Abomasal Bloat in Calves.

 By Heather Smith Thomas.

 Abomasal bloat is often blamed on ulcers, but these conditions are generally two very different problems, according to Dr. Geof Smith (former professor at North Carolina State University and now Dairy Technical Services Veterinarian at Zoetis Inc. at Raleigh, North Carolina).  “Ulcers are probably stress related, whereas bloat is more nutritional in origin.  Bacteria can be involved in some cases of bloat.  These bacteria come from the soil or are already present in the GI tract.  There are probably other risk factors as well,” he says.

“Many of these problems are man-made.  Often the dairy calf is on a feeding schedule and there might not be good mixing of milk replacer.  Feed consistency may vary.  Here in North Carolina, once-a-day feeding of dairy calves is popular, which can be a risk factor, as is cold milk replacer,” says Smith.

Affected calves go off feed and become dull.  In severe cases they are usually dehydrated, show signs of abdominal pain (colic—kicking at the belly, getting up and down repeatedly) and eventually go into shock and die within 6 to 48 hours.  At necropsy the abomasum is distended with gas, there is edema in the abomasum and forestomach, with hemorrhage and necrosis in the stomach lining.  Smith says this condition occurs most commonly in dairy calves, with some farms having frequent outbreaks.

It’s not always easy to figure out the cause.  “Some people try clostridial vaccines, but the bloat may be due to more than just bacterial infection; there are usually management issues involved, and several factors working together.”

Bacterial Infections
Sometimes calves develop gut infection that proliferates rapidly and produces gas and toxins.  If this condition is not treated quickly and reversed, toxins may get into the bloodstream and the calf goes into shock and dies within a few hours.  In other instances, the calf may just be dull and bloated (abomasum distended) and might not die as quickly.

A common type of gut infection in calves is caused by Clostridium perfringens, one of the Clostridia species normally found in the GI tract and passed in feces.  These bacteria rarely cause gut infections in adult animals, but can cause fatal disease in calves when conditions within the gut enable them to proliferate rapidly.  There are several types of C. perfringens, however, which can affect calves of different ages, and in different ways.

Other kinds of bacteria may be involved in causing bloat in young calves.  “Abomasal bloat generally affects calves one to three weeks of age and we usually don’t know exactly what causes it,” says Smith.

It may be due to excess fermentation of high-energy contents in the GI tract, allowing gas-producing bacteria to proliferate.  C. perfringens, Sarcina ventriculi or Lactobacillus species may play a role.  According to Smith, large amounts of fermentable carbohydrates in the abomasum (from milk, milk replacer or high energy oral electrolyte solutions) along with presence of fermentable enzymes produced by bacteria could lead to gas production and bloat.  This process could be exacerbated by anything that slows movement of ingesta through the tract.

These calves may or may not have diarrhea.  “Many have a big belly on both sides—rather than the typical rumen bloat seen in older animals.  The whole abdomen looks full, rather than just the left side,” says Smith.  

Nutritional Factors
“We often find clostridial bacteria involved, but if you just give a calf these bacteria experimentally, you can’t produce the disease.  There must be other factors as well.  Some of the things that seem to play a role in dairy calves include very high osmolality milk replacers or electrolyte solutions (high concentration of dissolved particles).  Normally, milk is isotonic, but some milk replacers or some electrolyte products you might give a sick calf have a lot more sugar or dextrose.  These have been shown to slow down the rate of abomasal emptying, causing back-up of GI tract contents,” he explains.

“Anything that slows abomasal emptying may be a risk factor.  The bacteria are probably always there in the stomach, but if they have more time to grow and proliferate, the calf could bloat,” says Smith. Some people call this condition sloshy gut.  When the calf moves around you can hear fluid sloshing.  

“When a farm has a problem with this, we don’t know whether it’s due to just the bacteria on the farm or if there are management issues that contribute,” says Smith.  

