REDUCTION OF THE VOLUNTARY WAITING PERIOD BY USE OF HORMONAL PROTOCOLS AND FIXED-TIME ARTIFICIAL INSEMINATION (FTAI) IN DAIRY COWS

Abstract

ABSTRACT: The aim of this study was to reduce the waiting voluntary period in dairy cows by administration of two different hormonal protocols for estrus synchronization and fixed-time artificial insemination (FTAI). One hundred twenty-eight Holstein dairy cows were studied. Three groups (G) were carried out: G1 (44 treated), G2 (34 treated) and G3 (50 as control). In the treated cows the following hormonal protocols was applied between 40 and 45 days post partum: G1- Day 0 (D0) - bovine intravaginal device containing progesterone (P₄) plus 1.0 mg of estradiol benzoate (EB), D8 - removal of the P₄, plus 0.5 mg of cloprostenol plus 400 IU of equine chorionic gonadotropin (eCG), D9 - 1.0 mg of EB and FTAI after 36 hours. G2 - D0 - P₄ intravaginal plus 50 mcg of gonadotropin-releasing hormone (GnRH), D7 - removal of the P₄ plus cloprostenol plus 400 IU eCG; D9 - 50 mcg of GnRH and FTAI 16 hours after. G3 – Control group inseminated 12 hours after the visual estrus. Results: G1 and G2 were inseminated (FTAI) respectively in the D55.5 and D56.8 after calving, while the G3 in the D84.5 (p<0.01).  The pregnancy rate in the G1, G2 and G3 was respectively 47.0, 46.1 and 35.8% (p>0.05).  In Conclusion: there was significant reduction in the voluntary waiting period in treated cows and higher pregnancy rate although not significant.