EFFECT OF MATERNAL DIETARY TRIIODOTHYRONINE ON EMBRYONIC PHYSIOLOGY OF TURKEYS

The objective of the present experiment was to feed triiodothyronine ( T3) to lines of turkey breeders selected for egg production and growth , and an unselected control line. The data were collected to determine a genetic basis for thyroid-mediated maternal effects on embryonic ph ysiology and livability. At 30 wk of age, turkeys of the three lines w ere photostimulated and half of each line was fed a diet containing .5 ppm T3. Maternal dietary T3 increased egg weight, reduced yolk solids and eggshell conductance constants, and increased albumen solids and water in eggs in all lines compared with control eggs. Hatchability in all lines was not affected by the dietary treatment (Control = 72.2%; T3 treatment = 70.7%), but there was a significant interaction betwee n dietary T3 and line of turkey for the time of embryonic mortality, t ime of hatching, and carbohydrate metabolism of the embryo. The T3 inc reased mortality of the Egg line and unselected line during pipping, i ncreased mortality of the Growth line in the plateau stage, but decrea sed its mortality during internal pipping. Reduced glycogen in liver a s well as a reduced gluconeogenesis were evident in embryos of the two selected lines fed T3. It is concluded that genetic lines may have di fferent metabolic patterns based on their genetic constitution in orde r to compensate for variations in egg solids and eggshell conductance constants. The metabolic patterns are reflected in different levels of embryonic blood plasma glucose; glycogen, and gluconeogenesis.