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

## TL;DR

This study shows that adding 5-HTP and melatonin to Hu sheep diets improves meat quality and shelf life by boosting antioxidants and amino acids.

## Contribution

The study introduces rumen-protected 5-HTP as an effective supplement for enhancing mutton quality and shelf life.

## Key findings

- RPT 5-HTP and MT reduced drip loss and malondialdehyde content in mutton.
- Both supplements increased melatonin levels and catalase activity in sheep muscle.
- Shelf life of mutton was extended by 22.08 h with RPT 5-HTP and 45.36 h with MT.

## Abstract

The antioxidant capacity of meat products is inherently linked to their shelf life and quality attributes. Melatonin (MT) and 5-hydroxytryptophan (5-HTP) are well known for their strong antioxidant properties. Direct MT supplementation may potentially inhibit endogenous MT synthesis, thereby reducing systemic MT levels in animals. Consequently, this study investigates the effects of rumen-protected 5-hydroxytryptophan (RPT 5-HTP) and melatonin (MT) supplementation on mutton quality and shelf life. The results show that all experimental groups reduced the drip loss of mutton. The RTP 5-HTP group reduced it by 18.58%, and the MT group reduced it by 33.87%. Additionally, both groups prolonged the shelf life of mutton, with the RTP 5-HTP group extending it by 22.08 h and the MT group by 45.36 h.

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 longissimus dorsi muscle of Hu sheep (p < 0.05). Compared to the control group, the malondialdehyde (MDA) content in the longissimus dorsi muscle was significantly reduced in the MT and RPT 5-HTP groups (p < 0.05), while catalase (CAT) activity was significantly increased in the MT group (p < 0.05). The drip loss of the longissimus dorsi muscle in Hu sheep was significantly reduced after supplementation with RPT 5-HTP and MT (p < 0.05). Essential amino acids, non-essential amino acids, sweet-tasting amino acids, and umami amino acids in the longissimus dorsi muscle of supplemented groups were significantly elevated (p < 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.