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.

Influence of diet-mediated maternal thyroid alterations on hatchability and metabolism of turkey embryos

Large White turkey breeder hens from a strain exhibiting poor hatchability were fed thyroid-altering diets. The following dietary treatments were fed to randomized groups of hens for 15 wk of egg laying: 1) 16.5% protein turkey breeder diet (control), 2) the control diet containing 2.1 ppm supplemental iodine, 3) the control diet containing .1% thiouracil, and 4) the control diet containing .5 ppm triiodothyronine (T3). Blood samples were taken from hatching embryos from hens fed each diet. Embryonic hearts and livers were weighted prior to and during pipping as well as after hatching. Blood plasma was analyzed for thyroxine (T4), T3, and glucose. Livers were assayed for glucose-6-phosphatase activity. Supplemental maternal dietary iodine elevated embryonic T4 concentrations prior to pipping. Dietary T3 and iodine increased hepatic glucose-6-phosphatase activity and blood plasma glucose concentration prior to pipping. Feeding thiouracil increased embryonic liver weights but decreased heart and body weights. Blood plasma T4 was elevated in embryos from hens fed thiouracil but blood glucose levels were depressed because of a lack of increased glucose-6-phosphatase activity. Feeding iodine decreased the enzyme activity at internal pipping. It is suggested from the data that maternal thyroid metabolism may influence hatchability via embryonic thyroid and carbohydrate metabolism during hatching.