DURATION OF FERTILITY IN AD-LIBITUM AND FEED-RESTRICTED CAGED BROILERBREEDERS

has been shown in previous studies that fertility can be reduced in ov erweight broiler breeder (BE) flocks. In an effort to determine the ef fect of ad libitum feeding on the duration of fertility in BE hens, 60 52-wk-old Shaver Starbro hens were randomly assigned to one of two tr eatments, ad libitum feeding (F) or restricted feeding (R) to maintain breeder target weights. All hens were reared to 52 wk under condition s of feed restriction. All birds were weighed individually on a weekly basis. At the beginning of each of two 4-wk study periods (56 to 60 w k and 60 wk to 64 wk), all birds were inseminated on 2 consecutive d w ith 0.05 mt pooled BE semen. All eggs were weighed and placed in a for ced air incubator the same day that they were laid. After 7 to 10 d of incubation, the eggs were broken out and scored macroscopically as fe rtile with live embryo, fertile with dead embryo (early embryonic deat h), or clear (assumed infertile). The duration of fertility was define d as the number of days from the day after the second insemination to the last fertile egg before two consecutive interfile eggs. Hen BW wer e significantly different between treatments within each of the two 4- wk studies. The mean BW of the F hens was 4,261 g in Study 1 and 4,448 g in Study 2. The BW of the R hens were 3,459 g in Study 1 and 3,565 g in Study 2. Egg production levels and average egg weight was not dif ferent between treatments in either study. In Study 1, the duration of fertility for the F hens (12.7 d) and the R hens (12.7 d) were not di fferent. In Study 2, the durations of fertility were significantly hig her (P < 0.05) in the R hens (12.7 d) than in the F hens (10.0 d). The se results support the theory that overweight BE have a reduced durati on of fertility that may contribute to a reduced fertility in artifici ally inseminated and naturally mated flocks.