Effects of Laminaria japonica Polysaccharide Supplementation in Aged Corn-Based Diets on Growth Performance, Nutrient Digestibility, Rumen Fermentation, and Muscle Antioxidant Status of Hu Sheep

Long-term storage can impair the feeding value of corn. This study evaluated whether dietary Laminaria japonica polysaccharide (LJP) could alleviate the adverse effects of aged corn in Hu sheep. Twenty-one male Hu sheep (39.05 ± 3.55 kg) were assigned to a normal-corn diet (NC), an aged-corn diet (AC), or the AC diet supplemented with 0.5% LJP (AC+LJP; n = 7) for 70 d, including a 14-d adaptation period. Compared with NC, AC reduced average daily gain, gain-to-feed ratio, the apparent digestibility of crude protein, neutral detergent fiber and acid detergent fiber, ruminal total volatile fatty acids, acetate and butyrate, and muscle glutathione peroxidase activity. LJP supplementation restored average daily gain, gain-to-feed ratio, and crude protein and neutral detergent fiber digestibility to levels comparable with NC. It also increased ruminal ammonia nitrogen, microbial crude protein, total volatile fatty acids, acetate, butyrate, and isobutyrate relative to AC, while reducing muscle malondialdehyde concentration and increasing total antioxidant capacity. Dietary treatment had little effect on carcass traits, most meat-quality variables, or overall rumen bacterial diversity. In conclusion, supplementation with 0.5% LJP partially alleviated the decline in nutrient utilization and rumen fermentation associated with aged corn and improved muscle antioxidant status. These findings support the potential use of LJP as a functional feed additive to improve the utilization of aged-corn-based diets in sheep.