Potentiation of Chlortetracycline in Laying Chickens

NUMEROUS experiments on the potentiation of antibiotics have been conducted with growing chickens. They have shown that potentiation of the tetracycline antibiotics may be accomplished in several ways. These include lowering the level of calcium (Price et al., 1959), substituting calcium sulphate for calcium carbonate (Stokstad et al., 1959) or the addition of terephthalic acid (TPA) to the ration (Peterson 1958, 1960; Shelton and Olson, 1958; Peterson et al., 1959; Price, et al., 1959; and Pensack et al., 1960). Each of these dietary modifications results in increased levels of antibiotic in the blood serum and in greater effectiveness of the drug. Although the above methods have been used for some time with starting and growing birds, their adaptation to laying birds has been slow. Since the calcium requirement of the laying hen is high, it has been reasoned that modifications of rations involving lower calcium levels would be deleterious. Consequently,…