AGE-RELATED-CHANGES IN EGG-PRODUCTION, FERTILITY, EMBRYONIC MORTALITY, AND HATCHABILITY IN COMMERCIAL TURKEY FLOCKS

Factors affecting production of Large White turkey hens were examined. Six flocks (n = 136 to 149 hens per flock) were housed at commercial facilities in the United States and two flocks (n = 40 hens per flock) were housed at commercial facilities in the United Kingdom (UK). Effe cts of time-in-lay on egg production and duration of clutches and paus es were determined using all flocks. Also, effects of time-in-lay, mol t, and characteristics of individual eggs (size, sequence position, gr ade, and incubational weight loss) on fertility, hatchability, and emb ryonic mortality were determined using the UK flocks. Each flock showe d a distinctive pattern of production; it increased initially to a pea k and decreased thereafter. Average duration of clutches and of pauses were correlated positively and negatively, respectively, with hen-day egg production. As production declined toward the latter half of lay, a greater proportion of short clutches and, therefore, of first-of-cl utch eggs were laid. During the course of the first cycle of lay, eggs became larger and a greater proportion were of low grade. Fertility a nd hatchability increased initially then decreased. Effects of time-in -lay differed after a forced molt. Egg size changed only slightly with time in the second cycle, and fertility and hatchability were greater in the second cycle than in the first cycle. In both cycles, sequence position affected grade (first-of-sequence eggs were of lower grade c ompared with eggs laid subsequently), and grade influenced percentage weight loss, fertility, hatchability, and embryonic mortality. The res ults of this study support selection of hens based on duration of clut ches. In addition, the single most significant preincubational variabl e for predicting hatchability was grade of the egg.