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COUNTRY LIFE IN BC • OCTOBER 2019 Clean cud promotes dental health in ruminants
Stomach washes away material that could damage teeth Grazing animals, by the
very nature of their foraging habits, frequently ingest bits of earth which can be abrasive to their teeth. This is especially true in dry regions or during periods of drought when the wind is constantly blowing and dust collects on vegetation.
Research by MARGARET EVANS
While horses developed longer teeth during their evolution to compensate for tooth wear, ruminants – cattle, sheep, goats and others – maintained shorter teeth. Scientists have often wondered how they protect their teeth and maintain their dental structure, especially when they not only graze on grass but also chew the cud before properly digesting the
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food. Cows enjoy some relaxation time to chew their cud, often lying down for a period of time to chew softened balls of food before fully digesting them. “We have always wondered
how ruminants living in the same habitat manage with shorter teeth,” said Jean- Michel Hatt, director of the Clinic for Zoo Animals, Exotic Pets and Wildlife at the University of Zurich, in a press release. Now, Hatt and his
research team have found the answer. By studying
the lower jaw of goats and observing chewing behaviour, chewing forces and dental microwear, their research has suggested that a ruminant’s digestive behaviour not only provides them with clean, properly digested food but also a reduction in the chewing load and unnecessary tooth wear. Ruminants have a multiple- chambered stomach system that includes the rumen, reticulum, omasum and abomasum. Grazing cows chew the food enough to moisten and swallow it, then fluids in the rumen soften the material further. The stomach system uses bacteria to digest the plants eaten. Rumen fluids wash the food which is then sorted either into material small enough to be digested or into larger pieces that have been softened and regurgitated to be chewed as cud once more before being fully digested.
While it has long been thought that the balls of cud
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are free from dust and sand, the research team for the first time tested various types of food to find their specific influence on dental wear and tear.
Through the use of computer tomography, the researchers studied goats fed diets containing sand and phytoliths (rigid microscopic structures of silica in some plants) for several months and were able to show that the sand and dirt ingested with the food were not just absorbed into the gastrointestinal tract but collected in specific locations. They were able to record that the upper rumen where food was washed before being regurgitated was
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comparatively depleted of sand. The abrasives became trapped and were actually collected in the abomasum, eventually passing through the bowel and expelled with the feces. Even though both ruminants and non-ruminants take up some abrasive material, the percentage of ingested sand and dirt would affect ruminants to some degree less than non- ruminants because of the process of washing and cleaning before fully digesting food. “We were able to show that
there was considerably less sand in the upper rumen, where the material to be ruminated is regurgitated, than in the ingested food itself,” said Hatt. “Organisms that develop such a washing system have a natural way to easily get rid of the rinsed-off material.”
He said it is only when animals ingest a large amount of sand all at once from, say, a poor food source with many contaminants, that complications can occur. The digestive process, Hatt explained, is one that shows
the evolutionary success of a multi-chambered stomach. Ruminants take in the food with some cursory chewing. Only once the dirt has been rinsed off the food in the rumen will the cleaned, softened balls of cud be returned to the mouth for a much more thorough job of chewing before being fully digested. With much more palatable food, a lessened chewing load, and all the sand, grit and dust washed off, the teeth are not subject to abrasive materials that would otherwise contribute to excessive dental wear and tear. With a well-functioning rumen, cud-chewing cows are healthier, will digest a greater percentage of their diet and, if dairy animals, will produce more milk.
Whether a multiple stomach system as in ruminants or a longer tooth and tooth roots as in horses, both natural strategies are products of evolutionary success for survival. Margaret Evans is a freelance writer based in Chilliwack specializing in agricultural science.
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