Effect of Form and Amount of Phosphorus and Phytase Supplementation on Phosphorus Utilization by Ruminants

dc.contributor.authorShanklin, Rachel Kristinaen
dc.contributor.committeechairFontenot, Joseph P.en
dc.contributor.committeememberWahlberg, Mark L.en
dc.contributor.committeememberRadcliffe, J. S.en
dc.contributor.committeememberSwecker, William S. Jr.en
dc.contributor.departmentAnimal and Poultry Sciencesen
dc.description.abstractThe use of animal manures to replace commercial fertilizer has increased the economic and environmental sustainability of agriculture. However, this practice has resulted in excess P being applied to the soil in some areas. Excess P may run-off into surface water and leach in the ground, causing eutrophication. Decreasing the amount of P fed and improving the utilization of P are two possible nutritional solutions to this problem. Two experiments were conducted to investigate the effects of levels of dietary P, chemical form of P, and phytase supplementation in ruminants. For Exp. 1, 24 steers (average BW = 229 kg) were allotted to two diets containing 0.12 and 0.19% dietary P for a 112-d growth trial. The steers were individually full-fed, weighed every 14 d, and blood samples were collected every 28 d. The steers fed the 0.12% P diet had increased (P<0.02) ADG during the first 28 d, after which there were no differences. They also had higher (P<0.05) feed intake. By d 56 serum P for the 0.12% P group was lower (P<0.01), and this difference continued for the remainder of the trial. For Exp. 2, 18 wether lambs (average BW = 23 kg) were allotted to the following six diets for each of two metabolism trials: 1) a negative control diet deficient in P, 2) control diet supplemented with inorganic P, 3) control diet supplemented with phytic acid, 4) control diet supplemented with phytic acid and phytase, 5) control diet supplemented with cottonseed meal, and 6) control diet supplemented with cottonseed meal and phytase. Each metabolism trial was preceded by a 5 wk depletion phase in which the lambs were fed a low-P diet. The metabolism trials consisted of a 10 d preliminary period followed by a 10-d collection of feces and urine. On the final day ruminal fluid, blood, and saliva were collected. At the end of the second metabolism trial 10th rib bones were collected from each lamb. Absorption of P was lowest (P<0.0001) for the low-P treatment, compared to the other treatments. There was no treatment effect on saliva P. Ruminal fluid P was higher (P<0.05) for lambs receiving P supplementation. Within supplementation treatments, ruminal fluid P was higher (P<0.05) for lambs fed organic P than for those fed inorganic P. Feeding CSM resulted in higher (P<0.001) ruminal fluid P than phytic acid. The addition of phytase to the diets with organic P resulted in more (P<0.04) P in the ruminal fluid. There was a decrease (P<0.003) in serum P associated with the low-P treatment. There was no difference in bone ash or breaking strength.en
dc.description.degreeMaster of Scienceen
dc.publisherVirginia Techen
dc.rightsIn Copyrighten
dc.subjectInorganic Phosphorusen
dc.subjectOrganic Phosphorusen
dc.titleEffect of Form and Amount of Phosphorus and Phytase Supplementation on Phosphorus Utilization by Ruminantsen
thesis.degree.disciplineAnimal and Poultry Sciencesen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.nameMaster of Scienceen
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