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

•Interval from last feeding of progestogen to estrus in mature gilts is related to time of ovulation.•Treatment of progestogen synchronized gilts with triptorelin at 120 h after last feeding of Matrix, increased synchrony of ovulation.•Treatment of progestagen synchronized gilts with 100 to 400 mg of triptorelin improved the proportion of gilts ovulating within a 24 h period.

Estrus and ovulation responses in Matrix-treated gilts may affect ovulation synchrony in response to triptorelin. In experiment 1, estrus and ovulation measures at 12 h 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 24-60 h 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 2 mL of gel containing placebo (Control) at 96 h, 200 μg of triptorelin at 96 h (TRP96), 120 h (TRP120) or 144 h (TRP144) after LMF. Estrus measures did not differ (P > 0.10) among treatments. The proportion of gilts ovulating 32-56 h 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), 100 μg (TRP100), 200 μg (TRP200), or 400 μg (TRP400) of triptorelin at 120 h 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 56 h after treatment increased (P < 0.05) with triptorelin compared to Control. Our results indicate that gilts receiving 100-400 μg of triptorelin at 120 h after LMF had the greatest ovulation synchrony 24-48 h following treatment. These studies provide important information for developing a procedure for a single insemination in synchronized gilts.