EFFECT OF REARING DIET ON PERFORMANCE OF EARLY MATURING PULLETS

Abstract

Leghorn chicks of a commercial strain were offered various feeding programs in an attempt to influence production and egg size of early maturing pullets. Feeding programs consisted of chick starter 0–8 wk, chick grower 8–15 wk; chick starter 0–8 wk, broiler starter 8–15 wk; broiler starter 0–8 wk, broiler grower 8–15 wk. Birds were housed either at 17 or 26 °C after initial brooding. Each treatment was represented by 10 cages of 10 birds each. After 7 days, 8 h of light at 10 lx intensity was provided daily. At 15 wk of age, birds were moved to laying cages (two birds per cage) and immediately subjected to a photoperiod of 14 h light. Birds were offered either a 17 or 20% crude protein (CP) diet. Rearing treatments and laying diets were arranged factorially, with each treatment represented by five replicate groups of four cages each. Conventional production parameters were measured throughout growth and a 36-wk laying period. Pullets fed broiler starter to 8 wk were heavier (P < 0.05) than birds fed chick starter, while regardless of diet, birds in the hot room were lighter (P < 0.05). At 15 wk, diet had no effect on body weight within the regular environment, while in the hot room birds fed broiler diets were significantly heavier (P < 0.05). Irrespective of diet, pullets consumed similar quantities of energy, but markedly different quantities of protein. In the first 28 days of egg production, birds reared on broiler diets produced more eggs (P < 0.05) of a heavier size (P < 0.05). These effects were not evident after this time and the magnitude of this early response was not of commercial significance. Egg production, shell quality, feed intake and mortaility were not influenced by rearing diet. Birds from the hot, rather than normal environment, consistently produced smaller eggs. It is concluded that high-protein, high-energy, broiler diets cannot by themselves be used successfully to induce early mature body size, and that the confounding factor for this is the pullets' voluntary limit to energy intake.