Oestrous cycle synchronization and oestrus induction in indigenous and European cattle in Tanzania

Abstract

SUMMARYFrom 1969 to 1971, 743 animals (indigenous Zebu and European dairy cattle, lactating or dry cows and heifers) received oestrous cycle synchronization treatments at government-owned and private ranches and farms in the Tanzanian highlands (West Kilimanjaro); 445 matching animals served as controls. Treatment schedules consisted of chlormadinone acetate (CAP) given daily for 14 days (10 mg/day) orally; or a single CAP injection (50 mg) followed by 4 or 5 days of oral treatment (10 mg/day) 9–12 or 11–15 days later. In addition, some groups received either estradiol valerate (5 mg) together with the CAP injection, or 10 mg/day mestranol from day 11 to 15, together with CAP; one treatment group received 1000 i.u. of HCG after the last CAP medication and were inseminated 12 and 24 h thereafter. Animals were either inseminated or bred naturally. With all treatment schedules, good synchronization, unimpaired fertility and consistently a significant reduction of anoestrus was achieved. Oestrogen treatments had no effects; treatment with 1000 i.u. of HCG was unsuccessful. Management factors, food supply and phase of reproductive life had significant impacts on treatment success and fertility. Synchronization can be used successfully under a wide range of management conditions to unfold existing potentials of artificial insemination in Bos indicus and Bos taurus in the tropics.