Optimizing phosphorus utilization by dairy cows

A case study of dairy farms


Team:

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

Funding:

UofM, PIN/MRAC, DFM

Objective:

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

Design:

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

Findings:

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.