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Timing of ovulation in gilts relative to last Matrix® feeding
Previous research has shown 85% of gilts treated with Matrix® will show estrus 4-9 days post last Matrix® feeding. Although this data is helpful in establishing when to AI, it would be beneficial to have a better understanding of timing of ovulation and not just have a range of timing of estrus. In this study we wanted to see if we could assess timing of ovulation in Matrix® treated gilts by performing transrectal ultrasonography. Between June and August of 2014, 3 groups consisting of 10 cycling gilts each were used to evaluate timing of ovulation relative to last Matrix® feeding using transrectal ultrasonography. These groups consisted of Landrace or Landrace/Large White gilts (Choice Genetics® USA) with an average age of 7.5 months and an average of 2 estrous cycles prior to Matrix® feeding over all 3 groups. Gilts were housed in gestation stalls in a mechanically ventilated barn during the duration of this study. Each gilt was fed 15mg of Matrix® daily for 14d per label instructions. Transrectal ultrasonography was performed starting 24 hours post last Matrix® feeding and then at 4 hour (n=10) or 6 hour (n=20) intervals, continuing until each gilt ovulated, or until day 9, whichever came first; 4 gilts did not ovulate. Ovulation was determined by either visualization of CL or the absence of follicles for 2 subsequent scans. From our results, we concluded that timing of ovulation relative to last Matrix® feeding was found to be 134.6 ± 13.4 hours (5.6 ± 0.56 days). Estrus detection was not performed during this study, but estrus detection performed at this farm typically finds that average estrus occurs at day 5.9 post last Matrix® feeding. Having greater knowledge of timing of ovulation relative to last Matrix feeding may allow investigation into more precise timing of insemination.
Keywords: Matrix®, ovulation and gilt