Simple and noninvasive method for assessment of digestive efficiency: Validation of fecal steatocrit in greenfinch coccidiosis model.

Animals' capability to absorb energy and nutrients from food poses a major internal constraint that affects the amount of resources available for allocation to maintenance, growth, signaling, and reproduction. Intestinal surface is the largest area of contact between immune system and microbial antigens; gut thus appears the main arena where trade-offs between immune function and other components of fitness arise. Assessment of the integrity of digestive machinery should therefore be of high priority in ecophysiological research.