The Incidence and Degree of Yolk Mottling in Eggs From Hens Fed Diets With and Without Nicarbazin

INTRODUCTION ALTHOUGH yolk mottling in fresh and stored eggs was reported almost 25 years ago (Almquist, 1933), and for years has been a generally recognized problem, little is known of its incidence in farm flocks and the nature of its occurrence. It is seen in held eggs more frequently than in fresh eggs (Romanoff and Romanoff, 1949). Preliminary studies conducted at the Merck Institute showed that the drug nicarbazin recommended as a coccidiostat for young chickens could cause an increase in the incidence and degree of yolk mottling if fed to laying hens. Subsequently, field and laboratory studies were initiated to determine the minimum level of nicarbazin in rations fed to hens that would cause the mottling effect. The data of these studies are reported herein. A preliminary report (Polin et al., 1956a) has already been published. EXPERIMENTAL White Plymouth Rock (W.P.R.) and New Hampshire (N.H.) hens were used in . . .