Behavior and Grazing Management
PHOENIX, Ariz. (Jan. 28, 2009) — Why do grazing animals choose to eat certain plant species and shun others? For 35 years, Utah State University researcher Fred Provenza has looked for answers, hoping they would help ranchers better manage their animals and landscapes. During a Cattlemen’s College session Wednesday at the 2009 Cattle Industry Convention, Provenza told his audience that palatability of plants is more than a matter of taste.
“It is the relationship between flavor and post-ingestive feedback from cells and organs in response to compounds in the forage,” Provenza explained.
Fred ProvenzaThe primary compounds contained in a food source include nutrients like energy, protein and minerals. There are secondary compounds, too, like akaloids, terpenes and tannins — substances once thought to be toxins. Provenza said even required nutrients can be toxic when consumed in sufficient excess, and under certain circumstances the secondary compounds can be beneficial to the animal.
“It is the relationships and concentrations of any and all compounds that influence palatability,” he added.
Provenza said research results of actual ranch management practices have demonstrated that learned behavior influences forage choices. Offspring learn to eat the same plants grazed by their mothers. They also gain “nutritional wisdom” by sampling different plants on their own. Animals may also choose to eat plants containing certain compounds, in order to correct a chemical imbalance in their regular diet. Providing animals with feed supplements containing certain compounds may also encourage animals to choose plants thought to be unpalatable. And genetics play a role as well.
“But genes do not equal destiny. The environment can turn genetic influences on and off,” Provenza insisted. “Animals learn. They adjust and adapt to the environment. They are more flexible than we give them credit for.”
Provenza and his colleagues are researching methods of managing cattle to broaden their diets to include sage brush, leafy spurge and other “weedy” species.
“There is potential for turning cows into weed managers by utilizing a more broad variety of plants. We believe we can increase animal performance, better utilize available forage and increase biodiversity of landscapes,” Provenza said. “To me, it makes sense ecologically and economically.”
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