Abstract
Simple SummaryZinc, an essential trace element for laying hens, plays an important role in biological processes, such as growth, tissue growth and repairment, skeletal development, and immune competence, which also has better effects on growth performance, biochemical indexes, and antioxidant capacity. Our previous work has shown that methionine hydroxyl analogue chelated zinc (MHA-Zn) has better effects on eggshell quality, the apparent retention of minerals and nutrients, trace element deposit, and metallothionein (MT) mRNA expression. The objective of the current study was to investigate the effects of different levels of MHA-Zn on antioxidant capacity and liver metabolism of aged laying hens. The results suggest that dietary supplementation of MHA-Zn levels at 80 mg/kg has better effects on antioxidant capacity and liver metabolism, as well as homeostasis of the body. This study aimed to investigate the effects of different levels of methionine hydroxyl analogue chelated zinc (MHA-Zn) on antioxidant capacity and liver metabolism of aged laying hens. A total of 960 57-week-old layers were fed a basal diet (Zn: 35.08 mg/kg) without extra zinc for two weeks, and then allocated to four treatments consisting of eight replicates of 30 birds each for 14 weeks. Four levels of Zn (zinc sulfate (ZnSO4): 80 mg/kg; MHA-Zn: 20, 40, 80 mg/kg) were added to the diet. The results indicated that compared with inorganic zinc, organic zinc of 80 mg/kg has a significant advantage in improving the antioxidant capacity of aged hens, which increased the level of Cu/Zn-superoxide dismutase (SOD) and the total antioxidant capacity (T-AOC) in the serum and liver, and reduced the concentration of malondialdehyde (MDA) of laying hens. The serum albumen composition was significantly modified, meanwhile, the level of total protein, globulin, and urea increased remarkably, whereas serum glutamic-oxaloacetic transaminase decreased notably in 80 mg/kg MHA-Zn groups. Compared with the 20 mg/kg MHA-Zn group, the metabolic profile of 40 and 80 mg/kg MHA-Zn groups was higher than that of the inorganic zinc group. Furthermore, integrated key metabolic pathway analysis showed that 40 and 80 mg/kg MHA-Zn groups participated in the regulation of glutathione metabolism, glycine, serine, and threonine metabolism. Therefore, this study suggests that 40 and 80 mg/kg supplementation of MHA-Zn can increase the activity of Cu/Zn-SOD and T-AOC and decrease MDA; additionally the 80 mg/kg MHA-Zn group has better antioxidant capacity. Meanwhile, the enhanced MHA-Zn promoted methionine (Met) synthesis and protein metabolism.
Highlights
Laying rate and egg quality decline during the later laying period, and these declines cause substantial economic losses
Zinc is a cofactor of the antioxidant enzyme Cu, Zn-superoxide dismutase (SOD1), and Zn supplementation significantly increased glutathione peroxidase (GPX) activity through modulation of Se status [3]
Compared with the control group, dietary supplementation with 80 mg/kg of methionine hydroxyl analogue chelated zinc (MHA-Zn) promoted the above indices in the liver and serum and significantly improved the activities of Cu/Zn-SOD and total antioxidant capacity (T-AOC) in the liver (p < 0.05)
Summary
Laying rate and egg quality decline during the later laying period, and these declines cause substantial economic losses. After 70 weeks of age hens have retained long-term vigorous lipid metabolism, which is related to oxidant stress and decreased immunity [1]. Anti-inflammatory and antioxidant properties of zinc have long been documented [2]. Some researchers believe that organic trace minerals can be more readily absorbed by the body, and organically bound Zn forms such as Zn-methionine (Met) and Zn-yeast [5]. Different studies have shown that dietary organic zinc reduced oxidative stress and enhanced immune response without affecting bird performance [6,7]. When broilers suffered coccidiosis vaccination, organic trace mineral complexes supplied in diets improved the immune response and lowered lesion scores [8]
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