Comparative effects of genistein and antibiotics on performance, meat oxidative stability, jejunal morphology, and ileal microbial community in broiler chicks

Abstract

The present study was conducted to investigate the effect of a supplementary isoflavone (genistein) on performance, meat oxidative stability, jejunal morphology, and ileal nutrient digestibility in broiler chicks. A total of 675 day-old male broiler chicks (Ross 308) were randomly assigned into the 5 pen replicates (15 chicks per each) for each of 9 experimental diets. Dietary treatments included a negative control diet (without any additive), 2 positive controls (virginiamycin or zinc-bacitracin, 20 mg/kg), and diets supplemented with 10, 20, 40, 80, 160, or 320 mg/kg of genistein. At d 28 of age, 3 randomly-selected chicks from each pen were euthanized to measure ileal bacterial counts and nutrient digestibility. Also, jejunal sections were collected in 10% formalin solution to evaluate morphological indices of epithelial cells. Results showed that antibiotics-diets and diets supplemented with 20–80 mg/kg genistein increased (P < 0.05) feed intake during the starter (1–21 d of age) and grower (22–42 d of age) periods compared with control birds. Furthermore, daily weight gain was influenced (P < 0.01) by dietary treatments in the starter period, so that the chicks fed both antibiotics and 20–80 mg/kg genistein-diets had the greater weight gains compared with other experimental groups. A similar pattern was observed during the grower period. Although the relative weights of pancreas, heart, and thigh were not affected, the birds fed either antibiotic- or 20–40 mg/kg genistein-diets had the greater carcass (P < 0.01) yields. Dietary supplementation of genistein caused significant decreases (P < 0.01) in serum concentrations of triglycerides and cholesterol compared with antibiotics-diets. Although serum concentration of high-density lipoproteins was not influenced, serum low-density lipoproteins levels were lower (P < 0.05) in genistein-supplemented groups. Dietary inclusion of 20–320 mg/kg of genistein increased meat oxidative stability as measured by malondialdehyde index. The greatest (P < 0.01) villi height (VH) was assigned to the birds fed antibiotics-diets, followed by those on 40 mg/kg genistein-diets. Feeding antibiotic-diets decreased (P < 0.05) crypt depth (CD), consequently increased (P < 0.01) VH to CD ratio. Dietary supplementation of antibiotics diminished ileal Salmonella (P < 0.001) and Escherichia coli (P < 0.01) counts compared with control birds. Similarly, supplemental genistein at the levels above 20 mg/kg reduced (P < 0.01) Salmonella enumeration. Dietary inclusion of both antibiotics and 20–80 mg/kg genistein increased (P < 0.01) digestibility coefficients of crude protein and ether extract, resulted in an improvement in energy digestibility. The present findings indicate that dietary supplementation of 20–80 mg/kg genistein can beneficially affect growth performance, carcass oxidative stability, and intestinal microflora in broiler chicks.