By DOUG WARNOCK
For the Capital Press
As livestock managers implement grazing plans with higher grazing density and shorter grazing times, they need to allow animals some opportunity to select among diverse plants and balance their intake of nutrients.
Research done by Juan Villalba and Frederick Provenza at Utah State University focuses on the ability of domestic animals to select from among the plants available to ingest the nutrients they need and to minimize their intake of plant secondary metabolites, the less-desired components.
Provenza and his colleague have done extensive research on animal behavior and the factors that influence animals in selecting what they eat. Animals learn through experience what plants or foods fulfill their needs and which ones to minimize to avoid discomfort.
Their experience is the result of learned behavior. The individual learns, first, from its mother as it follows her during the grazing process. Secondly, it learns from other animals in the herd or flock. When confronted with an unknown plant, an animal will usually try it, if other animals are eating it.
When an animal becomes adapted to an area, it will have learned much about the various plant species in that area and how they each can fit into its dietary needs. As conditions change over time, the animals living in a particular environment adapt to the changing conditions as a means of survival.
Villalba and Provenza point out that some of the dietary selection comes from the animals' genetic code, which is shaped by the environment through evolutionary time. Two other kinds of memories are involved as well:
* That acquired by experience through post-ingestive effects of food eaten.
* That acquired through social interactions with experienced animals.
Post-ingestive feedback is a built-in monitoring system in which signals are sent through the animal's system that indicate satiation, discomfort and other reactions, depending on the results in the body from the foods being digested. These reactions may change as the dietary needs of the animal changes. The reactions also may change as the nutritional composition of the plant changes according to seasonal growth and plant maturity.
Plant secondary metabolite components can often have negative effects in large doses, but may provide benefits in low concentrations. By having the ability to choose and select, the grazing animal can essentially balance its nutritive intake and control negative feedback from the less-desired feedstuffs.
Grazing animals learn about the effects of ingesting specific plants and learn to prefer those that provide needed nutrients and medicinal effects. They are able to avoid or minimize the intake of plant secondary metabolites and are able to mix foods in order to reduce their effects.
Managers can learn to use these grazing behavior principles and allow livestock to build their own diets, which will enhance general health and otimize production. Using the animals' selection knowledge to balance their diet makes for a more sustainable type of livestock operation.
Doug Warnock, retired after 35 years as an extension agent with Washington State University, consults and writes on ranch and farm management.