Abstract

Buserelin administered 24 h prior to A.I. increased ovulation rates in Sarda ewe. This study reports the effect of the same treatment on LH, E2 and P4 plasma levels. After a classic synchronization treatment of oestrous cycles, 24 multiparous Sarda ewes were submitted to A.I. (Day 0) 55 h after sponges removal. On Day – 1 12 ewes (Group T) were given a single i.m. injection of 4 μg/progestin buserelin (Receptal) and the remaining 12 ewes (Group C) acted as control. Blood samples were collected from each subject at 2-h intervals on Days – 1 and 0 (from 8:00 to 16:00 h) and twice on Day + 1 (8:00 and 15:00 h). LH concentration was assessed by ELISA (Reprokit), E2 and P4 by homologous radioimmunoassay. Buserelin caused in T subjects, compared to controls, an increase of LH (Day – 1), a decrease of E2 (Days – 1 and 0) and an increase of P4 concentrations (Day + 1). These differences were statistically significant (P < 0:05). The results are in agreement to our previous observations on follicular dynamics: the higher LH and P4 levels reflected the increased number of corpora lutea and the lower E2 level the decreased number of large follicles.

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