Faecal excretion of total and acid extractable phosphorus in dairy cows fed rations with different levels of phosphorus.
BACKGROUND
The phosphorus (P) originating from livestock operations causes eutrophication. Determination of acid extractable P (AEP) in cattle faeces has been proposed as a tool to identify excessive P feeding. The method has not yet been evaluated in controlled studies with cows subjected to individual recording of P intake. Thus the present study focused on investigating the relationship between different P fractions in faeces from cows fed rations with varying P content. The study also investigated whether AEP in faeces could be used to estimate dietary P intake in relation to the P requirement.


RESULTS
The results showed that acid extractable P predicted P overfeeding. P fed in excess of requirements was largely excreted as acid extractable P. The unavailable and/or inevitably lost P fractions in the diets were smaller than assumed.


CONCLUSIONS
This study demonstrates in experimental studies a positive relationship between measured AEP and indirectly calculated regulated P. Any P fed in excess of requirements was largely excreted as AEP. This fraction is thought to be the most mobile P fraction with regard to potential runoff losses. However, the unavailable and/or inevitably lost P fractions in the diets were smaller than assumed.
Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences, P.O. Box 7024, SE750, 07 Uppsala, Sweden.
Maria
M
Nordqvist
Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences, P.O. Box 7024, SE750, 07 Uppsala, Sweden.
Rolf
R
Spörndly
Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences, P.O. Box 7024, SE750, 07 Uppsala, Sweden.
Kjell
K
Holtenius
D000821:Animal Feed; D000818:Animals; D002417:Cattle / Q000378:metabolism*; D004032:Diet / Q000662:veterinary*; D005243:Feces / Q000737:chemistry*; D005260:Female; D009751:Nutritional Requirements; D010758:Phosphorus / Q000032:analysis*; D016226:Phosphorus, Dietary / Q000008:administration & dosage*
D016226:Phosphorus, Dietary; D010758:Phosphorus
dairy cows; diets; faecal excretion; phosphorus