Introduction:This study aimed to characterize the tissue distribution of key trace elements in fattening yaks and to establish empty body weight (EBW)-based prediction models for the net growth requirement (NRG) of copper (Cu), manganese (Mn), zinc (Zn), iron (Fe), selenium (Se), and cobalt (Co), as well as to derive their net maintenance requirement (NMR). Methods:A comparative slaughter plus graded feeding design was used. Forty approximately 4-year-old male yaks (234.20 ± 9.86 kg) were assigned to baseline slaughter (BL), midterm slaughter (M), and terminal slaughter groups stratified by intake: ad libitum (AL), 70% of ad libitum (IR70, n = 8), and 40% of ad libitum (IR40). Tissue concentrations of target elements were determined by ICP-OES and ICP-MS. Body weight and intake data were used to develop EBW-based NRG models and derive NMR. Results:Cu and Fe were primarily distributed in viscera, Mn predominantly in bone, and Zn, Se, and Co mainly in muscle. For the 230 to 320 kg body-weight range, the EBW-based NRG prediction models were: NRGCu = 2.7194 × EBW0.1827; NRGMn = 0.1302 × EBW0.3880; NRGZn = 17.1124 × EBW0.1092; NRGFe = 7.1755 × EBW0.5054; NRGSe = 0.0034 × EBW0.8043; and NRGCo = 0.0077 × EBW0.0974. The corresponding NRG values (mg/kg EBW) were Cu 7.08-7.58, Mn 0.99-1.15, Zn 30.31-31.57, Fe 101.21-122.08, Se 0.23-0.31, and Co 0.01. The NMR values (mg/d) were Cu 0.87, Mn 0.45, Zn 14.48, Fe 19.89, Se 0.11, and Co 0.01. Discussion:EBW-based models provide robust NRG and NMR parameters for Cu, Mn, Zn, Fe, Se, and Co in late-fattening yaks. These yak-specific values offer practical targets for precise mineral supplementation and ration formulation in yak production systems across Asia, helping prevent deficiency or excess and improve production efficiency.

After weaning, calves undergo a critical transition from liquid milk to solid feed. During this period, the digestive system is not yet fully mature and the rumen microbial community is still being established, which can easily lead to stress responses, growth retardation and other problems. Nutritional management and microecological regulation at this stage are crucial for rumen development, maturation of immune function and subsequent growth performance. Probiotics are regarded as an important nutritional and microecological strategy to alleviate weaning stress and promote the maturation of rumen and intestinal function. Therefore, in the present study, sixteen 8-month-old weaned yaks were randomly allocated to two groups (n = 8 per group): a composite probiotic group (CP) and a control group (CK). In the CP group, a composite probiotic preparation (Bacillus subtilis, Lactobacillus acidophilus and Bacillus licheniformis; viable count ≥ 1 × 1010 CFU/g) was supplemented at 0.2

Hypobaric hypoxia poses a serious threat to growth and development and can induce pronounced inflammatory responses. These effects are closely associated with the gut microbiota. However, the underlying mechanisms, particularly the role of gut microbiota in regulating hepatic metabolism under chronic hypoxic conditions, remain poorly understood. In this study, SD rats were used as recipients and assigned to three groups: a hypobaric hypoxia group (H), an antibiotic-treated group (HA), and an antibiotic-treated group receiving fecal microbiota transplantation from plateau zokors (HAM). All rats were maintained in a hypobaric hypoxia chamber simulating an altitude of 6000 m for 30 days. Subsequently, growth performance, routine hematological parameters, and multi-omics profiles were evaluated. Compared with the H group, both the HAM and HA groups showed significantly increased average daily gain (ADG) (p < 0.05), while the ADG/ADFI ratio was significantly higher in the HAM group than in the H group (p < 0.05). Monocyte count (Mon#) and monocyte percentage (Mon%) were significantly higher in the HA group than in both the H and HAM groups (p < 0.05). Microbiota analysis revealed significant enrichment of Lachnospiraceae_NK4A136_group in the HAM group, whereas Desulfovibrio was significantly enriched in the HA group (p < 0.05). Fecal metabolomics showed that ursodeoxycholic acid (UDCA) was significantly increased in the HAM group (p < 0.05). In the liver metabolome, the anti-inflammatory lipid FAHFA 18:1/20:3 was significantly elevated in the HAM group, whereas pro-inflammatory factors, including uric acid and leukotriene D4, were significantly reduced (p < 0.05). Correlation analysis further demonstrated that the abundance of Lachnospiraceae was positively correlated with FAHFA 18:1/20:3 and negatively correlated with uric acid and creatinine (p < 0.05). Collectively, these findings indicate that the gut microbiota can modulate gut-liver metabolism, alleviate inflammatory responses, and enhance the adaptation of rats to hypoxic environments. This study provides valuable insights into potential strategies for promoting sustainable animal health and adaptation under hypoxic conditions.

