Grazing yaks often face protein deficiency due to low-quality pasture, which limits milk production. This study aimed to investigate the effects of varying protein levels in concentrate supplementation on lactational performance, immune function, and rumen microbial and metabolites in grazing lactating yaks. Thirty-six lactating Qinghai Plateau yaks (172.78 ± 11.70 kg) were assigned to four treatments for 70 d (10 d adaptation + 60 d trial): grazing only (CON) or grazing plus 1.50 kg/d concentrate containing 15.09% (CP15), 17.00% (CP17), or 18.98% CP (CP19). Concentrate supplementation significantly increased average daily gain (ADG; 0.22 vs. 0.72–0.90 kg/d; p < 0.001) and milk yield (622.18 vs. 1094.25–1385.73 g/d; p < 0.001), and milk yield showed a linear increase with higher dietary protein levels (p < 0.001). Milk protein yield (29.99 vs. 56.00–68.60 g/d; p < 0.001) and milk lactose yield (40.71 vs. 79.85–93.53 g/d; p < 0.001) were also increased. Milk composition, including fat, protein, and lactose, also improved across supplementation groups, with the greatest enhancement observed at the CP17 group (p < 0.05). Rumen pH and volatile fatty acids did not differ between treatments, while microbial protein increased with supplementation (10.88 vs. 12.72–15.00 mg/dL; p = 0.041) and showed a linear response to dietary CP level (p = 0.033). Concentrate supplementation significantly altered the rumen microbial structure (ANOSIM, p = 0.036), enriching Succinivibrionaceae_UCG-002, Fibrobacter, Ruminobacter, and Succinimonas and reducing Saccharofermentans in CP17 yaks (p < 0.05). Untargeted metabolomics further indicated a marked shift in the ruminal metabolite profile. Compared with CON, CP17 yaks exhibited higher levels of calcium propionate, 2-nitrofuran, curvulalide, and 2,5-dihydroxybenzoic acid, but lower levels of 4-pyridoxic acid, L-carnitine, bitocholic acid, and taurodehydrocholic acid. Pathway enrichment analysis identified vitamin B6 metabolism as significantly enriched. Collectively, these findings suggest that moderate protein concentrate supplementation (CP17) may enhance lactation performance by modulating rumen microbiota and metabolism in lactating yaks.

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.

Yaks are important livestock in high-altitude regions, and their polled trait can effectively improve breeding and management efficiency. In this study, whole-genome resequencing combined with a GWAS was employed to identify a significantly associated region of approximately 273.6 kb on chromosome 1 (36,313,286-36,586,879 bp) in Xueduo yaks. This region contains 1001 significant single-nucleotide polymorphism (SNP) loci and is located within a long intergenic non-coding RNA (lincRNA) region. Candidate genes EPCIP, OLIG1 and PAXBP1 adjacent to this region were identified. Among these, the PAXBP1 gene plays a crucial role in neural crest development, suggesting that it may be a core gene regulating horn development in yaks. Further analysis of Ashdan yaks (a polled breed developed from Datong yaks) indicated that the two breeds share the same candidate genes and a subset of associated genetic variants for the polled trait, suggesting a degree of genetic conservation underlying this trait across yak breeds. This study provides a theoretical basis for polled yak breeding.

This study investigated the effects of starter feed supplementation on growth performance, immune-related parameters, intestinal microbiota, and metabolite profiles in preweaning yak calves. Twenty healthy 30-day-old male yak calves with similar body weight were randomly assigned to either a control group (A), receiving milk replacer and alfalfa hay, or a starter-supplemented group (AS), receiving milk replacer, alfalfa hay, and a concentrate-based starter feed. Growth traits, nutrient digestibility, serum immune indices, intestinal microbial communities, and metabolomic characteristics were evaluated. Compared with the A group, calves in the AS group exhibited greater total dry matter intake, final body weight, heart girth, cannon circumference, and apparent digestibility of calcium and phosphorus (p < 0.05). Average daily gain tended to increase but did not differ significantly between treatments (p > 0.05). Starter supplementation also increased serum concentrations of IgA, IL-6, TNF-α, M-CSF, and IFN-γ (p < 0.05). In contrast, jejunal TNF-α concentration was lower in the AS group than in the A group (p < 0.05). Microbial analysis demonstrated that starter supplementation modified intestinal bacterial community composition. In the jejunum, the relative abundances of Family_XIII_AD3011_group and Acetitomaculum were increased, whereas Bacteroidota and Bacteroides were enriched in the colon. Untargeted metabolomic analysis further revealed distinct metabolic profiles between groups, with differential metabolites mainly associated with amino acid metabolism, vitamin metabolism, and energy-related pathways. Overall, starter feed supplementation was associated with changes in nutrient utilization, immune-related indicators, intestinal microbial composition, and metabolic characteristics. These findings suggest that starter supplementation may facilitate dietary adaptation and support gastrointestinal function in preweaning yak calves.

