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Effect of time of OvuGelŪ administration on timing of estrus and ovulation and pregnancy rates in gilts synchronized for estrus
The effect of time of OvuGel® administration on timing of estrus and ovulation and pregnancy rates was evaluated in a study involving 448 gilts that had been synchronized for estrus by administering Matrix® for 14 d. A RCBD with the following treatments was used: 1) Control (no OvuGel® administration), 2) OvuGel® administration on d 5 (118 h) after the end of Matrix® administration (OV5), and 3) OvuGel® administration on d 6 (142 h) after the end of Matrix® administration (OV6). Control gilts were inseminated once per each morning of behavioral estrus; gilts administered OvuGel® received 1 insemination 24 h after OvuGel® administration. Gilts were randomly allotted to treatment within genetic line on the basis of similar live weight and stage of estrous cycle. Gilts were checked for estrus and ultrasonically scanned (trans-rectally; subsample of 250) at 12 h intervals from d 4 to 10 after Matrix® administration. Gilts on the OV5 and OV6 treatments exhibited estrus earlier (P < 0.05) than Control gilts (140.0, 140.9, and 151.3 h after the end of Matrix® administration, respectively; SEM 2.51). Ovulation occurred earlier (P < 0.05) for OV5 (164.8 h) than OV6 gilts (174.3 h) and earlier (P < 0.05) for OV6 than Control gilts (189.7 h; SEM 2.17). A greater (P < 0.05) percentage of Control gilts (100.0%) exhibited estrus at insemination than OV5 and OV6 gilts and more (P < 0.05) OV6 gilts (64.6%) exhibited estrus at insemination compared to OV5 gilts (40.4%). Gilts on the OV6 treatment had a lower (P < 0.05) interval from insemination to ovulation than OV5 gilts (8.2 vs. 22.8 h, respectively), and a greater (P < 0.05) percentage of OV6 gilts ovulated within 48 h after OvuGel® administration than OV5 gilts (92.5 vs. 70.9%, respectively). Pregnancy rate (percentage of total gilts allotted to the study that were pregnant at 35 d) was greater (P < 0.05) for Control and OV6 than OV5 gilts (74.5, 77.6, and 56.2%, respectively). Pregnancy rate (percentage of total gilts inseminated that were pregnant at 35 d) was greater (P < 0.05) for Control than OV5 and OV6 gilts (91.0, 56.2 and 77.6%, respectively) and greater (P < 0.05) for OV6 than OV5 gilts. These results suggest that in gilts the timing of estrus and ovulation and pregnancy rates depend on the time of OvuGel® administration following estrus synchronization, and in OvuGel® administered gilts, single insemination with normal fertility is achievable.
Keywords: OvuGel®, Gilt, Ovulation