Effects of level of feed intake and season on digestibility of dietary components, efficiency of microbial protein synthesis, rumen fermentation and ruminal microbiota in yaks

Effect of coconut processing by-product graded feeding on carcass traits and meat quality of lambs

The inclusion of by-product coconut mesocarp skins (CMS) in diets was evaluated in feedlot lambs. The objective of this study was to evaluate CMS levels effects on carcass traits and meat quality of lambs. Thirty-five male lambs with an initial body weight of 16.9 ± 2.93 kg were distributed in a completely randomized design with five CMS levels in total dry matter (0; 4.8; 9.6; 14.4 and 19.2%) and fed during 71 d until slaughter. High levels of CMS decreased the intake of dry matter and negatively affected the performance of lambs. Fat and protein contents of Longissimus lumborum muscle (P < 0.05) and the saturated fatty acid (FA) decreased (P < 0.001) whereas polyunsaturated FA increased (P < 0.01) with the inclusion of CMS. The ratio t10/t11-18:1 increased with the inclusion of CMS (P < 0.001). The instrumental color descriptors were unaffected by CMS levels. According to the effects on the investigated meat quality traits we recommend up to 4.8% CMS in diets of confined lambs.

Microbial Metagenomes and Host Transcriptomes Reveal the Dynamic Changes of Rumen Gene Expression, Microbial Colonization and Co-Regulation of Mineral Element Metabolism in Yaks from Birth to Adulthood

Yaks are the main pillar of plateau animal husbandry and the material basis of local herdsmen's survival. The level of mineral elements in the body is closely related to the production performance of yaks. In this study, we performed a comprehensive analysis of rumen epithelial morphology, transcriptomics and metagenomics to explore the dynamics of rumen functions, microbial colonization and functional interactions in yaks from birth to adulthood. Bacteria, eukaryotes, archaea and viruses colonized the rumen of yaks from birth to adulthood, with bacteria being the majority. Bacteroidetes and Firmicutes were the dominant phyla in five developmental stages, and the abundance of genus Lactobacillus and Fusobacterium significantly decreased with age. Glycoside hydrolase (GH) genes were the most highly represented in five different developmental stages, followed by glycosyltransferases (GTs) and carbohydrate-binding modules (CBMs), where the proportion of genes coding for CBMs increased with age. Integrating host transcriptome and microbial metagenome revealed 30 gene modules related to age, muscle layer thickness, nipple length and width of yaks. Among these, the MEmagenta and MEturquoise were positively correlated with these phenotypic traits. Twenty-two host genes involved in transcriptional regulation related to metal ion binding (including potassium, sodium, calcium, zinc, iron) were positively correlated with a rumen bacterial cluster 1 composed of Alloprevotella, Paludibacter, Arcobacter, Lactobacillus, Bilophila, etc. Therefore, these studies help us to understand the interaction between rumen host and microorganisms in yaks at different ages, and further provide a reliable theoretical basis for the development of feed and mineral element supplementation for yaks at different ages.

High energy level diet improves the growth performance and rumen fermentation of yaks in cold weather

To date, no research has been done on energy requirements for yaks in Tibetan cold weather. The findings of the current study provide proper energy requirements for yaks would facilitate scientific feeding of fattening yaks in cold weather. The metabolomics and 16s rRNA sequencing technologies were used to explore the underlying mechanism that affects the growth performance of yaks fed with different energy levels of diet in cold weather. Three groups of yaks (141.7 ± 3.34 kg) were fed with diets containing metabolizable energy 7.20, 7.89, and 8.58 MJ/kg DM (dry matter) and named the low-, medium-, and high-energy groups, respectively. The results showed that the average daily feed intake of the high-energy group was higher than that of the low-energy group (p  = 0.006). Plasma aspartate aminotransferase (p  = 0.004), alanine aminotransferase (p  < 0.001), and interferon-γ (p  < 0.001) in the high-energy group were lower than in the low-energy group. In contrast, superoxide dismutase (p  < 0.001), immunoglobulin G (p  < 0.001), and interleukin 2 (p  = 0.002) were higher than the low-energy group. The rumen microbial protein (p  = 0.025), total volatile fatty acids (p  = 0.029), and neutral detergent fiber digestibility (p  = 0.050) in the high-energy group were higher than in the low-energy group, whereas the acetate: propionate ratio (p  = 0.001) and ammonium nitrogen (p  = 0.001) were lower than in the low-energy group. The plasma metabolomics results displayed that yaks fed with a high-energy diet augmented the metabolism of arginine, proline, purine, taste transduction, pyrimidine, and glutathione pathways. The relative abundance of Methanobrevibacter in the high-energy group was lower (p  < 0.001), whereas the relative abundance of Methanosphaera (p  < 0.001) was higher than in the low-energy group. The results of the current study suggest that a high-energy diet in growing yaks during the cold season can improve growth performance, rumen microbial protein synthesis, antioxidants, and immunity.