The expansion of ruminant production has increased methane (CH4) emissions, highlighting the need for nutritional strategies that improve productivity while mitigating environmental impacts. Yaks, generally considered low CH4 producers, are increasingly raised under intensive winter-housed systems on the Qinghai–Xizang Plateau, highlighting the need to assess how dietary concentrate-to-forage (C:F) ratios affect both CH4 emissions and growth performance. This study investigated the effects of three dietary C:F ratios [L-C (48:52), M-C (60:40), H-C (72:28)] on growth performance, ruminal fermentation, microbial diversity (n = 6 per group) and CH4 emission (n = 3 per group) in winter-housed yaks. The results indicated that average daily gain (ADG) was significantly higher in M-C and H-C, while the feed-to-gain ratio (F/G) was significantly lower in M-C and H-C than in L-C (p < 0.05). Total CH4 production (g/day) did not differ among treatments (p > 0.05), while CH4 yield per unit body weight gain (CH4/BWG) was significantly reduced in M-C and H-C (p < 0.05). The protozoal count was significantly lower in H-C, and the proportions of isobutyrate and isovalerate were significantly higher in H-C and M-C compared with L-C (p < 0.05). 16S rRNA gene sequencing revealed that increasing the C:F ratio reduced the relative abundance of the archaeal genus Methanobrevibacter, while Thermogymnomonas exhibited a significant increase (p < 0.05). Collectively, these findings indicate that increasing the C:F ratio in winter-housed yaks improves growth efficiency and lowers CH4/kg BWG, with the M-C group showing the most favorable balance between productivity and environmental sustainability.

To investigate the intestinal development process of yak calves at different ages. Twenty-one healthy male yak calves from the same birth cohort, aged 60 ± 3 days and weighing approximately 40 kg, were selected for this study. A cross-sectional sampling design was applied to investigate age-dependent intestinal development. The calves were sampled at three developmental stages: approximately 3 months of age (BL, n = 7), 4 months of age (B, n = 7), and 5 months of age (AL, n = 7). These groups represented different developmental stages rather than dietary treatments. All groups were fed equal amounts of milk replacer and a basal diet, with concentrate provided before roughage. The experimental diet consisted of milk replacer, alfalfa hay (roughage), and starter feed (concentrate), with a concentrate-to-roughage ratio of 3:7. The adaptation period lasted 20 days, and the experimental durations were 30 days (BL group), 60 days (B group), and 90 days (AL group), respectively. At the end of each experimental period, five yak calves were randomly selected for slaughter sampling. Intestinal tissue morphology, microbial communities, and gene expression profiles were analyzed to investigate age-dependent intestinal development in yak calves. Using 16S rRNA sequencing and transcriptomic approaches, microbial alterations in the jejunum, ileum, cecum, and colon, as well as gene expression changes in the jejunum, were characterized at 3, 4, and 5 months of age. Differentially expressed genes were further analyzed by GO and KEGG enrichment analyses, and eight representative genes were validated using quantitative real-time PCR. The results demonstrated distinct developmental patterns among intestinal segments. The large intestine exhibited earlier functional maturation than the small intestine, with the colon showing relatively stable microbial and digestive characteristics from 3 months of age, whereas the cecum underwent continuous microbial succession associated with enhanced fiber-degrading potential. In contrast, the jejunal and ileal microbiota displayed dynamic age-related changes. Tax4Fun analysis indicated that the predicted microbial functional potential in the jejunum changed significantly during development, particularly in pathways associated with metabolism and biosynthesis. Transcriptomic analysis revealed that age-related changes in jejunal gene expression were mainly involved in epithelial development, immune regulation, and cellular differentiation. Among the identified differentially expressed genes, ROS1 and several immune-related genes may contribute to jejunal maturation and immune development. In conclusion, this study reveals coordinated morphological, microbial, and transcriptional changes during early intestinal development in yak calves. The integration of microbiome and transcriptome analyses provides new insights into the mechanisms underlying intestinal maturation and offers a theoretical basis for optimizing nutritional management during the pre-weaning and post-weaning periods.

