Comparison of Prostaglandin F2α and Two Potent Analogues for Synchronizing Estrus in Dairy Heifers

Cyclic dairy heifers (n = 84) were used to compare three different prostaglandin preparations for synchronizing estrus. Animals were first synchronized with norgestomet treatment. When animals reached days 10 to 12 of the treatment cycle (day 0 = estrus), animals were randomly allotted across prostaglandin treatment groups for each day of their estrous cycle. Heifers in Group I received 25 mg of prostaglandin F2α (Lm.), Group II received .5 mg of cloprostenol (i.m.), and Group III received 1 mg fenprostalene (s.q.). Heifers were then continually monitored for estrual behavior for 7 d. Following norgestomet removal, 88% of the animals exhibited estrus with a mean interval from implant removal to estrus of 45 h. A total of 89, 92 and 78% of the heifers exhibited estrus following prostaglandin F2α (PGF2α), cloprostenol (CLO), and fenprostalene (FEN) treatments, respectively. The time from injection to estrus for PGF2α, CLO, and FEN was 74, 70, and 70 h, respectively. There was a significant decrease in the number of animals that exhibited estrus (P<.05) in FEN compared with PGF2α and CLO treatments.