Skip to main content
Licentiate thesis, 2012

Assessing phosphorus overfeeding in dairy cows

Nordqvist, Maria


Faecal total phosphorus (TP) from dairy cows consists of a largely insoluble fraction and a soluble P fraction (SP), which mainly represents excess P. The soluble fraction increases proportionately with increased P feeding as excess P is mainly excreted with the faeces in soluble form. Determination of the acid-soluble P fraction in faeces has been suggested as a useful tool to identify excessive P feeding. The overall aim of this licentiate thesis was to gain a better understanding of how different fractions of faecal samples can be used as tools to map P (over)feeding in dairy cows. Paper I studied faecal excretion of different P fractions in 42 dairy cows fed a wide range of rations with varying P content ranging from approximately 70% up to 190% of their requirement. Faecal excretion of TP and SP was determined. The slope of the regression indicated that there was a significant relationship between actual measured SP and indirectly calculated regulated P. TP and SP were correlated and it was suggested that they can both serve as markers of P overfeeding Paper II screened intake and faecal excretion of P on Swedish commercial dairy farms, with special emphasis on comparing farms with organic (N=14) and conventional (N=15) production systems. In each herd, intake of P and other nutrients in feeds was determined for 10 cows in varying stages of lactation. Milk yield and faecal content of P (TP and SP) were also determined for these cows. The results indicated that cows in both management systems consumed more P than they required. However the level of overfeeding was higher for cows in conventional systems. Pooling faecal samples from lactating cows improved the correlation between faecal P concentration and calculated P requirements. SP and TP appeared to be equally good in reflecting P intake relative to predicted requirement. It was shown that slurry samples could be used to evaluate P feeding on herd level. In conclusion, this thesis showed that P overfeeding is greater in conventional dairy herds than in organic dairy herds and that both SP and TP in faecal samples can be used as markers of P overfeeding in dairy cows.


dairy cow; phosphorus; faeces

Published in

Rapport / Sveriges lantbruksuniversitet, Institutionen för husdjurens utfodring och vård
2012, number: 279
ISBN: 978-91-576-9081-4
Publisher: Dept. of Animal Nutrition and Management, Swedish University of Agricultural Sciences

Authors' information

Nordqvist, Maria
Swedish University of Agricultural Sciences, Department of Animal Nutrition and Management

UKÄ Subject classification

Animal and Dairy Science

URI (permanent link to this page)