Is waste milk any better afterwards?

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The dairy does a phenomenal job of raising calves. So, what’s going on with the pasteurized waste milk?

That’s the question Joey Ricks asked himself while working with a farm in Florida. The farm owner had called Ricks a month earlier, somewhat concerned about the rising cost of milk replacer and wondering what alternatives existed. Ricks, a nutritionist for Purina Mills, offered to help, but first wanted to know what the farm was currently feeding. He reviewed everything in the calf-feeding program, including the quality of pasteurized waste milk.

The results came as a surprise. Bacteria counts in the pre-pasteurized waste milk were actually lower — 660,000 colony forming units/ml. versus 2 million cfu/ml. plus — than the final pasteurized product being fed to calves. “I was shocked,” Ricks says.

Ricks recommended that the farm seal the tank where pre-pasteurized waste milk is stored so it is not exposed to the elements, along with feeding the milk more quickly once it comes out of the pasteurizer. The farm also switched from a 20/20 to a 28/20 milk replacer, so the final waste milk/milk replacer mix better matches the protein level in whole milk.  

The farm does not have updated bacteria counts, but manager Amadeo DePaz reported in November — after some of the changes were implemented — that overall calf health appeared to be better.

Pasteurization isn’t about putting the milk in a magic box and then not having to worry about it again. What happens pre-pasteurization and post-pasteurization can be just as important as the pasteurization itself.

A common problem

But, you say, pasteurization has to help — it kills bacteria, doesn’t it?  How in the world could you go wrong with that?

Pasteurization does not mean sterilization. Even if things go right, and you achieve a 95 percent to 98 percent reduction in bacteria, there are still going to be some residual amounts of bacteria that can grow back if things aren’t handled properly post-pasteurization.

At the particular farm that Ricks worked with, a night crew put the waste milk in the pasteurizer at 10:30 p.m. or so, let it cook for a while, and then let it sit until the calf-feeders were ready for it the next morning. “That milk was sitting there in a warm state for seven to eight hours (prior to feeding),” Ricks points out. It was more than enough time for bacteria to multiply.  

What Ricks observed on the Florida dairy is not that uncommon.

An ongoing study by Land O’Lakes Animal Milk Products Company has found there is much room for improvement.

As of last September, only one of the 67 farms participating in the Land O’Lakes study was below the recommended maximum bacterial count of 20,000 cfu/ml. in the waste milk fed to calves. And, bacterial counts post-pasteurization were similar to or higher than the counts prior to pasteurization on 59 percent of the farms. 

The number of farms in the study has since increased to 85, and some improvement has been seen, says Tom Earleywine, director of nutritional services for Land O’Lakes Animal Milk Products. Nine of the 85 tested pasteurizers have bacteria counts below the 20,000 cfu/ml. maximum. And, the percentage of farms with higher or equal bacterial counts post-pasteurization has fallen from 59 percent to 51 percent.  

Farms in the study reflect a wide range of management skill, Earleywine says. 

Pasteurization works

A study by Virginia Tech shows that pasteurization can work well with waste milk — if proper protocols are followed.

The study involved nine dairies and a large calf ranch in California within the last two years. Post-pasteurization bacteria counts were low, averaging 19,400 cfu/ml. immediately after pasteurization. That compared to an average of 1.6 million cfu/ml. prior to pasteurization, a 98.8 percent reduction.

The pasteurizers are doing their job. Are you doing yours?

Too many times, the calves don’t receive the milk until it has been out of the pasteurizer for an hour or more. What people don’t realize is that a small number of residual bacteria in the milk can multiply out of control. At some point above 40 degrees F, you can have a doubling of bacteria every 20 minutes, Earleywine says. The rate goes up with higher ambient temperatures.

And, milk is the perfect growth medium for bacteria. “If you are a microbiologist and you ever have trouble growing an organism, you put dried milk powder in there and that usually takes care of it,” says Bob James, dairy scientist at Virginia Tech.

In the Virginia Tech study, average bacteria counts that started off at 19,400 cfu/ml. immediately after pasteurization grew to 100,000 cfu/ml. or more within one hour of pasteurization. 

Don’t regard the pasteurizer as a cure-all or end-all. What comes out of the pasteurizer may be in good shape, but lots can happen between that time and the time calves are fed.

Have protocols in place

How you handle waste milk before and after it goes into the pasteurizer may be as important as the pasteurizer itself.

Make sure the bottles or buckets that receive the waste milk are clean. Dirty bottles and buckets simply reintroduce bacteria back into the system.

Virginia Tech research has shown that post-pasteurization bacteria counts are higher when farms use buckets as opposed to bottles. It often takes longer to feed with buckets, and that can give bacteria more time to multiply.

Sanitation is often a bigger challenge with buckets than it is with bottles.

Try to feed the waste milk as soon after it comes out of the pasteurizer as possible.    

When cleaning and sanitizing the pasteurizer, it is important to use the proper cleaning agent. Always follow manufacturer’s recommendations. When using a high-temperature, short-time pasteurizer, consider using a concentrated non-chlorinated cleaner rather than a chlorinated cleaner, because the combination of chloride, milk residue and heat can cause a residue to form on the inside of the pasteurizer that is very hard to clean.

Test regularly

Try to test the waste milk you are feeding at least once a month, recommends Tom Earleywine, director of nutritional services for Land O’Lakes Animal Milk Products. A large dairy may even think about doing it once a week, he adds, because with more calves and a hired labor force there is more room for error.

Test bacterial levels at three stages — pre-pasteurization, post-pasteurization and when the last calf is fed, Earleywine recommends. The last-calf-fed number is important, because it reflects what the calves are actually receiving.

Send samples to your milk processor or an independent lab for analysis.

Bart Hanson, co-owner of Amber Hills Ranch, a custom heifer-raising facility in Rupert, Idaho, has found it advantageous to do the testing himself.

Hanson has set up a fairly simple procedure to monitor how well his pasteurizer is working. He uses culture plates with a pre-prepared standard methods agar that he purchases from a microbiology supply company. The point is simply to see how much bacteria grows on the plates before the milk is pasteurized compared to after.

“If I test the milk before it’s pasteurized and I have (bacterial growth), and I test it again after it’s pasteurized and I get no growth, then I know the pasteurizer is working,” he says. 

He runs this test at least weekly, sometimes three times a week, depending on the time of year.

“If you are going to pasteurize milk, you have to learn how to read it and what you are getting back,” Hanson says.



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