Effects of Rumen-Protected 5-Hydroxytryptophan and Melatonin Supplementation on Antioxidant Capacity, Meat Quality, and Shelf Life of Hu Sheep

This study aimed to investigate the impact of dietary supplementation with RPT 5-HTP and MT on the meat quality and shelf life of Hu sheep. Thirty 4-month-old male Hu sheep with similar body weights (30.84 ± 1.16 kg) were randomly allocated into three groups (one sheep per replicate): a control group (fed a basal diet), a RPT 5-HTP group (basal diet + 222 mg/kg BW RPT 5-HTP), and an MT group (basal diet + 4 mg/d MT). The experimental period lasted 37 days, including a 7-day adaptation phase and a 30-day formal trial. The results show that supplementation with RPT 5-HTP and MT significantly increased MT levels in the <i>longissimus dorsi</i> muscle of Hu sheep (<i>p</i> < 0.05). Compared to the control group, the malondialdehyde (MDA) content in the <i>longissimus dorsi</i> muscle was significantly reduced in the MT and RPT 5-HTP groups (<i>p</i> < 0.05), while catalase (CAT) activity was significantly increased in the MT group (<i>p</i> < 0.05). The drip loss of the <i>longissimus dorsi</i> muscle in Hu sheep was significantly reduced after supplementation with RPT 5-HTP and MT (<i>p</i> < 0.05). Essential amino acids, non-essential amino acids, sweet-tasting amino acids, and umami amino acids in the <i>longissimus dorsi</i> muscle of supplemented groups were significantly elevated (<i>p</i> < 0.05). Both 5-HTP and MT extended the shelf life of mutton; compared to the control, the shelf life was prolonged by 22.08 h in the RPT 5-HTP group and by 45.36 h in the MT group. In conclusion, it was found that 5-HTP and MT had a certain effect on improving the antioxidant capacity of Hu sheep, thereby enhancing the meat quality of mutton and extending its shelf life, with the amino acid content in mutton being increased to improve its umami and flavor.