Phosphorus Partitioning During Early Lactation in Dairy Cows Fed Diets Varying in Phosphorus Content

¹ Department of Dairy Science, Virginia Polytechnic Institute and State University, Blacksburg

The effect of dietary P content on P partitioning and excretion during early lactation was evaluated in 13 cows fed diets containing 0.34 (no supplementary P), 0.51, or 0.67% P. All cows were fed a common prepartum total mixed ration (TMR) (0.28% P), followed by common TMR (0.51% P) for 7 d post-partum. On day 7, cows were randomly assigned to one of the three dietary P treatments. All treatment diets contained 16.6% CP, 15.2% ADF, 26.3% NDF, and 0.74% Ca. Total collections of milk, urine, and feces were conducted during weeks 3, 5, 7, 9, and 11 of lactation. Average body weight (591 kg), milk yield (47.9 kg/d), and DMI (25.2 kg/d) throughout the 10-wk trial were not affected by dietary P content. With increasing dietary P, however, linear increases in P intake (84.7, 135.2, and 161.5 g/ d), fecal P (42.3, 87.5, and 108.6 g/d), urinary P (0.32, 1.28, and 3.90 g/d), and total P excretion (42.6, 88.8, and 112.5 g/d) were observed. Apparent P digestibility (49.0, 34.4, and 32.8% of P intake) decreased quadratically with increasing dietary P. Phosphorus balance was highly variable, but cows fed the 0.34% P diet were in negative P balance longer than were cows fed diets containing 0.51 or 0.67% P. With increasing dietary P, serum concentrations of inorganic P increased linearly, but serum Ca and Mg concentrations decreased. Increasing dietary P increased fecal and urinary P excretion in early lactation cows. Increased duration of negative P balance and changes in blood mineral concentrations suggest that cows fed low P diets mobilized more P from body reserves than cows on medium- and high-P diets.

Key Words: phosphorus balance • phosphorus excretion • early lactation cow

Submitted on September 20, 2001
Accepted on December 17, 2001

This article has been cited by other articles:

				J. M. Moorby, P. H. Robinson, W. J. Fisher, and R. T. Evans Comparison of Red Clover and Ryegrass Silage for Dry Cows and Influence on Subsequent Lactation Performance J Dairy Sci, September 1, 2008; 91(9): 3501 - 3511. [Abstract] [Full Text] [PDF]

				S. R. Hill, K. F. Knowlton, E. Kebreab, J. France, and M. D. Hanigan A Model of Phosphorus Digestion and Metabolism in the Lactating Dairy Cow J Dairy Sci, May 1, 2008; 91(5): 2021 - 2032. [Abstract] [Full Text] [PDF]

				M. Hollmann, K. F. Knowlton, and M. D. Hanigan Evaluation of Solids, Nitrogen, and Phosphorus Excretion Models for Lactating Dairy Cows J Dairy Sci, March 1, 2008; 91(3): 1245 - 1257. [Abstract] [Full Text] [PDF]

				A. N. Hristov, W. Hazen, and J. W. Ellsworth Efficiency of use of imported nitrogen, phosphorus, and potassium and potential for reducing phosphorus imports on idaho dairy farms. J Dairy Sci, September 1, 2006; 89(9): 3702 - 3712. [Abstract] [Full Text] [PDF]

				M. L. Soupir, S. Mostaghimi, and E. R. Yagow Nutrient transport from livestock manure applied to pastureland using phosphorus-based management strategies. J. Environ. Qual., July 1, 2006; 35(4): 1269 - 1278. [Abstract] [Full Text] [PDF]

				R. O. Maguire, Z. Dou, J. T. Sims, J. Brake, and B. C. Joern Dietary Strategies for Reduced Phosphorus Excretion and Improved Water Quality J. Environ. Qual., November 7, 2005; 34(6): 2093 - 2103. [Abstract] [Full Text] [PDF]

				Z. Wu Utilization of Phosphorus in Lactating Cows Fed Varying Amounts of Phosphorus and Sources of Fiber J Dairy Sci, August 1, 2005; 88(8): 2850 - 2859. [Abstract] [Full Text] [PDF]

				R. L. Kincaid, D. K. Garikipati, T. D. Nennich, and J. H. Harrison Effect of Grain Source and Exogenous Phytase on Phosphorus Digestibility in Dairy Cows J Dairy Sci, August 1, 2005; 88(8): 2893 - 2902. [Abstract] [Full Text] [PDF]

				L. Chapuis-Lardy, J. Fiorini, J. Toth, and Z. Dou Phosphorus Concentration and Solubility in Dairy Feces: Variability and Affecting Factors J Dairy Sci, December 1, 2004; 87(12): 4334 - 4341. [Abstract] [Full Text] [PDF]

				B. E. Keene, K. F. Knowlton, M. L. McGilliard, L. A. Lawrence, S. M. Nickols-Richardson, J. H. Wilson, A. M. Rutledge, L. R. McDowell, and M. E. Van Amburgh Measures of Bone Mineral Content in Mature Dairy Cows J Dairy Sci, November 1, 2004; 87(11): 3816 - 3825. [Abstract] [Full Text] [PDF]

				W. P. Weiss and D. J. Wyatt Macromineral Digestion by Lactating Dairy Cows: Estimating Phosphorus Excretion via Manure J Dairy Sci, July 1, 2004; 87(7): 2158 - 2166. [Abstract] [Full Text] [PDF]

				H. Lopez, F. D. Kanitz, V. R. Moreira, M. C. Wiltbank, and L. D. Satter Effect of Dietary Phosphorus on Performance of Lactating Dairy Cows: Milk Production and Cow Health J Dairy Sci, January 1, 2004; 87(1): 139 - 145. [Abstract] [Full Text] [PDF]

				K. F. Knowlton, J. S. Radcliffe, C. L. Novak, and D. A. Emmerson Animal management to reduce phosphorus losses to the environment J Anim Sci, January 1, 2004; 82(13_suppl): E173 - 195. [Abstract] [Full Text] [PDF]

				A. D. Guyton, J. M. McKinney, and K. F. Knowlton The Effect of Steam-Flaked or Dry Ground Corn and Supplemental Phytic Acid on Phosphorus Partitioning and Ruminal Phytase Activity in Lactating Cows J Dairy Sci, December 1, 2003; 86(12): 3972 - 3982. [Abstract] [Full Text] [PDF]

				Z. Dou, J. D. Ferguson, J. Fiorini, J. D. Toth, S. M. Alexander, L. E. Chase, C. M. Ryan, K. F. Knowlton, R. A. Kohn, A. B. Peterson, et al. Phosphorus Feeding Levels and Critical Control Points on Dairy Farms J Dairy Sci, November 1, 2003; 86(11): 3787 - 3795. [Abstract] [Full Text] [PDF]

				Z. Wu, S. K. Tallam, V. A. Ishler, and D. D. Archibald Utilization of Phosphorus in Lactating Cows Fed Varying Amounts of Phosphorus and Forage J Dairy Sci, October 1, 2003; 86(10): 3300 - 3308. [Abstract] [Full Text] [PDF]