The experiment aimed to investigate the feasibility and accuracy of an automatic 3D point cloud-based measurement method for obtaining body size parameters of yaks under natural passage conditions, and to provide a non-contact data acquisition method for growth monitoring, group feeding, body weight estimation, and feed supply adjustment in plateau yak farms. Thirty healthy Mado yaks were selected, and a low-constraint acquisition passage equipped with top and bilateral depth cameras was constructed to synchronously collect 3D point cloud data during natural walking. To address flying point noise and blurred body contours caused by the thick coat of yaks, dual-scale voxel filtering and adaptive statistical outlier removal were used for point cloud preprocessing. To solve the problem of unclear key anatomical landmarks such as the withers and rump, anatomical prior constraints, weighted curvature analysis, and local quadratic surface RANSAC were combined for key point localization. To reduce the influence of walking posture changes on girth measurement, dynamic section projection and weighted ellipse fitting were proposed to automatically estimate chest girth, abdominal girth, and waist girth. Compared with manual measurements of six yaks, the mean absolute percentage errors of body height, body slant length, rump height, chest girth, abdominal girth, and waist girth were 2.19%, 6.30%, 4.18%, 4.88%, 3.36%, and 5.79%, respectively. The small-scale manual comparison test preliminarily showed that this method could automatically measure the main body size parameters of yaks under low-constraint natural passage conditions, providing basic data for group feeding, body condition assessment, and feed supply adjustment.

Background This study investigated the effects of rumen fluid-fermented roughage on the rumen microbiota and the growth performance of yaks. Twenty yaks with similar body conditions were randomly divided into two groups (n = 10 per group), and fed either a basal diet (CON) or 10% rumen fluid-fermented roughage. The experiment lasted 75 d, including a 15 d adaptation period and a 60 d treatment period. At the end of the experiment, serum and rumen fluid samples were collected and analyzed. The microbial communities and metabolomic profiles in the rumen fluid were analyzed using 16S rRNA sequencing and non-targeted metabolomics, respectively. Results Results showed a significant rise in serum alanine aminotransferase levels, while serum total protein and cholesterol concentrations decreased notably. Furthermore, rumen fluid ammonia nitrogen and acetic acid concentrations decreased significantly, while concentrations of yak rumen microbial protein, isovaleric acid, and valeric acid increased significantly. Rumen microbial diversity was enhanced, with decreased abundances of Firmicutes , Cyanobacteria , Klebsiella , Spirochaetota , fungi, and Pseudomonas , alongside increased populations of Anaeroplasma , Spirochaetota , Fibrobacter , and Succiniclasticum . Furthermore, the activity of the bile secretion pathway and concentrations of its metabolites—including deoxycholic acid, chenodeoxycholic acid, glycocholic acid, and glycodeoxycholic acid—were significantly elevated. Conclusions These findings indicate that rumen fluid-fermented coarse feed not only promotes yak growth but also enhances health by modulating metabolites associated with cellular proliferation, such as dUMP, adenylosuccinate, and DL-α-tocopherol. Consequently, rumen fluid-fermented coarse feed represents a beneficial dietary supplement for improving growth performance and overall health in yaks.

