The effect of the quality of roughage on the course of Trypanosoma vivax infection in West African Dwarf goats. I. Organic matter intake, body weight change and efficiency of nitrogen metabolism.

Twenty nine West African Dwarf goats were randomly allotted to either a diet of pelleted lucerne with a high N content (Crude protein level=172 g/kg DM; n=14) or chopped grass straw with a low N content (Crude protein level=68 g/kg DM; n=15). Nine animals fed lucerne and 10 animals fed grass straw were infected with Trypanosoma vivax to study its effects on feed intake and efficiency of N utilization during the first 6 weeks of infection. Infection reduced organic matter intake (OMI) from 55 (s.e. 2) to 38 (s.e. 2) g kg-0.75 d-1 (P<0.001). OMI was not affected by feed type (P>0.10). The relative decrease of digestible organic matter intake (DOMI) due to infection was the same in animals fed lucerne or grass straw (36 and 35%). Retention of N was lower in infected animals and in animals fed grass straw. By relating N retention to DOMI the efficiency of N utilization, corrected for feed intake level, was estimated. No effect of infection or feed type on the efficiency of N utilization was detected. One overall regression equation was estimated: N Retention=-0.45 (s.e. 0.04) 0.017 (s.e. 0.002)xDOMI (n=29; r2=0.86). Serum urea concentration was higher in the goats fed lucerne than in the goats fed grass straw; only in the lucerne group, infected animals showed a lower serum urea concentration post infectio (p.i.) than control animals. Serum creatinine concentration was higher in grass straw-fed animals than in lucerne-fed animals. From the former group, infected animals had a lower creatinine concentration p.i. than controls. It is concluded that infection affected feed intake, but not the efficiency of N utilization