The ever-frustrating abomasal bloat

As much as I like working with calves, working through an abomasal bloat issue has proven to be one of the most frustrating challenges I have encountered in veterinary practice.

For reference, abomasal bloat is a clinical syndrome that occurs primarily in milk-fed dairy calves. Occasionally, we observe the syndrome in nursing beef calves as well. Calves typically develop acute abdominal bloat, anorexia and depression that progresses quickly to recumbency and shock. Sudden death is sometimes reported as the main sign. Other less obvious signs might include grinding of the teeth, general lethargy, not finishing milk or inconsistent milk intakes (drink all at one feeding and only half or none at next feeding).

These less obvious signs can also be associated with abomasitis or abomasal ulcers, which can then perforate into the abdomen. In abomasitis, the lining of the abomasum becomes highly irritated or even slightly rotten with air inside the tissue, often with many tiny ulcerations. In cases of abomasal ulcers, there can be many tiny ulcerations and often larger deeper ulcers in the area where the abomasum meets the intestines. Diarrhea is not a consistent sign with abomasitis or abomasal bloat. Often, calves do not have fevers but are described to have “sloshy guts.” It is assumed that the primary cause of bloat and gut damage is Clostridium perfringens, though this is still debated among the industry.

When I work with farms with abomasal bloat or abomasitis problems, I approach the problem by hunting for situations where we “set up C. perfringens to thrive in the calf’s gut.”

Some important things to know about C. perfringens: It does not like oxygen, fat or water. It also does not survive well in pHs under 5.0 (i.e. the use of acidified milk feeding in some situations). It does like proteins, sugar, anaerobic environments and high osmolarity conditions.

The following reasons are the most common causes of abomasal bloat and abomasitis in my experience:

— High osmolarity: This is a measure of solute concentration. Abomasum muscle is expected to function best in fluids of 300 Osm/L. Cows’ whole milk and blood have an osmolarity of 300 Osm/L. High osmolarity fluids (over 500-600 Osm/L) can interfere with the smooth muscle function of the abomasum and delay emptying, which creates an opportunity for Clostridium to grow. Examples of high osmolarity fluids include hyper- concentrated or poorly mixed electrolytes, improperly mixed or very high solids calf milk replacer, high salt concentrations in water or the addition of supplements or electrolytes to milk replacer or whole milk.

— Dirty milk, moldy grain, or dirty feeding equipment: Dirty feeding equipment can inoculate the milk with high levels of bacteria (think bottles, buckets, nipples, feeding utensils or pasteurizers not functioning correctly). Feeding dirty milk or grain can inoculate the gut with unhealthy bacteria. Culturing milk can be helpful to identify areas of contamination. The use of an adenosine triphosphate meter can also help assess cleanliness of feeding equipment. Note that culturing milk replacer or calf milk with additives can be a little challenging to interpret these days due to the use of “good bugs” such as Enterococcus, Bacillus and other microbials that are also able to grow on cultures.

— Inaccessible or poorly palatable water (or water with high sodium levels): Water is needed by every calf, every day. Water helps keep the osmolarity of the abomasum normal and provides an oxygen-rich environment, which Clostridium does not thrive in. Water is also necessary for protein and lactose digestion. If water is not available, Clostridium can ferment the proteins and lactose instead, creating gas that is not easily expelled. Think of the saying, “dilution is the solution for pollution.”

— Too high or too low total solids of milk fed: I personally prefer solids between 11.8% minimum to 14% maximum. High solids are more of a concern than low solids for me. It is very important to feed water in addition to milk when you push solids over 13%.

— Dirty bedding. There are some instances where poor quality or dirty bedding has been implicated as a potential cause of abomasal bloat and abomasitis. It is important to use good quality bedding because all ruminants tend to graze their bedding, even at a young age.

— Inconsistencies during milk feeding: This might include milk fed too cold (under 100 degrees), inconsistent volumes fed at each feeding or large changes in times at feeding.

— Sudden changes from whole milk to milk replacer powder: This is a concern especially if the solids of the whole milk are significantly different than the milk replacer powder. I see some farms feeding whole milk for 3-4 days after birth and then switching calves to milk replacer powder. In some instances, the change in solids appears to cause cases of abomasal bloat and abomasitis.

As far as treatment is concerned, I can provide some general tips. Oral penicillin is highly effective against clostridium species without significantly affecting some of the other normal gut flora. Drenching with plain warm water can also be helpful due to the high oxygen concentration in water. I do not recommend using electrolytes as a part of the initial treatment because oral electrolytes can increase osmolarity and contain sugars that Clostridium use to grow. I would consider skipping one milk feeding to allow the abomasum to empty as ruminants cannot vomit but provide plain warm water instead. Direct-fed microbials are not particularly useful as a solution for abomasal bloat without addressing the root cause.

Megan Weisenbeck is one of six veterinarians at Northern Valley Livestock Services in Plainview, MN. She practices primarily dairy production medicine in Minnesota and Wisconsin. Megan can be reached at [email protected].