This study examined the effects of feeding level on energy and nitrogen metabolism and gas exchange in adult yaks, and estimated their maintenance energy and protein requirements. After a 15-day adaptation period, thirty-two healthy 4-year-old male yaks with similar body weight (235.96 +/- 12.46 kg) were randomly assigned to four groups (n = 8 per group): a baseline slaughter group (BL), an ad libitum group (AL), a 70% intake-level group (IR70), and a 40% intake-level group (IR40). The BL group was slaughtered on day 0 of the main trial to obtain baseline data. During the main trial, the AL, IR70, and IR40 groups were fed at 100%, 70%, and 40% of ad libitum dry matter intake (DMI), respectively. A digestion and metabolism assessment was conducted during the final 5 d of the main trial, and a respiratory gas exchange assessment during the final 3 d; animals in AL, IR70, and IR40 were slaughtered at the end of day 90. The results showed that increasing feeding level significantly increased final body weight, shrunk body weight, empty body weight, average daily gain, and total muscle weight. Values in the AL and IR70 groups were higher than those in the IR40 group (P < 0.05). Total fat weight, total gross energy intake, metabolizable energy intake, digestible energy, DMI, carbon dioxide production, and methane emission all increased gradually with increasing feeding level (AL > IR70 > IR40; P < 0.05). The methane conversion factor averaged 5.20% (range 4.89-5.51%). With increasing restriction, total gross energy digestibility increased (IR40 > IR70 > AL; P < 0.05), and total gross energy metabolizability was higher in IR40 than in AL (P < 0.05). Within the 230-320 kg body-weight range, the net energy requirement for maintenance was 291.07kJ center dot kg(-1) W0 center dot 75 center dot d(-1) , the metabolizable energy requirement for maintenance was 434.18 kJ center dot kg(-1) W0 center dot 75 center dot d(-1) , the efficiency of metabolizable energy utilization for maintenance was 0.67, and the net protein requirement for maintenance was 2.76 g center dot kg(-1) W0 center dot 75 center dot d(-1) . These findings provide reference data for precision feeding and methane energy loss assessment in yaks under plateau conditions.

This study evaluated the adaptability of Holstein cattle to high-altitude environments following their relocation from low-altitude regions (<500 m) to the Qinghai-Tibet Plateau (>3,500 m) and identified risk factors associated with physiological maladaptation. A cohort of 1,000 healthy Holstein heifers was relocated and monitored over a 5-mo period, with observations focusing on mortality rates, clinical symptoms, hematological parameters, and pulmonary arterial pressure. Postmortem examinations and 16S rRNA sequencing of gut microbiota were conducted. The observed mortality rate was 30.5%. The predominant clinical manifestations included anorexia, edema, pulmonary hypertension, and hematological abnormalities. Postmortem analyses confirmed that right-sided heart failure secondary to hypoxic pulmonary hypertension was the principal cause of mortality. Holstein heifers that survived exhibited a higher relative abundance of bacteria associated with energy metabolism, such as Tenericutes, TM7, Clostridium, Treponema, and Paludibacter, in comparison to those that did not survive. Immediate relocation to elevations exceeding 3,500 m presents significant risks. To mitigate these risks, it is recommended to restrict altitude transitions to 1,500 m or less. An alternative approach involves implementing a gradual acclimatization strategy, which includes adaptive rearing at elevations of 2,500 m or lower for a minimum period of 5 mo, alongside specific dietary modifications and probiotic supplementation. These findings provide both practical and theoretical foundations for the effective health management of Holstein heifers in high-altitude environments.

The yak is an iconic ruminant of the Qinghai-Tibet Plateau, yet segment-specific variation in its intestinal microbial functional potential and bile acid profiles under different feeding systems remains insufficiently characterized. Six healthy adult male yaks with similar body weights (320 ± 30 kg) were assigned to grazing (G) or stall-feeding (S) systems, with three animals per group, for a 90-day trial comprising a 10-day adaptation period and an 80-day formal experimental period. The individual yak was considered the experimental unit, and intestinal segments sampled from the same animal were treated as repeated observations. Liver tissue and digesta from the duodenum, ileum, cecum, and colon were analyzed using targeted bile acid metabolomics and shotgun metagenomics. Principal coordinate analysis based on Bray-Curtis dissimilarities showed segment-associated clustering of microbial communities, with PCo1 and PCo2 explaining 65.5% and 18.9% of the total variation, respectively. ANOSIM identified a significant intestinal-segment effect on microbial community composition (R = 0.2208, BH-FDR = 0.0144), whereas the overall feeding-system effect was not significant (R = 0.3747, BH-FDR = 0.1200). No statistically significant feeding-system differences were detected in Shannon, Simpson, Chao1, or ACE indices within individual intestinal segments (BH-FDR ≥ 0.800), and PERMDISP detected no significant differences in within-group dispersion (BH-FDR ≥ 0.1682). Bacillota and Bacteroidota were the dominant phyla. Descriptive functional profiling showed higher mean ileal abundances of GH2 (0.0035 vs. 0.0026), GH3 (0.0029 vs. 0.0024), and GH43 (0.0021 vs. 0.0013) in grazing yaks, whereas the starch-associated GH13 family showed its highest mean abundance in the colon of stall-fed yaks. These metagenomic patterns represent predicted genomic functional potential rather than gene expression, enzyme activity, or metabolic flux. Cecal total bile acid concentration showed a nominal between-group difference (unadjusted Welch’s p = 0.0109), but this difference did not remain significant after correction across the five anatomical sites (BH-FDR = 0.0545). In the colon, stall-fed yaks had a lower conjugated-to-unconjugated bile acid ratio and a higher secondary-to-primary bile acid ratio than grazing yaks (BH-FDR < 0.05). Feeding-system-associated descriptive patterns were observed in predicted microbial functional profiles, whereas statistically supported between-group differences were limited mainly to selected colonic bile acid ratios. Given the limited animal-level replication, these findings should be considered exploratory.