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.

This study was conducted to explore the effects of dietary protein restriction on growth performance, nutrient utilization, gut microbiota, and microbial metabolites in finishing pigs, as well as to elucidate potential sex-associated differences between gilts and barrows. A total of 36 gilts and 36 barrows at 110 days of age were allocated to six groups in a 3 × 2 factorial arrangement consisting of three dietary protein levels and two sexes. Dietary crude protein levels were 17%, 15%, and 13% during phase I, and 15%, 13%, and 11% during phase II. The whole feeding trial lasted 51 days. Overall, lowering dietary protein levels altered the digestibilities of crude protein, ether extract, calcium and phosphorus (P < 0.01), and exerted sex-specific influences on serum total protein and nitric oxide concentrations (P < 0.05). Among gut microbiota, five genera responded to protein restriction (P < 0.05), eight showed sex differences (P < 0.05), and six exhibited sex-specific responses to dietary protein levels (P < 0.05). Dietary protein restriction reduced gut microbiota-derived ammonia nitrogen and six of eight biogenic amines (P < 0.05); four of these metabolites differed between sexes (P < 0.05), and four showed protein × sex interactions (P < 0.05). The nitrogen-related metabolites were positively correlated with specific microbiota only in gilts (P < 0.05). In conclusion, dietary protein restriction induced sex-specific alterations in gut microbiota and nitrogen-associated metabolites in finishing pigs, and such metabolic responses were exclusively linked to microbiota changes in gilts but not in barrows.

The objective of this study was to investigate the effects of supplemental starter feeding on the development of the ruminal epithelium in suckling yak calves using transcriptomic analysis. Twenty healthy one-month-old male yak calves with similar body weights were selected and randomly assigned to two groups. The pre-feeding adaptation period lasted 14 days, followed by a 120-day experimental feeding period. At the end of the trial, five calves from each group were slaughtered, and samples of abomasum tissue and ruminal contents were collected for subsequent analyses. The results demonstrated that early concentrate supplementation markedly increased the final body weight and ruminal NH3-N concentration of calves in the RAS group compared with the control (RA) group (p < 0.05). Similarly, dry matter intake and ruminal microbial protein (MCP) content were significantly higher in the RAS group (p < 0.05). In contrast, the concentration of acetic acid in ruminal fluid was significantly higher in the RA group, whereas valeric acid concentration was higher in the RAS group. Furthermore, ruminal TNF-α, TNF-γ, and IL-2 concentrations were significantly elevated in the RAS group (p < 0.05), suggesting enhanced ruminal immune function. Transcriptomic analysis revealed that both up- and down-regulated gene expression contributed to the morphological development and overall health of the ruminal epithelium. Up-regulated genes were enriched in pathways related to chemical carcinogenesis, cytochrome P450 metabolism, steroid hormone biosynthesis, retinol metabolism, ascorbate and aldarate metabolism, drug metabolism-cytochrome P450, pentose and glucuronate interconversions, ovarian steroidogenesis, and porphyrin and chlorophyll metabolism. Conversely, down-regulated genes were mainly associated with cytokine–cytokine receptor interactions, mineral absorption, arachidonic acid metabolism, and viral protein interactions with cytokine receptors. Overall, early supplementation with concentrate feed enhanced the expression of genes associated with ruminal epithelial development, improved immune responses, and promoted better growth performance in suckling yak calves.