Effects of Different Dietary Protein Level on Growth Performance, Rumen Fermentation Characteristics and Plasma Metabolomics Profile of Growing Yak in the Cold Season

This experiment was aimed to compare the effects of two diets with different protein content on the growth performance, immune indexes, rumen fermentation characteristics and plasma metabolomics of growing yak in the cold season. A total of 24, 2-year-old healthy yaks with similar body weight (142.9 ± 3.56 kg) were randomly allocated to two isoenergetic diets with different protein content (10 vs 14%) according to a non-paired experimental design, and the protein of the diets was increased by increasing soybean meal, rapeseed meal and cottonseed meal. The growth performance experiment lasted 56 days. Four days before the end of the growth experiment, the digestion trial was conducted, and the rumen fluid and plasma was collected for measurement. The results showed that the average daily feed intake (p < 0.001) and average daily gain (p = 0.006) of yak fed a high-protein diet was significantly greater, while the feed conversion ratio was lower (p = 0.021) than that of yaks fed a low-protein diet. Plasma aspartate aminotransferase (p = 0.002), alanine aminotransferase (p < 0.001), malondialdehyde (p = 0.001), tumor necrosis factor-α (p = 0.032) and interferon-γ (p = 0.017) of the high-protein group were significantly lesser, whereas superoxide dismutase (p = 0.004) and interleukin-2 (p = 0.007) was significantly greater than that of the low-protein group. The rumen microbial crude protein (p < 0.047) and crude protein digestibility (p = 0.015) of yak fed a high-protein diet was significantly greater than that of the low-protein group. The metabolomics results showed that yaks fed a high-protein diet were elevated in protein digestion and absorption, arginine and proline metabolism, tryptophan metabolism, purine metabolism, butanoate metabolism, taste transduction, pyrimidine metabolism, pantothenate and CoA biosynthesis, glutathione metabolism and renin secretion pathways. It is concluded that a high-protein diet in the cold season can promote rumen microbial crude protein synthesis, enhance antioxidant and immune function and promote growth performance of yaks.

Effects of forage type on the rumen microbiota, growth performance, carcass traits, and meat quality in fattening goats

Forages fed to goats influence ruminal microbiota, and further contribute to affect growth performance, meat quality and its nutritional composition. Our objective for current study was to investigate the effects of different forages on growth performance, carcass traits, meat nutritional composition, rumen microflora, and the relationships between key bacteria and amino acids and fatty acids in the longissimus dorsi and semimembranosus muscles of goats. Boer crossbred goats were separately fed commercial concentrate diet supplemented with Hemarthria altissima (HA), Pennisetum sinese (PS), or forage maize (FG), and then slaughtered 90 days after the beginning of the experiment. Growth performances did not vary but carcass traits of dressing percentage, semi-eviscerated slaughter percentage, and eviscerated slaughter percentage displayed significant difference with the treatment studied. Meats from goats fed forage maize, especially semimembranosus muscles are rich in essential amino acids, as well as an increase in the amount of beneficial fatty acids. Our 16S rRNA gene sequencing results showed that the Firmicutes, Bacteroidetes, and Proteobacteria were the most dominant phyla in all groups but different in relative abundance. Further, the taxonomic analysis and linear discriminant analysis effect size (LEfSe) identified the specific taxa that were differentially represented among three forage treatments. The spearman's correlation analysis showed that rumen microbiota was significantly associated with the goat meat nutritional composition, and more significant positive correlations were identified in semimembranosus muscles when compared with longissimus dorsi muscles. More specifically, the lipid metabolism-related bacteria Rikenellaceae_RC9_gut_group showed positively correlated with meat amino acid profile, while genera Oscillospiraceae_UCG-005 were positively correlated with fatty acid composition. These bacteria genera might have the potential to improve nutritional value and meat quality. Collectively, our results showed that different forages alter the carcass traits, meat nutritional composition, and rumen microflora in fattening goats, and forage maize induced an improvement in its nutritional value.

