The adverse effects of sub-optimal incubation temperatures on chick yield and early chick quality

The ideal temperature that optimizes hatchability and chick quality is rarely uniform within large multi-stage setters. Also, temperatures in the hatcher are not adjusted for the metabolic heat production of the embryo. The present study measured low eggshell temperature at the start of incubation and high eggshell temperature at the end of incubation to estimate their significance to hatchability and quality of broiler chicks. Eggshell temperature (EST), based on an infrared thermometer, was assumed to relate to embryo temperature. A total of 1800 eggs from a single flock was divided and set in two setters. For the first 10 days of incubation, one incubator was set to attain an EST of 36.6¿C, considered to be low, while the other was set to 37.8¿C and represented an optimal temperature. EST was measured daily on sample eggs from each incubator to assure treatment intentions. On day 11 of incubation, the temperature in the low EST incubator was increased to 37.8¿C, in synchrony with the other incubator until egg transfer. On day 18 of incubation, half of the eggs from each setter were combined in each of two hatchers. The EST in one hatcher was set to 37.8¿C and the other to 39.5¿C, considered to be high. Low EST for the first 10 days slowed embryonic development compared to optimal EST and resulted in fewer healthy chicks at hatch. An EST of 36.6¿C also decreased weight loss during incubation, leading to increased body weight and yolk sac at hatch but decreased body length. High hatcher EST decreased yolk-free BW. Sample male chicks from each treatment were grown to 7 days of age. For the first 2 days post-hatch, body temperature was highest among those that received the optimum EST in the setter whereas those that had received the high EST of 39.5¿C in the hatcher subsequently had the lowest body temperature. Chicks incubated at 37.8¿C in both setter and hatcher gained more weight in the first week post-hatch than any other temperature combination. A deviation in EST from 37.8¿C decreased hatchability and performance. Low EST at the beginning of incubation was more adverse to chick quality than high EST at the end.