This study aimed to investigate the effects of feeding low-fat digestive health diets on the growth performance, serum biochemical parameters, and fecal microbiota composition in healthy Beagle dogs. A total of 28 healthy Beagle dogs aged 2.5 years and weighing (13.86±0.39) kg were randomly divided into two groups with seven replicates per group and two dogs per replicate (half male and half female). The control group was fed a standard complete adult dog diet, while the experimental group was fed a low-fat digestive health diet. The pre-test period was six days, and the formal test period was 24 days. The results showed that compared with the control group, the apparent digestibility of gross energy in the experimental group was extremely reduced (P<0.01). No significant differences were observed in initial body weight, final body weight, and average daily feed intake between the two groups (P>0.05). The blood lymphocyte count in the experimental group was significantly increased (P<0.05), while lymphocyte percentage, intermediate cell count, intermediate cell percentage, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, red blood cell distribution width coefficient of variation, and mean platelet volume were extremely increased (P<0.01). The serum alanine aminotransferase and alkaline phosphatase activities were extremely decreased in the experimental group (P<0.01). The Shannon index of the fecal microbiota was significantly increased in the experimental group (P<0.05). At the phylum level, the relative abundance of Actinobacteria in the feces was extremely increased in the experimental group (P<0.01). At the genus level, the relative abundances of Collinsella and Clostridium sensu stricto were extremely increased in the experimental group (P<0.01). The study shows that low-fat digestive health diets can reduce energy digestibility and modulate fecal microbiota composition in healthy Beagle dogs, showing a more advantages in weight management and intestinal health maintenance.

OBJECTIVE:The study investigated how varying protein levels in low-energy diets affected the microbiota, meat quality, and metabolomics of the longissimus dorsi muscle in yaks. The aim was to determine the optimal yak diet for growth and meat quality under low-energy conditions. METHODS:Twenty-four adult male yaks were divided into two groups of 12: the low-energy, medium-protein (LM) group and the low-energy, high-protein (LH) group. The study analysed rumen microbiota and longissimus dorsi muscle metabolites using 16S rDNA gene sequencing and untargeted metabolomic analysis. The effects of the diets on growth performance, meat quality and microbial community composition were evaluated. RESULTS:There were no significant differences in growth performance between the LH and LM groups. However, the LH group had a lower pH value at 45 minutes after death and was better for meat colour and tenderness. There were no significant differences in average daily gain, cooking loss, hardness, elasticity, adhesiveness, chewiness, or the pH at 24 hours after death in the longissimus dorsi muscle between the groups. Microbial community analysis revealed no significant differences in diversity indices; however, it did indicate distinct bacterial composition between the groups. Predictions of function suggested the LM group had a higher level of enrichment and a greater number of unique operational taxonomic units compared to the LH group. Metabolomic analysis revealed differences in muscle metabolites and metabolic pathways, with the LM group having a higher capacity for fatty acid and selenocompound metabolism, implying greater energy utilisation efficiency and antioxidant function. CONCLUSION:The study suggests that a diet with 14% protein, as part of low-energy diets, is best for increasing yak fattening. This is because it improves energy use and antioxidant function, without affecting growth.

