There are limited reports about the effect of different heat treatments on the quality and flavor of Black Tibetan sheep meat. The current study examined the effect of pan-frying, deep-frying, baking, and boiling treatment on the quality of Black Tibetan sheep meat; the amino acid, fatty acid, and volatile flavor compounds (VFCs) were investigated by a texture analyzer, ultra-high-performance liquid chromatography (UHPLC), gas chromatography (GC), and headspace-gas chromatography-ion mobility (HS-GC-IMS). The key VFCs were identified through orthogonal partial least squares discrimination analysis (OPLS-DA), and variable importance projection (VIP) values. In addition, Pearson’s correlations between meat quality parameters and key VFCs were examined. The sensory scores, including texture, color, and appearance, of baked and pan-fried meat were higher than those of deep-fried and boiled meat. The protein (40.47%) and amino acid (62.93 µmol/g) contents were the highest in pan-fried meat (p < 0.05). Additionally, it contained the highest amounts of monounsaturated and polyunsaturated fatty acids, such as oleic, linoleic, and α-linolenic acids (p < 0.05). Meanwhile, pan-fried and deep-fried meat had higher amounts of VFCs than baked meat. The OPLS-DA similarity and fingerprinting analyses revealed significant differences between the three heat treatment methods. Aldehydes were the key aroma compounds in pan-fried meat. Importantly, 3-methylbutyraldehyde and 2-heptanone contents were positively correlated with eicosenoic, oleic, isooleic, linoleic, α-Linolenic, and eicosadiene acids (p < 0.05). To sum up, pan-fried Black Tibetan sheep meat had the best edible, nutritional, and flavor quality.

For its role in the mediation of myoblast proliferation, fibroblast growth factor receptor 1 (FGFR1) was considered a functional candidate gene for growth performance in Tibetan sheep. Via the polymerase chain reaction-restriction fragment length polymorphism (PCR-PFLP) approach, four single nucleotide polymorphisms (SNPs) including g.14752C > T (intron 1), g.45361A > G (intron 7), g.49400A > G (3’UTR region) and g.49587A > T (3’UTR region), were identified in 422 ewes. The association analysis demonstrated that individuals carrying the AA genotype of g.49400A > G had significantly greater withers height, length than those with GG genotype (p < 0.05). Individuals with genotype AA of g.49587A > T had significantly greater weight and chest circumference than those with genotype TT (p < 0.01). Additionally, the individuals with Hap1/1 diplotypes (CAAA-CAAA) were highly significantly associated with weight and chest circumference than Hap1/2 diplotypes (CAAA-CAAT) (p < 0.05). The quantitative real-time polymerase chain reaction (qPCR) analysis revealed that the FGFR1 was detectable expressed in muscle tissues within three different age stage. Remarkably higher mRNA expression was detected at fetal lamb stage as compared with adult ewes (p < 0.01). The outcome of this research confirmed that both g.49400A > G and g.49587A > T of FGFR1 were involved in growth-related traits, which may be considered to be genetic markers for improving the growth traits of Tibetan sheep.

Previous research studies confirmed that both resveratrol (RES) and β-hydroxy-β-methyl butyric acid (HMB) improved growth performance by altering intestinal microbiota. However, the mechanism underlying of RES and HMB on intestinal function remains unclear in ruminant. In this study, supplements of RES and HMB alone or in combination were evaluated as promoters of antioxidant capacity, immune response and barrier function, and modulators of the microbiota and metabolite profiles in the jejunum of Tibetan sheep. A total of 120 two-month-old Tibetan rams were randomly divided into four treatments (n = 30 per treatment), which were supplemented with a basal diet with 1.5 g RES/d (RES group), 1.25 g HMB/d (HMB group), 1.5 g RES/d plus 1.25 g HMB/d (RES-HMB group), and without additions (Control group). The results showed that RES and HMB improved the antioxidant capacity (CAT, GSH-Px, SOD, and T-AOC), immunity (IgA, IgG, and IgM), and digestive enzyme activity (α-amylase, lipase, and chymotrypsin) of the experimental lambs (p < 0.05). Additionally, jejunal morphology including villus width, villus height, and muscle layer thickness exhibited a significant difference when rams were fed diets supplemented with RES and HMB (p < 0.05). Furthermore, the determination of fermentation parameters showed that the butyrate concentration in the RES-HMB group was greater than those in the C and RES groups (p < 0.05). When compared to the C group, barrier-related gene expression (MUC-2, ZO-1, and IL-10) was significantly increased in the RES-HMB group (p < 0.05). Dietary RES and (or) HMB supplementation significantly increased the abundance of Methanobrevibacter, Actinobacteriota and Bacillus (p < 0.05). The abundance of differential bacteria was positively associated with butyrate concentration (p < 0.05). Metabolome analysis revealed that alpha ketoglutarate, succinic semialdehyde, and diacetyl as well as butanoate metabolism pathways connected to the improvements in butyrate concentration by RES and (or) HMB supplementation. Collectively, our results suggested that RES and (or) HMB supplementation improved butyrate concentration via regulating the microbial community (Methanobrevibacter, Actinobacteriota and Bacillus) and metabolism (alpha ketoglutarate, succinic semialdehyde, and diacetyl), thus contributing to jejunal morphology, antioxidant capacity, immune response, digestive enzyme activity, and barrier function.

