The effects of chromium yeast on lipid metabolism, antioxidant status, and meat development in broilers under high stocking density.

The objective of this study was to investigate the effects of chromium yeast (Cr yeast) on lipid metabolism, antioxidant status, and gene expression related to meat development in broilers under high stocking density (HSD). A total of 480 22-day-old male Arbor Acre (AA) broilers with similar initial weight were randomly allocated to 6 groups, with 6 replicates per group. The groups consisted of a normal stocking density (14 broilers/m2, NSD) group fed a corn-soybean meal basal diet; high stocking density group (20 broilers/m2 , HSD) fed a basal diet; and four HSD groups fed basal diets supplemented with 200, 400, 800, or 1600 μg Cr/kg from Cr yeast. The experiment lasted from day 23 to 42. The results showed that compared to the NSD group, HSD elevated serum levels of insulin (INS), insulin-like growth factor-I (IGF-I), triglycerides, and high-density lipoprotein cholesterol (HDLC), increased hepatic activities of acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS), and decreased serum total cholesterol (TC) along with hepatic and breast muscle activities of hormone-sensitive lipase (HSL) and lipoprotein lipase (LPL) (P < 0.05). Compared with the HSD group, supplementation with 400 μg/kg Cr enhanced lipid breakdown in HSD-exposed broilers by elevating serum leptin content and increasing hepatic HSL and LPL activities, while simultaneously reducing serum INS, IGF-1, and TC levels, along with hepatic FAS activity (P < 0.05). HSD upregulated heat shock protein 70 (HSP70) mRNA expression while downregulated myostatin (MSTN) mRNA expression in breast muscle (P < 0.05), compared to the NSD group. Cr supplementation at 200, 800, and 1600 µg/kg significantly increased nuclear factor erythroid 2-related factor 2 (Nrf2) mRNA expression in breast muscle (P = 0.008) without affecting other antioxidant genes expression. Furthermore, supplementation with 800 and 1600 µg/kg Cr from Cr yeast elevated mRNA levels of both myogenic factor 6 (MyoF6) and MSTN, while downregulated fatty acid-binding protein 4 (FABP4) mRNA expression in breast muscle (P < 0.05). In summary, dietary Cr yeast alleviated HSD-induced metabolic stress by enhancing lipid breakdown and modulating the expression of key genes involved in muscle development and lipid metabolism, thereby supporting metabolic homeostasis and muscle function under HSD.