Rumen microbiota of indigenous and introduced ruminants and their adaptation to the Qinghai–Tibetan plateau

The grassland in the Qinghai–Tibetan plateau provide habitat for many indigenous and introduced ruminants which perform important ecological functions that impact the whole Qinghai–Tibetan plateau ecosystem. These indigenous Tibetan ruminants have evolved several adaptive traits to withstand the severe environmental conditions, especially cold, low oxygen partial pressure, high altitude, strong UV radiation, and poor forage availability on the alpine rangelands. Despite the challenges to husbandry associated with the need for enhanced adaptation, several domesticated ruminants have also been successfully introduced to the alpine pasture regions to survive in the harsh environment. For ruminants, these challenging conditions affect not only the host, but also their commensal microbiota, especially the diversity and composition of the rumen microbiota; multiple studies have described tripartite interactions among host-environment-rumen microbiota. Thus, there are significant benefits to understanding the role of rumen microbiota in the indigenous and introduced ruminants of the Qinghai–Tibetan plateau, which has co-evolved with the host to ensure the availability of specific metabolic functions required for host survival, health, growth, and development. In this report, we systemically reviewed the dynamics of rumen microbiota in both indigenous and introduced ruminants (including gut microbiota of wild ruminants) as well as their structure, functions, and interactions with changing environmental conditions, especially low food availability, that enable survival at high altitudes. We summarized that three predominant driving factors including increased VFA production, enhanced fiber degradation, and lower methane production as indicators of higher efficiency energy harvest and nutrient utilization by microbiota that can sustain the host during nutrient deficit. These cumulative studies suggested alteration of rumen microbiota structure and functional taxa with genes that encode cellulolytic enzymes to potentially enhance nutrient and energy harvesting in response to low quality and quantity forage and cold environment. Future progress toward understanding ruminant adaptation to high altitudes will require the integration of phenotypic data with multi-omics analyses to identify host-microbiota co-evolutionary adaptations enabling survival on the Qinghai–Tibetan plateau.

Characterization of gut microbiota dysbiosis of diarrheic adult yaks through 16S rRNA gene sequences

The ruminant gut microbial community has a strong impact on host health and can be altered during diarrhea disease. As an indigenous breed of the Tibetan Plateau, domestic yak displays a high diarrhea rate, but little research has been done to characterize the bacterial microbial structure in diarrheic yaks. In the present study, a total of 30 adult yaks, assigned to diarrhea (case, N = 15) and healthy (control, N = 15) groups, were subjected to gut microbiota profiling using the V3–V4 regions of the 16S rRNA gene. The results showed that the gut microbiome of the case group had a significant decrease in alpha diversity. Additionally, differences in beta diversity were consistently observed for the case and control groups, indicating that the microbial community structure was changed due to diarrhea. Bacterial taxonomic analysis indicated that the Bacteroidetes, Firmicutes, and Proteobacteria were the three most dominant phyla in both groups but different in relative abundance. Especially, the proportion of Proteobacteria in the case group was increased as compared with the control group, whereas Spirochaetota and Firmicutes were significantly decreased. At the genus level, the relative abundance of Escherichia-Shigella and Prevotellaceae_UCG-003 were dramatically increased, whereas that of Treponema, p-2534-18B5_gut_group, and Prevotellaceae_UCG-001 were observably decreased with the effect of diarrhea. Furthermore, based on our linear discriminant analysis (LDA) effect size (LEfSe) results, Alistipes, Solibacillus, Bacteroides, Prevotellaceae_UCG_003, and Bacillus were significantly enriched in the case group, while the other five genera, such as Alloprevotella, RF39, Muribaculaceae, Treponema, and Enterococcus, were the most preponderant in the control group. In conclusion, alterations in gut microbiota community composition were associated with yak diarrhea, differentially represented bacterial species enriched in case animals providing a theoretical basis for establishing a prevention and treatment system for yak diarrhea.

