Submitted to: NE-60 Regional Meeting
Publication Type: Experiment Station
Publication Acceptance Date: October 25, 1999
Publication Date: N/A
Interpretive Summary: Coccidiosis, an intestinal infection caused by intracellular protozoan parasites belonging to several different species of Eimeria seriously impairs the growth and feed utilization of livestock and poultry. Due to complex life cycle of organism and intricate host immune responses to Eimeria, coccidia vaccine development has been difficult. Understanding of basic immunobiology of pertinent host-parasite interactions and host immunogenetics involved in the control of coccidiosis susceptibility/resistance is necessary for the development of novel control strategy. Although many chicken DNA markers have been available during the last 10 years, DNA-based marker selection strategy for avian coccidiosis has not been tried. In this report, ARS scientists, in collaboration with other scientists at University of Delaware and Purdue Farms, Inc., carried out preliminary studies to determine the feasibility of using DNA markers to select for the coccidiosis-resistant chickens in broiler meat-type birds. Preliminary findings indicate that some polymorphic microsatellite markers show substantial correlation with disease resistant traits associated with coccidiosis. These results will provide necessary knowledge for poultry industry to develop logical genetic-based selection strategy for coccidiosis-resistant chickens. If successful, genetic control strategy will reduce economic loss associated with coccidiosis.
In this study, we observed significant differences between sexes in all body weight gains and INF-gamma levels after inoculation of Eimeria maxima. Males gained significantly more weight and showed lower INF- gamma levels PI than females, though the measurements in the controls were not different between sexes. Because of sex effects, sex factor should be taken into account in the evaluation of disease resistance. Dose effects were also observed in all parameters except BWG0-9 and NO9. The dose effects were linear for all parameters except for NO6. The correlation between weight gains and plasma carotenoid level was also observed in the present study. In terms of correlations among the parameters, body weight gains from days 6 to 9 PI showed better correlation with other parameters. To date, there are no other reports about correlation between IFN-gamma and other parameters. In the present study, IFN-gamma at Day 9 PI was positively correlated to NO6 levels. It appeared that IFN-gamma was correlated to oocyst output and BWG6-9, but the correlations were not significant. Infection indexes (II) calculated in this study may be a better reflective indictor of genetic resistance or susceptibility to coccidiosis. The II displays much higher correlations with the correlated parameters than that among the parameters. The II estimation is still premature and subjective.