Processing, Products, and Food Safety

were supplemented with 40 ppm T4 for 10 days. Of the 3 treatment groups, 1 was maintained under a 14-h light schedule and fed breeders’ diet while the 2 others were subjected to a drop in photoperiod to 6 h during or after supplementation, and were then fed a maintenance diet. Egg production, feed intake, body weight, molt and plasma levels of T4 were measured. All treated hens ceased laying within 20 days; however, several individuals spontaneously returned to lay when left on 14 h light, suggesting incomplete involution of the reproductive tract. T4 supplementation significantly reduced feed consumption (P < 0.001) and induced significant rapid body weight loss (P < 0.001). However, all hens returned to their initial body weight by experiment’s end. Most treated hens initiated molt within 8 days of supplementation and all completed molt by day 37. Plasma T4 levels in treated hens increased significantly by day 3 of supplementation (P < 0.05) and remained significantly higher than in controls until day 9 (P < 0.01). Levels returned to initial values by day 35. In conclusion, dietary supplementation with 40 ppm T4 was successful in inducing molt in spent turkey breeder hens. However, a drop in photoperiod seems necessary to completely reset the reproductive system.