Effect of early luteolysis in progesterone-based timed AI protocols in Bos indicus, Bos indicus × Bos taurus, and Bos taurus heifers》.pdf

Available online at Theriogenology 69 (2008) 167–175 Effect of early luteolysis in progesterone-based timed AI protocols in Bos indicus, Bos indicus Bos taurus, and Bos taurus heifers J.B.P. Carvalho a, N.A.T. Carvalho b, E.L. Reis c, M. Nichi c, A.H. Souza c, P.S. Baruselli c,* a ´ Vale do Paraıba Regional Station – Apta, Brazil b Vale do Ribeira Regional Station – Apta, Brazil c Department of Animal Reproduction, FMVZ-USP, Brazil Received 4 January 2007; accepted 20 August 2007 Abstract The objective of this study was to evaluate the effects of treatment with an intravaginal progesterone-releasing device (CIDR) and estradiol benzoate (EB) on follicular dynamics in Bos indicus (n = 23), Bos taurus (n = 25), and cross-bred (n = 23) heifers. To assess the influence of reduced serum progesterone concentrations during 8 days of treatment with a progesterone-releasing device on follicular dynamics, half of the heifers received PGF at CIDR insertion (Day 0; 3 2 factorial design). Mean (S.E.M.) serum progesterone concentrations during CIDR treatment varied (P 0.05) among genetic groups: B. indicus (5.4 0.1 ng/mL), B. taurus (3.3 0.0 ng/mL), and cross-bred (4.3 0.1 ng/mL). Maximum diameter of the dominant follicle (DF) was smaller (P 0.01) in B. indicus heifers (9.5 0.5 mm) than in cross-bred (12.3 0.4 mm) or