Variety is the Spice of Life
We've all head the old adage "Variety is the Spice of Life" but does it apply to livestock and wildlife? Research says yes. Animals are individuals no matter how similar they look. They have different abilities to tolerate and detoxify toxins. While they're nutritional needs are similar, each individual has its own unique needs for energy, protein, and minerals. Providing animals a variety of foods enables them to select a diet that meets their needs. Variety also enables animals to mix their diets to lessen the effects of naturally occurring toxins in plants.
Principle 1: Providing animals with a variety of foods on pastures and rangelands and in feedlots allows them to avoid toxins and balance diets to meet their own unique needs for nutrients.
Principle 2: Individuals within a species vary widely in their ability to tolerate toxins and their need for nutrients.
What happens when animals get nothing but the best?
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Feedlots. In a recent study, cattle fed barley, corn, alfalfa, and corn silage were compared with animals fed a chopped and mixed nutritionally balanced ration of those ingredients. Food selection varied widely among individuals offered a choice of the four ingredients throughout the 63-day trial. Intake of dry matter, energy, and protein all changed from day to day, as did ratios of protein to energy for animals fed free-choice. No two animals selected a diet similar to the total-mixed ration, and none consistently chose the same foods. Yet each animal apparently selected a diet that met its needs.
Animals offered the mixed-ration tended to eat more than animals offered a choice, but they did not gain at a faster rate. Animals offered a choice ate less, and they ate less of the more expensive grains so cost/lb of gain was about 20% less for the choice than for the mixed ration group. These findings suggest that: (1) individual animals can more efficiently meet their needs for energy and protein when offered a choice among ingredients than when offered to a single diet, even if it is nutritionally balanced and (2) giving animals choice in the feedlot may allow producers to reduce illness, improve performance and reduce costs.
Pastures. In another study conducted at Utah State University, beef calves had higher daily gains and the most efficient gains when they grazed pastures with four forage species (alfalfa, tall fescue, birdsfoot trefoil, meadow brome) rather than pastures with only one of these species. Livestock producers have also reported that cattle performed better when they graze pastures with a grass-legume mix rather than a pasture with only legumes even though energy and protein content are higher in the legume pasture than in the grass-legume pasture.
Pasture Design. Not only is variety important but how it's planted is also important. Animals are more productive if forage species are planted in rows rather than inter dispersed mixtures because they spend more time eating and less time searching for and selecting food. When sheep foraged on pastures planted in blocks of clover and grass rather than mixtures of the two species, they ate 25% more forage. Dairy cattle increased milk production by 11% when they grazed clover and grass planted in blocks rather than mixtures.
Diet mixing and increasing biodiversity. Most unpalatable plants contain toxins that reduce intake. Animals can learn to mix their diets in ways that lessen the effects of toxins and allow them to eat a greater amount of unpalatable species. Increasing intake of these species leads to a greater plant species diversity and ecosystem stability. See Training animals to eat unpalatable species.