Effects of dietary levels and types of fat on performance and mineral metabolism of broiler chicks.

Two experiments were conducted to investigate the effects of increasing dietary fat level from 0 to 9.0% and sources of supplemental fat (animal-vegetable fat or corn oil) on the performance and mineral metabolism in broiler chicks from day-old to 3 weeks of age. In experiment 1, increasing dietary fat level significantly (P less than .05) increased 3-week body weight and significantly (P less than .01) improved feed efficiency. There was no significant effect of the treatments on bone ash, bone magnesium, phosphorus, manganese, or zinc, although bone calcium content was significantly (P less than .01) reduced with increase in dietary fat level. Plasma minerals were not significantly affected by the diet treatments. In Experiment 2, neither source of fat, dietary calcium, nor vitamin D3 had any significant effect on performance parameters. Calcium and magnesium retention were significantly (P less than .05) reduced by dietary corn oil. Bone ash and magnesium were significantly (P less than .01) reduced when corn oil was the source of dietary fat, and there was a significant interaction between source of fat and dietary calcium level on bone calcium content. Increasing the dietary vitamin D3 from 1600 to 3200 IU/kg significantly (P less than .05) increased bone calcium content. Bone phosphorus, manganese, and zinc content were not significantly affected by the diet treatments. Plasma magnesium, phosphorus, and zinc content were not significantly affected by the diet treatments. It is concluded that increasing dietary fat, although beneficial for growth, was detrimental to calcium retention and bone calcification. Increasing dietary calcium does not seem to alleviate this problem.