HBS: Eradication through feed and feed bunk management


By James Tully, nutritionist,

Pine Creek Nutrition Services, Inc.

James Tully

We had a client experience a recent batch of Hemorrhagic Bowel Syndrome (HBS) or “bloody gut” cows. Most dairies by now have a fairly extensive file on HBS and all the potential causes. 

Whether you subscribe to the Aspergillus fumigatus model, the Clostridium perfringens type A model, or the general “bad silage” model, you have probably been disappointed with a product fixing your problem. If all cases of HBS were caused by a specific item, then logic would indicate using a product for that specific item would result in elimination of the disease. However, our observation has been that regardless of product use, HBS cows are still an issue. A number of years ago a client lamented that he could suffer with two cows dying from HBS per month and still be better off compared to feeding one of the products at 18¢ per head to his herd. 

Is it technical or is it practical?

Joe Monteiro, herd manager for James Ahlem Dairy in Hilmar, CA described HBS better than anyone. 

“I don’t care what you smart people say,” he said. “Here is what happens. The cow goes off feed, she gets diarrhea, then gets plugged up, and then she dies.”

Those of you that know Joe can assume that the above quote is a paraphrase of how he described it to me. I dare anyone try to argue against his accurate review of HBS. 

There are likely hundreds of reasons for cows going off feed on your operation. As previously mentioned, if HBS had one cause, then a certain product would always work. Our experience as nutrition consultants agrees with Joe’s – the specific cause may not be that important. However, an examination of two of the likely scenarios causing HBS may help with understanding the management to prevent HBS cows. 

Silage pile changes 

It is the change, not the silage or molds/mycotoxins associated with the silage. End of Pile Syndrome (EPS) offers the best explanation for how the change affects cows. A dairy in Maryland was the first opportunity for me to observe EPS. Although the top of one upright silo was exactly the same feed as the bottom of the one just emptied, the cows would get loose manure, a few would end up with watery diarrhea, a few more would get DAs, and milk dropped a couple of pounds after switching silos. Although silage pile changes occur before an HBS outbreak, any abrupt feed change would have a similar impact. 

Another item to consider is ration sorting. If HBS was always related to diet formulation or a specific ingredient, why would it only affect one or two cows? Or cows in multiple pens and yet not every cow? It would indicate to our group that the cow that suffers HBS ate a ration different than the cow eating beside her. We often see manure of very different consistency from two cows in the same pen. 

Regardless of moisture changes, ingredients, hay quality and countless other known causes of going off feed, it is the fact that one cow eats something different than another. 

A technical review from 2005 by Berghaus, et al. 2005 (JAVMA, 226:10) based on the 2002 NAHMS survey is a complete historical assessment of HBS cows. Many variables were put into a model for calculating odds ratios. A couple of key points were identified as causative for HBS. 

1. Feeding for high production may increase the risk factor of HBS. High production is defined as herds with RHA > 20,000, and no access to pasture. Herds that used grazing some of the year had fewer incidences of HBS. 

2. Herds that use MUN for regular monitoring and make changes based on MUN are at higher risk for HBS compared to herds that never use it. Reportedly this may be due to herds that use MUN may be more aggressive in their efforts for maximum milk production.

 The authors only briefly mentioned what I believe to be the most important factor regarding nutritionists who may be using MUN: “One possible explanation for this may be that operations that routinely use MUN may make alterations in the ration composition more frequently than do those operations that do not routinely use this measure.”

This again points to diet change as the causative agent for HBS. MUNs are just one tool for monitoring ration performance and should not be given too much weight when making ration changes.  

The conclusions from the authors of this “technical review” are as you would expect: “In conclusion, findings of the present study are consistent with results of previous investigations and suggest that management practices implemented to achieve high levels of milk production may increase the risk of HBS. Increased consumption of a high-energy diet seems to be the most plausible common pathway for all of the risk factors that have been described, although the mechanisms by which this may lead to disease is unknown. Further studies are needed to elucidate the role of specific microbial organisms in the pathogenesis of HBS.” This technical review may help clarify some practical points regarding HBS.  

