The Results of Autopsies on Trypanosome-Infected Cattle

Abstract

The interactions of trypanosomosis and plane of nutrition on health and productivity of multiparous and primiparous West African Dwarf (WAD) does were studied in a multi-factorial experiment including diet (supplementation or basal diet) and infection (infected or control). Experimental does were infected with Trypanosoma congolense at the beginning of the second week post-kidding and monitored for 16 weeks after infection. Trypanosome infection significantly reduced packed cell volume (PCV) (control: 30.1 ± 0.3% versus infected: 22.2 ± 0.3%; P < 0.0001). Regardless of infection, the drop in PCV from the pre-infection period to the end of the experiment was more severe in animals under restricted diet (interaction diet × period, P < 0.001). Trypanosome parasitaemia tended to be higher in the supplemented group than in the basal diet group (P > 0.05) and multiparous animals had a higher parasitaemia (score: 2.6 ± 0.1) than primiparous animals (score: 2.2 ± 0.1) (P < 0.05). Trypanosome infection as well as dietary supplement had a significant effect on lactation length. Milk off-take from trypanosome-infected does was significantly lower than that from the uninfected control group (17.5 ± 3.2 l versus 35.5 ± 3.2 l, P < 0.001) and there was a positive effect of plane of nutrition (supplemented: 32.8 ± 3.2 l and basal diet: 20.2 ± 3.5 l, P = 0.01). The drop in milk off-take due to trypanosome infection was more severe in the supplemented group (control: 46.7 ± 4.7 l versus infected: 18.9 ± 4.2 l) than in the group receiving a basal diet (control: 24.2 ± 5.0 l versus infected: 16.1 ± 4.7 l) (interaction infection × diet, P = 0.04) due to the number of does from the supplemented group that were withdrawn from the experiment. The effect of trypanosome infection on doe's live-weight was only noticeable during the first 8 weeks of lactation and there was no significant effect on offspring growth rate unless the mother died. Plasma total protein (TP), albumin and cholesterol concentrations were significantly reduced by the infection but were significantly increased by supplementation. Supplemented does had a higher level of cholesterol and a tendency for a higher parasitaemia. Does of high parity also had a higher cholesterol level than primiparous does and, based on the number of animals that were withdrawn from the experiment, they showed a lower resistance to the infection.