Reproductive performance of South African indigenous goats following oestrous synchronisation and AI
Dept. Anim., Wildl. and Grass. Sci., Fac. of Nat. and Agric. Sciences, University of the Free State, P.O. Box 339, Bloemfontein 9300, South Africa
The reproductive performance following oestrous synchronisation and artificial insemination (AI) was evaluated during the natural breeding season (autumn) in 90 indigenous (Boer and Nguni) South African goats. All does were synchronised for 16 days with medroxyprogesterone acetate (MAP) followed by an IM injection of 300 IU PMSG at progestagen withdrawal. Cervical inseminations were performed at a fixed time (48 h and 60 h) with fresh diluted Boer goat semen. No significant differences between Boer and Nguni goats were recorded with respect to oestrous response (98% and 93%) and the onset of oestrus (29.1 ± 0.9 h and 30.7 ± 0.8 h), respectively. The duration of oestrus in the Nguni goats (29.9 ± 2.0 h) was significantly (P < 0.01) shorter than in Boer goats (37.0 ± 2.1 h). Conception rates were 52% and 53%, litter size averaged 2.2 ± 0.2 and 2.0 ± 0.2 and the gestation period an average of 148.6 ± 0.9 days and 149.1 ± 0.8 days for Boer and Nguni goats, respectively, these differences being non-significant. Does with quadruplets had a significantly (P < 0.05) shorter gestation length (142.7 ± 2.1 days) than does with singles, twins and triplets (150.0 ± 0.9 days, 148.8 ± 1.0 days and 150.0 ± 1.1 days, respectively). The mean kid birth weight was 2.7 ± 0.5 kg with males being (2.8 ± 0.1 kg) significantly (P < 0.05) heavier than females (2.5 ± 0.1 kg) and crossbred kids (2.9 ± 0.1 kg) significantly (P < 0.01) heavier than pure Boer goat kids (2.4 ± 0.1 kg). Kid birth weight decreased with an increase in litter size, resulting in all birth weights for singles, twins, triplets and quadruplets being significantly (P < 0.01) different from each other (3.6 ± 0.4 kg, 3.1 ± 0.5 kg, 2.3 ± 0.6 kg and 1.6 ± 0.3 kg, respectively). The overall neonatal loss rate within 48 h postpartum was 22.2%, which increased significantly with an increase in litter size and was significantly (P < 0.01) higher for Boer goats (34.2%) than for crossbred kids (12.7%). The results indicate that oestrous synchronisation with progestagen is efficient and the duration of the induced oestrus is shorter in Nguni does than in Boer goat does. The conception rates obtained following oestrous synchronisation and AI were, however, very low and this aspect needs more attention. Litter size reduces birth weight and survival rate of indigenous South African goat kids. © 2004 Elsevier B.V. All rights reserved.