Leopold Center for Sustainable Agriculture

Guest columnist: Livestock and Diversity: Learning from Iowa's past

Back to Leopold Letter Summer 2009

By FRANCIS THICKE, Guest columnist

EDITOR'S NOTE: Livestock and Diversity is one of six core issues that help guide the work of the Leopold Center and clarify our role and response in critical areas. We asked dairy farmer Francis Thicke of Fairfield to explain why he believes diversity is important in his farm operation.

Twelve thousand years ago, in the wake of a glacier, the land that would become northern Iowa was a geologic wasteland. Glacial materials from the north had obliterated the biological diversity of the previous era. But then nature’s ecological processes began anew, creating–over 12 millennia–a prairie ecosystem with its fertile, productive soils.

How did that happen? Gradually, plants, animals and microorganisms colonized the desolate landscape, creating an increasingly diverse and complex ecosystem. The ecosystem’s plants and animals generated organic materials that soil microorganisms used to develop soils from raw geologic materials.

It has been estimated that 50 million bison once roamed the prairies and plains of North America. Bison herds roving the prairie landscape are a model we can use to design animal production systems that are resilient, energy-efficient, and biologically diverse.

Roving bison, prairie plants
When bison herds grazed the tall, deep-rooted prairie plants, they reposited their manure nutrients back to the soil, and their grazing activities stimulated regeneration and robustness of the ecosystem. When herds moved on to fresh prairie, the now-shortened plants had excess root mass and sloughed a portion of it into the soil as the plants recommenced their perennial cycle of capturing sunlight to produce new shoots and roots. The root mass released into the soil after the bison had grazed the prairie plants became food to sustain soil microorganisms and produce humus. Repeated grazing cycles of the roaming bison herds increasingly added to the soil’s fertility and productivity.

Modern livestock production systems can be designed and managed to mimic these ecological processes. These systems also can be more energy-efficient than current industrial animal production methods. The key is to find ways to harness the energy, efficiency and organizing power of nature’s ecology.

A grass-based dairy farm illustrates one way to mimic the prairie ecosystem. In a grass-based dairy, the landscape surrounding the milking barn is converted into a polyculture of grasses, legumes and forbs–some of which are planted and some that “volunteer.” This landscape of perennial plants is divided into segments (called paddocks) using inexpensive fencing materials, with cow lanes connecting all paddocks to the milking barn.

After each milking (twice a day) the cows are allowed to graze a new paddock area that is just large enough to provide the cows’ forage needs until the next milking time. As the cows rotate through the paddocks, grazed areas have time to recover, allowing plants to regrow to a stage of optimum nutrition for the next grazing episode.

Management is important. If paddocks are allowed too much recovery time, the plants will become overly mature and lose nutritional value. If grazed again too soon, some plant species will not recover fully and die, reducing pasture productivity and diversity. Under good management, plant diversity is maintained or increased and soil fertility is continuously regenerated.

When cows are kept in confinement, the cows’ forage must be mechanically harvested in the field, hauled to the facility, stored, then taken out of storage each day to feed the animals. And, the cows’ manure must be collected, stored and eventually hauled back to the fields. All these operations require fossil fuel energy.

By contrast, a well designed grass-based dairy accomplishes the same objectives by the farmer simply opening the gate to the next paddock. The cows harvest their own forage and spread their manure. And they enjoy their work!

Modern paradox
Allan Nation, editor of the Stockman Grass Farmer, summarized the irony of modern confinement animal production by pointing out that it is the nature of cows to move about and the nature of grass to stand in one place. But with confinement animal production we have turned it backwards and made the cows stand in one place and made the grass move to the cows.

Dairy farmers who switch from confinement to pasture-based systems find that cows are healthier in their natural environment. Improved animal health may also be partly due to a diet high in freshly grazed forage being better suited to ruminant animals than diets high in grain concentrates that are normally fed to cows in confinement systems.

An additional benefit of grass-based dairies is that milk produced by grazing cows is higher in nutritional components that nutritionists tell us are beneficial to human health, including omega-three fatty acids, conjugated linoleic acids, beta carotene, and some vitamins.

Two major challenges loom on the horizon of tomorrow’s agriculture: 1) a growing scarcity and rising cost of fossil fuel energy, and 2) an intensification of the effects of climate change, particularly manifested as greater extremes of weather events, including intense rainfall events and flooding.

One way to address both challenges is to put livestock back onto the landscape in ways that mimic nature’s ecology in order to create animal production systems that are energy-efficient, resilient, and biologically diverse. 

Back to Leopold Letter Summer 2009