Comparaison de l'effet de deux analogues de la prostaglandine F2α sur la synchronisation de l'œstrus chez la vache de boucherie

Abstract

The objective of this study was to compare the efficiency of cloprostenol and fenprostalene in synchronizing estrus. Before treatment, estrus was detected during 4.5 d for multiparous cows in exp. 1 (n = 105) and 7.5 d for primiparous and nulliparous females in exp. 2 (n = 86). Females that were not in estrus (exp. 1: n = 74 and exp. 2: n = 58) received at random, either 500 μg of cloprostenol (i.m.) or 1 mg of fenprostalene (s.c). Cattle synchronized with cloprostenol or fenprostalene that presented estrus within 5 d showed similar fertility rates (exp. 1: 86.1% vs. 88.0% and exp. 2: 89.3% vs. 72.2% for cloprostenol and fenprostalene, respectively) and PGF2α-estrus intervals (exp. 1: 68 h vs. 73 h and exp. 2: 57 h vs. 57 h). However, the incidence of synchronization (exp. 1: 97.3% vs. 67.6%, P < 0.001; and exp. 2: 93.3% vs. 64.3%, P < 0.01) and pregnancy rates (exp. 1: 83.8% vs. 59.5%, P < 0.05; and exp. 2: 83.3% vs. 46.4%, P < 0.01) were statistically higher for cloprostenol than for fenprostalene. In exp. 2, primiparous cows and heifers obtained similar reproductive performances. The fertility rate of cattle treated with cloprostenol in exp. 2 was higher than that of untreated cattle (89.3% vs. 50.0%, P < 0.001, n = 56). In exp. 1, the variance of interval to estrus was similar for both analogues, but in exp. 2, it was less variable after the administration of cloprostenol (P < 0.05). Intervals between cloprostenol injection and estrus (0–10 and 0–15 d) were shorter (P < 0.05) and less variable (P < 0.001) than fenprostalene–estrus intervals. These results indicate that cloprostenol has a better potential for estrus synchronization than fenprostalene. Key words: Cloprostenol, fenprostalene, estrus synchronization, prostaglandin F2α, beef cattle