Effects of methionine hydroxyl analog chelated zinc on laying performance, eggshell quality, eggshell mineral deposition, and activities of Zn-containing enzymes in aged laying hens

ABSTRACT The study aimed to determine the effects of methionine hydroxyl analog chelated zinc (MHA-Zn) on laying performance, eggshell quality and mineral deposits, and the activities of Zn-containing enzymes on aged laying hens. A total of 960 layers (Hy-Line Grey, 57 wk old) were fed a basal diet (Zn: 35.08 mg/kg) without extra zinc for 2 wk. During the ensuing 14 wk, birds were randomly divided into 4 groups according to body weight and laying rate, with 8 replicates per treatment, and each group had 8 replicates of 30 hens. Four levels of Zn (ZnSO4: 80 mg/kg; MHA-Zn: 20, 40, 80 mg/kg) were added to the diet, respectively. The results shown that dietary Zn did not affect laying rate, average egg weight, average daily feed intake, or feed conversion ratio (P > 0.05); however, compared to the inorganic group, dietary supplementation with 40 or 80 mg/kg MHA-Zn decreased broken egg rate significantly in the whole period (P 0.05), whereas dietary supplementation with 80 mg/kg MHA-Zn improved the Zn and Ca concentrations of eggshells and carbonic anhydrase (CA) activity of liver, and 40 mg/kg MHA-Zn increased Zn concentration of liver (P 0.05). Therefore, dietary supplementation with 40 mg/kg MHA-Zn can improve eggshell quality by promoting Ca deposition and CA activity.