What makes a cow stop eating?

You know that the cost of feeding cows is milk production's highest expense.

Therefore, much attention has been given to proper ration formulation, ration monitoring, feeding high quality forages and evaluating the cost of ration inputs to get maximum milk production and maintain cow health.

But getting individual cows to eat enough feed can often be a major challenge on dairy farms.

So, what makes a cow stop eating?

1. Rumen fill.

Cows stop eating when they are full. This seems like a simple statement, but often the driver of this fill is ration NDF level, which is correlated to the amount of ration fiber. A cow can eat approximately 1.3 percent of her body weight in NDF fiber per day. One of the reasons for a properly balanced ration is to ensure that the NDF level in the ration is correct. If feedstuff dry matter changes, it will affect the as-fed amount of NDF the cow consumes. If you don't monitor the dry matter of forages on at least a weekly basis, you may be underfeeding or overfeeding cows. If you do not obtain nutrient analyses, you cannot know the amount of NDF in the TMR. If you underfeed NDF, you are not providing enough fiber for the cow to maintain proper rumen health. 

2. Rumen pH level.

When the pH level of the rumen drops after a meal, the cow stops eating and starts to ruminate. Rumination provides salivary sodium bicarbonate to the rumen to buffer the effects of the lowered rumen pH. If your herd has subacute rumen acidosis (SARA), cows will not have consistent intakes because cows stop eating when that rumen pH drops. Diagnosis of SARA can be done by asking your veterinarian to evaluate rumen fluid samples via a process known as rumenocentesis. Often, rations can be properly formulated to prevent SARA, but improper feed handling and delivery is a risk factor for this disease. If the TMR is too dry, not mixed properly, cows are sorting or the feed is not delivered on a consistent basis, a herd may suffer from SARA. Every farm should routinely use a particle separator to test rations.

3. No feed available.

This is known as EBS or empty bunk syndrome. When feed cost is high, dairy producers sometimes try to cut costs by making cows clean up every bite of feed. A reasonable goal is to have at least 5 percent of feed refused. However, in situations where feed is not consistently available, weather affects intakes, or pens and bunk space is crowded, it may be desirable to feed for 10 percent refusals. Having a hungry cow with no feed to eat is extremely undesirable. Make sure that feed is available when cows are done milking to promote maximum intakes.

4. Overcrowding/competition.

If a cow is hungry and there is feed available, is there a spot for her at the table? Do cows have to compete for a place to ruminate and rest? Overcrowding cows or bunk space will lower intakes and is also a risk factor for SARA.

5. Illness. 

Individual cows will not eat if they do not feel well. Lame cows do not eat. Ketotic cows do not eat. Cows treated with excessive amounts of dextrose do not eat because they have high blood sugar levels. Cows with fevers do not eat. If a cow does not eat, there is something wrong and she needs to be examined and evaluated for follow-up care.

6. Heat stress/poor ventilation. 

Now is the time to evaluate your facilities for cow comfort before the summer heat arrives. 

Look at your cows today and consult with your veterinarian and nutritionist as to whether anything is preventing your herd from consuming as much feed as possible. 

Fred Gingrich is a practicing veterinarian and owner of Country Roads Veterinary Services, Inc., in Ashland, Ohio.