IntroductionThe nutritional level of the diet plays a crucial role in maintaining the balance of the yak rumen microbiota. To explore the relationship between dietary nutritional levels, the rumen microbiota, and muscle metabolites, we examined the characteristics of the yak rumen microbiota and muscle metabolome under different dietary nutritional levels.MethodsRandomly divide 24 yaks with similar body weights, [235.96 ± 12.46 kg], into three groups. These groups were subjected to three nutritional feeding levels: ad libitum feeding (AL), 70% of ad libitum intake (IR70), and 40% of ad libitum intake (IR40). When the yaks in the AL group gained 70 kg in body weight, they were slaughtered.ResultsThe results indicated that the ad libitum feeding group (AL) demonstrated superior edible meat quality in terms of Chroma L*, Chroma a*, and shear force, compared to the 70% intake group (IR70) and the 40% intake group (IR40). At the phylum level, the abundance of Patescibacteria was notably greater in the IR40 group compared to both the AL group and the IR70 group. At the genus level, the relative abundance of Succinimonas was higher in the AL group than in both the IR70 and IR40 groups. Untargeted metabolomics analysis revealed that the levels of metabolites such as 5-Methylcytosine, Cytosine, and Thymine were upregulated in the longissimus dorsi muscle of the AL group, which contributed to the enhancement of meat flavor. Furthermore, Spearman's correlation analysis revealed a notable relationship between the rumen microbiota and both meat quality and metabolite levels. pH45min is positively correlated with trans-Cinnamic acid. Methanobrevibacter exhibited a positive correlation with the concentration of 4-(Diethylamino)benzaldehyde, while Candidatus_Saccharimonas showed a positive correlation with the concentration of phenylacetylglycine.DiscussionThis study provides scientific evidence for understanding the impact of different nutritional feeding conditions on yak meat quality, rumen microbiota, and related muscle metabolomic pathways. It also reveals the potential impact of these factors on meat flavor. These findings offer important reference information for optimizing yak husbandry management, improving the formation of beef flavor compounds, and understanding their regulatory mechanisms.

IntroductionThere are few studies on the effect of rumen fluid transplantation on the fecal flora of yaks. Yak fecal flora is closely related to their health. This study aimed to evaluate the effects of rumen fluid transplantation on growth performance and fecal flora indicators.MethodsTwenty 6-month healthy male yaks (weight: 57.20 ± 7.80 kg) were selected from grazing yaks in an alpine meadow pasture at an altitude of approximately 3,400 m. They were then transferred to a farm and randomly divided into a control group (CON; n = 10) and a rumen fluid transplantation group (RT; n = 10). Separate single-pen rearing was performed in two pens using the same rearing environment and feeding method, and all yaks were earmarked for identification. In addition, 10 yaks that had been adapted to stall fattening feed in 1 month were selected as the rumen fluid donor group to provide fresh rumen fluid. Ruminal fluid transplantation trials were conducted on the 1st, 3rd, and 5th weeks. Overall, 1 L of ruminal fluid was transplanted to each yak in the RT and CON groups. The formal trial then began with both groups fed the same diet. After this, yak feed intake was recorded daily; yaks were weighed on days 1, 30, and 60 of the formal trial; and yak feces were collected directly from the ground on days 1, 4, 7, 14, 30, and 60 to compare the microbial composition of the feces using 16S rRNA sequencing data.ResultsThe results showed that rumen fluid transplantation significantly increased the alpha diversity of fecal microflora (P < 0.05), and on day 30 of the experiment, both the operational taxonomic unit (OTU) and Shannon index were significantly higher in the RT group than the CON group (P < 0.05). In the principal coordinate analysis (PCoA) plot, the intestinal flora of the RT group was significantly different (P < 0.05) on days 1–7 but not significantly different after day 14. In contrast, the intestinal flora of the CON group was significantly different (P < 0.05) on days 1–14 but not significantly different after day 30. Compared with the CON group, the relative abundance of Firmicutes in the RT group was significantly lower on days 1, 4, 7, and 14 (P < 0.05); the relative abundance of Bacteroidetes in the RT group was significantly higher on days 1, 4, 14, and 30 and significantly lower on day 7 (P < 0.05); the relative abundance of Tenericutes in the RT group was significantly higher on day 30 (P < 0.05); the relative abundance of Actinobacteria in the RT group was significantly higher on day 60 (P < 0.05); the relative abundance of Ruminococcaceae_UCG-005 in the RT group was significantly lower on days 4, 7, 14, and 60 (P < 0.05); the relative abundance of Unidentified in the RT group was significantly higher on days 1, 4, and 7 days (P < 0.05); and the relative abundance of Rikenellaceae_RC9_gut_group, Bacteroides, and Christensenellaceae_R-7_group in the RT group was significantly higher on day 1 (P < 0.05). Moreover, Actinobacteria was positively correlated with ADG and negatively correlated with DMI; Tenericutes was positively correlated with weight and negatively correlated with F/G. Metabolism of terpenes and polyketones, metabolism of other amino acids, and energy metabolism were higher in the RT group than in the CON group. LEfSe analysis showed that 32 species were more abundant in the RT group and 11 in the CON group. In conclusion, our findings suggest that rumen fluid transplantation improved the stability of the intestinal tract of yaks, improved the immunity of yaks, and reduced the occurrence of intestinal diseases; rumen fluid transplantation remodeled the structure of the intestinal flora, shortened the time of remodeling the intestinal flora of yaks during the transition period, and accelerated yak adaptation to digest housed rations, reducing the DMI. The findings of this study provide new insights into yak microbial community transplantation and a reference for improving feed efficiency in the yak industry.

