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ebek*
* ID TNO Animal Nutrition P.O. Box 65, 8200 AB Lelystad, The Netherlands
Department of Nutrition, Faculty of Veterinary Medicine P.O. Box 80.152, 3508 TD Utrecht, The Netherlands
Corresponding author:
H. Valk; e-mail:
h.valk{at}id.dlo.nl.
Phosphorus (P) balance, and blood plasma P and saliva P concentrations were measured in multiparous dairy cows through two lactations and two dry periods. The cows were fed three amounts of P at either 100, 80 or 67% of the Dutch P recommendation, actually resulting in dietary P concentrations of 3.2 to 3.9, 2.6 to 2.9 and 2.2 to 2.6 g P/kg dry matter during lactation for the three treatments, respectively. On the basis of plasma P values as low as 0.9 mmol/l and saliva P values as low as 5.1 mmol/l during the second lactation period within the experiment, the 67% group was considered to be deficient in P. By decreasing milk production, and thus lowering P losses with milk, P retention in the 67% group remained near zero. The P supply with the 80% ration was considered to be just sufficient. At high milk yield and marginal dietary P concentrations, plasma P and saliva P concentrations were decreased. The higher P intake in high-compared with low-producing cows resulted in a constant absolute fecal P excretion, due to the fact that the apparent P digestibility was raised with increasing milk yield. There was a direct relationship between milk P output and the percentage of apparent P digestibility for individual animals.
Key Words: phosphorus • blood plasma • dairy cow
Abbreviation key: P67 = dietary P at 67% of the requirement, P80 = dietary P at 80% of the requirement, P100 = dietary P at 100% of the requirement
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