Effect of increasing levels of apparent metabolizable energy on laying hens in barn system

OBJECTIVE: This experiment was to investigate the effect of increasing levels of apparent metabolizable energy (AME(n)) on the laying performance, egg quality, blood parameters, blood biochemistry, intestinal morphology, and apparent total tract digestibility (ATTD) of energy and nutrients in diets fed to laying hens. METHODS: A total of three-hundred twenty 33-week-old Hy-Line Brown laying hens (Gallus domesticus) were evenly assigned to four experimental diets of 2,750, 2,850, 2,950, and 3,050 kcal AME(n)/kg in pens with floors covered with deep litter of rice hulls. There were four replicates of each treatment, each consisting of 20 birds in a pen. RESULTS: AME(n) intake was increased (linear, p<0.05) with inclusion level of AME(n) in diets increased. Feed intake and feed conversion ratio were improved (linear, p<0.01), but hen-day egg production tended to be increased with an increasing level of AME(n) in diets. During the experiment, leukocyte concentration and blood biochemistry (total cholesterol, triglyceride, glucose, total protein, calcium, asparate aminotransferase, and alanine transferase were not influenced by increasing level of AME(n) in diets. Gross energy and ether extract were increased (linear, p<0.01) as the inclusion level of AME(n) in diets increased. CONCLUSION: Laying hens fed high AME(n) diet (i.e., 3,050 kcal/kg in the current experiment) tended to overconsume energy with a positive effect on feed intake, feed conversion ratio, nutrient digestibility, and intestinal morphology but not on egg production and egg mass.