Nearly all cows sort their feed to some degree. That is why the leftover feed is the larger and unpalatable portions of the feed. Depending on conditions, the amount of sorting varies widely.
The degree and overall effect of sorting on cow performance is worth your attention. To evaluate the level of sorting, look for certain symptoms that indicate feed sorting is a problem.
Watching the cows eat is informative, especially just after feed delivery. In a well-mixed and palatable ration, cows will eat aggressively from the top of the feed pile as soon as it is delivered.
The cow’s head often stays in one spot or moves slightly. Spilling from the cow’s mouth is relatively low, and consumption is rapid. As she progresses, you may see feed falling from her mouth, and eventually, the tell-tale hole burrowed into the feed all the way to the feeding surface. She is nibbling the fines or goodies as they fall into the funnel while leaving the less desirable feeds behind. This also occurs if the cow burrows through the feed, shifting feed concentrates into the hole. When this occurs, the feed in the bunk changes in appearance.
It is easiest to notice if the feed has been in front of the cows for some time and they have selected what they want. Given that cows have a pecking order, the result of feed sorting means different cows get different diets and intake.
Common contributors to ration sorting
- Particles are too long. The rule of thumb is that if the particles are longer than the width of the cow’s muzzle, she can sort it. Sorting is prevalent with “shredlage” for corn silage and longer chop lengths. Sorting can be more common if the feed left behind is not the favorite part of her diet (lower parts of Sudan stalks or corn cobs). The opposite of this effect is when the cow selects the free-choice long alfalfa hay because she likes it to the exclusion of other feeds in the partial-mixed ration. Both behaviors promote a diet different than intended by the producer. Processing long-stemmed baled hay before putting it in the mixer helps. Understand that using the mixer for this is time-consuming, reduces particle length of other feeds and puts excess wear on it.
- Lack of initial palatability. Dry diets are less palatable to begin with, and in dry diets, concentrates do not adhere together with the forage base. Cows prefer eating a mixed ration that is 50-66 percent dry matter. Wetter diets in the summer tend to be preferred over drier rations. Rations that are dry hay and dry concentrates (say 90 percent dry matter) respond well to adding moisture such as molasses, syrup or water. Having adequate moisture in the mixed ration will reduce feed sorting.
- Worn out mixers. Mixers get plenty of hard use, and as they wear, they become less efficient at mixing correctly. Further, some operations will overload their mixer to gain batch size, but they lose the benefits of proper mixing. Highly worn mixers require more mix time, causing particle reduction and less effective mixing action. Check the kick plate on the bottom of vertical augers for wear, and inspect feeds as they discharge from the mixer. Clumps of concentrates or forages in the mixed ration (often seen at the beginning or very end of feed unloading) indicate either too short of mix time or a mixer that isn’t operating correctly. Overloading always reduces mixer efficiency and promotes sortable diets. Overloading is the cause of the majority of improperly mixed rations. Mixers require routine maintenance and should be on a service schedule.
Sorting may become a health and financial issue. Cows that aggressively sort feed do not get a balanced diet. Mostly they get too much concentrate and not enough fiber. This is accompanied by shifts in manure consistency. The cow sorting for grains today is often slightly off feed the next day and sorting for fiber to correct her unhealthy rumen pH. The result is lower milk or components or acute digestive issues.
In a crowded pen, where bunk space may be limited, the aggressive cows sort out the goodies, and the passive cows eat the already-sorted feed. Neither animal meets her target feed requirements.