Effect of GnRH and D-Chloprostenol application on pregnancy and prolificacy rates on Pelibuey ewes

Abstract

ABSTRACTObjective. Was to evaluate the effect of GnRH and D-Chloprostenol application on pregnancy and prolificacy rates on Pelibuey ewes. Materials and methods. Forty five ewes were randomly allocated to one of three treatments: T1(n=15), day 0: sponges with 65 mg medroxyprogesterone acetate (MPA) + 200 IU equine chorionic gonadotropin (eCG) and sponge removal (day 12) + breeding by natural mating (days 12-15); T2 (n=15), day 0: 50 μg gonadotropin releasing hormone (GnRH) + 7.5 mg D-Chloprostenol (day 5) + 50 μg GnRH (day 7) + insemination at fixed time (AIFT) 12 to 14 h after last injection of GnRH; T3 (n=15), 100 μg GnRH (day 0) + 7.5 mg D-Chloprostenol (day 5) + 100 μg GnRH (day 7) + AIFT 12 to 14 h after last injection of GnRH. Results. The average concentration of progesterone (P4) in blood was 1.22 ± 0.74 ng/mL, which was used to verify ovarian activity at the beginning of the treatments. 100% of the T1 ewes presented estrus, beginning at 38.4±9.56 h after sponge removal. There were differences (p<0.05) for pregnancy rates, of 60, 33.33 and 46.66% respectively, among the treatments. Prolificacy was no different (p>0.05) among the treatments where the values were 1.2, 1.4 and 1.4 lambs/ewe for T1, T2 and T3, Conclusions. The results of this study show that the use of GnRH and D-Chloprostenol did improve pregnancy rates but did not improve prolificacy in tropical ewes