Effects of trypanosomiasis on reproduction of East African Zebu cows exposed to drug-resistant trypanosomes
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Preventive Veterinary Medicine;21(3): 237-249
Permanent link to cite or share this item: http://hdl.handle.net/10568/29507
Approximately 320 East African Zebu cows over 36 months of age were monitored monthly from 1986 to 1992 in nine village herds in an area of high trypanosomiasis risk in southwest Ethiopia where there was resistance to all available trypanocidal drugs. Cows were individually treated with diminazene aceturate when their packed cell volume either decreased below 26 percent and were detected parasitaemic, or when they showed clinical signs of trypanosomiasis. The average annual monthly trypanosome prevalence was 25 percent (range 18-39 percent). Average cow body weight was 196 kg but was 16 kg lower on average during 1988, a year when early rains failed. The median calving interval was 463 days ranging from 379 to 620 days for different years and seasons. Cows detected parasitaemic in more than half of the monthly samples taken over the period 1-150 days post partum had an average calving interval 39<+->18 (SE) days longer than those not detected parasitaemic. Calving interval was also inversely related to both post partum body weight and to the change in body weight between 1 and 150 days post partum. The median age at first calving was 40.5 months. Heifers detected parasitaemic at least once between 19 and 30 months of age calved at an average age 2.9<+->1.2 (SE) months older than those not detected parasitaemic. Over 8 percent of calvings resulted in abortions or still births and there was a significant increase from 7 to 10 percent in the rate of abortion associated with cases of parasitaemia detected during the last 3 months of pregnancy. Annual abortion rate and annual trypanosome prevalence also appeared to be correlated. Except for the high incidence of abortions the effects of trypanosomiasis on reproduction appeared generally to be small.