Correlates of resistance to gastrointestinal nematode infection in Nigerian West African dwarf sheep.

OBJECTIVE To investigate correlates of resistance to GI nematode infection in Nigerian West African dwarf (WAD) sheep. METHODS Thirty three sheep were randomly assigned to two groups, A (n=27) which were used for experimental infections, and B (n=6) which served as uninfected control. Each infected animal received weekly escalating infections with infective larvae (60%Haemonchus contortus (H. contortus) and 40%Trichostrongylus colubriformis (T. colubriformis) for 4 weeks. The responses of all the infected and control sheep were assessed by faecal egg count (FEC), worm burden (Wb), packed cell volume (PCV), body weight (Bwt), and body condition score (BCS). On the basis of their individual faecal egg output, Lambs in group A with epg ≤1,000 on any sampling day were classified as low faecal egg count (LFEC) phenotype (n=16), those with epg between 1,000 and 10,000 as intermediate (n=5) and lambs with epg > 10,000 as high feacal egg count (HFEC) phenotype (n=6). RESULTS The difference between the FEC classes was highly significant (P=0.001). The BCS and weight gained at the end of the experiment by the control and LFEC sheep was significantly higher (P≤0.05) than those of the intermediate and HFEC phenotypes. There was a significant and negative correlation between the parasitological measures and the trio of BCS, PCV and Bwt of sheep. CONCLUSION The result of the study indicated that the FEC, weight gain, PCV, and BCS are correlates and potential selection criteria of GI nematode resistant WAD sheep.