Different incubation conditions can cause eggshell temperature (EST) to deviate from optimum. Two experiments were performed to determine the effect of low EST at the start of incubation and high EST at the end of incubation on hatchability, chick quality, 6-wk live performance, and breast meat yield of broiler chickens. In each experiment, 1,800 eggs from a single flock were divided and set into 2 setters. From 0 to 10 d of incubation, one setter was set to attain an EST of 36.6 degrees C (considered low), whereas the other was set to 37.8 degrees C (the control temperature). Using an infrared thermometer, EST was measured daily on a sample of eggs to ensure treatment intentions. On d 11 of incubation, the temperature of the low EST setter was increased to 37.8 degrees C in synchrony with the other setter until transfer. On d 18 of incubation, eggs from both setters were combined into 2 equal groups and transferred to hatchers. The EST in one hatcher was set to 37.8 degrees C (control) and in the other to 39.5 degrees C (considered high) until 21 d of incubation. Hatched males were placed in battery cages (Experiment 1) or floor pens (Experiment 2) and reared on common feeds to 1 or 6 wk of age, respectively. Low EST in the first 10 d of incubation reduced hatchability, increased BW and chick yield, and reduced 1-wk gain compared with the control EST. Throughout rearing, BW was reduced for low EST chicks compared with control EST chicks; consequently, carcass, fillet, and tender weights were also reduced. High EST in the hatcher increased hatchability, and reduced BW, chick yield, and 1-wk gain compared with control EST in the hatcher. By 3 wk of age, there was no difference in BW between chicks in high EST and control EST treatments. Subsequent carcass and processing yields were also similar. Incubation at the control EST of 37.8 degrees C, particularly from 0 to 10 d, resulted in the best performance overall.

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The effects of CP intake on broiler breeder hen performance were evaluated. A flock of pullets was reared in floor pens from 0 d to 20 wk of age. At 20 wk of age, 96 pullets were randomly assigned to one of three feeding regimens with 14, 16, or 18% dietary CP. Daily feed allocation from 20 to 29 wk of age was identical for all three treatments and was based on the BW of the birds fed the 16% CP diet. Photostimulation occurred at 22 wk of age. At 29 wk of age, the hens were killed for determination of carcass characteristics. Dietary protein intake did not influence BW or BW gain throughout the trial. There were no differences in age at sexual maturity among treatments. From 25 to 28 wk of age, the hens on the 16 and 18% CP treatments had a significantly greater egg weight than did hens in the 14% CP group. The 14% CP treatment was unable to sustain as high a level of egg production as the other two treatments at 29 wk of age. The number of settable eggs was also lowest for the 14% CP treatment. The CP level in the diet did not affect the weights of the Pectoralis major or minor. Carcass composition was also not different among the treatments. Increased levels of CP in the prelay and early lay diets increased egg size and production rate although had minimal effect on carcass and ovarian parameters.

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