Design and biological effects of a vaginally administered gel containing the GnRH agonist, triptorelin, for
R V Knox1, K R Stewart2, W L Flowers3
1Department of Animal Sciences, University of Illinois, Urbana, IL, USA.
Abstract:
A novel gel formulation was selected for intravaginal delivery of the GnRH agonist (triptorelin) for synchronizing ovulation in pigs. Studies with gilt models were used to assess LH response profiles. The lowest dose of triptorelin that induced the most gilts to show an LH surge was 100 μg in 1.2% methylcellulose gel. This formulation had a similar effect in weaned sows while also advancing ovulation. The timing of administration was evaluated in sows after weaning. Administration at 96 h induced more sows to ovulate (58%) by 48 h compared to treatment at estrus (45%) or for controls (34%), but the desired level of ovulation synchrony was not achieved. As a result, greater doses of triptorelin were tested and 200 μg given at 96 h after weaning, induced 81% of sows to ovulate within 48 h after treatment. The best synchrony of ovulation occurred when given at 96 h after weaning compared to earlier or later intervals. The optimum time to give a single fixed time AI (SFT-AI) after administration of 200 μg of triptorelin in 1.2% gel (OvuGel®) at 96 h after weaning was tested. A SFT-AI at 22 ± 2 h after OvuGel achieved the highest fertility and was practical for staff during the normal work day. In field trials, a SFT-AI 22 ± 2 h after all weaned sows were treated with OvuGel improved (P = 0.04) farrowing rate to 82.5% compared to control sows weaned (80.1%), with no effect on numbers of pigs born alive (12.1). Research continues for identifying the advantages for use of OvuGel in different production systems, and potential application for use in gilts.
