Comparison of Growth Response of Chicks to Virginiamycin and Other Antibiotics

IT HAS been reported that continuous use of antibiotics for growth promotion of chicks resulted in a decrease in their effectiveness (Waibel et al., 1954; Libby and Schaible, 1955; Sherman et al., 1959). McGinnis et al. (1958) reported that erythromycin thiocyonate and oleandomycin phosphate improved growth of chicks while other antibiotics which had been used for several years failed to do so. Similarly, Wiese and Petersen (1959) observed that chicks responded much better to erythromycin and spontin than to penicillin. Heath and Bird (1962) on the other hand, found no long term changes in growth response of chicks to procaine penicillin or the tetracyclines during the period 1950 to 1961. Moreover, Creek and Schumaier (1960) obtained significant chick growth responses from oxytetracycline, penicillin, zinc bacitracin and oleandomycin as well as from erythromycin, spontin and tylosin. Teague (1962) also failed to demonstrate a consistent decrease in the effect of chlortetraclycine in…