216 DINOPROST ADMINISTRATION, PERIOD OF OVULATION, AND OVULATORY FOLLICULAR SIZE ON DAYS FOUR TO SIX OF ESTROUS CYCLE IN EWESP. M. P. Nascimento A , A. P. Oliveira B , F. Z. Brandao A , A. L. R. S. Maia A , P. H. N. Pinto C , M. E. F. Oliveira D , J. H. Bruschi E , J. H. M. Viana E and J. F. Fonseca F
A UFF, Niteroi, Rio de Janeiro, Brazil;
B EPAMIG, Belo Horizonte, Minas Gerais, Brazil;
C UFPR, Curitiba, Parana, Brazil;
D UNESP, Jaboticabal, São Paulo, Brazil;
E Embrapa Gado de Leite, Juiz de Fora, Minas Gerais, Brazil;
F Embrapa Caprinos e Ovinos, Ceará, Brazil
Reproduction, Fertility and Development 22(1) 266-266 http://dx.doi.org/10.1071/RDv22n1Ab216
Published: 8 December 2009
The aim of this study was to evaluate the effects of 2 doses of dinoprost at the time of ovulation on Days 4 to 6 of the estrous cycle in ewes. The experiment was conducted in the city of Piau (Minas Gerais, Brazil) from July to August 2008 during the local no-breeding season. Twenty-four ewes with body condition score 3.0 ± 0.75 were used for this experiment. The estrous cycle was synchronized with intravaginal releasing devices containing 0.33 g of progesterone for 6 days (Eazi-Breed CIDR®, Pfizer Animal Health, São Paulo, Brazil), and 12.5 mg of dinoprost (Lutalyse®, Pfizer do Brasil Saúde Animal, São Paulo, Brazil) laterovulvar plus 300 IU of eCG 24 h before device removal. Animals were monitored by transrectal ultrasonography every 8 h and subjected to 5 or 10 mg of dinoprost on Days 4, 5, or 6 of the cycle. Results were submitted to ANOVA and Tukey test, using all tests at the 95% confidence interval (SAEG program, Funarbe, Viçosa, Brazil). Data were reported as percentage or mean ± SD. The period from device removal to ovulation was 48.0 ± 7.07 h. The 5-mg dinoprost dose evoked similar (P > 0.05) results for Days 4, 5, and 6 regarding the time of ovulation after luteal gland regression induction [71.3 ± 28.6, 71.46 ± 30.4, and 68.2 ± 29.2 h for Days 4 (n = 4), 5 (n = 4), or 6 (n = 4), respectively] and follicle size (6.48 ± 0.34, 6.41 ± 0.35, and 6.5 ± 0.32 mm for Days 4, 5, and 6, respectively) at the time of ovulation. In animals that received 10 mg of dinoprost, the time of ovulation was affected (P ≤ 0.05) by Day of treatment [71.3 ± 27.6, 68.3 ± 30.6, and 64 ± 29.2 h for Days 4 (n = 4), 5 (n = 4), and 6 (n = 4), respectively]. However, there was no effect of the 10 mg on follicle size at ovulation (6.48 ± 0.34, 6.41 ± 0.35, and 6.3 ± 0.33 mm for Days 4, 5, and 6, respectively). There was no difference (P ≥ 0.05) on the size of ovulatory follicle(s) among animals with 1 (n = 4, 4, and 1 for Days 4, 5, and 6, respectively), 2 (n = 3, 3, and 4 for Days 4, 5, and 6, respectively), and 3 (n = 1, 1, and 3 for Days 4, 5, and 6, respectively) ovulations. The difference in the interval from luteal gland regression to ovulation in animals that received 10 mg of dinoprost on Day 6 of the estrous cycle suggests a higher sensitivity of corpora lutea at that moment. Results showed that both doses of dinoprost were capable of inducing early luteal gland regression; this fact supports the use of short-term protocols for the induction of estrus in ewes.
Pfizer Brazil, CNPq, FAPEMIG.