ABSTRACT Hypoxia has long posed a serious threat to the health of both animals and humans, causing respiratory acidosis, metabolic disorders, systemic inflammation, oxidative stress damage, and other issues, thereby endangering life and limiting development in high-altitude areas. Gut microbiota plays a crucial role in life activities and hypoxia adaptation. We transplanted the gut microbiota from small mammals, plateau zokors (Myospalax baileyi), from the Qinghai–Tibetan plateau (3,500 m) to Sprague–Dawley (SD) rats housed in a hypobaric chamber (equivalent to 6,000 m altitude) for 30 days. The results showed that microbiota transplantation significantly reshaped the gut microbiota structure of the rats, notably increasing the abundance of short-chain fatty acid-producing bacteria Lachnospiraceae and Prevotellaceae, alleviating hypoxia and acidosis, reducing pulmonary hypertension and right ventricular hypertrophy, increasing the production of anti-inflammatory substances like indole-3-lactic acid, and reducing the generation of pro-inflammatory substances, such as histamine and uric acid. It also decreased the expression of inflammatory genes like lgE, TNFα, and IFN-γ in the lung. Fecal microbiota transplantation from plateau-specific species to low-altitude SD rats effectively altered metabolism, changed gene expression, decreased pulmonary artery pressure, and enhanced plateau adaptability. This study demonstrates the potential effectiveness of treating hypoxic pulmonary hypertension through microbiota transplantation and offers insights into improving hypoxia adaptation.IMPORTANCEWe report the beneficial effects of FMT on respiratory capacity, lung metabolism, and lung gene expression in SD rats under hypoxic conditions. We revealed the inhibitory effects of gut microbiota on lung mast cells and histamine expression under hypoxic conditions. The study demonstrated the potential effectiveness of treating HPH through FMT and offers insights into improving hypoxia adaptation.

The study aimed to investigate the impact of the feed concentrate to roughage ratio transition on the microbial distribution and functions in yak feces. Twenty-four healthy male yaks at three years old with similar weight were fed a diet of 30∶70 for 1~60 days (Group C30 ), and converted to a diet of 70∶30 for 61~120 days (Group C70 ). The pre-test period was 15 days, and the formal test period was 120 days. Fecal samples were collected using the rectal fecal sampling method from six randomly selected yaks on day 60 and day 120 after feeding for 3~4 hours. The samples were sequenced using 16S rRNA gene sequencing technology to compare and analyze the fecal microbial community, and functional predictions were made using PICRUSt2. The results showed no significant differences in lineage diversity and diversity indices between the two groups (P>0.05). PCoA analysis revealed a significant difference in the composition of fecal microbial communities between the two groups (P<0.05). At the phylum level, the relative abundance of Actinobacteriota in Group C70 was significantly higher than in Group C30 (P<0.05). At the genus level, the relative abundance of unidentified taxa in Group C70 was extremely higher than in Group C30 (P<0.01), and the relative abundance of uncultured bacterium and Roseburia was significantly higher in Group C70 than in Group C30 (P<0.05), while the relative abundance of Lachnospiraceae_NK3A20_group, Olsenella, and Paeniclostridium was significantly higher in Group C30 than in Group C70 (P<0.05). At the KEGG level 2, the expression levels of functions such as energy metabolism, terpenoid and polyketide metabolism, interspecies biodegradation, and metabolism were lower in Group C70 compared to Group C30. The study indicates that the transition of feed concentrate to roughage ratio affects the richness and diversity of fecal microbial communities, significantly influencing the composition of microbial communities in yak feces. Transitioning from a low concentrate to roughage ratio to a high ratio reduces the relative abundance of fiber-degrading bacteria in the hindgut, promotes the proliferation of acid-producing bacteria, increases the proportion of Paeniclostridium.

