Effects of 1,25-dihydroxycholecalciferol and phytase on zinc utilization in broiler chicks.
Studies were conducted with corn-soybean meal diets to evaluate the effects of phytate phosphorus utilization on zinc absorption and retention in broiler chicks. In the first two experiments, zinc-65 was used to determine zinc absorption. Experiment 1 was a 2 x 2 factorial with 0 or 5 micrograms/kg dihydroxycholecalciferol and 0 or 40 ppm supplemental zinc. In Experiment 2, 5 micrograms/kg 1,25-dihydroxycholecalciferol [1,25-(OH)2D3] or 750 units/kg phytase or both were added to a diet containing 35 ppm zinc. The diets in Experiment 3 were similar to Experiment 2 except that 600 units/kg phytase was fed. Experiment 4 was similar to Experiment 3 except that dietary phosphorus was decreased by .15%. There were no treatment effects on body weight in Experiments 1 and 2. Zinc absorption was higher in zinc-deficient birds in Experiment 1, but there were no other effects on zinc-65 absorption or retention. Body weight was increased by 1,25-(OH)2D3 in Experiments 3 and 4 and by phytase in Experiment 4. Phytate phosphorus retention was increased by phytase and 1,25-(OH)2D3 and was increased additively when both sources were fed. Dietary 1,25-(OH)2D3 increased zinc retention at times during Experiments 3 and 4, but this response was inconsistent. Phytase did not affect zinc retention. Phytase plus 1,25-(OH)2D3 increased zinc retention synergistically in Experiment 3. Bone zinc was increased by 1,25-(OH)2D3 and phytase, and there was an additive effect in Experiment 3. Plasma zinc and alkaline phosphatase were not affected. The results suggest that supplemental zinc may be decreased in a corn-soybean meal diet when phytate phosphorus utilization is enhanced.
Department of Poultry Science, University of Georgia, Athens 30602.
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KD
Roberson
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Edwards
D010832:6-Phytase / Q000008:administration & dosage*; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D015519:Bone Density / Q000187:drug effects; D002117:Calcitriol / Q000008:administration & dosage*; D002645:Chickens / Q000378:metabolism*; D005527:Food, Fortified; D015994:Incidence; D008297:Male; D010009:Osteochondrodysplasias / Q000453:epidemiology / Q000662:veterinary; D010758:Phosphorus / Q000378:metabolism; D011201:Poultry Diseases / Q000453:epidemiology; D013977:Tibia; D015032:Zinc / Q000008:administration & dosage / Q000378:metabolism*
D010758:Phosphorus; D010832:6-Phytase; D002117:Calcitriol; D015032:Zinc