Attainment of puberty in South African indigenous ram lambs

Abstract

This study aimed to evaluate the attainment of puberty in indigenous sheep breeds: 7 ram lambs of the Bapedi, Namaqua-Afrikaner and Zulu sheep breeds were studied. Data was collected biweekly: Scrotal circumference was measured using a measuring tape; blood samples were collected from the jugular vein and analysed using a competitive enzyme immunoassay (EIA); semen was collected using an electro-ejaculator and semen samples were evaluated for macroscopic and microscopic characteristics; sexual behaviour activities recorded were nudging, pawing, bleating, licking, Flehmen’s response, pelvic thrust, mounting, penile erection, and nosing; and body weight was measured using a livestock scale. Neither of the three breeds displayed sexual behaviour activities at 3 months, with Namaqua-Afrikaner ram lambs only displaying sexual behaviour at 4.5 months (1 month later than Bapedi and Zulu ram lambs) and being classified as late-maturing. The most observed sexual behaviour activity was nosing. In addition, Bapedi, Namaqua-Afrikaner and Zulu ram lambs had similar bodyweights for 66.6% of the study period and similar blood serum testosterone levels for 88.9% of the study period, showing the homogeneity of these breeds. However, Bapedi, Namaqua-Afrikaner and Zulu ram lambs had significantly different scrotal circumferences for the entire study period (P<0.05). This was also the case for most studied semen parameters, except for semen volume, medium velocity, viability, membrane integrity and mid-piece abnormalities - Bapedi and Zulu rams had significantly different sperm cell concentrations at 7 and 8 months (1.4 ± 0.61 x 109 / mL and 4.3 ± 0.52 x 109 / mL, respectively for Bapedi ram lambs) and there was also a significant difference in the progressive progression of Bapedi ram lamb semen compared to Zulu ram lamb semen at 7 months (34.4 ± 9.3% and 73.9 ± 4.5% respectively), as well as in other semen characteristics. All three breeds produced satisfactory semen at 7 months of age. For all studied parameters, Pearson correlations were performed, and the strongest correlation was 0.60 between body weight and scrotal circumference. In conclusion, this study indicated that South African indigenous sheep attained puberty at the age of 7 months. The current study also recommended that there should be more research on indigenous sheep breeds for improved reproductive performance and conservation strategies.