Effect of serial blood sampling on interpretation of estradiol-17 beta involvement in laying hen calcium metabolism.

Effects of long-term, low levels of exogenous estradiol-17 beta and dietary calcium on calcium metabolism and laying hen performance, and effects of serial blood-sampling, were studied. Significant 3-way (P less than 0.01) and 2-way (P less than 0.05) interactions involving sampling obscured possible main effects (Exp. 1); no main effects were found in absence of blood sampling (Exp. 2). Estradiol-17 beta appears to increase calcium utilization with very low dietary calcium only. Relatively small brachial vein samples taken only every 3-4 weeks have substantial confounding effects on interpretation of data.