The Relative Growth Stimulating Effects of Several Antibiotics on Chicks Raised in Old and New Batteries

IN CHICK experiments reported by Waibel et al. (1954) and by Libby and Schaible (1955), the growth-stimulating effects of antibiotics decreased with their continuous use over a long period of time in a given environment. In experiments conducted in new environments not previously occupied by chickens, the feeding of antibiotics to chicks failed to produce a significant growth increase (Coates et al., 1952). McGinnis et al. (1958) presented data which showed that antibiotics, which had been used routinely in their laboratory, improved growth of poults only slightly, while two “new” antibiotics, oleandomycin phosphate and erythromycin thiocyanate, significantly improved the growth rate of poults. A recent move into a new animal laboratory and the purchase of two new batteries created an opportunity to investigate the growth-stimulating effects of antibiotics fed to chicks in old and new batteries located in a new laboratory. The following experiment was conducted to study the comparative …