The Differential Susceptibility of Yoruba Ecotype Nigerian Indigenous Chicken Varieties To Newcastle Disease

This experiment was conducted to assess and compare the susceptibility of the varieties of Yoruba indigenous chicken ecotype: Yoruba Smooth Feathered (YSF), Yoruba Frizzled Feathered (YFF) and Yoruba Naked Neck (YNN) to Newcastle disease. A total of sixty (60) 16 weeks old chickens were used comprising of twenty (20) chickens per variety. The assessment of their susceptibility to Newcastle disease was by evaluation of clinical signs, humoral response, mortality, pathology following contact with Newcastle disease infected chickens. The experimental chickens developed clinical signs of Newcastle disease from day 9 after infection. Haemagglutination inhibition (HI) titre was determined on days 0, 21and 28 post-infection. On day 0, the HI titre of the 3 genotypes were below 3log2, on day 21, there were significant differences within the group (P<0.05) where in YNN had the highest mean HI titre of 7.5. There was decrease in the mean HI titre in all on day 28 with the YNN having the least reduction (P<0.05). The antibody titre against Newcastle disease was higher in the YNN than all the other varieties. The mortality commenced on day 10 after infection with 70% mortality in YSF, 40% in YFF and 30% in YNN. The proventricular, enteric and caecal tonsilar haemorrhages associated with the disease were more frequent and severe in YSF. This finding indicated that YFF and YSF may possibly be more susceptible to Newcastle disease than the YNN. It was concluded that indigenous chickens of Yoruba ecotype in Nigeria differ in their susceptibility to ND with YNN being possibly the most resistant to Newcastle disease followed by YFF and the least, YSF.