Influence of Dietary Calcium Excess during Growth on the Performance of Laying-type Chickens

Abstract

Two experiments were conducted to determine the effect of dietary calcium excess during growth on the performance of chickens. In Experiment 1, 8 diets of two levels of available phosphorus and four levels of calcium were fed growing chickens during 4-20 weeks of age. Dietary available phosphorus levels were 0.4% (normal) and 0.6%, and calcium levels were 0.75 (normal), 1.75, 2.75 and 3.75%, respectively. In Experiment 2, 6 diets of 6 calcium levels (0.75, 2.25, 2.75, 3.25, 3.75 and 4.25%) with normal available phosphorus level (0.4%) were fed growing chickens during 10-20 weeks of age. After 20 weeks old, conventional laying diet (calcium 2.75%) were fed all the pullets.The results were as follows.1. The pullets fed diets containing 2.75% calcium or above with normal phosphorus level during growing period (4-20 and 10-20 weeks of age) showed significantly lowered growth and feed efficiency compared with normal growing diet (available phosphorus 0.4% and calcium 0.75%). Adverse effect of growth and feed efficiency by dietary calcium excess disappeared with increasing dietary phosphorus level.2. Sexual maturity, egg production, egg weight and feed efficiency during laying period, were not significantly affected by dietary calcium and phosphorus levels in growing period.3. About 1/4 of the pullets fed the diet containing 3.75% calcium and 0.4% available phosphorus during 4-20 weeks of age, died of kidney damage (kidney enlargement and uric acid deposition on kidney, liver and heart).It may be concluded that feeding high calcium diets containing 2.75% (standard calcium level of conventional laying diet) or above to growing chickens must be avoided. Also it was shown that adverse effect of dietary calcium excess was eliminated by the addition of phosphorus to the diet.