The author is an assistant professor and extension dairy specialist at Iowa State University.

High-quality forages are the foundation of a productive and healthy dairy herd. However, the way feed is managed from the field to the cow is crucial for maximizing a producer’s investment in forages. Regarding feed management, the “three rations” concept provides a valuable framework for solving problems and preventing them before they start.

If you have ever taken an animal nutrition course, you have heard about the three rations. For those who have not, the three rations on a dairy farm are the ration on paper, the ration delivered to the cow, and the ration the cow consumes. The ration on paper is what your nutritionist has balanced for you, while the ration delivered to the cow was mixed and dropped in the feedbunk. Ultimately, however, the only ration that matters to the cow is the one she consumes.

Along the way from ration balancing to animal intake, there are many opportunities for error, and the more we can do to minimize this error, the better the ration consumed by the cow. These errors can negate all the care and effort made in putting up quality forages, especially if it means that the cow eats around, or sorts, these forages. A diet built on high-quality forages promotes rumen health and milk fat yield, so it is crucial to consume these forages in a ration as it was balanced.

Picky eaters

Sorting occurs when a cow eats the parts of the total mixed ration (TMR) that are appealing to her and leaves the rest. If a TMR is like a salad, sorting would be the equivalent of eating only the things you like in the salad. I leave behind onions when I eat a salad; for others, it might be tomatoes. As humans, we are hopefully eating enough diverse food in our diets that choosing not to eat all of the ingredients in our salad is probably harmless. For the dairy cow that depends on a perfectly balanced TMR to meet the demands of high milk production, this can mess up a nutritionist’s hard work and spell trouble.

So, how do we prevent sorting? Researchers have given us a few options.

 Particle size. Particles that are too long are a major cause of sorting. It is common wisdom to say that the forages in the cow’s diet should be shorter than her mouth is wide; however, growing evidence shows cows can still sort out these particles. Particles that are an inch long are less sortable than particles that are four inches long, and they still provide effective fiber for rumen health.

This is a crucial consideration in dry cow diets, as these are high in lower quality forage. The forage in these diets fills the rumen, which makes the cow feel satiated without providing much energy, resulting in overconditioning. Additionally, a full rumen around calving may help prevent displaced abomasum, but sorting of these diets can result in metabolic issues around calving.

 Liquid feeds. A TMR that is too dry is easier to sort. Adding a little liquid to the diet can help the ration stick together better, especially the small particles that might settle out. This can include the fragile but valuable leaves on forages, which provide highly digestible fiber. It also promotes the consumption of longer, less palatable particles from forages, which provide effective fiber for rumen health.

Adding water to the diet is a simple and cost-effective solution, especially when the diet is overly dry. Other liquid feeds discourage sorting and provide additional benefits, perhaps by including additives for improved health and production. Molasses, for example, is an excellent liquid feed solution for rumen health. In addition to promoting the consumption of longer, less palatable forage particles, the sugar in molasses provides an energy source for fiber-digesting bacteria, helping the rumen break down forages more effectively and promoting milk fat production.

 Feed push ups. Routinely pushing up feed throughout the day not only keeps the diet within reach of the cows and promotes intake, but it will also gently mix the ration. Sorting cows will often push the long particles away and dig to the bottom of the pile for the smaller, more tasty particles. You might notice these “birds’ nests” or holes that cows have dug with their mouths in the feed at the bunk. Pushing up feed covers these holes back up, slowing down sorting and encouraging her to eat the long particles, too.

 Measuring sorting. Are your cows sorting in the first place? The Penn State Particle Separator (PSPS or Shaker Box) is a tool that your nutritionist might already be carrying in the trunk of their car or the bed of their truck. Comparing the particle size distribution of a fresh TMR sample to a sample after cows have had a chance to sort through it can show whether sorting is occurring. If the two samples are dramatically different, that is a good indication that your cows are sorting their feed. But don’t just look at how much feed is in each sieve — pay attention to what the feed looks like. Are the particles in the top sieve very long? If so, they are likely to get sorted out, even if they are not a high proportion of the ration.

Good forage management does not stop at harvest. Ensure that your feeding protocols maximize your forage instead of sapping your investments.

This article appeared in the February 2025 issue of Hay & Forage Grower on page 22.

Not a subscriber?Click to get the print magazine.