Project description:The yak rumen microflora has more efficient fiber-degrading and energy-harvesting abilities than that of low-altitude cattle; however, few studies have investigated the effects of dietary energy levels on the rumen bacterial populations and the relationship between rumen bacteria and the intramuscular fatty acid profile of fattening yaks. In this study, thirty yaks were randomly assigned to three groups. Each group received one of the three isonitrogenous diets with low (3.72 MJ/kg), medium (4.52 MJ/kg), and high (5.32 MJ/kg) levels of net energy for maintenance and fattening. After 120 days of feeding, results showed that increasing dietary energy significantly increased ruminal propionate fermentation and reduced ammonia concentration. The 16S rDNA sequencing results showed that increasing dietary energy significantly increased the ratio of Firmicutes to Bacteroidetes and stimulated the relative abundance of Succiniclasticum, Saccharofermentans, Ruminococcus, and Blautia populations. The quantitative real-time PCR analysis showed that high dietary energy increased the abundances of Streptococcus bovis, Prevotella ruminicola, and Ruminobacter amylophilus at the species level. Association analysis showed that ruminal acetate was positively related to some intramuscular saturated fatty acid (SFA) contents, and Prevotella was significantly positively related to intramuscular total polyunsaturated fatty acid content and negatively related to intramuscular total SFA content. This study showed that high dietary energy mainly increased ruminal amylolytic and propionate-producing bacteria populations, which gave insights into how the effects of dietary energy on rumen bacteria are related to intramuscular fat fatty acids of fattening yaks.
Project description:The microbial community of the yak (Bos grunniens) rumen plays an important role in surviving the harsh Tibetan environment where seasonal dynamic changes in pasture cause nutrient supply imbalances, resulting in weight loss in yaks during the cold season. A better understanding of rumen microbiota under different feeding regimes is critical for exploiting the microbiota to enhance feed efficiency and growth performance. This study explored the impact of different dietary energy levels on feed efficiency, rumen fermentation, bacterial community, and abundance of volatile fatty acid (VFA) transporter transcripts in the rumen epithelium of yaks. Fifteen healthy castrated male yaks were divided into three groups and fed with low (YL), medium (YM), and high energy (YH) levels diet having different NEg of 5.5, 6.2, and 6.9 MJ/kg, respectively. The increase in feed efficiency was recorded with an increase in dietary energy levels. The increase in dietary energy levels decreased the pH and increased the concentrations of acetate, propionate, butyrate, and valerate in yak rumens. The increase in the mRNA abundance of VFA transporter genes (MCT1, DRA, PAT1, and AE2) in the rumen epithelium of yaks was recorded as dietary energy level increased. High relative abundances of Firmicutes and Bacteroidetes were recorded with the increase in dietary energy levels. Significant population shifts at the genus level were recorded among the three treatments. This study provides new insights into the dietary energy-derived variations in rumen microbial community.
Project description:Changes in dietary composition affect the rumen microbiota in ruminants. However, information on the effects of dietary concentrate-to-forage ratio changes on yak rumen bacteria and metabolites is limited. This study characterized the effect of three different dietary concentrate-to-forage ratios (50:50, C50 group; 65:35, C65 group; 80:20, C80 group) on yak rumen fluid microbiota and metabolites using 16S rRNA gene sequencing and liquid chromatography-mass spectrometry (LC-MS) analyses. Rumen fermentation parameters and the abundance of rumen bacteria were affected by changes in the dietary concentrate-to-forage ratio, and there was a strong correlation between them. At the genus level, higher relative abundances of norank_f__F082, NK4A214_group, Lachnospiraceae_NK3A20_group, Acetitomaculum, and norank_f__norank_o__Clostridia_UCG-014 were observed with a high dietary concentrate-to-forage ratio (P < 0.05). Combined metabolomic and enrichment analyses showed that changes in the dietary concentrate-to-forage ratio significantly affected rumen metabolites related to amino acid metabolism, protein digestion and absorption, carbohydrate metabolism, lipid metabolism, and purine metabolism. Compared with the C50 group, 3-methylindole, pantothenic acid, D-pantothenic acid, and 20-hydroxy-leukotriene E4 were downregulated in the C65 group, while spermine and ribose 1-phosphate were upregulated. Compared to the C50 group, Xanthurenic acid, tyramine, ascorbic acid, D-glucuronic acid, 6-keto-prostaglandin F1a, lipoxin B4, and deoxyadenosine monophosphate were upregulated in the C80 group, while 3-methylindole and 20-hydroxy-leukotriene E4 were downregulated. All metabolites (Xanthurenic acid, L-Valine, N-Acetyl-L-glutamate 5-semialdehyde, N-Acetyl-L-glutamic acid, Tyramine, 6-Keto-prostaglandin F1a, Lipoxin B4, Xanthosine, Thymine, Deoxyinosine, and Uric acid) were upregulated in the C80 group compared with the C65 group. Correlation analysis of microorganisms and metabolites provided new insights into the function of rumen bacteria, as well as a theoretical basis for formulating more scientifically appropriate feeding strategies for yak.
