Abstract

Mutton and lamb sales continue to grow globally at a rate of 5% per year. However, sheep farming struggles with low profit margins due to high feed costs and modest carcass yields. Selecting those sheep expected to convert feed efficiently and have high carcass merit, as early as possible in their life cycle, could significantly improve the profitability of sheep farming. Unfortunately, direct measurement of feed conversion efficiency (via residual feed intake [RFI]) and carcass merit is a labor-intensive and expensive procedure. Thus, indirect, marker-assisted evaluation of these traits has been explored as a means of reducing the cost of its direct measurement. One promising and potentially inexpensive route to discover biomarkers of RFI and/or carcass merit is metabolomics. Using quantitative metabolomics, we profiled the blood serum metabolome (i.e., the sum of all measurable metabolites) associated with sheep RFI and carcass merit and identified candidate biomarkers of these traits. The study included 165 crossbred ram-lambs that underwent direct measurement of feed consumption to determine their RFI classification (i.e., low vs. high) using the GrowSafe System over a period 40 d. Carcass merit was evaluated after slaughter using standardized methods. Prior to being sent to slaughter, one blood sample was drawn from each animal, and serum prepared and frozen at −80 °C to limit metabolite degradation. A subset of the serum samples was selected based on divergent RFI and carcass quality for further metabolomic analyses. The analyses were conducted using three analytical methods (nuclear magnetic resonance spectroscopy, liquid chromatography mass spectrometry, and inductively coupled mass spectrometry), which permitted the identification and quantification of 161 unique metabolites. Biomarker analyses identified three significant (P < 0.05) candidate biomarkers of sheep RFI (AUC = 0.80), seven candidate biomarkers of carcass yield grade (AUC = 0.77), and one candidate biomarker of carcass muscle-to-bone ratio (AUC = 0.74). The identified biomarkers appear to have roles in regulating energy metabolism and protein synthesis. These results suggest that serum metabolites could be used to categorize and predict sheep for their RFI and carcass merit. Further validation using a larger (3×) and more diverse cohort of sheep is required to confirm these findings.

中文翻译：

---

绵羊残留采食量和胴体价值的候选血清代谢物生物标志物。

摘要

羊肉和羊肉的全球销售额继续以每年 5% 的速度增长。然而，由于饲料成本高和胴体产量适中，养羊业的利润率很低。在生命周期中尽早选择那些有望有效转化饲料并具有高胴体价值的绵羊，可以显着提高绵羊养殖的盈利能力。不幸的是，直接测量饲料转化效率（通过剩余饲料摄入量 [RFI]）和胴体品质是一项劳动密集型且成本高昂的程序。因此，已经探索了对这些性状的间接、标记辅助评估作为降低其直接测量成本的一种手段。发现 RFI 和/或胴体价值的生物标志物的一种有前景且可能廉价的途径是代谢组学。使用定量代谢组学，我们分析了与绵羊 RFI 和胴体价值相关的血清代谢组（即所有可测量代谢物的总和），并确定了这些性状的候选生物标志物。该研究包括 165 只杂交公羊羔，它们在 40 天的时间内使用 GrowSafe 系统直接测量饲料消耗以确定它们的 RFI 分类（即低与高）。屠宰后使用标准化方法评估胴体品质。在被送往屠宰场之前，每只动物抽取一份血样，制备血清并在 -80 °C 下冷冻以限制代谢物降解。根据不同的 RFI 和胴体质量选择血清样品的子集，以进行进一步的代谢组学分析。使用三种分析方法（核磁共振波谱、液相色谱质谱法和电感耦合质谱法），可对 161 种独特的代谢物进行鉴定和定量。生物标志物分析确定了三个重要的（P < 0.05) 绵羊 RFI 的候选生物标志物 (AUC = 0.80)、7 个胴体产量等级的候选生物标志物 (AUC = 0.77) 和 1 个胴体肌肉与骨骼比率的候选生物标志物 (AUC = 0.74)。鉴定出的生物标志物似乎在调节能量代谢和蛋白质合成方面发挥作用。这些结果表明，血清代谢物可用于对绵羊的 RFI 和胴体价值进行分类和预测。需要使用更大（3×）和更多样化的绵羊群进行进一步验证以确认这些发现。