Different effects of dietary β-hydroxy-β-methylbutyrate on composition of fatty acid and free amino acid, and fatty metabolism in the different muscles of broilers

In the study, 336 broiler chickens were selected to explore dietary effects of different β-hydroxy-β-methylbutyrate (HMB) levels (0 (control), 0.05, 0.10, and 0.15%) on the compositions of fatty acids and free amino acids, and lipid metabolism in the different muscles of broilers. In the breast muscle, dietary HMB supplementation hardly affected the free amino acid composition (P > 0.05). Compared to the control group, dietary 0.10 and 0.15% HMB supplementation decreased the content of C18:1n9c and thus the monounsaturated fatty acid (MUFA), and dietary 0.15% HMB supplementation increased the sum of saturated fatty acids (SFA) (P < 0.05). Moreover, compared to the control group, dietary 0.05 and 0.10% HMB increased the mRNA expression of proliferator activated receptor-γ and the activity of fatty acid synthase (FAS), and dietary 0.10% HMB increased the acetyl-CoA carboxylase activity (P < 0.05). In the leg muscle, dietary 0.10 and 0.15% HMB increased the MUFA content and decreased the polyunsaturated fatty acid (PUFA) content, the PUFA to SFA ratio, the mRNA expression of sterol regulatory element binding proteins-1c, and the activities of acyl-CoA oxidase 1 and acetyl-CoA synthetase (P < 0.05). Moreover, dietary 0.10% HMB decreased the activities of hydroxy-3-methylglutaryl-CoA synthase 1 and FAS in comparison to the control group (P < 0.05). Dietary 0.05% HMB decreased the contents of essential amino acids and nonessential amino acids (NEAA), and dietary 0.15% HMB decreased the NEAA content (P < 0.05). In summary, dietary 0.10% HMB supplementation had superior efficiency on lipogenesis in the breast muscle of broilers. However, dietary HMB supplementation, especially at the level of 0.05 and 0.15%, decreased meat nutritional values and the lipogenesis in leg muscles.