Let’s first agree that nearly all cows sort their feed to some degree. That is why the leftover “scrape out” feed is always the coarse, large and unpalatable portions of the feed. It is apparent, however, as we compare different herds and rations that the amount of sorting varies greatly.
We need to be concerned with the degree of sorting and the overall effect this has on the cows. In order to evaluate the level of sorting, I look for certain “symptoms” that may help dairy producers recognize when feed sorting becomes a problem.
Sorting behaviors and signs
Watching the cows eat is always informative, especially just after feed delivery. In a well-mixed and palatable TMR, cows will put their heads down and begin eating aggressively off 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 fairly low, and consumption is rapid. A warning sign I look for is a majority of cows circling with their noses and nibbling. This is often accompanied with lots of feed falling from their mouths and eventually the tell-tale hole burrowed into the feed all the way to the feeding surface where she then nibbles the fines or goodies as they fall into the funnel while leaving the less desirable feeds behind. This feed changes in appearance the more it is in front of the cows as they select what they want and leave the rest behind. The result then is different cows getting different diets and often shows up as variable manure consistency, acidosis and up-and-down intakes on a cow-to-cow basis.
The causes are many, but let me mention the most common contributors to over-sorting.
Overly long feed particle length
This has been made worse by the over-promoted “shredlage” concept for corn silage and longer chop lengths. The old adage is, “If the particles are longer than the width of the cow’s mouth, then she can sort it.” This is especially true if it is not the favorite part of her diet. The opposite of this is the cow that selects the long alfalfa hay because she likes it to the exclusion of other feeds in the TMR. Both behaviors promote a consumed diet different than the intended TMR. Processing long-stemmed baled hay or straw before putting it in the mixer really helps. Understand that using the mixer for this is time-consuming, reduces particle length of other feeds and puts excess wear on it.
The ration is too dry
Dry diets are less palatable to start with, and separating concentrates from forage is made easier as they do not adhere together. Summer diets should be 46 to 48 percent dry matter (DM), and winter diets should be 48 to 50 percent DM. Getting moisture correct can greatly reduce feed sorting, as can the addition of molasses-based liquid additives.
The mixer is not working properly
Mixers see very hard use, and as they wear, they become less effective at mixing correctly. Further, many dairies overload their mixer to gain efficiency but 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 generally inspect feeds as they are discharged from the mixer. Many mixers need wear-related maintenance when I look inside them. Clumps of concentrates or forages in the TMR (often seen in the beginning or very end of feed unloading) indicate either too short of mix time or a mixer that isn’t working correctly. Overloading always reduces mixer efficiency and promotes sortable diets. It also makes up for the majority of improperly mixed TMRs.
What happens to the cows after sorting?
This is where sorting becomes 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 end result is lower milk or components, and at its worst, sorting can cause hemorrhagic bowel syndrome and acute digestive issues like diarrhea and even DAs (displaced abomasums).
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 gets her requirements met when this occurs. I sometimes see several animals in a crowded lactation group that are much thinner than their pen mates simply due to their inability to compete for bunk space. They have to settle for the “leftovers.”
So if you suspect that sorting feed is a problem on your dairy, have a talk with your nutritionist and veterinarian, and decide which of the many causes are affecting your feeding program. It is important to determine the cause and severity before an effective course of action can be taken. PD
PHOTO: Staff photo.
