Effects of Zinc Glycinate on Growth, Immunity, and Intestinal Health in Broiler Chickens

The objective is to investigate the effects of dietary zinc form and concentration in broiler chickens. Day-old broiler chicks (n = 6) were allotted to treatments in a 2 x 3 factorial arrangement to examine supplemental zinc from sulfate (ZS) and glycinate (ZG) and concentration (40, 80, and 120 mg/kg). In healthy conditions, no difference in poultry performances is to be expected between organic and inorganic zinc sources, supplemented at the same zinc dose to the diets. We found that on day 21, zinc supplemented at 80 mg/kg increased body weight gain (BWG) by 113 g compared to zinc supplemented at 40 mg/kg (P < 0.01). Similarly, on day 35, zinc supplemented at 120 mg/kg increased BWG by 155 g compared to zinc supplemented at 40 mg/kg (P < 0.05). On day 35, zinc supplemented at 120 mg/kg increased feed intake by 239 g compared to zinc supplemented at 40 mg/kg (P < 0.05). The villi length on day 21 was increased by 63 pm in birds supplemented at 120 mg/kg compared to 40 mg/kg (P < 0.05). On day 21, cecal tonsil gene expression of interleukin 1 beta (IL-113) was higher by 2.5 and 2.4-fold in the ZG80 mg/kg group than the ZG-40 mg/kg and ZS-120 mg/kg groups (P < 0.01), and interleukin 10 (IL-10) was lower by 2-fold in the ZS-120 mg/kg group than ZS-40 mg/kg, while IL-10 was lower in the ZG-40 mg/kg than ZS-40 mg/kg group (P < 0.01). On day 35, cecal tonsil gene expression of IL-113 was overall higher by 1.3-fold in the ZG group compared to ZS (P < 0.05). On day 21, spleen gene expression of transforming growth factor-beta (TGF-13) was higher by 1.4-fold in the ZG-80 mg/kg group compared to ZG-40 mg/kg (P < 0.05). On day 35 spleen gene expression of lipopolysaccharide-induced TNF factor (LITAF) was lower in the ZG-80 mg/kg group compared to ZS-80 mg/kg (P < 0.05). On day 35 jejunum gene expression of claudin-2 was higher by 2.1-fold in the ZG-80 mg/kg group than ZS-80 mg/kg (P < 0.05). This study supports that zinc supplementation at 120 mg/kg improves the growth performance of broiler chickens. This is accompanied by improvements in intestinal morphology and modulation in immunity through an altered cytokine production profile.