Last update: August 16, 2011 03:09:27 PM E-mail Print

 

THE ROLE OF SEMINAL PLASMA IN THE ABILITY OF THE RONDERIB AFRIKANER RAM TO INCREASE THE OVULATION RATE OF MERINO EWES

 

P R King, W J Wiese*, W A Coetzer**, & P A Schlebusch

Grootfontein College of Agriculture, Middelburg Cape, 5900

*Regional Veterinary Laboratory, Middelburg Cape, 5900

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

Stellenbosch, 5900

 

 

Ronderib Afrikaner rams and Ronderib Afrikaner teaser rams increase the ovulation rate of Merino ewes on average by 19 % when compared to the ovulation rate of ewes running with Merino rams. The Ronderib Afrikaner ram and teaser ram physically stimulate the ewe and both ejaculate seminal plasma when mating. Ovine seminal plasma contains exceptionally high levels of prostaglandins (50 ug\ml) but the physiological effect thereof is not known. Because of the higher sexual activity of the Ronderib Afrikaner ram the possibility exists that more seminal plasma and therefore more prostaglandins are deposited in the vagina of the Merino ewe during oestrus compared to that deposited by the Merino ram. The prostaglandin concentration in the seminal plasma of the Ronderib ram could also be higher than that of the Merino ram. The following experimental design was followed to investigate the effect of the seminal plasma of the Ronderib Afrikaner ram on ovulation rate. The urethra of two Ronderib Afrikaner rams was surgically ligated and a 1 cm section was removed between the bulbous part of the urethra and the sigmoid flexure. A foleys catheter (no 24) was surgically inserted into the bladder in order to drain urine through the abdominal wall. These rams were not capable of ejaculating seminal plasma after the operation. Two hundred Merino ewes were devided on a stratified body mass and age basis into three groups. One group was mated to two vasectomized Afrikaner rams (group A). The second group was mated to the Ronderib Afrikaner rams not capable of ejaculating (group B) while the third group was mated to two vasectomized Merino rams (group C). Each ram was fitted with a raddling harness to identify ewes displaying overt oestrus. Nine days following oestrus ovulation rate was determined laparoscopically. The ovulation rate of group C (control) was 142 % compared to the 162 and 161 % of group A and B respectively. The difference in ovulation rate between the control group and groups A and B was 20 and 19 % respectively (P<0.01). From these results it can be concluded that the seminal plasma of the Ronderib Afrikaner ram is not the cause of the observed higher ovulation rate in Merino ewes.

 

Published

Proceedings 31st SASP congress