Research Note Effects of preincubation and higher initiating incubation temperature of long-term stored hatching eggs on hatchability and day-old chick and yolk sac weight

We studied the effect of increased initial incubation temperature and repeated preincubation of 35-d stored eggs from 46 week old Ross 308 parental stock on the hatchability and day-old chick and yolk sac weight. Two different temperatures were applied during the first 36h and they were combined with four preincubation treatments during storage. One half of the hatching eggs (2400) were incubated for the first 36h at an incubation temperature of 38.3 oC, and the second half were incubated at a higher temperature of 39.2 oC. Four different preincubations were applied; none, once at the 7th day of hatching egg storage, twice at the 7th and 12th days of storage and three times at the 7th, 12th and 19th days of storage. Both preincubation and increased temperature had negative effects on hatchability (P<0.001). The interaction between these two factors was also significant (P<0.05). These two factors also negatively affected early and late embryonic mortality (P<0.001). However, middle embryonic mortality was not influenced. Live weight, weight of residual yolk sac and yolk sac proportion were not affected by repeated preincubation nor by increased temperature over the first 36h of incubation (P>0.05). A higher initial temperature decreased chick yolk free body mass (P<0.05).Although neither increased initial temperature in the setter nor repeated preincubation affected one day old chick weights, these treatments were not suitable for long-term stored eggs because of decreased hatchability and impairment of one day chick quality expressed as yolk free body mass.O