THE INFLUENCE OF GRADED DIETARY ENERGY ON DYNAMICS OF Trypanosoma congolense INFECTION IN WEST AFRICAN DWARF GOATS

Abstract

Malnutrition increases goats’ susceptibility to diseases thereby hindering their profitable production. Low calorie diet and infection have impact on health and survival of livestock. The influence of Graded Dietary Energy (GDE) on dynamics of Trypanosoma congolense (Tc) infection in goats is not fully elucidated. The influence of GDE levels on Tc infection in West African Dwarf (WAD) goats was therefore investigated. A preliminary survey for trypanosomes involving 675 goats was conducted during the dry and rainy seasons in Ogbomoso, Oyo State using standard techniques. Fifty four goats were randomly divided into three dietary groups A, B and C of 18 animals each and fed with 2426.7 or 2548.6 or 2670.4 kcal/kg isonitrogenous diet. After four weeks on the respective diet, 1.0 x 106/ml of Tc were administered intraperitoneally to 14 goats from each group AI, BI and CI , while four goats from each group served as non-infected controls AC, BC and CC. The animals were monitored for body weight changes post-infection, and after treatment with diminazene aceturate on week 5. Blood and serum samples collected weekly for 10 weeks, were assessed for changes in parasitaemia, haematology, serum biochemistry, complement levels and lymphocyte proliferation using standard methods. Data from the survey were analysed using descriptive statistics and Students’t-test, experimental data by ANOVA while parasite counts were correlated with haematology, serum biochemistry, and complement levels at p < 0.05. Dry season prevalence rate (4.5%) was significantly higher than that of rainy season (2.3%).While mean parasite count of group AI at weeks 3-5 was significantly higher than those of BI and CI, growth was retarded significantly in AI than BI and CI. Post-treatment growth acceleration was significantly higher in CI than BI and AI from weeks 7-10 but, CC grew at a significantly higher rate than BC and AC throughout the experimental period. Mean erythrocytic values fell with highest decline in AI than BI and CI from weeks 3-5 with normocytic normochromic anaemia. Mean serum Na+ , Ca2+, PO42- , globulin and transaminases increased from weeks 2-5 while mean serum K+, HCO3-, total protein, albumin, complement C3, total and alternative haemolytic complement levels decreased, being significant only in group AI. In all infected groups increased parasitaemia correlated negatively with erythrocytic values, serum K+, HCO3-, total and alternative haemolytic complement levels and positively with serum Na+, PO42-, total protein, globulin and transaminases. Mean lymphocyte count per minute within stimulated infected groups from weeks 1-5 were significantly increased in the order of CI > BI > AI, while unstimulated control cells maintained uniform response over a 72–hour period. Following treatment with berenil®, mean erythrocytic values and other parameters returned to pre-infective values by week 10, but earliest in group CI at Week 8. The prevalence of caprine trypanosomosis was higher in dry than rainy season. Increased dietary energy intake in goats increased their tolerance to Tc infection. It is recommended that dietary energy along with other nutrients be adequately provided for goats to reduce clinical effects of trypanosomosis.