EFFECTS OF TRYPANOSOMA-VIVAX INFECTION DURING PREGNANCY ON FEED-INTAKE, NITROGEN-RETENTION AND LIVEWEIGHT CHANGES IN WEST-AFRICAN DWARF EWES

The effects of infection with T. vivax in mid- or late pregnancy on fo od intake and utilization, liveweight changes, abortion rate and lamb growth rate were investigated in West African Dwarf ewes at Ibadan, Ni geria in 1990. Rate of liveweight gain by ewes infected during mid-pre gnancy (IMH) was 16 g/day compared with 33 and 37 g/day for the uninfe cted ewes offered medium (CM) or high (CH) plane diets. Although diges tibility coefficients were not affected, intake of digestible organic matter was higher in CH ewes than in IMH and CM ewes. Nitrogen retenti on at mid-pregnancy on a metabolic size basis was higher in CH ewes th an in CM and IMH ewes. Lamb birth weight and survival rate were lower in infected ewes. Ewes infected in mid-pregnancy (IMH) and in late pre gnancy (ILH) had mean birth weights of 1.4 and 1.0 kg compared with CM and CH ewes, which had mean birth weights of 1.9 and 2.0 kg respectiv ely. Observed survival rates were 63, 15, 75 and 80% for lambs nursed by IMH, ILH, CM and CH ewes respectively. During the first 6 weeks pos tpartum, lamb growth rate in all groups did not differ. However, durin g weeks 7-12 postpartum, lambs nursed by IMH ewes had significantly lo wer growth rates. Weaning weight was also lower in lambs from IMH (5.0 kg) dams than in lambs from CM and CH dams (7.1 kg). Infection during late pregnancy was more severe and all infected ewes lost weight due to reduced feed intake and fever. T. vivax infection in sheep is respo nsible for reproductive wastage, abortion, poor lamb growth and ewe mo rtality.