The effects of work and two planes of nutrition on trypanotolerant draught cattle infected with Trypanosoma congolense.

Thirty-two N'Dama bulls aged 3 to 4 years were used to study the interactions between work, tl"ypanosomosis and nutrition. The bulls were randomly allocated to two treatments, working (W) and non-working (N). Half in each treatment were placed on an andropogon hay basal diet (B), the other half on a better quality groundnut hay diet (H). Five days a week, four pairs ~f animals in the BW group and and four pairs in the HW group pulled weighted sledges four times around a 2056-m track. Loads !L1ere set to ensure energy expenditure u'as equil'alent to 1.4 times maintenance. After 4 weeks all 32 bulls were injected intradermally with 104 Trypanosoma congolense organisms. The trial continued for a further 8 weeks. Trypanosome infection caused a significant (P < 0.001) decline in packed cell volume (PC V), and the anaemia was more severe (P < 0.05) in working animals; three pairs in the HW group and two pairs in the BW group u'ere withdrawn because PCV fell below 17%. Diet had no effect on PCV or parasitaemia. Infection caused a decline in food intake (P < 0.001) but u1ith significant interactions between diet and work. Intake patterns were similar in the BN and BW groups whilst the HW animals consumed significantly more groundnut hay compared with the HN group (P < 0.01). However, nutrition had no significant effect on lap times or the team's ability to work under trypanosomosis challenge. Post-infection, diet was the dominant factor determining weight change, HN and HW animals weighed sign~ficantly more than BN and BW animals (P < 0.01) and the interaction between period, diet and work demonstrated that BW had the lowest weights in the latter stages of the trial (P < 0.05). The results suggest that supplementation with better quality forages confers no benefit to an animal infected with trypanosomes. Nor can trypanotolerant cattle sustain long periods of work if subiected to a primary challenge of