Effects of estrus synchronization using Matrix followed by treatment with the GnRH agonist triptorelin to control ovulation in mature gilts.

Estrus and ovulation responses in Matrix-treated gilts may affect ovulation synchrony in response to triptorelin. In experiment 1, estrus and ovulation measures at 12h intervals after last Matrix feeding (LMF) were analyzed. For the 398 gilts that displayed estrus, 87.4% were detected on Days 6-8 after LMF. Duration of estrus was 24-60h for 85.6% of gilts and negatively correlated with interval from LMF to estrus (r=-0.53, P<0.0001). The estrus to ovulation interval was positively correlated with duration of estrus (r=0.61, P<0.0001). In experiment 2, gilts (n=96) received intravaginal treatment with 2mL of gel containing placebo (Control) at 96h, 200μg of triptorelin at 96h (TRP96), 120h (TRP120) or 144h (TRP144) after LMF. Estrus measures did not differ (P>0.10) among treatments. The proportion of gilts ovulating 32-56h after treatment was greater for TRP120 and TRP144 (P<0.01) compared to other treatments. The treatment to ovulation intervals for all triptorelin treatments were shorter (P<0.001) than Control. In experiment 3, gilts (n=86) received placebo (Control), 100μg (TRP100), 200μg (TRP200), or 400μg (TRP400) of triptorelin at 120h after LMF. There was no effect of treatment (P>0.10) on estrus or on interval from LMF to estrus. The proportion of gilts ovulating by 40, 48 and 56h after treatment increased (P<0.05) with triptorelin compared to Control. Our results indicate that gilts receiving 100-400μg of triptorelin at 120h after LMF had the greatest ovulation synchrony 24-48h following treatment. These studies provide important information for developing a procedure for a single insemination in synchronized gilts.