Improving estimations of phosphorus bioavailability for lactating dairy cows

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dc.contributor.authorJarrett, Jamie Pearlen
dc.contributor.committeechairKnowlton, Katharine F.en
dc.contributor.committeememberJames, Robert E.en
dc.contributor.committeememberHanigan, Mark D.en
dc.contributor.committeememberHarrison, Josephen
dc.contributor.committeememberShang, Chaoen
dc.contributor.committeememberAkers, Robert Michaelen
dc.contributor.departmentDairy Scienceen
dc.date.accessioned2017-04-06T15:44:07Zen
dc.date.adate2011-11-15en
dc.date.available2017-04-06T15:44:07Zen
dc.date.issued2011-10-14en
dc.date.rdate2016-10-03en
dc.date.sdate2011-10-28en
dc.description.abstractPhosphorus (P) is an instrumental nutrient in numerous physiological processes, but can have detrimental environmental impact if fed in excess. Increased P intake in dairy cows leads to increased fecal excretion of P and a reduction in efficiency of use. Variability in P concentration or availability in feedstuffs can exacerbate P excretion. To investigate variability in P between and within feedstuffs, 170 feed samples (forages, concentrates, and by-products), were collected from across the U.S., classified by region fed, and analyzed for total P, inorganic P, and phytate. Forages contained a greater proportion of P in the inorganic form and less total P and phytate as compared to concentrates and by-products. The majority of total P (71.2, 81.8, and 81.9% of total P in forages, concentrates, and by-products, respectively) was associated with inorganic P and phytate. The enzyme phytase has been used successfully in swine and poultry nutrition, as a feed additive, to increase available P and reduce the need for supplemental inorganic P. An experiment was conducted to investigate the effect of phytase use and forage particle length, using a 2 x 2 factorial, on P availability in lactating dairy cows. Total P intake of the four diets was similar (P > 0.15). Total tract digestibility of total P tended (P < 0.10) to be reduced and total P excretion was increased (P < 0.05) with phytase supplementation. Milk fat yield, protein yield, 3.5% FCM, and ECM were increased (P < 0.05) with addition of exogenous phytase to the diet. This indicates that phytate may contain some anti-nutritional factors that reduce availability in other nutrients used for milk production. Variation in P compounds between feeds, and variation in P digestion and production performance with exogenous phytase suggests opportunity for improvement in prediction of P availability from feeds for lactating cows.en
dc.description.degreePh. D.en
dc.identifier.otheretd-10282011-141717en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-10282011-141717/en
dc.identifier.urihttp://hdl.handle.net/10919/77248en
dc.language.isoen_USen
dc.publisherVirginia Techen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectphytaseen
dc.subjectPhosphorusen
dc.subjectlactating dairy cattleen
dc.subjectbioavailabilityen
dc.titleImproving estimations of phosphorus bioavailability for lactating dairy cowsen
dc.typeDissertationen
dc.type.dcmitypeTexten
thesis.degree.disciplineDairy Scienceen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

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