A comparison of average daily gain, apparent digestibilities, energy balance, rumen fermentation parameters, and serum metabolites between yaks (Bos grunniens) and Qaidam cattle (Bos taurus) consuming diets differing in energy level

Yaks (Bos grunniens), indigenous to the harsh Qinghai-Tibetan Plateau, are well adapted to the severe conditions, and graze natural pasture without supplements all year round. Qaidam cattle (Bos taurus), introduced to the Qinghai-Tibetan Plateau 1,700 years ago, are raised at a lower altitude than yaks, provided with shelter at night and offered supplements in winter. Based on their different backgrounds, we hypothesized that yaks have lower energy requirements for maintenance than cattle. To test this hypothesis, we measured average daily gain (ADG), apparent digestibilities, energy balance, rumen fermentation parameters, and serum metabolites in growing yaks and cattle offered diets differing in metabolizable energy (ME) levels (6.62, 8.02, 9.42 and 10.80 MJ/kg), but with the same crude protein concentration. Six castrated yaks (155 ± 5.8 kg) and 6 castrated Qaidam cattle (154 ± 8.0 kg), all 2.5 years old, were used in 2 concurrent 4 × 4 Latin square designs. Neutral and acid detergent fiber digestibilities were greater (P < 0.05) in yaks than in cattle, and decreased linearly (P < 0.05) with increasing dietary energy level; whereas, digestibilities of dry matter, organic matter, crude protein and ether extract increased (P < 0.05) linearly with increasing energy level. The ADG was greater (P < 0.001) in yaks than in cattle, and increased (P < 0.05) linearly with increasing energy levels. From the regressions of ADG on ME intake, the estimated ME requirement for maintenance was lower (P < 0.05) in yaks than in cattle (0.43 vs. 0.57 MJ/kg BW^0.75). The ratios of digestible energy (DE):gross energy and ME:DE were higher (P < 0.05) in yaks than in cattle, and increased (P < 0.05) linearly with increasing dietary energy level. Ruminal pH decreased (P < 0.05), whereas concentrations of total volatile fatty acids (VFAs) and ammonia increased (P < 0.01) with increasing dietary energy level, and all were greater (P < 0.05) in yaks than in cattle. Concentrations of ruminal acetate and iso-VFAs were greater (P < 0.05), whereas propionate was lower (P < 0.05) in yaks than in cattle; acetate decreased (P < 0.001), whereas butyrate and propionate increased (P < 0.001) linearly with increasing dietary energy level. Serum concentrations of β-hydroxybutyrate were lower (interaction, P < 0.001) in yaks than in cattle fed diets of 9.42 and 10.80 MJ/kg, whereas non-esterified fatty acids were greater (interaction, P < 0.01) in yaks than in cattle fed diets of 6.62 and 8.02 MJ/kg. Concentrations of serum leptin and growth hormone were greater in yaks than in cattle and serum insulin and growth hormone increased (P < 0.01) linearly with increasing dietary energy level. Our hypothesis that yaks have lower energy requirements for maintenance than cattle was supported. This lower requirement confers an advantage to yaks over Qaidam cattle in consuming low energy diets during the long winter on the Qinghai-Tibetan Plateau.

