Vitelline Membrane Strength and Egg Yolk Mottling

Four levels of cottonseed meal ranging from 0 to 18% of the diet and ferrous sulphate in three levels ranging from 0 to 531 grams per 45.4 kg. of ration were used in the twelve experimental rations. Ten hens were randomly placed in each ration treatment, three production periods were used, and the days of storage ranged from 28 to 48 days. The effect of these factors on yolk mottling and vitelline membrane strength was measured. Some yolk mottling was found in all rations with highly significant effects attributable to cottonseed meal, ferrous sulphate, and days of storage. An increase of cottonseed meal in the ration caused an increase in the mottling score. The incorporation of ferrous sulphate had the effect of decreasing the amount of yolk mottling until the cottonseed meal level reached 18% of the diet. Individual hen reaction to the inclusion of cottonseed meal in the ration was also noted in the study. Considerable variation was noted among the various loci on the yolk with regard to vitelline membrane strength. This study showed a stronger vitelline membrane at the lower portion of the yolk (area near chalazae closest to the pointed end of the shell).