Optimizing phosphorus utilization by dairy cows


Source: University of Manitoba

A case study of dairy farms


Project Leader:  Dr. Kees Plaizier, Dept. Animal Science,

Email: plaizier@ms.umanitoba.ca

Co-Investigators: Dr. Kim Ominski (U of M), Dr. Emma McGeough (U of M)
Industry Partner: Dairy Farmers of Manitoba




To identify factors that affect how efficiently dairy cows use phosphorous.


The survey involved 10 dairy farms in Manitoba, using 30 dairy cows in different stages of lactation from each farm.


The results concluded that even when a safety margin is used, the P content in the diet of dairy cows can safely be reduced.

The results of the study show that on average:
• Diets contain 0.41 per cent of P on a dry matter basis,
• 64.9 per cent of the P in the feed was not digested and was excreted in the feces, and
• 34.6 per cent of the P in the feed ended up in the milk.

These values varied a lot among cows and farms, which suggests that they can be improved on many farms. The Dietary P requirement of peak, mid, and late lactation cows is 0.32 per cent of dry matter, which is much lower than the average P content of the diets that we found in this study.

Approximately half of the cows that were part of the project received more P than required. Even when a safety margin is used, the P content in the diet of dairy cows can safely be reduced on many farms. The efficiency of P decreased when lactation progressed and milk yields decreased.

Precision feeding, which means better matching of the supply with the requirements of P, will therefore enhance P utilization and reduce the P content of manure. Precision feeding can be achieved by group feeding with diets formulated for the P requirements of groups and the delivery of P supplements to individual cows through feeding stations.