Abstract The traditional grazing system of the Qinghai-Tibet Plateau faces challenges such as feed shortages, despite the abundance of pastures during the warm season. However, the impact of supplemental feeding on yak meat quality during this period still requires further investigation. A total of 30 male yaks (with similar genetic backgrounds, aged 2.5–3 years, weighing 94.56 ± 3.9 kg) were evenly and randomly assigned to two groups: the traditional grazing group (G) and the supplemental feeding group (SF). This study evaluated the effects of supplementation on yak meat quality and metabolic characteristics, aiming to identify effective dietary strategies to improve the physical and nutritional quality of yak meat. Non-targeted metabolomics (UHPLC-QE-MS) was used to analyze biomarkers of meat quality. Results revealed that the SF group exhibited superior meat quality, with a 39.6% reduction in shear strength, a 22.4% reduction in cooking loss, a 15% increase in PUFA/SFA ratios, and an 18% increase in essential amino acid content. Metabolomic profiling indicated distinct differences between the two groups, with the SF group demonstrating significant upregulation of beneficial metabolites (e.g., pyruvic acid, L-tyrosine, and eicosapentaenoic acid) and downregulation of harmful metabolites (e.g., sulfates). These changes improved protein turnover, lipid metabolism, and glycolytic activity, enhancing meat tenderness, flavor, and nutritional value. This study provides novel insights into the metabolic mechanisms underlying feed-induced quality changes, highlighting the practical value of supplemental feeding in overcoming the limitations of traditional grazing systems and reducing ecological pressure on grasslands.

Both yaks and Simmental are dual-purpose highland varieties, but the mechanisms behind the differences in their milk production are not yet fully understood. This study compared milk composition, rumen microbial communities, and metabolomes across a range of lactation stages for both breeds. Yak milk yields were lower and it had higher levels of fat, protein, long-chain and polyunsaturated fatty acids, key amino acids, and essential minerals than Simmental milk. The microbial community of yak rumen exhibited unique characteristics, with the Family_XIII_AD3011_group persistently enriched and positively correlated with rumen fermentation parameters and milk quality, and the content of glutamate and glutamine in yak rumen was higher than in Simmental and positively correlated with milk quality. Therefore, key microorganisms and metabolites in yak rumen are crucial factors for high-yield dairy production, providing new insights to enhance milk production in ruminant dairy cattle.

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.

Understanding the nutritional protein requirements of yak calves is the basis of precise feed formulation. Regulating feed protein can reduce environmental effects, which is particularly crucial for the rearing and management of yak calves. In this study, we used a combination of comparative slaughter, feeding, and digestibility trials to determine the net protein requirements of suckling yak calves. Thirty-five yak male calves with similar weights at 60 d of age were divided into 5 groups: early slaughter (ES) and mid term slaughter (MtS); and ad libitum feeding (AL; also used as the late slaughter group), feeding at 70% of AL rate (R70), and feeding at 40% of AL rate (R40). The ES, MtS, and AL groups were used for comparative slaughter trials, whereas the AL, R70, and R40 groups were used for ad libitum feeding experiments. The results indicated that at different feeding levels, low feeding levels were not conducive to calf growth. For yak calves with BW of ∼40 to 90 kg, the nitrogen digestibility ranged from 49.36% to 59.32%, and the nitrogen retention rate ranged from 36.59% to 48.97%. The net protein requirement for yak calf maintenance is 2.90 g/kgW0.75 × d-1. The equation for the net protein requirement for yak calf growth is net protein requirement for growth (kg) = 0.0540 × EBW0.0833 (kg). Muscle metabolomics results indicated that the protein content in the muscle tissue did not increase with feeding level or BW. With an increase in the feeding level, the nutritional protein level provided by the diet increases, which regulates changes in steroid hormone biosynthesis, ovarian steroidogenesis, cortisol synthesis and secretion, and carbon metabolism, promoting an increase in hormone-like metabolites in the muscle tissue. These data we obtained provide guidance for the efficient rearing of yak calves and provide basic data for further research on the nutritional requirements.

