EFECTO DEL NúMERO DE APLICACIONES DE CLOPROSTENOL SOBRE LA REGRESIóN DE CUERPOS LúTEOS, EL RETORNO AL CELO Y LA OVULACIóN, DESPUéS DE UN TRATAMIENTO SUPEROVULATORIO EN DONANTES DE EMBRIONES BOVINOS

the purpose of the present study was to evaluate the effect of prostaglandin (pg) treatment schedule on luteal regression and return to estrus in superovulated cows. a group of 44 donor cows were randomly assigned to two groups on the day of ova/ embryo collection (day 0). the first group (n = 23; clo 0 & 7) was treated with 500 μg of cloprostenol on days 0 and 7 after embryo recovery; the second group (n = 21; clo 0, 1 & 7) received an additional treatment with cloprostenol on day 1. all animals were scanned by transrectal ultrasonography on days 0 (embryo recovery), 4, 7, 10 and 13 to evaluate cl regression and subsequent ovulation. estrus detection was done twice daily (am/pm) starting on day 4. there were no significant differences between groups in the percentage of animals returning to estrus (60.8% and 52.3%, respectively), or the intervals from the first pg treatment to estrus (7.2 ± 0.3 vs 7.3 ± 0.5 days), or ovulation (8.5 ± 0.9 vs 9.8± 0.9 days). all cows had luteolysis before the end of the experiment. animals that had 4 cl or less ovulated earlier than cows that had 5 or more cl (p<0.01). in summary, there was no difference in luteal regression and the return to estrus and ovulation in donor cows treated with cloprostenol twice or three times after superovulation. it would not appear to be necessary to treat donors with pg 7 days later, since all cows had luteal regression after the first pg treatment.