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How to prevent and treat abomasal bloat in young calves

Progressive Dairyman Editor Karen Lee Published on 31 March 2017

Abomasal bloat is a condition commonly found in the dairy and beef industries, but certain situations have increased the number of these cases in young calves in the past five to 10 years.

Researchers are finding a strong management and nutritional component to this deadly disease and, with that, have identified ways to prevent it from happening.



At the PDPW Calf Care Connection in October, Geof Smith, DVM, North Carolina University, answered the following questions regarding abomasal bloat: What is it? What causes it? What can be done to prevent it? How it can be treated?

What is it?

Abomasal or abdominal bloat is a syndrome that occurs in calves at 1 to 2 weeks old.

“A lot of times, they’ll die anywhere from six hours to a couple of days after this happens,” Smith said. “Some calves will respond to treatment, but typically mortality or death loss will be pretty high with this.”

Abomasal bloat in calves is different than rumen bloat witnessed in older heifers or cows where they develop gas in the rumen.

Since these young calves have mostly abomasal digestion, the distended abdomen will typically occur on the right side of the calf. It could potentially expand on both sides if the abomasum gets so big it goes across to the other side.


In addition, these calves will go off milk, act depressed or lethargic, have droopy ears, may grind their teeth or kick at their belly. If you gently push on the abdomen, you may hear a sloshy or watery sound.

Smith said a necropsy would reveal a very distended abomasum. The interior will be red or hemorrhagic and appear as if the tissue contains gas bubbles (like bubble wrap).

What causes this?

The exact cause of abomasal bloat is unknown; however, there have been several suggestions proposed.

Clostridium perfringens is the bacteria most often thought to be involved. Smith said that when these calves are cultured after death, they could generally grow Clostridium perfringens.

In addition, if normal calves are inoculated with Clostridium perfringens, this condition can be reproduced. However, cultures from a healthy calf are also able to grow Clostridium perfringens.

“It is probably not just clostridial bacteria that’s causing this,” Smith said. “There are other factors likely involved.”


Researchers at Oklahoma State University were able to reproduce abomasal bloat by feeding a combination of milk replacer, cornstarch, glucose and water. Simply inserting bacteria in the milk replacer was not enough to reproduce this syndrome, Smith said.

He added that the authors of the study concluded several things have to happen to produce abomasal bloat.

  1. An excess of fermentable carbohydrates in the stomach, likely from milk or maybe an oral electrolyte solution

  2. A fermentative enzyme capable of sustaining rapid fermentation, which can come from bacteria

  3. Something that slows abomasal emptying. “Abomasal emptying is something that I think is very important and is a major component of this syndrome,” Smith said.

There are two main factors that control how long food sits in the stomach. First is the volume of milk per feeding. Most of the time, two liters of milk empties in about 90 minutes. Four or five liters of milk can sit there from three to five hours.

The second factor is the calorie content or the osmolality of the diet. “Osmolality basically refers to how concentrated that solution is,” Smith explained.

Adding powder to whole milk will increase the osmolality of the milk.

In addition, high-osmolality milk replacers are somewhat common now, with replacers containing higher amounts of protein and fat compared to years past. Milk and blood have an osmolality of 300 mOsm per liter, whereas some milk replacers, mixed according to label directions, can be twice that amount at 600 mOsm per liter.

“We can use these milk replacers fine, but we have to be a little careful because we are going to prolong the time that milk sits in the stomach of the calf. We’re going to slow abomasal emptying and potentially cause bloat.”

Oral electrolytes are the same; those with lower osmolality are going to empty from the stomach much faster than those with a higher osmolality.

Other risk factors of abomasal bloat that have been identified by veterinarians include feeding accelerated-growth milk replacers; feeding poor-quality, plant-based milk replacers; sudden changes in milk replacer – particularly herds switching from milk to milk replacer on a daily basis; feeding a large volume of milk once a day; feeding oral electrolytes in milk; a lot of additives included in whole milk; increasing the powder content of milk replacer without equally increasing the amount of water; poor mixing; cold milk replacer; not offering water to calves; erratic feeding schedules and heat and cold stress.

What can be done to prevent it?

Smith argued that while there is a clostridial component of this syndrome, abomasal bloat is more of a nutritional disease. Therefore, prevention methods focus around feeding.

“We need to make sure we’re feeding milk or milk replacer with a total solids of less than 15 percent,” he said.

This can be determined using a Brix refractometer, if not on a daily basis, at least on a regular basis to make sure a consistent product is being fed to the calves.

“If you’re just feeding whole milk every day and not putting anything in it, you may not be having major issues,” Smith said. “If you’re putting pasteurized milk balancer or other things in there or, certainly, if you’re using milk replacer, you need to be checking this on a regular basis.”

Smith said when he visits a farm, he will take a Brix reading from milk fed to the first calf, from the middle calf and from the last calf. A lot of variation between these readings indicates a mixing error.

Another preventative measure is to keep a consistent feeding schedule. Deciding what time of day is not as important as feeding at the same time every day.

Avoid large volumes per feeding. Smith said more research needs to be done to define “large volume,” but until then, consider other factors involved. The higher osmolality, the lower the volume he would like to see fed. “We have very good data in the industry that calves fed three times per day do a little bit better than calves fed two times per day,” Smith added.

Make sure the milk or milk replacer is warm from the first to the last feeding, and be sure to offer water to calves at all times.

How can you treat abomasal bloat?

The treatment for abomasal bloat in calves is different than the treatment for rumen bloat in adult cattle.

Some people will insert a needle in the calf’s flank while it is standing to let the gas escape. Smith said the downside of this is that eventually the abomasum is going to fall off the needle without getting all of the gas out. In addition, the puncture up high might result in leakage of that fluid into the abdomen.

He recommended to sedate the calf and then roll it on its back. The air will rise to the top and a catheter or 16-gauge needle can be inserted in the belly to get the gas out. Having someone squeeze the belly a little bit can help in gas removal. In this location, any fluid should leak outside of the calf.

Smith also suggested putting the calf on penicillin, either through the needle in the stomach, orally or intramuscular.

Smith said he would typically skip one feeding for the calf as well, even though he is not a fan of withholding milk from calves.

“I don’t want to put new milk in there that’s just going to start fermenting and rebloat,” he said. “If two, three or four hours go by, and you want to give them some water or dilute electrolytes, that’s OK – but generally I like to give these animals a little bit of a break.”

Some people will vaccinate either the cow or the calf to prevent clostridia. “There is no research whether that will help or not,” he said. “Again, I think this is more of a nutritional disease that we come after from a management component.”

Farms experiencing a lot of abomasal bloat can consider adding a vaccination but should also review the risk factors to determine what might be slowing abomasal emptying.

Smith also called for more research to be done to evaluate the ideal total solids level, volume levels per feeding and other factors that could potentially impact the prevalence of abomasal bloat.

“I’m certainly a proponent of feeding calves more. I think we’ve been underfeeding calves for a long time, but I think we need to figure out how to do this safely without major impact on gut health,” Smith said.

When cases of abomasal bloat are on the rise, consider the risk factors, use management methods to prevent more incidences and treat calves accordingly.  end mark

Karen Lee
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