The Response of Serum Inorganic Phosphorus Level in Laying Hens Fed Low Levels of Dietary Phosphorus

Abstract

Three experiments were conducted to determine the effects of feeding low levels of dietary phosphorus on the serum inorganic phosphorus level of laying hens. A phosphorus deficient diet containing .30% total phosphorus, all of plant origin, was fed to hens for 3 days in Experiment 1 and 4 weeks in Experiment 2. In Experiment 3, seven different levels of dietary phosphorus were fed. Blood serum inorganic phosphorus level was determined at different durations of feeding the experimental diets. All the blood samples were collected immediately following oviposition from the hens that had laid both on the day before and the day of bleeding in each experiment. The serum phosphorus level of hens previously fed .75% phosphorus was 4.12 mg/100 ml in Experiment 1 and 4.72 mg/100 ml when fed .75% phosphorus in Experiment 3. Serum phosphorus level of hens fed the diet containing .30% phosphorus decreased to between 2 and 3 mg/100 ml within 24 hr and remained at this level for 4 weeks. There were no significant differences in serum phosphorus levels of hens fed levels of dietary phosphorus between .375% and 1.40%. Decreasing dietary phosphorus from .30% to .22% further decreased the serum phosphorus level. It is concluded that the hen is capable of maintaining a normal blood phosphorus level over a wide range of dietary phosphorus, but decreases her serum phosphorus level immediately when fed suboptimal levels of phosphorus.