Use of discriminant analysis for the evaluation of coccidiosis resistance parameters in chickens raised in hot humid tropical environment.

Coccidiosis endemicity remains a major challenge in poultry production in the tropics and all over the world. In order to develop predictive tool for identification of chickens that are at risk of coccidiosis among Nigerian indigenous chickens, body weight gain (BWG) and hematological variables were determined for chickens infected with Eimeria tenella (female = 60, male = 63) and uninfected (female = 51, male = 45). The hematological variables analyzed include the following: packed cell volume (PCV, %), white blood cells (WBC, × 106/µl), and red blood cells (RBC, × 106/µl), as well as differential leucocyte percentages of neutrophils, lymphocytes, monocytes, and eosinophils. Body weight gain was determined at days 3, 6, 9, 12, and 15. Of the 12 variables analyzed, BWG at day 3, monocyte, PCV, and WBC in males and BWG at days 6, 9, and 12, PCV, and WBC in female chickens showed significant (P ≤ 0.01) difference between the infected and uninfected. Stepwise discriminant analysis evolved a model that could distinguish uninfected from Eimeria-infected chickens. Packed cell volume, WBC, BWG at day 3, and lymphocytes emerged the most discriminant between uninfected and Eimeria-infected chickens in male chickens. In female chickens, PCV, RBC, and BWG at day 3 were identified as most discriminant variables in separating the uninfected from Eimeria-infected chickens. Therefore, this study suggests that routine blood test and estimates of body weight gain could serve as a useful tool for identifying chickens that may be at risk of coccidiosis, enabling improvement of preventive measures.

Genetic differences in the body weight and haematological traits of Nigerian indigenous chickens infected with Eimeria tenella.

In an effort to shed more light on the tolerance of indigenous chickens to coccidiosis, we compared the body weight, faecal oocyst load and haematological parameters based on sex and genotypes of Eimeria tenella-infected chickens. Three hundred chicks from three genotypes (normal-feathered, frizzle-feathered and naked-neck) of Nigerian indigenous chickens which comprised 100 birds per genotype were raised for 6 weeks. At 3 weeks old, each chick was weighed and faecal, and blood samples were collected before inoculation. Subsequently, the birds were weighed and faecal samples collected at days 1, 3, 6, 9, 12 and 15 post-inoculation. Blood samples were collected from 50 chicks per genotype at 3 and 5 weeks post-inoculation. Blood parameters were determined and faecal samples subjected to McMaster egg counting technique. Results showed genotype, and sex had significant effects on body weight from day 1 to 15 post-inoculation. Normal-feathered chicks had the highest body weight while frizzle-feathered chicks showed lowest body weight at post-inoculation. E. tenella was identified in caecal and lower intestinal mucosa of the genotypes, but genotype had no significant effect (p > 0.05) on the lesion score. There were no significant differences in haematological values among genotypes (p > 0.05) except for lymphocytes where naked-neck chicks had the highest lymphocytes' count (1.83 ± 0.02 %), followed by normal-feathered (1.79 ± 0.02 %) and the frizzle-feathered (1.68 ± 0.02 %). The present values of body weight, faecal oocyst and haematological parameters obtained seemed not to be convincing enough to suggest that the genotypes were different in terms of tolerance to coccidiosis.