Abstract
An experiment was conducted to compare several methods of synchroni-zation of estrus by means of progestogen alone or prostaglandin F2α (PGF2α) associated either with or without progestogen.
Two hundreds and forty Merino ewes were divided into 6 groups: Group 1 was control, Group 2 was treatment of 16 mg PGF2α intramuscularlly at the unknown stages of the estrous cycle, Group 3 was treatment of intravaginal sponge impregnated with 60 mg 6-methyl-17-acetoxyprogesterone (MAP) for 13 days, Group 4 was treatment of intravaginal sponge impregnated with 60 mg MAP for 7 days and 16 mg PGF2α intra-muscularlly at the removal of sponges, Group 5 was treatment of intravaginal sponge impregnated with 500 mg crystal progesterone for 13 days, and Group 6 was treatment of intravaginal sponge impregnated with 500 mg crystal progesterone for 7 days and 16 mg PGF2α intramuscularlly at the removal of sponges.
In group 1 (control), only 67.5% of 40 ewes had been exhibiting estrus during the 17 days. The percentages of ewes showed estrus for 7 days after treatments were 60.0%, 67.6%, 77.5%, 61.1% and 65.0% in groups 2, 3, 4, 5 and 6, respectively. Overall, there was no significant difference between the five different methods of syn-chronization (X2=3.45, d.f. 4), although group 4 (MAP-FPGF2α) appeared to be better than other methods (77.5%). The pattern of synchronized estrus in the groups treated with PGF2α became wider than that of groups treated with intravaginal sponges im-pregnated with progestogens.
From the results obtained, PGF2α treatment associated with MAP intravaginally for 7 days, appeared to be more effective methods than the treatment of PGF2α or progestogen alone for the control of estrus in cycling ewes.