“In one study, researchers were able to reproduce the disease, but in order to do this they had to give calves milk replacer with corn starch and extra glucose, mixed with water—a very rich energy product.  It probably provided nutrients for bacteria to grow, and then slowed down the turnover of milk in the stomach,” he explains.

If the calf has trouble making the transition from monogastric digestion to rumen digestion, sometimes the abomasum fills with fluid or gas, according to Dr. Murray Jelinski (Western College of Veterinary Medicine, Saskatchewan).  “As it becomes distended, the abomasum may become flaccid and loses its muscle tone.  The muscles of the lining may become fatigued when it gets this full,” says Jelinski.  Food doesn’t move through very well, and the calf goes off feed.

“If the vet opens up one of these poor-doing calves surgically, searching for an ulcer, the abomasum will be like a huge, fluid-filled sausage.  It may contain rank curds of milk, bits of straw, and whatever else the calf has been eating.  Typically the entire lining is red and irritated, but you don’t find any ulcers.  These calves have an abomasitis and we don’t know whether it is from an infection like Clostridium perfringens type A or some other pathogen,” he says.

The actual diagnosis is often challenging, because Clostridial organisms are often found in the gut of healthy animals.  Perfringens Types A, C and D may be present and never cause a problem, so just finding them when a calf experiences a gut problem or dies does not mean they were the cause.  “If there is necrotic tissue, type A will be there anyway.  But in some of the early work done with ulcers, people cultured C. perfringens type A and figured that it was the cause of the ulcers,” says Jelinski.

Treatment
The way Smith treats abomasal bloat is to roll the calf on its back, clip and scrub the appropriate area of the belly, and stick a long needle (with plastic catheter over it) into the abdomen.  “I have someone squeeze on the calf’s belly while I stick the needle into the abomasum.  I pull the needle back out as soon as I get the catheter into place, so it won’t puncture something it shouldn’t.  With the catheter in place we squeeze the belly, and try to get as much gas out of that stomach as possible,” says Smith.

“It’s important to put the calf on its back.   Some people try to stick the needle in with the animal standing, like we would in a bloated cow, poking the rumen.  But with these bloated young calves, it isn’t the rumen that’s full.  If the calf is standing, even if you get the needle into the abomasum, as soon as a little gas comes out of the abomasum it drops off the needle and everything shifts.”  You’ll get leakage of fluid into the abdomen, which puts the animal at risk for peritonitis.  The rumen is easy to access because it sticks up against the skin, whereas the abomasum is lower in the belly.

You can’t relieve this bloat by passing a stomach tube, because the tube only goes into the rumen.  “You can’t get a tube through the rumen into the abomasum.  A tube works for cows or big calves with a bloated rumen, but a baby calf’s rumen is not developed yet, and in this instance the gas is in the abomasum instead of the rumen.  The calf must be on its back when the catheter is inserted,” he says.  

After letting the gas out of the abomasum, Smith gives the calf penicillin, assuming the infection is clostridial.  “Penicillin is an excellent antibiotic for any type of clostridial disease,” he says.

After he’s gone to a farm to do this a few times, he may train the farmer or farm manager how to do it.  “But if they are having on-going problems, I want them to tell me, because I need to go out there and try to figure out what’s going on.  If a dairy is losing 3 or more calves per month from this condition, we need to do more diagnostics and figure out what’s happening, and how we might prevent it,” he says.

Vaccination
Vaccination can sometimes help, if the problem is caused by C. perfringens type C or D.  There is also a vaccine for C. perfringens type A, which has been implicated in some of these infections.  Some labs will create an autogenous vaccine from a culture, to target a specific pathogen on your place.
“But vaccine alone won’t halt a problem if the farm management is inadequate,” says Smith.  “It’s like putting lipstick on a pig.  It doesn’t address the underlying problem.  Outbreaks are often due to some kind of management reason.  In a dairy for instance, the neighbor down the road may be using the same milk replacer and he’s not having a problem,” says Smith.