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I wondered aloud and asked him, is there an herbivory response? Say in cattle, sheep, and deer?” Herbivory is simply the “eating of plants,” and the two scientists agreed the topic seemed like a fertile area for research. It was already established that exposure to air pollutants can make a plant’s cell walls more “lignified,” or rigid and woody. They thought tougher cell composition could have ramifications for the ruminants that graze grasses, such as cattle, sheep, buffalo, and goats.
The digestive systems of ruminants are adapted to handle fibrous herbaceous material. Their stomachs have four compartments, with the first two separating food into liquids and solids. Then the solids are regurgitated and chewed to decrease the size of fiber particles—as in “chewing the cud”—before the food is swallowed again and passed into the stomach’s other chambers. “Non-ruminants like rabbits, horses, and humans would compensate for decreased nutrition by eating more,” Muntifering says. “But ruminants are unable to eat more as fibrosity and lignification of forage are increased.” Increased fiber content and lignification in the plants that ruminants eat actually lowers an animal’s intake, because the rumen—the main compartment in the four-chambered stomach, where microbial action starts breaking down the plant mass—physically fills up. Muntifering and Chappelka, along with Dr. Stephen Ditchkoff (an Auburn wildlife biologist), have collected flora from the rumens of cows and deer to determine the effect of ozone exposure on the various microorganisms that digest grasses and forage material. “You can inoculate vegetation with bacterial cultures and see how extensively the microorganisms degrade the forage,” Muntifering says. “In our experience, when you incubate or inoculate forages that
are more fibrous and lignified, the fiber-degrading microorganisms are less effective.” Muntifering’s and Chappelka’s research program now is regarded universally as the international center of excellence on the effects of air pollution on forage quality for agriculturally important ruminant livestock and wildlife. They collaborate extensively with U.S., Canadian, and European centers of excellence on a variety of vegetation types, and have experimented with both annual and perennial plants using diverse experimental systems in different kinds of environments. Europeans are paying close attention to their research. The reason is economic; European foods are held to strict standards, and pollution from Italy’s teeming Po Valley is wreaking havoc on vegetation in the Swiss Alps, where “first cheese” is produced from the early lactation of cattle. Similarly, the pigs that produce Italy’s famed porchetta dine on acorns. And in Spain olive trees could be affected. “If you start messing with the chemistry of the foliage in the forage in the Swiss Alps, or of the oak trees that produce acorns, or of the olive trees in Spain, the Europeans are going to take action,” Muntifering says. In their atmospheric deposition field site in Auburn, the two researchers grow forage in 24