EFFECT OF HEN AGE, BODY-WEIGHT, AND AGE AT PHOTOSTIMULATION - 1 - EGG, INCUBATION, AND POULT CHARACTERISTICS OF COMMERCIAL TURKEYS

Turkeys from two BW groups (which averaged 11.8 and 12.9 kg, Normal an d Heavy, respectively) were photostimulated at either 29 or 31 wk of a ge to determine what effects age-associated changes in hen carcass cha racteristics, egg weight, and egg components have on subsequent poult weight at hatching during the first 10 wk of production. Carcass measu rements were determined from a subsample of hens 3 wk after photostimu lation (PS). Subsamples of eggs from each PS age and BW group were sel ected for yolk and albumen measurements. All other eggs from these hen s were individually weighed and incubated at 2-wk intervals during the first 10 wk of lay (4 to 14 wk after PS). All incubated eggs were rew eighed at 25 d (transfer) and poults were individually weighed at hatc h. Hen BW at PS had no effect on ovarian weight and follicular size or number 3 wk later. Hens photostimulated at 31 wk had 18.7 g heavier o varies 3 wk after PS than hens photostimulated at 29 wk (P less than o r equal to 0.06), primarily due to one additional follicle of greater than or equal to 20 mm (P less than or equal to 0.04). During the firs t 10 wk of lay, egg weight increased 7.8 g, 4.4 g of which was due to increased yolk weight. Eggs from Normal BW hens weighed significantly less than those from Heavy BW hens only when hens were subjected to PS at 29 wk. Egg weight at transfer relative to egg weight at set was si gnificantly increased from hens 4 to 6 wk after PS compared with the f our older production ages (6 to 8, 8 to 10, 10 to 12, and 12 to 14 wk after PS). There was a significant increase in poult weight with incre asing hen production age but no changes in poult weight relative to eg g weight at set. Ln conclusion, hen BW at PS had minimal effects on eg g component weights and subsequent poult weight at hatching.