The relationship of production status to serum calcium and phosphorus in hens

The effect of production status on the serum levels of calcium and phosphorous of laying hens was examined. Commercial-type White Leghorn hens, 66 weeks of age, were selected on the basis of whether or not they had laid an egg each day during a two-day period. A five ml. blood sample was collected via anterior heart puncture from each of the selected hens and subjected to serum calcium and phosphorus analyses. Serum phosphorus varied significantly in relation to whether or not a bird laid an egg the day before and/or the day of blood collection. Except for birds which were reproductively inactive, serum calcium was less affected by production status than was serum phosphorus. It was hypothesized that the variations were related to the physiological changes in shell calcification activity, bone resorption and remineralization, intestinal absorption of minerals and muscular activity. It was suggested from the results that birds selected for serum mineral analyses should be of similar production status.