Last update: August 16, 2011 12:16:50 PM E-mail Print




P R King, W A Coetzer* & D M E Pieterse

Grootfontein College of Agriculture, Middelburg Cape, 5900

*Department of Human and Animal Physiology, University of Stellenbosch,

Stellenbosch, 6700


The ovulation rate of Merino ewes mated to vasectomized Ronderib Afrikaner rams is on average 19% higher than that of Merino ewes mated to vasectomised Merino rams. When the ewes mated to the Ronderib Afrikaner teaser rams are inseminated with Merino semen, their lambing percentage is also on average 19% higher than that of inseminated Merino ewes mated to Merino teaser rams. In practice, however, many farmers synchronize their ewes to facilitate the artificial insemination of the ewes. The following experimental design was followed to determine whether Ronderib Afrikaner teaser rams are capable of also increasing the ovulation rate of synchronized Merino ewes. All ewes were synchronized with progesterone sponges (14 days) and thereafter divided into groups on a stratified mass and age basis. Thirty six ewes (Group A) were mated to one Ronderib teaser ram while 36 ewes (Group B) were mated to one Merino teaser ram (2.7 % ram: ewe ratio). Four Ronderib Afrikaner teaser rams and four Merino teaser rams were allocated to 36 ewes respectively (Groups C and D - 11 % ram: ewe ratio). The rams were placed among the ewes on sponge withdrawal and were left with the ewes until after oestrus. Nine days following oestrus, ovulation rate was determined laparoscopically in all ewes. Each treatment was repeated and the results obtained were pooled as no significant differences occurred between the repetitions of each treatment. The ovulation rate of group A was 142 % compared to the 130 % of group B (P<0.O5). The 12 % difference in ovulation rate was smaller than expected and can probably be attributed to the low ram: ewe ratio. For groups C and D the ovulation rate was 130 and 127 % respectively (P>0.05). In groups C and D the ram: ewe ratio was probably too high because the Ronderib rams were constantly trying to form harems and were therefore not as active among the ewes as usual. This could be a possible explanation for the insignificant difference (3%) in ovulation rate between groups C and D. To fully utilize the Ronderib Afrikaner ram effect when ewes are synchronized, it is essential that further work be done on the ram: ewe ratio, ewe flock size and kraal size.



Proceedings 31st SASAP congress