Influence of phosphorus intake on excretion and blood plasma and saliva concentrations of phosphorus in dairy cows.
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.
Valk
H
H
ID TNO Animal Nutrition, Lelystad, The Netherlands. h.valk@id.dlo.nl
Sebek
L B J
LB
Beynen
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AC
D000818:Animals; D002417:Cattle / Q000378:metabolism*; D004063:Digestion; D005243:Feces / Q000737:chemistry*; D005260:Female; D010758:Phosphorus / Q000032:analysis* / Q000097:blood*; D016226:Phosphorus, Dietary / Q000008:administration & dosage*; D012463:Saliva / Q000737:chemistry*
D016226:Phosphorus, Dietary; D010758:Phosphorus