I believe Joe Monteiro is closer to knowing the cause of HBS than is any scientist. A change causes a disturbance in rumen microbial populations and the cascade of rumen upset begins. In the dairy cow rumen change is generally toward lactic-acid producing bugs. This alteration in rumen pH causes the cow to go off feed. When severe enough, we get damage to the intestine. Perhaps looking for ‘intestinal casings’ and generally loose manure will allow you to get ahead of a potential HBS occurrence. The bad bacteria found in these animals are purely opportunistic. In more than a few cases, E. coli and salmonella are also found. Again, this is opportunistic bugs taking advantage of a situation. 

Other items to consider  

1. Too much grain. Of course this may be causative. And yes, we feed more grain to get more milk. However, Mike Allen, Michigan State University, will tell you that high production cows can tolerate high amounts of fermentable grain. Later lactation, lower producing cows do not tolerate highly fermentable carbohydrates nearly as well. Perhaps this is one reason we see increased incidence of HBS in later lactation cows? High production cows can tolerate the high grain with optimum management because rate of passage and rumen dilution rates do not allow for significant rumen pH alterations. If there is an abrupt ration change later in lactation we could easily see upset stomachs. 

2. Molds and mycotoxins. Of course these may be causative. Yet I have seen some terrible silage management and nasty-looking almond hulls fed to herds making 90 lbs. of energy-corrected milk and no HBS cows. 

3. Identify any pattern you can. Is it older cows?  What stage of lactation? Did you change loads of hay? Was any new ingredient introduced? Even if fed at a small amount. Were cows in free stalls allowed access to corrals? Have you begun using new feeding equipment? Is there a new water source? Was work done on wells? Were wells started for irrigation? Did weather change? 

4. Sorting and/or crowding. Sorting generally occurs when rations are dry and particle size allows the cow to select grain. Forcing some cows to eat what others left is identical to a sorted ration. Are you expanding? Most herds that are expanding will keep a few extra cows.  

5. Empty Bunk Syndrome (EBS) is a big factor for rumen upsets. Slug feeding, like sorting, will cause a significant change in rumen microbial population. 

Each of these potential causes by itself may be handled by the rumen. However, what we don’t know is how a combination of factors will affect the rumen. Crowded cows, eating moldy silage, after a weather event such as rain are prime candidates for rumen upsets. 

Final recommendations 

Avoid using products to fix problems. Products don’t fix problems, management does. Never forget the First Law of Dairy Management: “Do the same thing, at the same time, every day.”

Obviously, change is going to happen, and being prepared will offer the best success at managing the change in the cow’s rumen. Joe’s initial comment is the key: “Cows go off feed.” Knowing the causes of why cows go off feed will help manage the rumen bugs. The rumen is a hybrid between a batch fermenter (beer and wine) and continuous flow fermenter (distillation). The cow eats a large meal then lies down and chews the cud, essentially allowing the rumen to batch ferment the diet. If this pattern is interrupted, the fermentation is stopped. Anything that violates the First Law of Dairy Management will interrupt fermentation. 

 The specific example regarding End of Pile Syndrome illustrates our lack of complete understanding of HBS. Why does changing silage where we went from feeding from one upright silo to the other result in a change? The feed literally went in one silo, when it was full they immediately went to filling the next one. This resulted in what should have been a good transition into the next feed, consistent with our clients saying “Why blend the silages? We put them up right after each other.” This syndrome also happens in well-managed bunker silos. Invariably, we get a call about a few more loose cows, some diarrhea, HBS, and loss of milk as they jump right into the new pile.

Incorporate the following feed management steps to reduce the likelihood of having HBS cows. 

1. Transition any feed change over as long a period as possible. 

2. Avoid feeding ingredients that are known to be contaminated with mycotoxins. 

3. Feed rations that are technically sound. 

4. When you know a change is imminent, feed extra yeast and/or direct-fed microbials. I am not too particular which one – as long as it is from a reputable company. There are not that many companies capable of growing rumen active microbial products, so it shouldn’t be too hard to find a good product with research supporting its action. The only personal thought would be feed double the dose for a 7- to 14-day period during the change. 

5. Extra buffer may also be suggested. Today’s diets may be lacking in effective fiber, “scratch factor.” Adding a pound or two of ground straw or rough grass hay will also help buffer the rumen. Monitor the TMR to insure that the added “scratch factor” isn’t being sorted.

Eradicating HBS without knowing all the causes isn’t possible. Use some of the practical information presented here to minimize the impact of this syndrome on your operation. 

- To contact Dr. James K. Tully, PhD, PAS, dairy nutritionist, e-mail him at Jim@pinecreeknutrition.com or call him at (209) 667-4181.