Growth and development of Leghorn pullets subjected to abrupt changes in environmental temperature and dietary energy...

Four trials were conducted to note the response of pullets to changes in environmental temperature and energy level at 56 days of age. In each trial, birds were fed diets providing either 2,500 or 3,000 kcal ME/kg throughout rearing, or with a single diet change from 2,500 to 3,000 and 3,000 to 2,500 kcal ME/kg occurring at 56 days. Each of the four diet scenarios was tested with six replicate caged groups each containing 10 pullets. In Trials 1 and 2 environmental temperature was maintained at 18 and 30 C, respectively, to 126 days. In Trials 3 and 4, temperature was changed at 56 days from 18 to 30 C and 30 to 18 C, respectively. Regardless of environmental temperature conditions, diet change per se had minimal effect on growth and development. Rather dietary energy level used from 56 to 126 days had the greatest effect on growth, with birds fed the highest energy content diet generally being heaviest. However, this effect was not significant (P greater than .05) in all trials, which is probably related to a lack of effect on energy intake under such conditions. Final body weight was more closely associated with energy intake than with protein intake and energy intake was maximized when high-energy diets were used after 56 days of age. Consumption of high-energy diets after 56 days, regardless of trial conditions, always resulted in increased carcass fat content at 126 days. It was concluded that abrupt and major changes in environmental temperature or dietary energy as used in these trials have little deleterious effect on pullet development. Conditions prevailing during later stages of growth have a far greater effect than changes per se in these parameters.