The unique conditions leading into the spring of 2013 may be leading us into even more potential problems. A dry growing season last summer combined with poor forage growth in the fall has left almost no standing forage in many pastures. In short, as we approach spring there is not much out there, and if forecasts are correct conditions for spring growth may not be great either. On the cow side of the pasture/ livestock equation, in many cases we are looking at some mighty hungry individuals. Hay is scarce and expensive and concentrates are higher than many of us can remember them ever being. This has led many producers to design a management program to “get ‘em through the winter” rather than meeting the cattle’s nutritional requirements.
Under good growing conditions the primary plants have no trouble holding their own, but under poor or marginal conditions of soil fertility and moisture the less desirable species become much stronger competitors. Additionally in many of these pastures some of the perennial grasses and forbs have died, leaving a vacuum that undesirable species may well fill. Many of these undesirable species have the potential to be toxic to livestock if consumed in sufficient quantities. Nature’s normal defense against toxicity problems is that most toxic plants have very poor palatability and are not usually consumed if more desirable forage plants are present in adequate supply. In our current scenario, however, along comes old mama cow. After months of not having her dry matter intake requirements met she is just looking for anything that will satisfy her hunger, and under the circumstances it may be toxic species that she would not ordinarily choose to consume.
There are a wide variety of plants with toxic potential in Oklahoma pastures. Many of them we don’t think of as toxic because they don’t usually cause problems under normal circumstances, but the potential is there. Several different plants can cause gastrointestinal upsets, including oleander, ivy, iris, pokeberry, wisteria, and mistletoe. (Oh, no, surely not the state flower!) Lupine causes breathing difficulty. Mushrooms can cause gastrointestinal upset and breathing difficulty. Oak leaves and shoots, under certain conditions, can cause kidney damage which may not show up until weeks or months after the toxin is ingested. Oral irritation is caused by ingesting poison ivy, poison oak, rosary pea, and castor bean.
There are many other plants that have the potential to cause toxicity. Some of these would be cockle burr, red maple, common yarrow, wild onion, Indian hemp, milk weed, aster, beggersticks, musk thistle, larkspur, curly dock, nightshades, and death camas. This is by no means a complete list and the species found in your area will vary greatly. If in doubt enlist the help of your local veterinarian or take a sample of suspect plants to your county extension office for identification.