A fecal test for assessing phosphorus overfeeding on dairy farms : evaluation using extensive farm data

2010

Article référencé dans le Web of Science WOS:000274102500042

Dou Z., Ramberg C. F., Chapuis Lardy Lydie, Toth J. D., Wu Z., Chase L. E., Kohn R. A., Knowlton K. F., Ferguson J. D.

Journal of Dairy Science, 2010, 93 (2), p. 830-839 ISSN 0022-0302

Managing P on dairy farms requires the assessment and monitoring of P status of the animals so that potential overfeeding may be minimized. Numerous published studies have demonstrated that for lactating dairy cows, increasing P concentrations in diets led to greater P excretion in feces. More recent work reported that inorganic P (P-i) in 0.1% HCl extracts of feces (fecal extract P-i, g/kg) closely reflects dietary P changes. This has led to the proposal that 0.1% HCl fecal extract P-i may serve as an indicator of the animal's P status (adequate or excessive) when compared with a benchmark value. Here, we present the results of an extensive evaluation of the proposed fecal P indicator test. With samples (n = 575) from >90 farms, fecal total P (TP, g/kg) and fecal extract P were positively correlated with dietary P (X, g/kg): TP = 1.92X - 0.17 (R-2 = 0.36); fecal extract P = 1.82X - 2.54 (R-2 = 0.46). Fecal extract P was responsive to dietary P changes, whereas the remaining P, calculated as TP minus fecal extract P, was not. A provisional benchmark value of fecal extract P representing near-adequate P status was set at 4.75 g/kg. Assessment of the farm data using the benchmark indicated that 316 out of 575 data points were associated with possible P overfeeding. Advantages of the fecal-based test over feed-based analysis to assess P status are discussed. The fecal extract P method is a simple and practical test that can be used as an assessment tool for helping dairy producers improve P management and reduce their environmental footprint.

Sciences du milieu [021] ; Sciences du monde animal [080]

Fonds IRD [F B010049268]

fdi:010049268