FOLLICULAR DEVELOPMENT AND EMBRYO RECOVERY FOLLOWING 3 VERSUS 8 FSH INJECTIONS IN HEIFERS

Ovarian follicular dynamics and embryo yield were studied during 2 dif ferent FSH regimens for superovulation of cattle. Twenty heifers were given intramuscular injections of FSH (total of 35 mg NIH) either once daily for 3 days (Group 3x1) or twice daily for 4 days (Group 4x2). A t 72 h after the first FSH injection, each animal was injected with 0. 75 mg cloprostenol. Inseminations were performed at 12 h and 24 h afte r the onset of heat. Transrectal ultrasonography was performed on the day of the first FSH injection, the day of cloprostenol injection, the day of insemination and finally on the day of embryo recovery (day 6 or 7 after heat). The numbers of small (2-4 mm), medium (5-9 mm) and l arge (>10 mm) size follicles were recorded. The total number of corpor a lutea, eggs and transferable embryos were recorded on the day of emb ryo recovery. No differences were found between the 2 groups in either of the parameters studied (p>0.05). It can be concluded that treatmen t with this FSH preparation once daily for 3 days gives a folliculogen ic and superovulatory response similar to a treatment regimen where it is given twice daily for 4 days.