| Sumario: | This study reports the results of investigations on the effects of Trypanosoma vivax infection in pregnant and lactating West African Dwarf ewes on digestible organic matter intake (DOMI), live weight changes, milk yield pattern, lamb birth weight and growth rate. During pregnancy and lactation, DOMI was lower (P<0.05) in infected ewes. Rate of weight gain did not differ between infected and control animals before 14 weeks post-breeding (eight weeks post-infection). Infected ewes had low maternal weights and poor body condition at parturition, which were associated with low (P<0.01) lamb birth weights and survival. Abortion rate was 15% in the infected ewes with a lamb mortality rate of up to 85%. Lambs born by infected dams had lower weaning weights compared with lambs from control ewes.
In lactating dams, neither milk yield nor composition was affected by infection during the first half of lactation. However, during late lactation infected ewes produced less (P<0.05) milk and lost more weight compared to uninfected lactating ewes. Growth rates of lambs nursed by control and infected dams did not differ in the pre-weaning period. The findings suggest that Trypanosoma vivax infection was responsible for the observed abortions, ewe mortality, reduced ewe live weight gain and lamb birth and weaning weight in pregnant ewes. It is also concluded that infection of early lactating dams did not affect lamb performance, milk yield and composition although significant differences were encountered in milk yield during late lactation.
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