CANNULAS - EYES ON THE RUMEN, WINDOWS TO THE FUTURE
- Mardi Ford
- The Observer
Have you ever paused to ponder the bovine digestive system? It is a fascinating and delicately balanced ecosystem all on its own. Beneath that deceptively placid demeanor, there's a whole lot of action going on inside a cow.
It is in the rumen, the largest section of a cow's four-part stomach, where the major digestive work takes place. At approximately 103 degrees Fahrenheit, the rumen is a huge fermentation vat filled with forage, water, bacteria, protozoa and fungi.
"It's like a swamp in there," says Tim DelCurto, Oregon State University associate professor and superintendent of OSU's ag research center in Union for the past 13 years.
DelCurto's research on nutritional management for cattle has taken him into the inner workings of the rumen. Literally.
As early as the 1920s, DelCurto says, experiments began in cutting an opening to the rumen in order to study it. On a cow's left side, the rumen lies right up next to the flank, below the rib cage making it easily accessible.
A hole is cut surgically into the cow's side and a plastic cannula is inserted into the hole, opening a window of possibilities for study.
For example, the cannula's direct access to the rumen allows the effects of different types of forage in the digestive process to be studied.
The inner wall of the rumen is covered with papillae. By reaching into the opening through the cannula, the rumen wall can actually be pulled out and looked at. DelCurto says the size and shape of the papillae evolve and change in order to adapt to the type of feed they need to digest. Many health problems with ruminants can be traced to rapid diet changes such as converting from grass to grain diets. Damage by over feeding has also been observed.
To facilitate their studies, DelCurto and his graduate students have discovered that the fine mesh of a lingerie bag filled with feed and inserted into the rumen still allows the digestive process to take place on the contents of the bag. The lingerie bag can then be removed and the end product scientifically analyzed before it moves beyond the rumen.
Sometimes the research does have its drawbacks, though.
As for the cow, DelCurto says they don't pay much attention to the cannulas, other than they may even enjoy their built-in pressure valve. A lot of gas is generated by the fermentation process going on in that swamp.
"Cows with cannulas don't bloat," DelCurto says.
Cattle belong to a suborder of mammals known as ruminants, along with sheep, goats, deer, elk, bison and even giraffes.
Cattle stomachs, like all ruminants, are divided into four compartments Â— the rumen, the reticulum, the omasum and the abomasum. Each compartment has a specific function and purpose. The rumen is the first division of the stomach where food collects after being swallowed Â— unless what is swallowed happens to be a piece of barbed wire that falls down to the reticulum, a compartment conveniently located right beneath the esophagus. It's designed to hold any hardware cows inadvertently swallow.
Everything else heads on over to the rumen for processing before being regurgitated, rechewed and reswallowed. Eventually fully digested food moves into the omasum. The omasum's function is to absorb the tens of gallons of water needed for a ruminant's digestive process. A mature cow normally generates five gallons of saliva each day.
DelCurto says a cow's huge digestive system takes up most of the room inside the cow Â— sort of a digestive system on legs.
"A typical 1,000-pound cow will hold somewhere between 250 to 280 pounds of forage, water and bugs in her digestive system," he says. Of that, anywhere from 6 percent to 10 percent is just the bugs Â— bacteria, protozoa and fungi.
DelCurto's area of expertise is in range beef cattle nutrition and management. Without the bugs, he says, cattle have no way to break down the forage they eat into the highly digestible proteins they need.
DelCurto calls it a very symbiotic relationship. Without the bugs, they'd eat and eat and eat and starve to death in the process. In reality, he says, a good feeding program feeds the bugs, not the cattle.
"I tell my 4-H kids, if they commit to feeding that steer twice a day they can't take a night off just because they went to the movies and got home late, and decide it'll be OK to double feed him in the morning," he says.
DelCurto explains that the bugs can't wait for breakfast. They begin to die. In the morning, double feed overtaxes a now weakened digestive system and an unhealthy animal is the result.
"The health of the bugs determines the health of the animal," he says. Ensuring the health of the bugs and stimulating the proper growth is one reason the industry has moved toward adding probiotics to feed in recent years.
The results of this type of research drives the use of cannulas and the study of bovine digestion. Research being done on cattle nutrition and management by DelCurto and others at the Union station will contribute to a greater understanding of how best to manage grazing lands for the future.
DelCurto says there's a lot of talk about sustainable grazing and the impact different species of mammals have on different species of forage. When it comes to ruminants and forage species preference, DelCurto says cattle are generalists Â— even eating certain types of weeds Â— while deer and elk are picky eaters.
"We don't want to graze any species out of existence. As we look at how grazing impacts the system, in the future we can move vegetation in the direction we want it to go," he says.