[Synchronization of estrus in heifers by means of gestagenic preparations].

Studied were the synchronizing effect, the course of treatment, the combination of the gestagens CAP and MGA with PMS as well as their effect on the conception rate in heifers. A total of 143 heifers of the Bulgarian Brown breed (89 test and 59 control), aged 17--18 months, weighing 350--360 kg on an average, were used in the experiment, divided into three test and three control groups. I test group. Twenty-five animals were given daily one tablet of Synchrorosyn-Peach, the tablet containing 10 mg active chloromadinoacetate. The course of treatment lasted 15 days. II test group. Thirty-six animals were treated daily with 5 g of the premix preparation MGA-100 in the course of 20 days, the heifers being divided into two subgroups of 18 animals each. Each heifer of the first subgroup was injected with 2500 IU PMS. III test group. Twenty-eight animals were given MGA-100 at the same rate as in the II test group, but in the course of 14 days. Half of the test heifers were injected with 2500 IU PMS each on the day when the treatment with MGA-100 was discontinued. It was found that the oral administration of Synchrosyn-P for fifteen days and MGA-100 for 20 days results in a synchronized estrus in 84, resp. 44 per cent of the heifers, with a total conception rate of 76 and 94 per cent, respectively. The combined use of MGA-100 and PMS (2500 IU) enhanced the synchronizing effect. The shorter period of feeding with MGA-100 (14) days lowered both the synchronizing effect and the total conception rate, regardless of its combining with 2500 IU of PMS.