The Effect of Feeding Various Levels of Calcium and Phosphorus on the Performance and Absorption of Chlortetracyline of Caged Layers

IT IS APPARENT that the presence of certain calcium and phosphorus salts inhibit the efficacy of broad-spectrum antibiotic activity (Price et al., 1957a, b, 1959; Stokstad et al., 1959; Peterson, 1960; and Boyd et al., 1960). Deleterious effects on egg production following deletion of dietary calcium and phosphorus have been reported. Deobald et al. (1936) reported that egg production had virtually ceased by the fourteenth day after the removal of calcium supplement. O’Rourke et al. (1954) stated that a ration containing 0.19 percent phosphorus did not support hatchability and egg production. Patterson et al. (1960) obtained a slight but consistent detrimental effect on egg production and shell strength by feeding a low-calcium diet for five days to laying birds. Donovan et al. (1960) observed that egg production was lowered about 10 percent by feeding a diet containing 0.119 percent calcium during a five-day period; however, the detrimental effect was quickly …