Growth Performance and Meat Quality Evaluations in Three-Way Cross Cattle Developed for the Tibetan Plateau and their Molecular Understanding by Integrative Omics Analysis

Despite of favorable
characteristics of high protein, low fat,
and free-pollution, yak meat has intrinsically poor performance in
tenderness and color, which is ever challenging yak sector. To this
end, a three-way cross system was first developed for high quality
beef of the Tibetan Plateau using Angus cattle (Bos taurus) as terminal sire to mate with 1/2 yak (F1) generated from♂Qaidam
cattle (Bos taurus) × ♀yak (Bos
grunniens). The withers height, chest girth, and body weight
of 1/4 yak (F2) were all great higher than that of yak and 1/2 yak
(P < 0.01), especially at later period, suggesting
the faster growth rate of 1/4 yak. Also the dressing percentage was
much better in 1/4 yak (P < 0.01). Tenderness
and meat color were both significantly improved in 1/4 yak with some
unpleasant sacrifice of PUFAs, such as EPA and DHA, and meat protein,
given the significantly lower shear force and higher L* (P < 0.01). A total of 769 genes, including SREBF1, GHR, and FASN, the widely recognized
causal genes of meat quality, were identified from 11947 differently
expressed genes by the data integration of transcriptome, GWAS and
QTL. These genes were significantly enriched for important pathway
and GO terms, such as insulin signaling pathway, fatty acid biosynthesis,
calcium signaling pathway, metabolic pathway, and cellular response
to stress (P < 0.01). And 12 promising candidates
were exemplified with annotation of H3K4me3 data from divergent meat
quality, such as OSTF1, NRAS1, and KCNJ11. Interestingly, 75 high-altitude adaptive candidate
genes were also detected in the list. This study is a first step toward
high quality beef of the Tibetan Plateau and provides useful information
for their molecular understanding.

尽管牦牛肉具备高蛋白、低脂肪、无污染的优良特性，但其内在的嫩度与色泽表现欠佳，长期以来都是牦牛产业面临的核心难题。为此，本研究针对青藏高原优质肉牛培育，首次构建了三元杂交体系：以安格斯牛（Bos taurus）为终端父本，与由♂柴达木牛（Bos taurus）×♀牦牛（Bos grunniens）杂交获得的1/2牦牛血统F1代个体进行配种。结果显示，1/4牦牛血统F2代个体的体高、胸围与体重均极显著高于纯繁牦牛及1/2牦牛血统F1代（P < 0.01），且该优势在生长后期尤为明显，表明1/4牦牛血统个体的生长速度更快；同时，其屠宰率也极显著优于纯繁牦牛与F1代（P < 0.01）。在肉品质方面，1/4牦牛血统个体的嫩度与肉色均得到显著改善，但同时伴随多不饱和脂肪酸（PUFAs，如二十碳五烯酸EPA、二十二碳六烯酸DHA）及肌肉蛋白质含量的小幅损失，具体表现为剪切力极显著降低、肉色亮度值L*极显著升高（P < 0.01）。通过整合转录组、全基因组关联分析（GWAS）与数量性状位点（QTL）数据，从11947个差异表达基因中筛选得到769个候选基因，其中包括SREBF1、GHR与FASN等已被广泛证实的肉质性状因果基因。上述候选基因显著富集于多条重要通路及基因本体（GO）术语，包括胰岛素信号通路、脂肪酸生物合成通路、钙信号通路、代谢通路以及细胞应激反应等（P < 0.01）。结合不同肉质性状个体的H3K4me3修饰数据进行注释，最终筛选出12个极具研究价值的候选基因，例如OSTF1、NRAS1与KCNJ11。值得注意的是，该候选基因列表中还包含75个高原适应性候选基因。本研究为青藏高原优质肉牛培育迈出了关键第一步，同时为相关分子机制解析提供了重要参考依据。