Final Report Executive Summary

This pilot project began in February 2004 and ran through August 2005. It was based on a growing body of research indicating that behavior of livestock is flexible and that it can be effectively modified and managed to 1) enhance and maintain biodiversity of rangelands, 2) restore pastures and rangelands dominated by invasive species and 3) improve wildlife habitat.

The purpose of this project was to translate results of research into actual steps to teach cows to eat weeds. By doing so we hoped to be able to use cattle as an alternative to or in concert with herbicides to reduce weed species invasion and to begin restoration of native biodiversity at Grant-Kohrs Ranch National Historic Site.

During the summer of 2004 we effectively used behavior modification tools to teach a small herd of heifers to eat three weeds people commonly believe cattle will not eat:   Canada thistle, Leafy spurge, and Spotted knapweed. Animals were trained in dry lot over a two-week period. They continued to eat the target weeds in trial pastures for one month and then when placed with the main herd. Unfortunately, riparian area use restrictions prevented us from trying animals on leafy spurge in the field in 2004.

The greatest "Ah-Ha" of this project was HOW cows eat leafy spurge. My initial expectations were that they would bite off stems and eat entire plants. However, in two separate attempts to have th ecows and calves eat leafy spurg in pasture, I discovered that they stripped leaves and flowers off the stems. This is also how sheep and goats graze this plant. This could add a degree of complexity to the training process because, in addition to learning that the plant is edible, the cows also have to learn new foraging skills in order to include it in their diet.

Where Do We Go From Here?

This pilot project was the first step in taking results of research and transferring it to the field as useable techniques. While we were able to successfully demonstrate that cows can be trained to eat Canada thistle, leafy spurge and spotted knapweed, there are numerous questions for which we don't yet have answers. These include:

Can cows eliminate weeds?
      Eliminating weeds through the use of prescribed grazing requires intensive management. It may be possible to get rid of weeds by carefully choosing stocking densities, and grazing duration and timing, and by making adjustments based on seasonal changes and precipitation variation. The grazing manager would have to understand the growth requirements of both the species to be protected and the species being eliminated. Unfortunately, in the case of many weeds, we do not have concrete information on their responses to grazing. Thus, the manager would need to pay attention to weed responses and adjust and adapt the grazing system accordingly. He/She would also have to be prepared to stay with it long-term, understanding that managing vegetation is no different than managing the hair on top of one's head. Both vegetation and hair will continue to grow and change over time and one "haircut" can't last forever.
      For those interested in using cows as a weed management tool, it may be more economically viable to simply look at cows as a way to prevent weeds from getting out of hand. By teaching cows to eat weeds, the producer can increase the amount of forage available and can reduce the competitive advantage weeds have typically had when animals avoided eating them.

Once cows learn to eat weeds, can they focus on weeds alone?
      It was not our intent, nor do we believe it is possible, to create animals who avoid other forages and eat only weeds. Based on the research available, we understand that animals will always need to eat a mixture of forages to remain healthy. By training the cows to eat weeds we anticipate that they will continue to include them in their diet.

How much of a weed can a cow eat?
     Because this is a first of it's kind effort, we do not know what percentage of a cow's diet can be made up of a particular weed. Research in this area is just beginning to provide answers that we will eventually be able to translate into techniques for the field. What research results do tell us is that nutrients can offset effects of toxins to allow an animal to eat more, that certain toxins can offset the effects of other toxins, again allowing an animal to eat more, and that experience mixing nutrients and toxins and toxins and toxins is critical to success. There is also research ongoing in the field of minerals and their effect on diet selection. Since this is a new and complex field, grazing managers interested in working with their animals on weed management will need to follow the developing literature, pay attention to the learning environments they provide their animals, and track their observation of intake and health.

Can cows eat leafy spurge?
     The short answer is yes. Our herd ate leafy spurge in dry lot and in pasture without any of the negative effects previously thought to be associated with leafy spurge consumption.
     The longer answer is that while we have evidence that cows can and will eat leafy spurge in pasture, we don't know as much as we'd like about the circumstances under which they can and will eat it. How much variety is enough? What time of year is best? Is pressure required, and if so, how much?

Are there long-term effects on meat, longevity, reproduction, etc.?
     Because of the short life span of this particular study, we can't answer these questions. The literature suggests that there should be no effects on any of these things, and since animals deal with a variety of nutrients and toxins in their diets on a daily basis, one could conclude that these new weeds would not pose additional threats. Our first year of calving produced healthy calves from each heifer, and our second year of calving is just beginning as we complete this report. We'll know more as time goes on and Grant-Kohrs Ranch will continue to keep records and observe effects on their herd.