Project description:Yak suffers severe starvation and body weight reduction in the cold season and recovers relatively rapid growth in the warm season every year. Herein, we investigated the effects of starvation and refeeding on the growth, feed efficiency, blood biochemistry and rumen microbial community as well as functions of yaks. The results showed that starvation significantly reduced the body weight of yaks. Serum glucose and triglyceride concentrations significantly decreased, and ?-hydroxybutyric acid and non-esterified fatty acid levels were significantly increased during the starvation period. Starvation also dramatically inhibited rumen microbial fermentations. Whereas, refeeding with the same diet significantly increased the feed efficiency, nutrient digestibility together with rumen acetate, propionate and microbial protein productions compared with those before starvation. The 16S rDNA sequencing results showed that starvation mainly decreased the ruminal protein-degrading bacteria Prevotella and propionate-producing bacteria Succiniclasticum populations and dramatically increased the denitrifying bacteria Thauera populations. Refeeding reduced the Euryarchaeota population and increased propionate-producing bacteria Succinivibrionaceae UCG-002 and starch-degrading bacteria Ruminobacter populations when compared with those before starvation. The predicted microbial metabolic pathways, related to amino acid and starch metabolisms, were also significantly altered during the starvation and refeeding. The results indicated that the rumen microorganisms and their metabolism pathways changed with feed supply, and these alterations in part contributed to yak adaption to starvation and re-alimentation. This study is helpful for enhancing the understanding and utilization of this natural character of yaks to explore and improve their growth potential.
Project description:This study provides a clear and accurate dynamic transcriptome profile of mRNAs in rumen, reticulum, omasum and abomasum of yaks. The results include high-quality genomic data and help to elucidate the important roles of these mRNAs in regulation of growth, development and metabolism in yaks, and to further understand the molecular mechanisms underlying metabolic regulation of yak stomach tissues. At the same time, it provided a theoretical basis for age-appropriate weaning and supplementary feeding in yaks.
Project description:This study examined the effect of the ratio of dietary metabolizable energy (MJ) to nitrogen (g) content (ME:N) on average daily gain (ADG), blood biochemical indices, rumen fermentation parameters, and rumen bacterial community in yaks. Thirty-six male yaks, aged 2-3 years, were divided into three groups and received a ME:N ratio of 0.42 (HY), 0.36 (MY,) or 0.32 (LY) MJ/g. Dry matter intake ranged between 3.16 and 3.63 kg/d and was lesser (p < 0.001) in the LY group than the other two groups. ME intake increased (p < 0.001) with an increase in the ME:N ratio, while N intake did not differ among groups. The ADG was 660 g/day for the MY group, which was higher (p < 0.005) than the 430 g/day in the LY group, while the HY group gained 560 g/day and did not differ from the other two groups. Feed intake to ADG ratio ranged between 5.95 and 7.95, and numerically was highest in the LY group and lowest in the MY group. In general, the concentration of ruminal total volatile fatty acids (p < 0.03) and molar proportions of propionate (p < 0.04), increased, while the molar proportion of acetate (p < 0.005) and the acetate:propionate ratio decreased (p < 0.001) with a decrease in the ME:N ratio. The molar proportion of butyrate did not differ among groups (p = 0.112). Group MY had higher ruminal NH3-N content than group HY and had a higher serum glucose content but lower urea content, lactate dehydrogenase, and creatine kinase content than group LY. In ruminal bacteria at the phylum level, the relative abundance of Firmicutes (F) was greater and of Bacteroidetes (B) was lesser, while the F:B ratio was greater in group MY than in groups HY an LY. We concluded that the yaks consuming the diet containing a ME:N ratio of 0.36 MJ/g had the best performance of the three groups.