Eficiência de duas doses de D-cloprostenol para sincronização de estro em bovinos nas diferentes fases do ciclo estral

Abstract

The synchronization of estrus in bovines through the administration of luteolytic agents as prostaglandin F2 (PGF2) or its analogues has been widely used in reproductive programs of embryos transfer (ET) The luteolytic agents cause lysis of the corpus luteum resulting in the manifestation of estrus It is a practical and less expensive method when compared to other synchronization techniques and exhibits fertility indexes which are similar to the natural ones since there is no interference of factors such as bodily condition and nutrition among others The purpose of this paper was to verify the efficiency of the intramuscular administration of different doses (normal and reduced) of a luteolytic agent in different phases of the estrous cycle (dioestrus) and the responsivity time (interval administration-estrus) The experiment was carried out in Água Limpa farm in the city of Fama State of Minas Gerais Brazil in the period between November 2004 and January 2005 Two-hundred and eighty-eight applications of sodic D-cloprostenol were made whit the aim of synchronizing the estrus in crossbred heifers used as receptors in an embryo-transfer program The animals were observed in the natural estrus classified and grouped in accordance with the day of the cycle Group A corresponded to the animals injected on the 6th-8th day of deoestrus day 0 being considered as estrus Group B on the 9th-11th day Group C on the 12th-14th day and Group D the heifers on the 15th-17th day of dioestrus All the groups were subdivided into two some animals received 75 g (1ML) of sodic d-cloprostenol by intramuscular injection others received 150 g (2ML) As for total efficiency the 2ML dose showed a better response (p<0,01) 77,15% than the 1ML dose 50,55% Groups A (6 to 8) and B (9 to 11) showed nearly equal values (p<0,05) for total efficiency 66,67% for 2ML and 36.36% for 1ML in Group A and 78.43% and 56.67% respectively for Group B Groups C (12 to 14) and D (15 to 17) showed no differences (p<0,05) in efficiency between groups or doses 73.58% (2ML) and 52.00% (1ML) for Group C and 73.58% and 52.00% respectively for Group D For interval application to the beginning of estrus the following results were found Group A presented an average interval of 58 hours significantly differing (p<0,05) from the other groups 73.43 hours for Group B 79.06 hours for Group C and 75.23 hours for Group D The present study demonstrated that the dose of 1ML of D-cloprostenol is similar to the dose of 2ML as of the 12th day of the cycle Therefore a subdose may be an alternative to reduce costs in an ET program since one knows the stage of the estral cycle of the females