White-Leghorn Chickens Are Less Susceptible To The HaemoPathological Effects Of Avian Coccidiosis Compared To Commercial Broilers

Abstract

The present study was conducted to investigate the differences in susceptibility of the whiteleghorn breed of chicken to the haemo-pathological effects of avian coccidiosis when compared to commercial broilers. An experiment was performed with twenty-day-old  chicks (10 whiteleghorns and 10 broilers) which were grown for 3-weeks before infecting them. The chicks were first confirmed to be free  from intestinal parasites then 5 birds each, randomly selected from the two breeds, were orally inoculated with Eimeria oocyst.  Thrombocyte numbers and packed cell volumes (PCVs) were measured to indicate thrombocytopaenia and anaemia respectively. This was determined from blood obtained from the chicks on the 10th day post-inoculation. An estimate of the effect-size revealed that  coccidiosis produced a negligible effect (a 5% decrease) on the thrombocyte number of white-leghorns. However, no effect was observed  on the PCV of the same breed. On the contrary, a 47% decrease in the thrombocyte number and a 29% decrease in the PCV of broilers can  be attributed to coccidiosis. The extensive system of breeding white-leghorns satisfied the conditions necessary for natural selection  of favourable traits to occur in the breed. This might explain the difference in susceptibility to the haemo-pathological effects caused by Eimeria parasites because commercial broilers that are managed intensively, do not survive long enough, thereby disrupting natural  selection. The difference implies that an apparently healthy flock of white-leghorn may be a reservoir of the infection, which could be  transmitted to susceptible breeds.