INCUBATION RELATIVE-HUMIDITY EFFECTS ON ALLANTOIC FLUID VOLUME AND HATCHABILITY

Four incubation trials were conducted to evaluate the effects of incub ation RH on hatchability, allantoic fluid volume, and embryo weight. I n Trial 1, White Leghorn eggs were incubated at a RH of 55 or 69% and a dry bulb temperature of 37.8 C and hatchability was determined. In T rial 2, hatchability and allantoic fluid volume were determined (Day 1 4 of incubation) for eggs incubated at 43, 55, or 69% RH. In Trial 3, allantoic fluid volumes and embryo weights were determined on Days 10, 12, 14, and 16 of incubation for eggs incubated at 40, 55, or 70% RH. In Trial 4, hatchability, allantoic fluid volumes, and embryo weights were determined on Days 13, 14, and 15 of incubation for eggs incubat ed at 40, 55, or 70% RH from hens 34 and 49 wk of age. There were no d ifferences (P > .05) in hatchability between eggs incubated at 55 or 6 9% RH in Trial 1, or among eggs incubated at 43, 55, or 69% RH in Tria l 2. In Trial 4, hatchability was highest for eggs from 34-wk-old hens incubated at 55% RH. In Trial 2, percentage egg weight loss per day o f incubation (.68, .55, and .40%) and projected 19-d weight loss (12.9 , 10.45, and 7.6%) decreased significantly with increased incubation R H of 43, 55, and 69%, respectively. Allantoic fluid volume (as a perce ntage of initial egg weight) on Day 14 of incubation significantly inc reased with the increase in RH; 13.86, 15.45, and 17.93% for RH of 43, 55, and 69%, respectively. In Trial 3, allantoic fluid volume peaked on Day 14 of incubation and volume increased or decreased with corresp onding incubation RH; 14.05, 16.25, and 19.44% for RH of 40, 55, and 7 0%. In Trial 4, allantoic fluid volume was greatest on Day 13 of incub ation and volume increased or decreased with corresponding incubation RH 13.38, 16.91, and 18.68% for eggs from 34-wk-old hens and 11.12, 13 .77, and 16.59% for eggs from 49-wk-old hens. Eggs from 49-wk-old hens had lower allantoic fluid volumes, but higher initial egg weights due to greater percentage egg weight loss during incubation. Incubation e gg weight loss in different RH appears to result from the correspondin g depletion of the allantoic fluid reservoir.