Abstract
The aim of the study was to compare the effect of age and live body weight on the oestrus response, duration, pregnancy rate and lambing rate among South African indigenous sheep breeds (Zulu sheep = 36, Bapedi sheep = 26, Damara sheep = 10 and Namaqua Afrikaner sheep = 9). Control Intravaginal Drug Release Dispensers (CIDR’s) were inserted into the vagina for 10 days. The twitching of tail and standing to be mounted in the presence of the teaser ram were most targeted signs of oestrus. Data were subjected to an appropriate analysis of variance (ANOVA). The scores were subjected to 1:1 Frequency table and a Chi-Square (χ²) test for the equal proportions test. One Bapedi ewe loss CIDR before removal date hence was removed from the experimental animals. All Namaqua Afrikaner (100%) ewes responded to the synchronization protocol with the longest oestrus duration (70.7±7.2 h). However, Namaqua Afrikaner sheep scored the lowest rate for conception (44%) and lambing (44%). No significant different (P>0.05) observed for the onset of oestrus among the breeds. Four years old ewes responded better to oestrus synchronization than ≤3, 5 and ≥6 years. Nevertheless, ewes that were ≥6 years old had higher conception rate (94%) and lambing rate (84%). Zulu sheep had higher (89%) lambing rate than Damara (60%) sheep and Namaqua Afrikaner (44%) sheep. Lighter ewes had higher conception (83%) and lambing rate (90%) than heavier (77 and 64%) and moderate (68 and 78%) weights, respectively. In conclusion, Zulu sheep were more fertile than other South African indigenous breeds following oestrus synchronization. On the other hand, young ewes (≤3 years) produced heavier lambs and weaning weight but had higher mortality rate due to inexperience.
Highlights
Reproductive efficiency is a critical trait but low heritable (Safari et al, 2005) and governed by various factors such as environmental conditions, season, management system and nutrition (McManus et al, 2020)
The importance of South African indigenous sheep lies within their ability to reproduce under harsh environmental conditions (Kunene et al, 2009)
Eight-one South African indigenous ewes (Zulu sheep = 36, Bapedi sheep = 26, Damara sheep = 10 and Namaqua Afrikaner sheep = 9) are left at the Agricultural Research Council (ARC), Irene and were all used in this study
Summary
Reproductive efficiency is a critical trait but low heritable (Safari et al, 2005) and governed by various factors such as environmental conditions, season, management system and nutrition (McManus et al, 2020). Zulu sheep along with Bapedi sheep are Nguni type found in wet areas of eastern coast and characterised as fat-tailed and small body framed size (Kunene and Fossey, 2006; Molotsi et al, 2020; Maqhashu et al, 2020). Uncontrolled mating in rural areas is another factor found to ground genetic erosion of these breeds (Mavule et al, 2016; Selepe et al, 2018) that inhibits adaptive responses to harsh environmental conditions (Bijlsma and Loeschcke, 2012)
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