Effects of dietary rumen-protected betaine supplementation on the antioxidant status of lambs

Abstract

As a methyl group donor and organic osmolyte, betaine has been widely used in livestock production, but the antioxidant defence properties of betaine in lambs have not been determined. The objective of this study was to investigate the effect of dietary betaine and rumen-protected betaine (RPB) supplementation on the growth performance and antioxidant status of lambs. A total of sixty male Hu sheep (approximately 30 kg body weight) were randomly assigned into five treatments and fed basal diets (Con group), basal diets with 2.2 g/d betaine supplementation (B-2.2 group), basal diets with 2 g/d RPB supplementation (RPB-2 group), basal diets with 4 g/d RPB supplementation (RPB-4 group), and basal diets with 6 g/d RPB supplementation (RPB-6 group) for 70 d. After the feeding experiment, the antioxidant indexes in the serum, Longissimus dorsi (LD) and liver were measured. Dietary supplementation of RPB increased the average daily gain (ADG) and decreased the feed-to-gain ratio (F/G) of lambs (P < 0.05), whereas treatments had no significant effect on the average daily feed intake (ADFI). The activity of glutathione peroxidase (GSH-Px) in the serum was increased in the RPB-2 group (P < 0.05); the activities of superoxide dismutase (SOD) and catalase (CAT) in the LD were increased in the RPB-4 group (P < 0.05);and the total antioxidant capacity (T-AOC) and the activities of SOD, CAT and GSH-Px in the liver were all elevated in the B-2.2 group (P < 0.05). The concentrations of malondialdehyde (MDA) in the serum, LD and liver decreased in the RPB-2 group (P < 0.05). In addition, the mRNA expression levels of SOD, CAT, nuclear-related factor 2 (Nrf2), Kelch-like ECH-associated protein1 (Keap1) and peroxiredoxin 3 (PRDX3) in the LD were increased in the B-2.2 group (P < 0.05), and the mRNA expression levels of CAT, Keap1 and PRDX3 in the liver were increased in the RPB-2 group (P < 0.05).Considering both growth performance and antioxidant status, 2.0 g/d RPB is recommended as a supplement for lambs.