Effect of energy intake and L-carnitine on fattening performance, carcass traits, meat quality, blood metabolites, and gene expression of lamb

Abstract

• LPL and FASN were increased in adipose tissues with energy intake increasing, while LIPE and SCD were decreased. • L-carnitine supplementation did not improve growth performance and mutton quality. • L-carnitine could be used as a potential feed additive to inhibit fat accumulation in sheep. A 70-day feeding experiment was conducted on Tan sheep ( Ovis ) to study the effects of energy intake (low, medium, or high) and/or L -carnitine supplementation (0 or 200 ppm) on fattening performance, carcass traits, meat quality, and expression of lipid metabolism associated genes. A 2 × 3 factorial arrangement was designed, 144 lambs (14.21 ± 0.30 kg) were randomly divided into six groups of four replicates (six lambs per replicate). At the end of feeding experiment, 24 lambs were slaughtered and sampled to analyze indexes. The results showed that live body weight (LBW), average daily gains (ADG), tail fat weight, GR values, and carcass weight increased with increasing energy intake. Increased energy intake significantly increased cooked meat percentage, shear force, and the content of crude protein (CP), ash, and crude fat (EE) in muscle. L -carnitine supplementation significantly reduced tail fat weight, GR values, and the content of CP and EE in muscle, while cooked meat percentage and water loss rate significantly increased. However, L -carnitine supplementation did not affect the LBW and ADG indexes. The effects of L -carnitine or energy intake did not significantly affect amino acid compositions of the longissimus dorsi (LD) muscle. High-energy intake resulted in higher blood urea nitrogen concentrations; in contrast, no significant effects of energy intake were observed on total cholesterol (TC), triglyceride (TG), and glucose (GLU) concentrations. In addition, L -carnitine supplementation in the high-energy group reduced GLU serum concentrations, but did not affect the concentrations of TC and TG. The investigation of gene expression showed that lipoprotein lipase and fatty acid synthase were significantly increased in the liver, tail fat, and subcutaneous fat with energy intake, while lipase E (hormone sensitive type) and stearoyl-CoA desaturase gene expression were significantly decreased. Furthermore, the effects of L -carnitine supplementation on gene expression were opposite to those of energy intake. Significant interaction was found between energy intake and L -carnitine supplementation for EE content in muscle, blood biochemical index, and amino acid compositions in the LD muscle. In conclusion, high-energy diets promote animal growth and production performance, while accelerating fat deposition. L -carnitine supplementation had slightly effect on the improvement of performance and lamb quality, while effectively counteracting the negative influence of high-energy intake, particularly inhibiting fat accumulation.