Silent information regulator 2 (SIRT2) is a member of the sirtuin family of class III NAD (nicotinamide adenine dinucleotide)-dependent protein deacetylases and may regulate senescence, metabolism and apoptosis. The aims of this study were to investigate whether the SIRT2 gene could be used as a candidate gene in the breeding of Qinchuan cattle. Real-time polymerase chain reaction (RT-PCR) results showed that among all types of tissue that were analyzed, the highest mRNA expression levels of the gene were found in subcutaneous fat. DNA sequencing of 468 individual Qinchuan cattle identified two novel, single nucleotide polymorphisms (g.19501 C > T and g.19518 C > T) in the 3' untranslated region (3'UTR) of the SIRT2 gene. The frequencies of SNP g.19501 C > T and g.19518 C > T were in Hardy-Weinberg disequilibrium in all the samples (chi-square test, χ² < χ_0.05²). An association analysis showed that the two loci were significantly correlated with some body size traits and the H₂H₂ (-CT-CT-) diplotypes performed better than other combinations. These results indicated that the variations in the SIRT2 gene and their corresponding genotypes may be considered as molecular markers for economic traits in cattle breeding.

The dietary crude protein level could affect ruminal fermentation parameters and the microflora of ruminants. The present study’s aim was to investigate the effects of different protein level diets on ruminal morphology, fermentation parameters, digestive enzyme activity, microflora and metabolites of Tibetan sheep. Ninety weaned lambs (initial weight of 15.40 ± 0.81 kg, 2 months old) were selected and randomly divided into three groups (six pens/treatment, five rams/pen). Dietary treatments were formulated with 13.03% (high protein, HP), 11.58% (moderate protein, MP) and 10.20% (low protein, LP), respectively. Compared with LP, both papillae length and papillae width were significantly promoted in HP and MP (p < 0.05). The concentrations of ammonia nitrogen, total VFAs, propionic acids and butyric acids in HP were significantly increased compared to those in MP and LP (p < 0.05). The activities of protease and α-amylase in HP were significantly greater than those of LP (p < 0.05). For the ruminal microbial community, higher proportions of phylum Prevotella 1 and Succiniclasticum and genus Rikenellaceae RC9 gut group and Ruminococcus 1 were observed in HP (p < 0.05). A total of 60 differential metabolites (DMs) (28 up, 32 down) between HP and MP; 73 DMs (55 up, 18 down) between HP and LP; and 65 DMs (49 up, 16 down) between MP and LP were identified. Furthermore, four pathways of the biosynthesis of unsaturated fatty acids, tryptophan metabolism, bile secretion and ABC transporters were significantly different (p < 0.05). The abundance of phylum Prevotella 1 was negatively associated with stearic acid and palmitic acid but positively associated with the taurine. The abundance of genus Ruminococcus 1 was negatively associated with stearic acid, oleic acid, erucic acid, Indole-3-acetamide and palmitic acid but positively associated with 6-hydroxymelatonin. In conclusion, a 13.03% CP level improved ruminal morphology, fermentation parameters and digestive enzyme activities through modulating the microbial community and regulating metabolism in Tibetan sheep.