EMBRYONIC VIABILITY AND METABOLISM IN TURKEY LINES SELECTED FOR EGG-PRODUCTION OR GROWTH

Lines of turkeys selected genetically for rapid growth or egg producti on and their respective randombred control populations were examined f or physiological factors influencing their hatchability. Hatchability of fertile eggs was improved (P less-than-or-equal-to .05) in the grow th line but not in the egg production line when compared with randombr ed control populations. Embryonic mortality of both selected lines was lower during the 1st wk of incubation but higher during pipping than that observed for the mortality of the randombred control embryos. Egg shell conductance constants were lower (P less-than-or-equal-to .05) i n genetically selected lines compared with constants for eggs of the r andombred control strains, which suggests that embryos from selected l ines have less access to oxygen. Thus, genetic selection regardless of whether for growth or egg production reduced oxygen consumption durin g external pipping and for hatched poults, so the reduction cannot be attributed specifically to growth or egg production. Metabolic rate as measured by oxygen consumption during external pipping and posthatch was reduced (P less-than-or-equal-to .05) in the embryos of the select ed lines compared with controls. Thus, oxygen availability rough eggsh ells prior to pipping may be vital in determining survival rates of la te embryos. Lower oxygen consumption would cause embryos to rely more on stored glycogen for energy during pipping. Hepatic and cardiac glyc ogen stores and blood plasma glucose concentrations indicated the embr yos of growth and egg production lines had less (P less-than-or-equal- to .05) stored glycogen than control embryos. The data suggest that th ere may be a relationship between carbohydrate accrual prior to pippin g, its utilization during pipping, and subsequent embryonic survival d uring pipping and hatching among the lines and that these differences may be associated with the genetics of growth or egg production.