, microbial protein synthesis, and protozoal population in Thai native beef cattle. The roughage source was urea–calcium-hydroxide-treated rice straw. The findings suggest that supplementing with a R:C ratio of 40:60 and a LY of 4 g/hd/d boosted nutrient digestibility, volatile fatty acid (VFA) production, propionic acid (C₃) in particular, and microbial protein synthesis while lowering protozoal population.

Abstract

The objective of this research is to investigate the effect of yeast (Saccharomyces cerevisiae) adding and roughage-to-concentrate ratio (R:C ratio) on nutrients utilization, rumen fermentation efficiency, microbial protein synthesis, and protozoal population in Thai native beef cattle. Four Thai native beef cattle, weighing an average of 120 ± 10 kg live weight, were randomly assigned to four dietary treatments using a 2 × 2 factorial arrangement in a 4 × 4 Latin square design. Factor A was the level of roughage-to-concentrate ratio (R:C ratio) at 60:40 and 40:60; factor B was the levels of live yeast (LY) supplementation at 0 and 4 g/hd/d; urea–calcium-hydroxide-treated rice straw were used as a roughage source. Findings revealed that total intake and digestibility of dry matter (DM), organic matter (OM), and crude protein (CP) were increased (p < 0.05) by both factors, being greater for steers fed a R:C ratio of 40:60 supplemented with 4 g LY/hd/d. Ruminal ammonia nitrogen, total volatile fatty acid (VFA), and propionate (C₃) were increased (p < 0.05) at the R:C ratio of 40:60 with LY supplementation at 4 g/hd/d, whereas rumen acetate (C₂) and the C₂ to C₃ ratio were decreased (p < 0.05). With a high level of concentrate, LY addition increased total bacterial direct counts and fungal zoospores (p < 0.05), but decreased protozoal populations (p < 0.05). High-concentrate diet and LY supplementation increased nitrogen absorption and the efficiency of microbial nitrogen protein production. In conclusion, feeding beef cattle with 4 g/hd/d LY at a R:C ratio of 40:60 increased C₃ and nutritional digestibility while lowering protozoal population.

Diet Transition from High-Forage to High-Concentrate Alters Rumen Bacterial Community Composition, Epithelial Transcriptomes and Ruminal Fermentation Parameters in Dairy Cows

Effects of changing diet on rumen fermentation parameters, bacterial community composition, and transcriptome profiles were determined in three rumen-cannulated Holstein Friesian cows using a 3 × 4 cross-over design. Treatments include HF-1 (first high-forage diet), HC-1 (first high-concentrate diet), HC-2 (succeeding high-concentrate diet), and HF-2 (second high-forage diet as a recovery period). Animal diets contained Klein grass and concentrate at ratios of 8:2, 2:8, 2:8, and 8:2 (two weeks each), respectively. Ammonia-nitrogen and individual and total volatile fatty acid concentrations were increased significantly during HC-1 and HC-2. Rumen species richness significantly increased for HF-1 and HF-2. Bacteroidetes were dominant for all treatments, while phylum Firmicutes significantly increased during the HC period. Prevotella, Erysipelothrix, and Galbibacter significantly differed between HF and HC diet periods. Ruminococcus abundance was lower during HF feeding and tended to increase during successive HC feeding periods. Prevotellaruminicola was the predominant species for all diets. The RNA sequence analysis revealed the keratin gene as differentially expressed during the HF diet, while carbonic-anhydrase I and S100 calcium-binding protein were expressed in the HC diet. Most of these genes were highly expressed for HC-1 and HC-2. These results suggested that ruminal bacterial community composition, transcriptome profile, and rumen fermentation characteristics were altered by the diet transitions in dairy cows.

Long-term high-grain diet altered the ruminal pH, fermentation, and composition and functions of the rumen bacterial community, leading to enhanced lactic acid production in Japanese Black beef cattle during fattening

To increase intramuscular fat accumulation, Japanese Black cattle are commonly fed a high-grain diet from 10 to 30 months of age although it can result in the abnormal accumulation of organic acids in the rumen. We explored the effect of long-term high-concentrate diet feeding on ruminal pH and fermentation, and its effect on the rumen bacterial community in Japanese Black beef cattle during a 20-month fattening period. Nine castrated and fistulated Japanese Black beef cattle were housed with free access to food and water throughout the study period (10-30 months of age). The fattening stages included Early, Middle, and Late stages (10-14, 15-22, and 23-30 months of age, respectively). Cattle were fed high-concentrate diets for the experimental cattle during fattening. The body weight of the cattle was 439 ± 7.6, 561 ± 11.6, and 712 ± 18.5 kg (mean ± SE) during the Early, Middle, and Late stages, respectively. Ruminal pH was measured continuously during the final 7 days of each stage, and rumen fluid and blood samples were collected on day 4 (fourth day during the final 7 days of the pH measurements). The 24-h mean ruminal pH during the Late stage was significantly lower than that during the Early stage. Total volatile fatty acid (VFA) during the Late stage was significantly lower than during the Early and Middle stages, but no changes were noted in individual VFA components. The lactic acid concentration during the Late stage was significantly higher than that during the Early and Middle stages. The bacterial richness indices decreased significantly during the Late stage in accordance with the 24-h mean ruminal pH. Among the 35 bacterial operational taxonomic units (OTUs) shared by all samples, the relative abundances of OTU8 (Family Ruminococcaceae) and OTU26 (Genus Butyrivibrio) were positively correlated with the 24-h mean ruminal pH. Total VFA concentration was negatively correlated with OTU167 (Genus Intestinimonas), and lactic acid concentration was correlated positively with OTU167 and OTU238 (Family Lachnospiraceae). These results suggested that long-term high-grain diet feeding gradually lowers ruminal pH and total VFA production during the Late fattening stage. However, the ruminal bacterial community adapted to feeding management and the lower pH during the Late stage by preserving their diversity or altering their richness, composition, and function, to enhance lactic acid production in Japanese Black beef cattle.