Variation among individual White-Leghorn hens in the concentration of minerals in the albumen and yolk content of their eggs.

1. The mineral composition of the albumen and yolk was determined in several eggs from each of a number of individual hens from the same White-Leghorn strain. X-ray fluorescent spectrometry was used to undertake two independent series of analyses. A total of 8 minerals (calcium, chlorine, iron, magnesium, phosphorus, potassium, sodium, sulphur) were included in the analyses of the yolk and the same minerals, but excluding iron (which is present in only small amounts), in the albumen. 2. There was considerable variation between individuals in the mineral concentration in their eggs (coefficients of variation ranged between 3.8% for sodium to 19.9% for calcium in the albumen, and between 4.3% for phosphorus to 11.8% for iron in the yolk). 3. At the same time, the moderately high repeatability of mineral concentration (t = 0.4-0.6) in successive eggs from the same hen for several of the minerals analysed is indicative of some positive control by the hen of the mineral composition of her eggs. 4. There was a highly significant correlation (P < or = 0.001) between the mean concentration of potassium in the albumen and the hatchability of the eggs, supporting the claim that a deficiency of potassium in the egg could be the basis of some failures in hatchability. 5. The study also revealed variation among individual birds in the concentration of iron in the yolk which was negatively correlated (P < or = 0.01) with hatchability. No clear basis could be suggested for this variation among individual birds.