165 Novel insights into pubertal South African indigenous Ovis aries males

To conclusively determine an animal’s attainment of puberty is crucial for reproductive efficiency. Despite the prevalence of smallholder and livestock keeper systems in sub-Saharan Africa, there is a paucity of research on the physiology and reproductive capability of various indigenous breeds, that may be pivotal in mitigating the effects of climate change on agriculture in the region. In this study, pubertal semen parameters, blood serum testosterone (BST) concentrations and bodyweights of South African indigenous ram lambs were determined to assess the age at which they attained puberty. Seven ram lambs each of the Bapedi, Namaqua-Afrikaner and Zulu breeds were randomly selected from their respective pure-bred flocks. They had ad libitum access to water and natural pasture. From the age of 4 to 8 months, beginning in summer, the ram lambs were weighed using a livestock scale biweekly. On weighing days, a 10-mL blood sample was collected from the jugular vein and the blood serum harvested by pipetting then stored in 2-mL tubes at −20°C until analysed using a competitive enzyme immunoassay to determine BST concentrations. In addition, a transrectal electro-ejaculator was used to collect semen samples in pre-warmed 15-mL graduated tubes after decontamination of the prepuce. For semen volume, visual appraisal of the graduated tube was used; for total semen motility, a Sperm Class Analyser version 6.3 (Microptic, Spain) was used; for sperm abnormalities, nigrosin-eosin stain and the Olympus BX51 microscope was used; and for semen concentration, a spectrophotometer (Jenway, United Kingdom) was used. Using PROC GLM and PROC REG statements in SAS Studio 3.8, this study found that at all ages except 4.5 and 6 months of age, the studied breeds had similar bodyweights ranging from 17.3 ± 1.3 kg to 27.3 ± 2.4 kg (P > 0.05), similar BST concentrations ranging from 3.1 ± 0.6 ng mL⁻¹ to 6.3 ± 1.0 ng mL⁻¹ (P > 0.05), and similar semen volume ranging from 0.3 ± 1.0 mL to 0.6 ± 1.0 mL (P > 0.05). The homogeneity of bodyweights and BST concentrations between these breeds supports fundamental animal science research that claims that breeds in similar environments will have comparable phenotypic characteristics; and second, that a male’s testosterone production is influenced by his bodyweight due to a strong direct correlation between bodyweight and scrotal circumference. Strikingly, Bapedi and Zulu sheep had significant within-breed increases in sperm cell concentration between 7 and 8 months of age (P < 0.05), as well as significant within-breed decreases in the number of sperm abnormalities between 7 and 8 months (P < 0.05); however, at all ages, Namaqua-Afrikaner ram lambs had more sperm abnormalities e.g. 4.5 ± 2.2 tail abnormalities at 7.5 months of age compared with 1.1 ± 0.9 and 1.4 ± 0.8 for Bapedi and Zulu, respectively. This finding is compelling evidence for claims that Namaqua-Afrikaner sheep are “late-maturing” and had incomplete spermatogenesis which caused increased abnormalities because they were physiologically younger than the other two breeds at the sampling dates. Lastly, this study also found that all studied breeds ejaculated good quality semen (>70% total semen motility) from 7 months of age. Corresponding 95% confidence intervals at this semen parameter were (18.80, 28.82) and (3.34, 8.75) for bodyweight and BST concentrations, respectively. A new perspective on male smallstock attainment of puberty has been gained through this study and it is recommended that more studies explore the accelerated, innovative use of these hardy and disease-tolerant breeds for sustainable smallstock production in the region.