Soybean dregs produced by the soybean processing industry were agricultural waste with significant treatment costs. To explore economical and efficient treatment methods, this study used pyrolysis technology to convert soybean dregs into biochar with resource utilization value. Soybean dregs biochar was applied to concrete to research the impacts of different incorporation methods and dosages on concrete properties. The physical properties of soybean dregs biochar after pyrolysis at various temperatures were characterized using BrunauerEmmett-Teller (BET), X-ray diffraction (XRD), Fourier transforms infrared spectrometer (FTIR), and Scanning electron microscope (SEM). The influences of soybean dregs biochar on the mechanical properties and microstructure of concrete were analyzed. The results revealed that soybean dregs exhibited a rich pore structure and a large specific surface area after pyrolysis at high temperatures, which effectively filled the internal pores of concrete and enhanced the compactness of the paste structure. Regardless of the incorporation method, the mechanical properties improved with a biochar content of 2 %-4 % compared to the control group. However, as the content increased further, the mechanical properties of concrete began to exhibit a decreasing trend. Furthermore, replacing 3 % of sand with biochar in concrete demonstrated the greatest improvement in mechanical properties, surpassing the effects of replacing cement or acting as a filler. This substitution resulted in a 12.32 % increase in compressive strength and a 16.42 % increase in tensile strength.

This study examined the effects of supplemental feeding on the weight and meat quality of grazing yaks on the Tibetan Plateau. Thirty male yaks (2.5-3 years old) with similar characteristics were randomly assigned to two groups: the traditional grazing group (G) and the supplemental feeding group (SF). The SF group received 1.5 kg of supplemental feed daily. After 120 days, slaughter performance and meat quality were compared. The results showed that the SF group had significantly higher live weight (137.2 kg vs 175.3 kg, P < 0.001) , carcass weight (63.6 kg vs 89.5 kg, P < 0.001) , and net meat yield (34.0 % vs 40.2 %, P < 0.001) compared to the G group. Moreover, the SF group exhibited lower cooking loss, drip loss, and shear force, indicating improved meat quality (P < 0.05) . Amino acid analysis revealed that the SF group had higher total amino acids (TAA, 13.25 g/100 g vs 14.14 g/100 g, P < 0.001) and essential amino acids (EAA, 5.19 g/100 g vs 6.03 g/100 g, P > 0.05) content, the ratios of EAA/TAA and EAA/NEAA increased by 4 % and 10 %, respectively. Additionally, compared to the G group, the SF group had lower saturated fatty acids (SFA, 43.25 vs 39.22, P < 0.001) and higher polyunsaturated fatty acids (PUFA 11.49 % vs 13.74 %, P < 0.001), particularly omega-3 fatty acids (2.81 % vs 5.31 %, P < 0.001), with a lower n-6/n-3 (2.88 % vs 1.44, P < 0.001) ratio. Principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) confirmed the effects of supplementation on amino acids and fatty acids. In conclusion, supplemental feeding significantly improved yak growth and meat quality, particularly in amino acid and fatty acid composition, providing valuable insights for grazing management on the Tibetan Plateau.

The yak industry constitutes a pivotal segment of livestock development across the Qinghai–Tibetan Plateau and adjacent pastoral regions. Existing studies have shown that supplemental feeding for grazing yaks significantly improves meat quality and growth performance, but its effect on enteric methane (CH4) emission from yaks has never been reported, so the present experiment aimed to investigate the effect of supplemental feeding of grazing yaks on CH4 emissions in three different periods of the warm season. Thirty male yaks were randomly assigned to two groups, with 15 yaks per group, The groups were designated as the grazing group (GR), with traditional grazing methods and with an initial body weight of 94.56 ± 3.9 kg, and the supplemental feeding group (GRS) with an initial body weight of 95.01 ± 4.1 kg, which received 1500 g/d of supplemental feed for 120 days. The methane emissions of the two groups were measured at the late regreening period (LRP), the greening-grass period (GGP), and the browning period (BRP) using the SF6 tracer method. The results showed that GRS increased (p < 0.01) the total DMI during warm season but decreased (p < 0.01) the forage intake at the LRP and GGP, resulting in a significantly reduced methane yield per kg of BW gain and per kg of DMD in warm-season grazing yaks (p < 0.01), a significantly reduced methane production per kg of DMI and methane energy to gross energy ratio in grazing yaks during the GGP (p < 0.05), and a similarly significantly decrease in methane production per kg of DMI and methane energy to gross energy ratio in grazing yaks during the BRP (p < 0.01). In conclusion, supplemental nutrition for grazing yaks during the warm season in alpine grasslands significantly enhances growth performance, reduces methane emissions, and improves dietary energy utilization efficiency.

