مرکز منطقه ای اطلاع رساني علوم و فناوري -

چكيده لاتين :

The objectives of this work were the determination of the age at puberty (Experiment 1) and the onset ofbreeding season (Experiment 2) ofthe Baladi goat breed in an extensive rearing system. In experiment 1, 56 females of 4 months of age were used between June and December 2004. They were separated into two equal groups according to the date ofbirth, early in February (P) and late in March (f). Subsequently, the onset ofthe breeding season was determined in 22 females 18 months old (Cl) and 24 adults 3-4 years old (C2) (Experiment 2). Weights were measured every ]0 days. Puberty and onset of breeding season were determined by daily heat detection and by measuring plasmatic progesterone every]0 days. Approximately at the age of9 months, ]4% ofearly born females were detected in heat (P>0.05), had a progesterone concentration of 5.0 ± 2.4 ng mr-l and reached 69% of adult body weight. At the end of the experimental period, none of the late born females showed puberty signs despite reaching 43% ofadult body weight. The onset of seasonal breeding took place on September] 1h and occurred in Cl three weeks later than in C2 (P<0.05). On this date, 5% ofC] and 38% ofC2 exhibited cyclicity (P<0.05). A feak of 86% ofCl and 92% ofC2 showed high concentrations ofprogesterone on October 71 • Early born females reached two thirds ofadult body weight in their first breeding season, which is suitable to mating if this season is prolonged. For adult females, the date of1h October could be adopted as the breeding date for kidding synchronization.