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

Lines of turkeys selected genetically for rapid growth or egg production and their respective randombred control populations were examined for physiological factors influencing their hatchability. Hatchability of fertile eggs was improved (P less-than-or-equal-to .05) in the growth line but not in the egg production line when compared with randombred 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. Eggshell conductance constants were lower (P less-than-or-equal-to .05) in genetically selected lines compared with constants for eggs of the randombred control strains, which suggests that embryos from selected lines have less access to oxygen. Thus, genetic selection regardless of whether for growth or egg production reduced oxygen consumption during 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 selected lines compared with controls. Thus, oxygen availability rough eggshells prior to pipping may be vital in determining survival rates of late embryos. Lower oxygen consumption would cause embryos to rely more on stored glycogen for energy during pipping. Hepatic and cardiac glycogen stores and blood plasma glucose concentrations indicated the embryos of growth and egg production lines had less (P less-than-or-equal-to .05) stored glycogen than control embryos. The data suggest that there may be a relationship between carbohydrate accrual prior to pipping, its utilization during pipping, and subsequent embryonic survival during pipping and hatching among the lines and that these differences may be associated with the genetics of growth or egg production.