Effect of feeding different levels of dietary copper on production performance, egg quality traits and egg yolk cholesterol content in CARI-Red layers

An experiment was conducted involving one hundred and five (n=105) CARI Red layers during 29 to 45 weeks of age (114 days) following completely randomized design (CRD) and evaluate optimum dietary copper (Cu) levels for production performance, egg quality traits and egg yolk cholesterol content. A basal diet having 17% CP, 2700 Kcal ME/kg and 7 mg Cu/kg was prepared. Six other experimental diets were formulated by addition of desired levels of Cu sulphate to achieved 50, 75, 100, 125, 150 and 175 mg Cu/kg diets. Each of such diets was offered ad-libitum as mash to the laying hens randomly divided into seven groups of 15 birds each. Results indicated that the hen day egg production, egg weight, feed intake, feed conversion ration and body weight change did not differ significantly due to different dietary treatments. Similarly, the egg quality traits i.e. shape index, albumin index, yolk index and egg shell weight also did not differ significantly due to different dietary treatments. However, the egg shell thickness was significantly (P<0.05) higher at 100, 125 and 175 mg/kg Cu than other dietary treatments. The content of cholesterol in egg yolk was significantly (P<0.01) lower in groups given diets containing 125, 150 and 175 mg/kg Cu than other dietary treatment. Egg yolk weight did not change significantly due to different dietary treatments. No significant effect of Cu supplementation was observed on cholesterol concentrations due to experimental periods. Significantly (P<0.05) higher yolk weight was observed at 90 days than 45 days of experimental period. Based on the results, it was concluded that, if the production performance and egg quality are the criteria, the requirement is very low i.e. 7 mg Cu/kg diet; but if minimum cholesterol levels are the appropriate response criteria, then the requirements of Cu is 125 mg/kg diet, which decreases the yolk cholesterol concentration by 18% without affecting the performance.