The objective of this study was to evaluate the effect of reducing dietary protein levels on barrows during the late fattening period. Fifty Duroc × Landrace × Yorkshire barrows with body weights averaging 76.30 ± 6.57 kg were randomly divided into normal protein (NP) and low protein (LP) groups. The feeding experiment lasted for 55 days. Dietary crude protein (CP) contents were 13.5% in the NP and 11.5% in the LP during days 1–28 and 12.5% and 10.5% during days 29–55, respectively. Results showed that compared with the NP, the LP increased the average daily gain (ADG) of barrows during days 29–55 (p < 0.05); enhanced the digestibility of nutrients, including dry matter (p < 0.01), CP (p < 0.01), calcium (p < 0.01), and phosphorus (p < 0.05); and decreased serum blood urea nitrogen (p < 0.01), total cholesterol (p < 0.05), and free fatty acids (p < 0.05). Lowering dietary CP increased fecal Lactobacillus abundance (p < 0.01); reduced concentrations of fecal ammonia nitrogen, histamine, butylamine, putrescine, 1,2-heptaenediamine, p-cresol, and indole-3-acetic acid (p < 0.01); and had no negative effects on meat quality (p > 0.05). These results suggested that reducing dietary CP by 2% could improve growth, promote efficient nutrient utilization, increase beneficial fecal microbiota abundance, and reduce the emission of fecal malodorous compounds in late-fattening barrows.

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.

OBJECTIVE:This study aimed to elucidate the mechanisms underlying milk composition divergence between naks (female yaks) and Simmental cows (S-cows) by integrating longitudinal multi-omics analyses of gut microbiota and metabolomes. METHODS:We determined the gut microbiota and metabolites of both species over a 54-day period (day 26 to 80 of lactation) of ten naks and ten S-cows. Gut microbiota dynamics were assessed via 16S rRNA sequencing, while serum and fecal metabolomes were profiled using ultra-high performance liquid chromatography-tandem mass spectrometry. Statistical analyses included Wilcoxon rank-sum tests, linear discriminant analysis effect size (linear discriminant analysis>2, p<0.05), and Spearman correlations (r>0.70). RESULTS:Milk yield was lesser (0.53-0.91 vs. 2.07-3.88 kg/d) but concentrations of fat (5.63%-6.30% vs. 3.30%-3.74%), protein (5.66%-6.30% vs. 3.39%-3.74%), and conjugated linoleic acid (CLA) (1.74%-2.35% vs. 1.40%-1.75%) were greater (p<0.001) in nak than Scow milk. Species-specific microbial signatures emerged. In naks, the g-Family-XIIIAD3011-group and g-norank-Ruminococcaceae were correlated with bile acid metabolism and CLA synthesis via 13-hydroxyoctadecadienoic acid transport. Additionally, the naks gut had a greater concentration of 13-hydroxyoctadecadienoic acid, a precursor of CLA, which may be transported to mammary cells via phosphatidylcholine and converted to CLA under the catalysis of fatty acid desaturase2. S-cows harbored g-Succinivibrio and g-Eubacterium-ruminantium-group, which are linked to galactose utilization and mTORmediated amino acid allocation. Metabolomics revealed naks-enriched steroid biosynthesis and taurine pathways (false discovery rate<0.05), while S-cows exhibited a lactating network associated with greater milk yield. CONCLUSION:Host-specific gut microbiota mediated nutrient allocation trade-offs. Naks optimized lipid-rich milk through bile acid and CLA metabolic networks, whereas S-cows enhanced yield via microbial-galactose synergies. This research underscores the pivotal role of the gut microbiome in mediating milk composition and suggests that microbiome manipulation could be a promising strategy to enhance milk quality in ruminants.