Changes in Blood Metabolic Profiles Reveal the Dietary Deficiencies of Specific Nutrients and Physiological Status of Grazing Yaks during the Cold Season in Qinghai Province of China

This study aimed to investigate the changes in the blood metabolic profiles of grazing yaks during the cold season to reveal their physiological status and seek the nutrients needed to be supplemented. Six castrated yaks (3 years old) with 166.8 kg (standard deviation = 5.3) of liveweight grazed in the Qinghai-Tibetan Plateau were used as experimental animals without supplementary feeding. Blood samples of each animal were collected in October and December 2015, and March 2016 for the analysis of serum biochemicals and metabolome. Results showed serum indices involved in protein metabolism in grazing yaks showed greater differences during the cold season than the metabolisms of energy or minerals. Cold stress in December had minor effects on the serum metabolic profiles of yaks compared with those in October. Yaks in October and December shared seven differential serum metabolites and enrichments of the “arachidonic acid metabolism” and “glycine, serine, and threonine metabolism” pathways compared with those in March caused by the shortage of feeds. Summarily, the nutrient deficiency would be influential on the physiological status of grazing yaks during the cold season, especially on the protein metabolism, which could be improved by supplementary feeds.

Average Daily Gain and Energy and Nitrogen Requirements of 4-Month-Old Female Yak Calves

There is little information available on milk intake and energy and nitrogen requirements of growing yak calves. This study aimed to fill this important gap, as this information could be beneficial in designing a system to wean yak calves earlier than in natural time. We determined the average daily gain and energy and nitrogen balances and requirements of 4-month-old female yak calves (48.8 ± 2.45 kg, n = 8). The calves were allowed to suck once a day and were fed an ad libitum concentrate: hay diet at a ratio of 60:40. Milk intake averaged 540 ± 26 g/d, yielding 2.28 ± 0.112 MJ/d, which was 13% of the gross energy intake (GEI). The digestible energy intake (DEI):GEI ratio was 0.681, metabolizable energy intake (MEI):DEI was 0.913, and MEI:GEI was 0.621. The average daily gain of the calves was 433 ± 153.1 g/d, which consisted of 78.0 ± 8.99 g protein, 52.7 ± 23.74 g fat, and 302.3 ± 95.1 g water, that is, 18.0% protein, 13.0% fat and 69.8% water. There were 130.7 g of body solids and 9.06 MJ of energy in every kg of body mass gain. Of the MEI, 25.17 kJ were required for 1 g of body mass, 83.40 kJ for 1 g of body solids, and 2.62 kJ for 1 kJ of retained energy (RE), and RE was 36.6% of MEI. The maintenance energy requirement was 5.35 MJ/d, the efficiency of utilization of energy for growth (k_g) was 0.72, and the heat increment of feeding for growth was 0.28 (1.55 MJ/d). Digestible nitrogen (N) was 0.685 while retained N (RN) was 0.489 of N intake. The N requirement for maintenance was 11.73 g/d or 0.61 g N/kg^0.75 per day, while the biological value (BV) of N was 91.1%. The energy and N requirements for yak calves were relatively low, which could be explained, at least in part, by the high efficiency of utilization of energy and high BV of N when compared to other livestock. These findings could be beneficial in designing early weaning systems for the many Himalayan households depending on yak production for their livelihoods.

Yak Gut Microbiota: A Systematic Review and Meta-Analysis

The yak (Bos grunniens) is closely related to common cows (Bos taurus), but is clearly a distinct species. Yaks are of substantial importance to food and leather production in certain high-altitude regions of Asia. The animal is increasing elsewhere as well, mainly because of the perceived health benefits of its milk. Like all ruminants, the animal harbors a complex community of microbial cells in its gut, crucial for its physiology. Despite yaks being important domestic animals, the composition of its gut microbiota and how the composition is guided by its specific high-altitude environment remains largely uncategorized. Hence, online databases (Embase, Medline ALL, Web of Science Core Collection, Cochrane Central Register of Controlled Trials, and Google Scholar) were searched for articles on yak intestinal microbiota. The pooled taxonomic abundance was compared between regions, sexes, different age groups, and feeding patterns. The gut microbiota distribution across different yak intestinal segments was established through pooled average taxonomic abundance. A total of 34 studies met the inclusion criteria and yielded information on 982 unique yak gut microbiota samples. An analysis of overall pooled microbiota revealed a segmented microbial community composition of the yak gut. Yak rumen microbiota was significantly influenced by difference in region, sex, and feeding patterns, the latter factor being dominant in this respect. Yak microbiome is shaped by the feeding strategy and provides an obvious avenue for improving health and productivity of the animal. More generally, the current segmental description of physiological gut microbiome provides insight into how the microbiology of this animal has adapted itself to help comping yaks with its high-altitude habitat.

