The effect of dietary iodine on the hatchability of eggs from two commercial strains of turkeys.

Supplemental dietary iodine (3.5 mg/kg) was fed to two commercial strains [British United Turkeys (B) and Nicholas (N)] of turkey breeder hens. The basal diet contained .7 mg/kg of iodine. Observations were made on hen body weights, feed consumption, hatchability, egg weights, and egg functional characteristics to test the hypothesis that there are differences between commercial strains of turkey breeder hens in the dietary iodine requirement for reproductive success. Supplemental iodine decreased (P less than or equal to .05) functional egg characteristics of both strains. Egg production and hatchability were influenced by an interaction between strains and dietary iodine (P less than or equal to .05). In Strain B hens, egg production and hatchability declined (P less than or equal to .05) when hens were fed supplemental iodine but in Strain N hens no effects on hatchability were observed and egg production increased (P less than .05) with iodine supplementation. The decline in hatchability of eggs from Strain B hens was due to significant (P less than or equal to .05) increases in embryonic mortality during the 1st wk of incubation and during pipping. The treatments resulting in depressed hatchability caused embryos to rely more (P less than or equal to .05) on glycogenolysis than gluconeogenesis during pipping and hatching. The Strain B embryos utilized gluconeogenesis more during pipping (P less than or equal to .05) than Strain N embryos and embryos from Strain B iodine-fed hens had a lower rate of gluconeogenesis than those from hens not fed iodine. It is concluded that there are differences among strains of turkey breeder hens in their dietary iodine requirement for optimal hatchability.