Phosphorus bioavailability in the chick: effects of protein source and calcium level.
Three experiments utilizing 1,104 broiler cockerels were conducted to establish optimum dietary conditions for the determination of phosphorus (P) bioavailability. The reference P source was KH2PO4. A response-surface design and purified diets containing casein as the protein source were utilized in Exp. 1 Various levels of calcium (Ca) and P supported near-maximal gain in tibia ash. Optimal gain in tibia ash was attained at 1.8% Ca and .55% total (highly available) P. Regression equations describing the gain in tibia ash in response to added P from KH2PO4 for diets in Exp. 2 that contained casein and isolated soybean protein had different (P less than .05) slopes. Diets moderately limiting in available P exhibited reduced gain in tibia ash content if more than 1.4% total Ca was present. A corn-soybean meal diet was utilized in Exp. 3. Partitioning of tibia ash gain into effects due to basal diet, added P from KH2PO4, or P from the test ingredient was investigated. Sunflower meals containing 42 or 28% crude protein were evaluated for P bioavailability. The P content of the meals was 21.6 and 22.7% available, respectively. The fiber of the sunflower hull did not interfere with P availability. Selection of diet ingredients is discussed with respect to the development of P bioavailability values for use in practical diets.
D000818:Animals; D001682:Biological Availability; D001842:Bone and Bones / Q000378:metabolism; D002136:Calcium, Dietary / Q000494:pharmacology*; D002364:Caseins; D002645:Chickens / Q000378:metabolism*; D004044:Dietary Proteins / Q000494:pharmacology*; D006368:Helianthus; D008274:Magnesium / Q000378:metabolism; D008297:Male; D008903:Minerals / Q000378:metabolism; D010758:Phosphorus / Q000378:metabolism*; D013025:Glycine max
D002136:Calcium, Dietary; D002364:Caseins; D004044:Dietary Proteins; D008903:Minerals; D010758:Phosphorus; D008274:Magnesium