Puberty in Anglo-Nubian and Saanen female kids raised in the semi-arid of North-eastern Brazil

Abstract

Fifteen Anglo-Nubian and 14 Saanen female kids were used to evaluate the age at puberty when raised in a semi-arid environment. The kids were monitored from 90 days of age until all females showed, at least, one (first) oestrous period. The kids were weighed at 15-day intervals and the occurrence of oestrus was checked twice a day. Blood samples were taken weekly and assayed for progesterone in order to detect luteal function. The age at puberty was defined as the date of first oestrus followed by luteal function. After puberty, the oestrous cycles were observed and classified as short (<17 days), normal (17–25 days) or long (>25 days) in length. The initial and final body weights were, respectively, 14.6±1.2 and 34.0±2.0 kg for Anglo-Nubian kids, and 17.4±1.2 and 40.1±2.5 kg for Saanen kids. From 150 days of age, the Saanen goats were heavier ( P <0.05) than the Anglo-Nubian. The daily weight gain (ADG) (90 days to puberty) was greater ( P <0.05) in Saanen than in Anglo-Nubian female kids (0.096±0.045 kg versus 0.069±0.013 kg, respectively). Saanen female kids achieved puberty earlier (147.8±21.1 days versus 256.3±69.6 days; P <0.05) and at a lower body weight (22.5±1.7 kg versus 26.4±5.6 kg; P <0.05) than those of the Anglo-Nubian breed. Regarding both age and weight at puberty, it was observed that Saanen kids achieved puberty earlier and more synchronized ( P <0.05) than Anglo-Nubian kids. When comparing the percentage of adult body weight at which that the goats attained puberty, no significant differences were observed between the Anglo-Nubian and Saanen kids (50.9% versus 45.1%, respectively). All oestrous cycles observed in Anglo-Nubian goats were of normal length (17–24 days). However, in the Saanen breed 16, 76 and 8% of oestrous cycles were short, normal and long, respectively. After puberty, 31.0% of females showed, at least, one period of luteal function not preceded by oestrus (Anglo-Nubian: 13.3% versus Saanen: 50.0%, P <0.05). During the same period, at least one oestrus not followed by a period of luteal function was observed in 13.8% of the goats (Anglo-Nubian: 13.3% versus Saanen: 14.2%). In conclusion, when raised in North-eastern Brazil, Saanen female kids attained puberty sooner than Anglo-Nubian kids and, consequently, require different reproductive management systems.