- Ronderib Afrikaner ram effect on fertility : 1. Effect of Ronderib Afrikaner rams on the fecundity of Merino ewes
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RONDERIB AFRIKANER RAM EFFECT ON FERTILITY: 1 THE EFFECT OF
RONDERIB AFRIKANER RAMS ON THE FECUNDITY OF MERINO EWES.
P R King and D Wentzel
Grootfontein College of Agriculture,
Results on the effect of Ronderib Afrikaner rams on reproduction in Merino ewes over a 5-year period indicated that the lambing percentage of Merino ewes mated to Ronderib Afrikaner Rams was higher than that of Merino ewes mated to Merino rams. This elevated lambing percentage was brought about by a higher fecundity (19%) in the Ronderib Afrikaner mated Merino ewes while the percentage ewes that lambed in each group did not differ significantly. This increased fecundity could be the result of the following: 1. The Ronderib Afrikaner having a better semen quality than that of the Merino. 2. A higher early embryonic death rate has been reported for purebred embryos as compared to that of crossbred embryos. 3. A ram effect on ovulation rate. The following experimental design was followed to investigate the above-mentioned hypothesis. A group of 100 Merino ewes were joined with three vasectomized Ronderib Afrikaner rams while the control group was joined with three vasectomized Merino rams for a period of six weeks. All rams were fitted with radling harnesses to identify ewes displaying overt oestrus for subsequent artificial insemination with Merino semen. From the reproductive data obtained the fecundity of the ewes exposed to Merino rams, was 135% as compared to 157% of those exposed to Ronderib Afrikaner rams( P < 0.01 ). The experimental procedures followed excluded the former two possibilities as possible causes for the difference in fecundity recorded. These results seem to suggest a direct ram effect on ovulation rate.
Proceedings 29the SASAP congress L4.7., Merino newsletter March 1991