Objective: Appropriately increasing dietary protein levels during winter production can improve meat quality and enhance nutritional value. Here, we examined the effects of dietary protein levels under low-temperature conditions (14°C) on growth performance, meat quality, and protein synthesis pathways in growing-finishing pigs. Methods: Forty-eight pigs randomly assigned to 4 treatments (T1, T2, T3, T4). Four weight stages (25-50, 50-75, 75-100, 100-125 kg) were set, with T1 protein levels at 15.93%, 14.92%, 13.56%, 11.36% per stage, and T2/T3/T4 at 104%/108%/112% of T1 respectively. Results: T2 shortened the production cycle and exhibited the lowest feed/gain ratio throughout the entire growth period. It also significantly improved the meat quality characteristics of the longissimus thoracis muscle (p<0.05), as evidenced by reduced drip loss and cooking loss, alongside increased protein and amino acid content. Additionally, T2 and T4 upregulated IGF-1 and SLC38A2 gene expression while elevating p-mTOR, p-S6K1, and p-4E-BP1 protein levels to enhance protein synthesis. Although T4 enhanced meat nutritional value, it resulted in reduced early growth performance. However, upregulation of MuRF1 gene expression in T3 indicated accelerated protein degradation processes. Conclusion: In this study, increasing dietary protein levels to 104% under low winter temperatures shortened the swine production cycle and improved meat quality and nutritional value. This regulatory effect may be associated with the activation of the mTOR signaling pathway.
Xie et al. (Mon,) studied this question.