Vitelline Membrane Chemical Composition in Natural and Induced Yolk Mottling

Abstract

Two experiments were conducted with White Leghorn hens. In Experiment 1, the birds were fed 0, 30, 60 or 120 p.p.m. nicarbazin in the diet for four 28-day periods. All levels of nicarbazin increased yolk mottling, decreased egg size, and 120 p.p.m. reduced egg production. Yolks of the eggs from hens fed the nicarbazin-free diets had a 70.7% incidence of yolk mottling and 5.0% were considered objectionable. With nicarbazin in the diet, all eggs had mottled yolks and 60.0, 85.5 and 98.9% were objectionable for 30, 60 and 120 p.p.m. nicarbazin in the diet, respectively. In Experiment 2, hens were fed 0 or 60 p.p.m. nicarbazin in the diet for six 28-day periods. Eggs from both treatments were examined fresh (within 24 hours of oviposition) or after two weeks storage at 12 or 22°C. Egg yolks from the nicarbazin-free birds had a 51.0% incidence of yolk mottling when fresh which increased to 100% after storage. There were 1.1, 22.0 and 44.7% objectionable yolks in the fresh eggs; eggs stored at 12°C.; and eggs stored at 22°C., respectively. Nicarbazin in the diet significantly increased the mottling. Yolk moisture was increased by mottling, storage and nicarbazin in the diet. The moisture content of the vitelline membrane increased with degree of mottling and storage. Protein content of the vitelline membrane decreased as the degree of mottling increased and lipid content was higher from mottled yolk vitelline membranes in fresh eggs but was much lower after storage. The ash content of the vitelline membranes was essentially the same in all treatment groups. Vitelline membranes from naturally mottled and nicarbazin mottled yolks showed no gross chemical differences if the degree of mottling was the same.