Relationship of the Egg Formation Cycle to Antibiotic Blood Level in Laying Hens

Abstract

CERTAIN dietary modifications have been shown to increase the absorption of the tetracycline antibiotics. This was first noted by Peterson (1958), who reported that the incluson of terephthalic acid (TPA) in broiler feeds increased the antibiotic content of the blood serum by three to fourfold. This finding was substantiated by Price and Zolli (1959), who also reported that a similar increase in the serum antibiotic could be obtained by reducing the calcium content of the diet of chicks to 0.18%. Harms and Waldroup (1961a) reported that decreasing the calcium content of the feed slightly below the level required by four-week old chicks gave maximum potentiation benefits as measured by the antibiotic content of the blood serum.Since the calcium requirement of the laying hen is higher and is more critical than for the broiler, a procedure was developed by Brown and Bachmann (1959) for use with laying hens. They reported …