Submitted to: Journal Of Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 6, 1999
Publication Date: N/A
Interpretive Summary: Little information is available on the growth patterns of embryos from lines of turkeys selected for growth or egg production. Genetic selection for growth has had a negative impact on embryonic survivability of turkeys. Understanding the metabolic constraints on embryonic growth in these embryos may provide information on how to reduce the mortality of turkey embryos. The purpose of this study was to determine differences in embryonic growth rates in turkey embryos derived from hens selected for either egg production or growth rate. In addition, the effect of added dietary iodide on embryo development was evaluated. The results of this study showed that embryos from turkeys selected for growth rate were heavier that those selected for egg production. Inclusion of iodide in the maternal diet increased embryo growth rates. The results suggest that dietary iodide may modulate the growth rate of embryo in a positive manner. These results will be of interest to other scientists and turkey producers.
Embryonic growth of a turkey line (F) selected for 16-wk body weight was measured in relation to egg weight at hatching and at 4-day intervals. These results were compared to those of the respective randombred control population (RBC2). Genetic selection for increased 16-wk body weights resulted in increased embryo weights beginning at day 16 of incubation compared to those of controls. Eggs from F weighted 10 g more than those of RBC2 but the poults at hatching were only 8 g heavier. Conductance constants indicated that only .9% of the difference could be accounted for by water vapor loss. Embryonic growth of turkey line (E) selected for 180 day egg production was also measured. Eggs from E weighed 15 g less but produced poults weighing only 7 g less than controls. Eggshell conductance was depressed in E compared to controls but accounted for only 1.4% of the difference between hatchling weights. Genetic selection for egg production reduced embryo weights only at hatching. When iodide was included in the maternal diet of these genetic lines, embryonic growth was altered in all lines of turkeys. Growth rates at 16 and 20 days of incubation were accelerated in E- RBC1 comparisons, but depressed in F/RBC2 comparisons when additional iodide was fed to the dams. All lines fed the maternal iodide exhibited smaller poults at hatching and eggs from iodide-fed hens hatched at a lower rate than controls.