Abstract
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 were randomly assigned to four treatments (T1, T2, T3 and T4) with protein levels of 15.93%, 14.92%, 13.56%, and 11.36% for each treatment. Protein level of T2, T3, and T4 was 104%, 108%, and 112% of T1, respectively. Growth performances were studied at four weitht stages (25–50, 50–75, 75–100, 100–125 kg).Results: Throughout the entire growth period, T2 shortened the production cycle and exhibited the lowest feed/gain ratio. It also significantly improved the meat quality characteristics of the longissimus thoracis muscle (pIGF-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 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.