The adaptive strategies of yaks to live in the Asian highlands

The yak (Bos grunniens), an indigenous herbivore raised at altitudes between 3,000 and 5,000 m above sea level, is closely linked to more than 40 ethnic communities and plays a vital role in the ecological stability, livelihood security, socio-economic development, and ethnic cultural traditions in the Asian highlands. They provide the highlanders with meat, milk, fibres, leather and dung (fuel). They are also used as pack animals to transport goods, for travel and ploughing, and are important in many religious and traditional ceremonies. The Asian highlands are known for an extremely, harsh environment, namely low air temperature and oxygen content and high ultraviolet light and winds. Pasture availability fluctuates greatly, with sparse pasture of poor quality over the long seven-month cold winter. After long-term natural and artificial selections, yaks have adapted excellently to the harsh conditions: 1) by genomics, with positively selected genes involved in hypoxia response and energy metabolism; 2) anatomically, including a short tongue with a weak sense of taste, and large lung and heart; 3) physiologically, by insensitivity to hypoxic pulmonary vasoconstriction, maintaining foetal haemoglobin throughout life, and low heart rate and heat production in the cold season; 4) behaviourlly, by efficient grazing and selecting forbs with high nutritional contents; 5) by low nitrogen and energy requirements for maintenance and low methane emission and nitrogen excretion, namely, ‘Low-Carbon’ and ‘Nitrogen-Saving’ traits; 6) by harboring unique rumen microbiota with a distinct maturation pattern, that has co-evolved with host metabolism. This review aims to provide an overview of the comprehensive adaptive strategies of the yak to the severe conditions of the highlands. A better understanding of these strategies that yaks employ to adapt to the harsh environment could be used in improving their production, breeding and management, and gaining benefits in ecosystem service and a more resilient livelihood to climate change in the Asian highlands.

Lambs fed diets containing by-product from coconut processing: histomorphometry characteristics in the digestive and renal systems

This study aimed to evaluate the histological characteristics in the digestive and renal systems of lambs fed diets containing coconut by-product (CB). A total of 35 male lambs with an initial weight of 16.9 ± 2.93 kg were distributed in a completely randomized design with five levels of CB in the diet (0; 4.8; 9.6; 14.4 and 19.2% in total dry matter). Samples of the liver, kidney, rumen, and intestine were histomorphometrically evaluated, and the data were submitted to regression analysis, at a 5% error probability. The inclusion of CB linearly decreased the dry matter intake and caused a quadratic effect for the height of ruminal papillae, absorption area, epithelium thickness, as well as for average daily gain. The inclusion of CB linearly increased the mucous layer and reduced the submucosal layer, as well as promoted a decrease in goblet cells in the small intestine. The inclusion of CB did not influence hepatic glycogen; additionally, the histopathological examination did not reveal liver damage or congestion, vacuolization, and necrosis of the renal tissue. Therefore, our results indicate that CB can be included in lambs diet up to the level of 7.2% without causing changes in the histomorphometry characteristics of the gastrointestinal tract and changes in liver and kidney tissue that compromise animal performance.