IntroductionThe dietary protein level plays a crucial role in maintaining the equilibrium of rumen microbiota in yaks. To explore the association between dietary protein levels, rumen microbiota, and muscle metabolites, we examined the rumen microbiome and muscle metabolome characteristics in yaks subjected to varying dietary protein levels.MethodsIn this study, 36 yaks were randomly assigned to three groups (n = 12 per group): low dietary protein group (LP, 12% protein concentration), medium dietary protein group (MP, 14% protein concentration), and high dietary protein group (HP, 16% protein concentration).Results16S rDNA sequencing revealed that the HP group exhibited the highest Chao1 and Observed_species indices, while the LP group demonstrated the lowest. Shannon and Simpson indices were significantly elevated in the MP group relative to the LP group (P < 0.05). At the genus level, the relative abundance of Christensenellaceae_R-7_group in the HP group was notably greater than that in the LP and MP groups (P < 0.05). Conversely, the relative abundance of Rikenellaceae_RC9_gut_group displayed an increasing tendency with escalating feed protein levels. Muscle metabolism analysis revealed that the content of the metabolite Uric acid was significantly higher in the LP group compared to the MP group (P < 0.05). The content of the metabolite L-(+)-Arabinose was significantly increased in the MP group compared to the HP group (P < 0.05), while the content of D-(-)-Glutamine and L-arginine was significantly reduced in the LP group (P < 0.05). The levels of metabolites 13-HPODE, Decanoylcarnitine, Lauric acid, L-(+)-Arabinose, and Uric acid were significantly elevated in the LP group relative to the HP group (P < 0.05). Furthermore, our observations disclosed correlations between rumen microbes and muscle metabolites. The relative abundance of NK4A214_group was negatively correlated with Orlistat concentration; the relative abundance of Christensenellaceae_R-7_group was positively correlated with D-(-)-Glutamine and L-arginine concentrations.DiscussionOur findings offer a foundation for comprehending the rumen microbiome of yaks subjected to different dietary protein levels and the intimately associated metabolic pathways of the yak muscle metabolome. Elucidating the rumen microbiome and muscle metabolome of yaks may facilitate the determination of dietary protein levels.

本试验旨在研究不同精粗比对牦牛粪便菌群结构的影响.选取24头体重相近、健康的3岁公牦牛,随机分成2组,分别饲喂低精粗比饲粮(35∶65,C35组)和高精粗比饲粮(65∶35,C65组).预试期为15 d,试验期为90 d.运用16S rDNA高通量测序技术对粪便菌群结构变化进行分析.结果表明:1)2组共检测出1702个操作分类单元(OTU),其中两组共有的OTU数目为1273个,占总OTU数目的74.79％;C35组的物种数、Chao1指数与Shannon指数显著高于C65组(P<0.05).2)在门水平下,C35组牦牛粪便中髌细菌门和蓝藻菌门极显著高于C65组(P<0.01),放线菌门显著高于C65组(P<0.05);C65组牦牛粪便中拟杆菌门、螺旋体门显著高于C35组(P<0.05).3)C35组牦牛粪便中瘤胃球菌属极显著高于C65组(P<0.01),毛螺菌科_NK3A20显著高于C65组(P<0.05);C65组牦牛粪便中未培养的属极显著高于C35组(P<0.01),未培养细菌属、拟普雷沃氏菌属、密螺旋体属显著高于C35组(P<0.05).4)利用PICRUSt预测粪便微生物的代谢途径和功能,在KEGG2水平,C65组复制和修复、翻译、核苷酸代谢、其他次生代谢物的合成、细胞生长和死亡的基因家族相对丰度极显著高于C35组(P<0.01).综上,饲粮精粗比显著影响了牦牛粪便菌群的多样性与丰富度.且饲喂高精粗比饲粮(65:35)促进了牦牛粪便中非纤维降解菌的增殖,提高了拟普雷沃氏菌属的丰度值,但抑制了毛螺菌科的生长,研究结果丰富了对牦牛粪便菌群结构的认识.

