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

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 to 80 mg/kg genistein increased (P < 0.05) feed intake during the starter (1 to 21 d of age) and grower (22 to 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 to 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 to 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 to 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 to 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 to 80 mg/kg genistein can beneficially affect growth performance, carcass oxidative stability, and intestinal microflora in broiler chicks.