Abstract:
The objective of this study was to determine the effect of BCS and parity that affect the conception of the extensively farmed South African beef cows postpartum. The cows were synchronised using the 7-day Co-Sync + progesterone releasing device protocol. Body condition score (BCS) was recorded on the day of insemination. Recording information (cow identification numbers, previous calving records, cow age, inter-calving period, last calving date, cow mass and the number of calves. It also contained the Estimated Breeding Values (EBV) for Heifer fertility as well as Cow Fertility). Mixed model analyses were used to analyse the data that was obtained for the study. The cows (n = 42) that were included in the current study had a conception rate of 83,33%. The time of artificial insemination (AI) was shown to not have a significant effect (p > 0.05) on the conception rate of the cow. The weight change of the cow between weaning and calving for the second parity preceding the current one, showed to not have a significant effect (p > 0.05) on the current conception rate. The results show that there was a significant effect within the various parities for the major factors that were studied, e.g. Body condition score (p = 0,021), days to AI (p = 0,031) and the EBV for Fertility for the cow (p = 0,006) had significant effects on the conception rates in the cows.
The BCS within the weighted parity, has a significant effect on the conception rate in the cows. The cows that were found to be over conditioned (>3,75) were more likely not to conceive, and the cows that had a BCS of 3,00 had the best conception rates. The number of days that the cow is given for a recovery period was important to consider as the cows that were inseminated too early had a higher probability of not conceiving. The prime parity group was parity 6, which has the highest conception rate. The link between BCS and parity was important as cows that are not found in the correct BCS category and fall outside of the prime parity groups are the cows who struggle to conceive. The EBV of Fertility for the cow has a significant effect on the conception rate and can be an important tool for farmers to use when selecting replacement heifers for their herds. The time of day that AI takes place, may have an effect on the conception but more research needs to be done on this, this current study did not show any significant results and therefore no link can be made to what time of day would be optimal for maximised artificial insemination.
