Disappearance of phosphorus in phytate from concentrates in vitro and from rations fed to lactating dairy cows.
Objectives were to determine concentrations of P in phytate in selected concentrates, disappearance of P in phytate from these concentrates in vitro, and extent of hydrolysis of phytate in vivo. Total P and P in phytate were determined for eight concentrates; 32 to 81% of total P was in phytate. Six concentrates were incubated in vitro to determine the extent of phytate disappearance from solids and its appearance and disappearance from solution. Greater than 90% of P in phytate disappeared from solids between 6 and 8 h of incubation in vitro (wheat middlings, rice bran, hominy, soybean meal, and dried distillers grains) or between 12 and 24 h (cottonseed meal). Phosphorus in phytate in solution was hydrolyzed by 12 h except for cottonseed meal (by 24 h). Hydrolysis of the inositol ring to release P in vivo was greater than 99%, based on total fecal collection from 11 cows and the use of Cr as an indigestible marker in excreta, and between 94 to 98% for the same samples when acid detergent lignin was used as an indigestible marker to calculate phytate disappearance. These results further indicate that P in phytate should be considered available to lactating dairy cows when rations to meet their P requirements are being formulated.
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Dairy Science Department, University of Florida, Gainesville 32611-0920.
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Wilcox
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D000821:Animal Feed; D000818:Animals; D002417:Cattle / Q000378:metabolism*; D005243:Feces / Q000737:chemistry; D005260:Female; D006868:Hydrolysis; D007408:Intestinal Absorption; D007774:Lactation / Q000378:metabolism*; D016018:Least-Squares Analysis; D010758:Phosphorus / Q000378:metabolism* / Q000493:pharmacokinetics; D010833:Phytic Acid / Q000378:metabolism* / Q000493:pharmacokinetics
D010758:Phosphorus; D010833:Phytic Acid