FR 25. Zebu females fertility artificial insemination after hormonal implant application
To study the seasonal effect on fertility of synchronized cows with hormonal implants, 155 zebu Bos indicus females were treated 3 location of the dry tropic near Colima City, 37 in Tecoman, 63 in CoquimatlÃ n and 55 in Cuauhtemoc. A non parametric design of randomly aleatory blocks was employed. Animals in the experiment were non pregnant females, most of them inside their oestrus cycle and with their calves. With an average body score of 7, on a scale from 1 to 9. In order to get a regular oestrous a subcutaneous hormonal implant was applied in the back side of the ear (3 mg of norgestomet) as well as an intramuscular dose of 5 mg of estradiol valerates plus 3 mg of norgestomet at the beginning of the trial. The implant was mantained during 9 days,after the implant was removed artificial insemination was carried out with Bos indicus semen between 52-54 h withdrawal. The average rate fertility obtained in the 4 seasons of the year with AI: service was 47.0 %. The average rate fertility by season was as follows: in winter 37.9 %, spring 57.9 %, summer 53.9 % and fall 38.3 %. According to a Friedmanâ€™s test and the hypothesis for proportions; no stadistically significant fertility differences were found (P>.1) between seasons, nor farms.