An ongoing evaluation by Land O’Lakes Animal Milk Products has revealed that both the nutritional content and the bacteria levels of pasteurized waste milk can vary tremendously from farm-to-farm, and, potentially, from day-to-day on the same farm.

Starting in 2006, Land O’Lakes began evaluating dairy calf-milk-pasteurization processes (78 dair-ies to date). An independent dairy quality assurance lab approved the sampling and shipping proto-cols used and conducted the quality analysis of the milk samples.

The goal of the project was not to discourage waste-milk pasteurization, but to help dairies deter-mine whether or not the process was doing the job they hoped it would, and assist them in correcting imperfections as necessary.

Waste milk intended for calf feed was evaluated for nutritional content, including fat, protein and to-tal solids; and bacteria count, measured via standard plate count in colony forming units (cfu) per mil-liliter (mL), both pre- and post-pasteurization.

Fluctuating nutrition levels
The results showed that nutrition levels varied considerably, with the percent of solids ranging from 8.99% to 17.51%. Protein content varied from 2.23% to 5.58%. Fat levels ranged from 2.69% to 9.47%.

Bob James, PhD, Virginia Tech Dairy Science professor, notes an increasing amount of research points to the importance of feeding calves on an adequate and even plane of nutrition. “If the milk calves are fed varies excessively in quality or supply of nutrients, a slight savings in feed cost may be more than offset by increased illness or death losses,” James says.

More than half of the farms involved in the evaluations noted that they incur periodic supply short-ages, when they have less waste milk available than they need to feed all of the calves on milk. In such cases, supplemental nutrients must be provided from the bulk tank or milk replacer.

Bacteria still present
James says an important goal of a waste-milk-pasteurization program should be to reduce bacteria numbers in the milk to 20,000 cfu/mL or lower. “Pasteurization by no means equals sterilization,” he points out. “It should, however, reduce bacteria numbers significantly. A well-managed pasteurization program will lower bacteria numbers by approximately 98%.”

James, who has seen similar results in his research of pasteurization that did not successfully lower bacteria counts, says the problem is not pasteurization itself. Rather, it is the processes followed to perform the pasteurization, including equipment sanitation, and the handling and storage of the milk before and after pasteurization takes place. 

From the Land O’Lakes studies

  • Twenty-five percent of the dairies had the same bacteria levels coming out of the pasteurizer as go-ing in. In all  cases, that level was 2,000,000 cfu/mL, the highest measurement possible in the study.
  • Thirty-four percent had bacteria levels that were higher in the post-pasteurized samples than the milk going into the pasteurizer.
  • Forty-one percent produced post-pasteurization samples with lower bacteria, but only one dairy met the 20,000 cfu/mL goal.