By D.S. Dillard and W.L. Flowers, North Carolina State University Department of Animal Science
OvuGel currently is the only product approved for ovulation induction in swine in the United States and is given 96 hours post-weaning followed by a single insemination 20 ± four hours later. This protocol assumes that most of the sows in a herd have pre-ovulatory follicles by Day 4 post-weaning.
It has been well documented that weaning-to-estrus intervals vary considerably due to a number of environmental conditions and field studies conducted with OvuGel using the approved regimen have produced equivocal fertility results (Theriogenology 112, 44-52). Physiological and behavioral signs associated with pro-estrus and estrus are due to estrogens produced by pre-ovulatory follicles and could provide a way to adjust the timing of ovulation induction in herds with variable weaning-to-estrus profiles.
Over the past three years, studies were conducted on commercial swine farms to investigate the effectiveness of administering OvuGel at either signs of pro-estrus or estrus followed by a single insemination 20 + four hours later. Control treatments in each of these situations were sows either in pro-estrus or estrus at the same time as sows treated with OvuGel but they were bred once each day of estrus. Results from the two different approaches are summarized in Tables 1 and 2.
Table 1: Effect of administration of OvuGel to sows at pro-estrus after weaning.
Table 2: Effect of administration of OvuGel to sows at estrus on Days 4 or 5 post-weaning.
There were no statistical differences between reproductive performance of the control sows which were bred once each day of estrus and sows treated with OvuGel either at proestrus or estrus. On most commercial farms detection of estrus tends to be more consistent among technicians than identification of pro-estrus so this might be the easiest approach to implement without additional training. As mentioned previously, OvuGel is currently approved for use in sows at 96 hours, or four days, post-weaning. Consequently, treatment of weaned sows exhibiting signs of pro-estrus or actually in estrus on Day 4 post-weaning is consistent with its use approved by the Food and Drug Administration. Administration of OvuGel to pro-estrus or estrus sows after Day 4 post-weaning is equally effective from a reproductive standpoint but is an extra-label use of the product.