Rumen Bacterial Community of Grazing Lactating Yaks (Poephagus grunniens) Supplemented with Concentrate Feed and/or Rumen-Protected Lysine and Methionine

Simple Summary

Ruminal microorganisms, especially bacteria, play a vital role in utilizing fibrous material in ruminants. The yak is a bovid on the Qinghai-Tibet Plateau that traditionally only grazes natural pasture all year. During lactation, energy intake of yaks is often well below requirements, and yaks lose body weight. Today, to mitigate body weight losses during lactation, suckling yaks are often offered supplementary feed. This study examined the effect of dietary supplements on rumen bacteria in lactating yak. The yaks were offered supplementary concentrate feed (C), rumen-protected Lys and Met (RPA), or both (RPA+C). The ratio of the relative abundance of Firmicutes to Bacteroidetes in RPA+C was greater than in the RPA group, while there was no difference between C and RPA+C. The intakes of supplements resulted in a number of alterations in the abundances of bacteria at the genus level. When supplemented with C, yaks increased the concentration of ruminal total volatile fatty acids (VFAs), acetate, and butyrate. These results demonstrate that supplementary feed: (1) alters the composition of rumen microbiota and VFAs of lactating yaks; and (2) can be used to manipulate the composition of rumen microbiota.

Abstract

Traditionally, yaks graze only natural pasture all year round without supplements. Forage intake of lactating yaks is below energy and protein requirements, even in the summer, and suckling yaks lose a substantial amount of significant body weight. Today, to mitigate the loss in body weight, supplementary feed is being offered to lactating yaks. However, the effects of supplementary feed on ruminal bacterial communities in lactating yaks is unknown. In the current study, we examined the effect of supplementary feed on ruminal microbiota, using 16S rRNA sequencing, and on volatile fatty acids (VFAs). Twenty-four lactating yaks of similar body weight (218 ± 19.5 kg) and grazing natural pasture were divided randomly into four groups and received different supplements: (1) rumen-protected amino acids (RPA); (2) concentrate feed (C); (3) RPA plus C (RPA+C); and (4) no supplements (control-CON). The concentrations of total VFAs, acetate, and butyrate were greater (p < 0.05) when supplemented with concentrate feed (C and RPA+C) than without concentrate feed (CON and RPA). Bacteroidetes (B) and Firmicutes (F) were the dominant ruminal bacterial phyla in all groups. The ratio of relative abundance of F:B in RPA+C was greater than in the RPA group, while there was no difference between CON and RPC (interaction, p = 0.026). At the genus level, the relative abundances of Absconditabacteriales_SR1, Bacteroidales-RF16-group, Bacteroidales_BS11_gut_group, Prevotellaceae, and Rikenellaceae_RC9_gut_group were lesser (p < 0.05) with supplementary concentrate feed (C and RPA+C) than without concentrate feed (CON and RPA), whereas Butyrivibrio_2 and Pseudobutyrivibrio were greater (p < 0.05) with supplementary rumen-protected amino acids (RPA and RPA+C) than without rumen-protected amino acids (CON and C). These results demonstrate that supplementary feed: (1) alters the composition of rumen microbiota and concentrations of ruminal VFAs in lactating yaks; and (2) can be used to manipulate the composition of rumen microbiota.

Rumen Microbiota of Tibetan Sheep (Ovis aries) Adaptation to Extremely Cold Season on the Qinghai-Tibetan Plateau

The Qinghai-Tibet Plateau is characterized by low temperatures and hypoxia, and this feature is more obvious in the winter. However, it is not clear how Tibetan sheep adapt to extreme cold climates. To address this, we used physiological methods combined with next-generation sequencing technology to explore the differences in growth performance, forage nutrient digestion, serum biochemical indexes, and rumen microbial communities of Tibetan sheep (Ovis aries) between the summer and winter. In the summer, owing to the high nutritional quality of the forage, the Tibetan sheep showed enhanced forage degradation and fermentation though increased counts of important bacteria in the rumen, such as Bacteroidetes, Prevotella_1, Prevotellaceae_UCG-003, Ruminococcus_1, Saccharofermentans, and Ruminococcaceae_UCG-014, to improve the growth performance and increase serum immunity and antioxidant status. In the winter, owing to the low nutritional quality of the forage, the Tibetan sheep presented low values of forage degradation and fermentation indicators. The relative abundance of Firmicutes, the Firmicutes/Bacteroidetes ratio, microbial diversity, interactive activity between microorganisms, and metabolism were significantly increased, implying that the rumen microbiota could promote the decomposition of forage biomass and the maintenance of energy when forage nutritional value was insufficient in the winter. Our study helps in elucidating the mechanism by which Tibetan sheep adapt to the high-altitude harsh environments, from the perspective of the rumen microbiota.

