Making sure your cows are eating the same ration you mixed is an ongoing challenge for dairy producers.

Spending some time observing what gets left in bunks after feeding can go a long way in helping you get the job done, says Herb Bucholtz, Michigan State University dairy nutritionist.

“One of the reasons for feeding a TMR in the first place is to ensure that cows consume correct proportions of all ration ingredients with each bite they eat,” explains Bucholtz. “But if cows sort through the TMR and consume only the ingredients they like, what are you gaining?

“Setting up a program to evaluate the TMR for sorting can be a very useful management tool,” he adds. “The time and effort it takes to collect and evaluate data will pay for itself by helping you control nutritionally related challenges like milk production drop-offs or increased cases of metabolic health problems.”

Routine visual observation of the feed bunk a few hours after feeding is a good starting point for determining how much TMR sorting is going on.

“Sorting of corncobs, stones and spoiled feed can be pretty easy to spot,” notes Bucholtz. ”It can take a little more investigating to get a handle on what other ingredients cows might not be eating.”

A Penn State forage particle separator can give you an idea of how much long-particle sorting is going on. Bucholtz recommends running a sample through the particle separator right after you mix a feed batch. Then collect and analyze a bunk sample a few hours before the next feeding and compare results.

Deciding where in the bunk to draw the sample requires a deft touch.

“Look for an area that's been representatively worked over by the cows instead of a spot that's just about been cleaned out or where the feed has barely been touched,” he says. “Then do three repetitions with the separator to get a good working average.”

Bucholtz warns against relying exclusively on “book values” (percentages of material you should find on each separator screen).

“These published numbers are basically averages of results collected in thousands of repetitions over a period of time,” he says. “But there are always some deviations from averages. The important thing is to establish some kind of sorting baseline for your own herd. Work from that reference point each time you use the separator.”

Among the steps you can take to limit sorting:

  • Monitor ingredient quality. Spoiled, unpalatable feeds tend to increase sorting.

    “Feeders should get into a routine of checking feeds for signs of spoilage every day,” notes Bucholtz.

    If you do make ingredient changes based on observations, remember to rebalance the ration accordingly.

    “Maybe you're seeing too many corncobs and decide to back off a little on corn silage amounts,” says Bucholtz. “Just remember that the nutritionist took those corncobs into account as a fiber source when the ration was formulated. You'll need to recalculate to account for the fiber you're giving up.”

  • Watch forage particle length. With both silage and dry hay, longer particles in the ration are easier for cows to sort. The major challenge for producers and nutritionists: shortening up particle length too far will set cows up for a variety of digestive or metabolic ailments.

  • Get feed in front of cows more often. Dairies feeding several times a day can reduce feed waste by adding sorted material from each feeding back into the next batch of TMR. If you're feeding once every 24 hours, push up feed several times a day.

    “Cows will still sort the feed,” the dairy nutritionist points out. “But each time you refeed or push feed up, you'll be remixing the ingredients. That should make it tougher for cows to sort.”

  • Add liquid. Drier feeds are easier for cows to sort than wet feeds. Adding liquid ingredients to a TMR can help bind drier/longer ingredient particles to finer particles, making sorting more difficult. Water and molasses are the liquids most commonly used for this purpose, but both have drawbacks.

“In the Upper Midwest, adding water can lead to problems with ration freezing in the winter months and feed heating in warm weather,” says Bucholtz.

“Molasses is a good alternative, but it will add to your overall ration costs.”

Substituting high-moisture ingredients like haylage or corn silage for drier ingredients like dry hay or straw is another option.