本试验旨在研究饲粮不同蛋白质水平对舍饲牦牛生长性能、瘤胃发酵参数及菌群结构和功能的影响.试验选取36头体重为(200±20)kg、健康状况良好的成年公牦牛,随机分为3组,每组3个重复,每个重复4头牦牛.在饲粮代谢能(10.6 MJ/kg)一致的前提下,分别配制低蛋白质水平饲粮(12％,LP组)、中蛋白质水平饲粮(14％,MP组)、高蛋白质水平饲粮(16％,HP组).预试期15 d,正试期90 d.结果表明:1)MP组牦牛平均 日增重显著高于LP组和HP组(P＜0.05);LP组干物质采食量显著高于HP组(P＜0.05);LP组料重比显著高于MP组和HP组(P＜0.05).2)LP组微生物蛋白浓度显著低于HP组(P＜0.05);MP组丙酸浓度显著低于HP组(P＜0.05).3)3个试验组共鉴定出11 989种瘤胃液特征序列,共有1 165种瘤胃液特征序列(ASVs),占总数的9.72％,LP组、MP组和HP组的ASVs数量分别为3 437、4 184和3 903种,其独占种数分别为1 351、1 978和1 790种;LP组Shannon指数显著低于MP组和HP组(P＜0.05);LP组Simpson指数显著低于MP组(P＜0.05).4)在门水平上,MP组螺旋体门(Spiro-chaetota)相对丰度显著高于其他2组(P＜0.05);LP组广古菌门(Euryarchaeota)相对丰度显著低于其他2组(P＜0.05);在属水平上,LP组与MP组克里斯藤森菌科_R-7(Christensenellaceae_R-7)相对丰度均显著低于HP组(P＜0.05).5)利用PICRUSt2来预测瘤胃细菌的代谢途径及功能,在KEGG2水平上,氨基酸代谢、能量代谢、辅助因子和维生素的代谢在HP组显著富集(P＜0.05);碳水化合物代谢、脂质代谢在LP组显著富集(P＜0.05);LP组其他氨基酸代谢显著低于HP组(P＜0.05).综上所述,饲喂相同代谢能不同蛋白质水平饲粮对舍饲牦牛生长性能、瘤胃发酵类型、瘤胃细菌丰富度、瘤胃菌群结构和瘤胃细菌代谢功能途径均会产生影响.饲喂14％蛋白质水平饲粮的舍饲牦牛具有较高的平均日增重、较低的料重比与较高的养殖效益,瘤胃微生物蛋白浓度较高,瘤胃菌群丰富度和多样性较高,且具有相对较高的蛋白质消化代谢及能量转化利用能力.综合考虑,当饲粮代谢能为10.6 MJ/kg时,推荐舍饲牦牛饲粮蛋白质水平为 14％.

Fermented feed is rich in probiotics, organic acids and other components, which is easy to digest and absorb by animals, and has high nutritional value. The palatability of the fermented feed is good, with a low content of anti-nutrient factors. It can improve the digestibility and utilization rate of animal feed, stabilize the structure of animal intestinal microorganisms, and enhance the immunity of the body. The paper mainly elaborates the concept and action mechanism of the fermented feed, reviews the effects of the fermented feed on the intestinal health, feed utilization rate, feeding cost and animal production performance, analyzes the problems existing in the application of the fermented feed in animal production, and prospects the future application of the fermented feed, in order to provide reference for the efficient utilization of fermented feed in animal breeding.

Under the background of domestic feed end prohibition, it has become a hot research direction to search for high-quality feeds that can improve animal performance and immunity and reduce feed to gain ratio. Compared with conventional feed, fermented feed can improve the performance and immunity of animals, reduce feed to gain ratio, and regulate the balance of rumen flora. In the paper, the types, mechanism, nutritional value of fermented feed and its application in ruminant breeding are reviewed, in order to provide reference for the development of fermented feed and its application in yak breeding in Qinghai-Tibet region.