Hemorrhagic Bowel Syndrome: An Animal Health Mystery

By James D. Chapman, Ph.D., PAS, Dipl. ACAN

In more than 40 years working in animal health and nutrition, I’ve dealt with a number of mysteries – why do some animals get sick and not others? What causes a certain disease outbreak? The most complex mystery of all that I’ve encountered is Hemorrhagic Bowel Syndrome (HBS), a devasting disease that causes almost certain death in affected dairy cows.

Records of dairy cows with HBS-like symptoms began appearing in the 1960s when healthy cows would suddenly become sick and die for no obvious reason. In 1991, a veterinarian from the University of Idaho was the first to report a diagnosis from a case of sudden death in dairy cows, originally describing the cause as a ‘Point Source’ hematoma, an acute bleeding within the small intestine, which led to blood loss and bowel obstruction from the formation of blood clots.

What makes HBS especially challenging is there are few visible symptoms, and it progresses very rapidly. Affected cows may have bloody feces, but by the time it is discovered, it is usually too late to save the animal.

Impact of HBS

According to the National Animal Health Monitoring System, HBS occurs in about 2 % of cattle. Many in the animal health industry believe the true number is actually larger because few cows are necropsied to determine the cause of death.

HBS can be very frustrating for dairy producers. It usually affects healthy cows in the first phase of lactation, when they are most productive. Hemorrhagic Bowel Syndrome is difficult to diagnose and even if it is detected, there are few treatment options. The disease also causes suffering for the animal.

Keeping animals healthy is our top priority at Phibro Animal Health both because we know it is important to our customers and because we believe it is key to help keep families healthy and to feed our world. Finding a way to reduce the impact of HBS is important to us.

Solving the Mystery

Once HBS was identified in the early 1990s, researchers began investigating what could be causing it. Various suspected causal agents were eventually ruled out. About 20 years ago, I began working with researchers at Oregon State University who tested a theory that Aspergillus fumigatus (A. fumigatus) could cause HBS.

This mold is ubiquitous in the environment and commonly found in feed. At the Phibro Innovation Center, we’ve tested more than 4,500 feed samples for the presence of A. fumigatus. Of those tested more than 81.6% tested positive for A. fumigatus.

In fact, A. fumigatus can cause lung infection in humans, especially people who are immunocompromised. Cattle can be exposed to this mold through their feed, in particular silage.

But HBS is sporadic, not all cattle who are exposed to the mold are affected. These researchers believed that a combination of ingesting the mold when the animal is also experiencing stress creates an environment where the mold becomes resident in the intestines, where it then grows very rapidly. Cows who have recently calved and are high producers are the most susceptible because of the many stressors they are exposed to during these times. While there are other theories about the cause of HBS, this seems the most logical.

What Can Be Done About HBS?

Because there is no way to treat HBS, it is critical to look at how to prevent it. This means reducing the conditions that allow it to develop.

Researchers at Oregon State developed a feed additive designed to support the immune system so cattle who ingest mold would not be as affected. This product is known as OmniGen? nutritional specialty product and is available from Phibro Animal Health Corporation. Feeding OmniGen must also be combined with good animal care, cow comfort, good nutrition, and all the things that go along to keep an animal healthy.

It's still a mystery as to how cows develop HBS. So far, researchers have been unable to replicate it in animals under study. The disease is very sporadic and can be unpredictable, although there is some evidence to show that it does occur during certain phases of the lactation cycle, generally early. It is known that the immune system is how both humans and cows protect themselves against the mold. It appears that supporting a cow’s immunity system provides some defense against HBS.

As we continue to decipher this mystery, we learn more about how nutrition and animal health work together to keep animals healthy.

?