Experiments were performed with growing chicks to assess the effects of rations deficient in energy and
protein on feed intake, quantity of
monensin ingested, and overall anticoccidial efficacy. Experiment 1 employed a 4 X 2 X 2 factorial design where four levels of
monensin (0, 70, 90, and 110 ppm) were added to rations containing either 17 or 23.5% crude
protein. In Experiment 2, identical levels of
monensin were added to diets containing either 2600 or 3200 kcal metabolizable energy/kg. Both studies were conducted in the presence and the absence of
infections produced by Eimeria acervulina, E. maxima, and E tenella. Chicks fed diets deficient in
protein consumed significantly more feed and gained less weight than those fed rations adequate in
protein. Likewise,
protein-deficient chicks consumed more
monensin per kilogram of
body weight gain. In Experiment 2,
weight gain and feed intake were greater in birds fed adequate energy, but the quantity of
monensin consumed per kilogram of
weight gain was greatest in energy-deficient chicks. In both experiments coccidial lesions and oocyst output were controlled more effectively as
monensin dosage was increased. Neither
protein nor energy interacted significantly with
monensin when lesion scores and oocyst output were evaluated. Thus, these studies indicate that
coccidiosis control offered by the
monensin concentrations studies is independent of the
protein or energy content of the ration.