Six experiments were conducted to evaluate the effects of diet,
bacitracin, and
body weight restrictions on the intestine of the broiler chick.
Bacitracin, at levels of 11 and 55 ppm, significantly increased
body weight, significantly reduced small intestine weight, but had no significant effect on liver weight of chicks fed a
soybean protein and
sucrose-based diet. The greatest effects were observed in the ileum where weight, moisture, length per unit of
body weight, and dry matter per unit of length were all significantly reduced. The least effects were observed in the duodenum where weight and length per unit of
body weight were significantly reduced and dry matter per unit of length was significantly increased. Intestinal weight, as a percent of
body weight, was not significantly affected when
body weight was suppressed with a high level of
nicarbazin added to a practical diet, but it was significantly reduced when
bacitracin was added to the semipurified diet and chicks were restricted in food intake to 70% of controls. A level of 55 ppm of
bacitracin added to the practical diet had no significant effect on
body weight, intestinal weight, or liver weight. As discussed, the observed changes in the intestine, due to
bacitracin, are probably indirect and most likely reflect the action of the
antibiotic on the intestinal microflora.