JOURNAL OF APPLIED POULTRY RESEARCH, vol.21, no.3, pp.460-466, 2012 (SCI-Expanded)
The effects of dietary supplementation with phytase (PHY) and prophylactic levels (250 mg/kg) of Cu from various Cu sources (Cu sulfate, Cu lysine, and Cu proteinate) on eggshell quality and P retention of layers that were fed low available P (aP) diets (0.11%) were assessed. In the first experiment, 120 Lohmann Brown hens, 40 wk of age, were assigned to 5 dietary treatments to evaluate eggshell quality (8 replications per treatment and 3 birds per replication). At 45 wk of age, 8 chickens in each treatment were placed in metabolic cages individually and subjected to the same treatments as in experiment 1 to determine P retention. No significant differences were observed among the treatments in terms of eggshell thickness, eggshell weight, percentage of damaged eggs, and specific gravity at the end of the first experiment. Feed consumption of the hens fed the Cu lysine diets was significantly less than feed consumption of hens fed diets that were not supplemented with Cu and hens fed diets supplemented with Cu proteinate in the second experiment (P < 0.01). The inclusion of PHY to a low-aP (0.11%) diet effectively supported and allowed almost the same eggshell quality and P retention compared with the high-aP (0.24%) diet. Therefore, feeding diets low in P (0.11% aP) together with 300 units of PHY and Cu from 3 different sources in the current experiment did not result in any decrease in eggshell quality. However, the use of supplementary Cu to provide 250 ppm from Cu lysine in laying hen diets that contained 0.11% aP and 300 units of PHY was concluded to decrease P retention (P < 0.05).