Comparative disease resistance to Newcastle disease in Nigerian local ecotype chickens: Probable genetic influence
AbstractA study was conducted to determine the genetic resistance of two Nigerian ecotypes chicken and exotic breed cockerel (black Nera) to Newcastle disease by evaluating their clinical, haematological and humoral
responses to experimental Newcastle disease virus infection.. The chicks from the three genotypes were infected with 1ml of 105 ELD50 of Hertz 33 Newcastle disease virus inoculums orally. Their responses to infection were
monitored through clinical signs and mortality, haematological parameters and antibody titres values on days 0, 3, 7, 14 and 21 post infection. There was no adverse clinical manifestation and mortality in all the chicks throughout the experimental period. There was also no significant difference (p>0.05) between the mean packed cell volume of all the three genotypes from day 0 up to day 21 post infection though Fulani ecotypes had the highest value at day 21. Lymphocyte counts did not show any significant difference (p>0.05) on day 0 and 3 but there was significant difference (p<0.05) in the count from day 7 to 21 with Yoruba ecotypes having the highest count. The antibody titres of exotic breed was significantly higher (p<0.05) than that of the local ecotypes on day 0)
but on day 3, 7, 14 and 21 Yoruba ecotype antibody titres was significantly higher (p<0.05) than the other two genotypes. Decrease was observed in the antibody titres level of all the genotypes on day 21 with exotic breed
having the least value. From this study, it was shown that Yoruba ecotype chicken had higher immune response to Newcastle disease virus than Fulani ecotype and exotic breed and that the mean antibody titre of log21.5 and log22 provided protection to the chicks against Newcastle disease as none of the infected chicks show clinical signs and died. Furthermore, it was safely assumed based on the results that Yoruba ecotype chickens are early responder to Newcastle disease and hence are more resistant to Newcastle disease than the other two genotypes.