The use of Challenge conditions and coccidiosis challenges in an experiment makes the interpretation of research as it applies to commercial conditions more difficult. I have found that reducing density and feeding a consistently good quality diet will enable a production manager to determine which products work in his operations and the products that give a positive return.
David Wicker Ph. D. Those are very good points and highlight the difficulty of taking results obtained in small scale research (where we can expect a proportion of birds - i.e. the negative control - to show the ill effects of the challenge) and attempting to learn what works in the field (where the loss of productivity would be unacceptable).