Estimating energy utilization in laying hens: what are the best response criteria?

Abstract

An experiment was conducted to evaluate the effects of varying dietary energy on the performance and energy storage in laying hens from 36 to 52 wk of age. A total of 252 Hy-Line W-36 laying hens were housed in cages with 3 birds per cage and 12 replicate cages per treatment. Birds were control fed 1 of 7 experimental diets ranging in dietary energy from 2,750 to 3,050 kcal/kg with a 50 kcal/kg difference among each of the diets. Egg production, energy intake, feed intake, egg weight, egg mass, and feed efficiency were calculated every 2 wk so that performance data could be analyzed every 2 wk using repeated measures analysis. Hens were weighed every 4 wk for repeated measures analysis and carcass total, lean, and fat mass were determined at 52 wk using dual X-ray absorptiometry. Correlations between dietary energy and energy intake with performance parameters, and body composition were generated. Dietary energy (kcal/kg) was significantly correlated with all performance parameters except hen housed egg production (HHEP; P = 0.07) and lean carcass mass (P = 0.60). For dietary energy, the highest correlations were total carcass mass (r = 0.60) and carcass fat mass (r = 0.54). Energy intake (kcal/d) was significantly correlated with all performance parameters except feed intake (P = 0.18). The highest correlations were between energy intake and total carcass mass (r = 0.63) or body weight (r = 0.51). These results suggest that dietary energy has a more pronounced effect on body mass and fatty tissue over the short run (16-wk period) before direct performance responses are observed. Therefore, hen body weight and composition can be used as a more sensitive measurement of shorter-term hen energy status than egg production or feed efficiency.