AN EVALUATION OF FOOD-INTAKE, DIGESTIVE PHYSIOLOGY AND LIVE-WEIGHT CHANGES IN NDAMA AND GOBRA-ZEBU BULLS FOLLOWING EXPERIMENTAL TRYPANOSOMA-CONGOLENSE INFECTION

The effects of experimental Trypanosoma congolense infection on the di gestive physiology and nutrient utilization in Gobra zebu and N'Dama c attle were Examined in a 16-week trial. A pair-feeding procedure permi tted examination of the effects of both food intake and trypanosomosis infection. Twenty Gobra and 16 N'dama bulls aged between 1 and 2 year s were paired on a live-weight basis within each breed. One of each pa ir was chosen at random to serve as an uninfected control while the ot her was inoculated intradermally with 10(4) T. congolense in mice bloo d in the 6th week of the experiment. Packed cell volume and parasitaem ia data were collected weekly throughout the trial. Total dry-matter i ntake (TDMI) and live-weight changes were measured weekly in all anima ls during the 16-week trial. Rate of passage (RoP) and dry matter dige stibility were evaluated before and after infection. While infection s ignificantly depressed TDMI in both breeds (P < 0.05), neither infecti on nor breed affected the RoP and the apparent digestibility of the dr y matter. Significant changes in live weight attributable solely to th e infection were observed in both breeds. Loss of body weight was more severe (P < 0.05) in infected Gobra bulls compared with N'dama bulls possibly implying a superior efficiency of nutrient utilization by the N'dama during infection. In the course of the trial, one N'dama and t hree Gobra bulls that presented severe clinical symptoms of trypanosom osis were treated and withdrawn from the experiment along with their p air-fed controls. In conclusion, the RoP and the digestive efficiency were not affected by infection and breed differences. Also, the trypan otolerance mechanism does not seem to be affected by anorexia but rath er by the ability to conserve body reserves during infection.