Abstract
ABSTRACT The objective of this study was to investigate the optimal zinc (Zn) requirement of broiler chickens based on Zn retention. On the day of hatch, 350 male Ross 308 broilers were randomly assigned to seven treatments with five replicates of ten birds each. Zinc was supplemented as ZnSO4·7H2O at 0, 20, 40, 60, 80, 100, or 120 mg/kg in the starter diet (fed from 1 to 21 d of age) and at 0, 16, 32, 48, 64, 80, or 96 mg/kg in the grower diet (fed from 22 to 42 d of age). The analyzed Zn levels were 34.98 and 27.57 mg/kg in the basal starter and grower diets, respectively. Supplemental Zn levels did not influence body weight gain, feed intake, feed conversion ratio, or liver Zn content of broilers at 21 and 42 d of age (p>0.05). Tibia ash Zn content of 21-d-old broilers increased when Zn supplementation level increased from 0 to 40 mg/kg Zn in (p<0.05). The highest breast muscle Zn content in 42-d-old broilers was observed when 100 and 80 mg Zn/kg was supplemented in the starter and grower diets, respectively. Fecal Zn content, Zn intake, Zn excretion, and Zn retention of 31- to 33-d-old broilers linearly increased with supplemental Zn levels (p<0.05). Zinc retention values, calculated as the difference between Zn intake and Zn excretion, were negative, about zero, and positive when starter/grower diets were supplemented with 0/0 and 20/16, 40/32, and 60/48 and 120/96 mg/kg, respectively. These results indicate that supplementing 40 and 32 mg Zn/kg in starter and grower diets, respectively, promote the growth performance of broiler chickens, while reduce Zn excretion in the environment.
Highlights
Zinc (Zn) is an essential trace element for poultry, and contributes for the maintenance of growth performance (Liu et al, 2011), skeletal development (Ao et al, 2007; Tomaszewska et al, 2017), and immune function (Kidd et al, 1996) of broiler chickens
The body weight gain (BWG), Feed intake (FI), and feed conversion ratio (FCR) of 21- and 42-d-old broilers were not influenced by supplemental Zn levels (p>0.05, Table 3)
No linear or quadratic relationships were observed between supplemental Zn levels and growth performance parameters (p>0.05)
Summary
Zinc (Zn) is an essential trace element for poultry, and contributes for the maintenance of growth performance (Liu et al, 2011), skeletal development (Ao et al, 2007; Tomaszewska et al, 2017), and immune function (Kidd et al, 1996) of broiler chickens. The Feeding Standards of Chickens in China Recent research has shown that the optimal levels of supplemental Zn for the performance of broiler chickens range between 12 and 60 mg/ kg for (Ao et al, 2007; Huang et al, 2007; Liu et al, 2011). These data suggest that the Zn supplementation recommended by the Feeding Standards of Chickens in China 2004) may be higher than the Zn requirement for broiler chickens and should be revised
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