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SPECIAL CALCIUM APPETITE AND THE EFFECT OF ESTRADIOL-17-BETA ON CALCIUM METABOLISM IN THE LAYING HEN
Abstract
An experiment was conducted to study calcium appetite and dietary calcium level related to laying hen performance. The results showed that as dietary calcium level was increased, there was a decrease in free-choice supplemental calcium intake. However, all birds (except controls) consumed very large amounts of calcium, appearing to have little or no ability to reduce consumption of the free-choice calcium supplement even after their requirements had been met. Neither dietary calcium level nor total calcium intake affected feed intake. Hens that received the supplement produced significantly more eggs than did the controls. There were no significant differences in egg shell strength, egg weight or total plasma calcium; however, ionized plasma calcium was significantly lower in some treatment groups than in the control group. The results indicate that although laying hens possess a special appetite for calcium, they cannot regulate calcium intake. Such an appetite is probably a learned phenomenon rather than a homeostatic control. The results also showed that 3.5% dietary calcium may not be sufficient to support optimum egg production in hens past 50 weeks of age. Two experiments were conducted to study the effect of dietary calcium level, plasma estradiol-17(beta) and/or blood sampling on calcium metabolism and laying hen performance. The results indicated no significant effect, in either experiment, of blood sampling, dietary calcium level or plasma estradiol-17(beta) on feed intake, egg shell strength, total plasma calcium, ionized plasma calcium, tibia ash or tibia calcium. There were several significant interactions in the experiment that contained bled birds, but none were noted in the other experiment. Such interactions included a three-way interaction between blood sampling, dietary calcium level and plasma estradiol-17(beta) on body weight gain and egg production, a two way interaction between blood sampling and dietary calcium level on bone strength, and a two way interaction between blood sampling and estradiol-17(beta) on egg weight. The results showed no definitive effect of plasma estradiol-17(beta) on calcium metabolism in the laying hen with the levels of plasma estradiol-17(beta) and age of birds used in this study. The data strongly indicated no effect of dietary calcium level on feed intake, and suggested that more attention should be given to blood sampling effects in experiments that involve bleeding.
Subject Area
Anatomy & physiology|Animals
Recommended Citation
TAHER, ABDULMUNAEM IBRAHIEM, "SPECIAL CALCIUM APPETITE AND THE EFFECT OF ESTRADIOL-17-BETA ON CALCIUM METABOLISM IN THE LAYING HEN" (1985). ETD collection for University of Nebraska-Lincoln. AAI8518708.
https://digitalcommons.unl.edu/dissertations/AAI8518708