150 USING A LUTEINIZING HORMONE SURGE DETECTION TEST, PREDI'BOV®, TO OPTIMIZE THE TIME OF ARTIFICIAL INSEMINATION DURING A SUPEROVULATION PROTOCOL IN A HOLSTEIN HEIFERS HERD

Abstract

Insemination of superovulated bovine donors in due time is of central importance for fertilization and embryo viability. A preliminary test focusing on LH surge detection during superovulation (unpublished datas) indicated that one quarter of the donors present LH surges 12 to 24 h before heat observation (which could correspond, in the case of AI after heat observation, to post ovulation AI). Therefore, it was hypothesised that the average number of embryos per flush could be improved by inseminating donors with early LH surge 12 h after the beginning of the LH peak whenever the heat occurs.In a donor herd station, a trial was performed with 54 Holstein heifers, equipped with Heatime® tags (system detecting the peak activity linked to the heat) collected twice or 3 times after the following superovulation protocol: D-6 to D-11 = reference heat; D0 = input of an implant of norgestomet (Crestar®); D2 8:00 = first FSH (Stimufol®) injection (FSH1); D4 8:00 = cloprostenol (Estrumate®) injection; D4 16:00 = implant removal; D5 8:00 = FSH7 and first LH surge detection test (Predi'Bov®); D5 16:00 = FSH8 and 2nd Predi'Bov® test. Two AI's at interval of 8 to 16h were done (AI's were performed either at 9:00, or between 17:00 and 19:00). For the standard protocol (= STA), thefirst AI occurred after heat observation or activity peak detection by Heatime (whatever the Predi'Bov® test results were). For the adjusted protocol (= ADJ), the first AI occurred from 11 to 16 h after the first positive Predi'Bov® test result or like STA protocol if both results were negative. Heifers followed alternately the 2 protocols, 27 beginning with the ADJ protocol, 27 others with the STA one. LH surge precocity was not repeatable among donors. In the case of an early LH surge detection (one positive Predi'Bov® test), the heat activity peak occurred from 2 to 8 h after the FSH8 for 44% of the flushes, from 8 to 24 h after FSH8 for 54% of the flushes and never for 2% of the flushes. When no early LH surge was observed, the heat activity peak occurred more than 8 h after FSH8 for 78% of the flushes. Interval of heat activity peak-FSH8, IA1-heat activity peak and IA1-early LH surge were highly variable but did not effect the mean number of viable embryos. However, we observed a significant effect (P = 0.04) of the precocity of the heat on the average number of total embryos: 13.8 ± 8.4 v. 11.1 ± 8.1 when the interval heat activity peak-FSH8 had been respectively <8 h or ≥8 h, respecively. Among the 148 collections, 74 were done after the STA protocol, 74 after the ADJ protocol and 70 followed an early LH surge. The adjustment of the AI depending on the detection of an early LH surge (ADJ protocol) had a significant positive (P = 0.04) effect on the mean percentage of viable embryos per flush (52% ± 28 in STA group and 62% ± 31 in ADJ group). Nevertheless, regarding the mean number of viable embryos, this effect failed to reach significance (P = 0.23) (respectively 5.7 ± 5.1 in STA group and 6.7 ± 6.7 in ADJ group). A larger study on more animals is necessary to obtain a significant difference in the number of viable embryos.