The Rumen Bacterial Community in Dairy Cows Is Correlated to Production Traits During Freshening Period

The rumen microbiome plays a vital role in providing nutrition to the host animal, thereby influencing ruminant production. Despite its importance, it is not fully understood how variation in the ruminal bacteria community composition influences dry matter intake (DMI), milk yield and ruminal fermentative parameters in dairy cows, especially during freshening period. Here, we hypothesized that during early lactation, high DMI cows having a different ruminal microbiota than low DMI cows, and that this difference persists over time. To test this, we enrolled 65 fresh and determinzed their DMI using an auto-feed intake recording system. Fourteen days after calving, the 10 animals with the lowest (LFI) and the 10 animals with the highest (HFI)-average DMI were selected for further analysis. Rumen fluid was collected from these two cohorts at 1 (Fresh1d) and 14 days (Fresh14d) after calving and their ruminal microbiota were assessed using 16S rRNA sequencing. Volatile fatty acid (VFA) concentrations were also quantified. Comparison of the ruminal microbiotas between Fresh1d and Fresh14d showed that Fresh14d cows had a significantly higher relative abundance of VFA—producing microbes (P < 0.05), such as Prevotella_7 and Succinivibrionaceae_UCG-001. This was commensurate with the concentrations of acetate, propionate, butyrate, valerate and total VFAs, were also significantly (P < 0.05) increased in Fresh14d cows. We also found that the differences in the ruminal microbiota between LFI and HFI cows was limited, but DMI significantly altered (P < 0.05) the relative proportion of bacteria in the families Coriobacteriaceae, and Succinivibrionaceae. Furthermore, specific operational taxonomic units belonging to the Anaeroplasma was significantly (P < 0.05) correlated with DMI and milk yield. Taking together, our findings provide a framework for future studies of freshening period cow that seek to better understand the role of the ruminal microbiota during this critical period in the lactation cycle.

Altitude influences microbial diversity and herbage fermentation in the rumen of yaks

BACKGROUND

Rumen microbiota in ruminants are vital for sustaining good rumen ecology, health, and productivity. Currently, limited information is available regarding the response of yaks (Bos grunniens) to fluctuating environments, especially the rumen microbiome. To address this, we investigated the diet, rumen bacterial community, and volatile fatty acids (VFA) of rumen fluid of yaks raised in the great Qinghai-Tibet plateau (QTP) at 2800 (low altitude, L), 3700 (middle altitude, M), and 4700 m (high altitude, H) above sea level.

RESULTS

The results showed that despite a partial diet overlap, H yaks harbored higher fibrous fractious contents than the M and L grazing yaks. Bacteria including Christensenellaceae_R-7_group, Ruminococcus_1, Romboutsia, Alloprevotella, Eubacterium coprostanoligenes, Clostridium, Streptococcus, and Treponema were found to be enriched in the rumen of yaks grazing at H. They also showed higher rumen microbial diversity and total VFA concentrations than those shown by yaks at M and L. Principal coordinates analysis (PCoA) on weighted UniFrac distances revealed that the bacterial community structure of rumen differed between the three altitudes. Moreover, Tax4fun metagenome estimation revealed that microbial genes associated with energy requirement and carbohydrate metabolic fate were overexpressed in the rumen microbiota of H yaks.

CONCLUSIONS

Collectively, our results revealed that H yaks had a stronger herbage fermenting ability via rumen microbial fermentation. Their enhanced ability of utilizing herbage may be partly owing to a microbiota adaptation for more energy requirements in the harsh H environment, such as lower temperature and the risk of hypoxia.