Managing Pastures and Livestock to Minimize the Impacts of Lupine
By Steve Paisley, UW Extension Beef Cattle Specialist
This may seem to be an odd time to talk about lupine toxicity and livestock – we generally think about lupines earlier in the summer, when they are actively blooming and more noticeable, but the actual real concern about lupine toxicity begins mid- to late-summer for mid- and late-spring calving herds.
Lupine plants in the western U.S. typically have characteristic blue flowers, although lupine may also be pink, white or yellow. Lupines tend to grow in several ecosystems: foothills and mountain ranges, in open and wooded hillsides and sagebrush and aspen communities.
There are actually six species located in the western states that have some level of toxic effects: silky lupine (L. sericeus), tailcup lupine (L. caudatus) velvet lupine (L. leucophyllus) silver or silvery lupine (L. argenteus) lunara lupine (L. formosus) and yellow lupine (L. sulphureus). Lupines get their toxicity from alkaloid compounds found in vegetative growth, and especially seeds and seedpods. While all six of these species have some toxic effects, only one species, velvet lupine, contains the specific alkaloid anagyrine that has been linked with calf deformity symptoms. Lupine toxicity typically has tetragenic (causing birth defects) affect on grazing livestock. In beef cattle, typical symptoms include cleft palates, as well as “crooked calf” or “windswept” calves, those with crooked legs and irregular muscle development.
There are several factors that affect the severity of lupine’s toxic affects. Some of these factors include:
1) The total amount of lupine consumed by the animal. Eating one to two pounds of lupine may poison cattle, and smaller amounts may also be poisonous if consumed daily for three to seven days. Sheep can be affected by eating as little as one-quarter pound per day, if it is consistently consumed over a three- to four-day period.
2) Stage of plant maturity. Lupine vegetative growth tends to be more toxic early in the season, when the plant is actively growing. Seeds and pods, formed later in the growing season, are even more toxic.
3) The tetragenic (birth) defects in cattle mainly occur when lupine is consumed between day 40 and day 100 of gestation. It is during this critical fetal development stage that lupine has its greatest affect on the gestating calf. Gestational studies conducted in sheep, goats and cattle indicate the alkaloid compound anagyrine has a sedative, or tranquilizing, affect on the fetus. Cattle consuming lupine on a consistent basis between day 40 and day 100 have developing fetuses that essentially become immobile. Cleft palate deformities develop mainly because the tongue of the “sedated” calf remains near the roof of the mouth, hampering palate development. Similarly, lack of fetal movement of the calf also contributes to the characteristic muscle and bone abnormalities associated with the “crooked calf” or “windswept” appearance, as the sedated fetuses remain in the same position inside the cow for an extended period of time.
Important management issues to consider are the respective timing of forage availability, forage quality, stage of plant maturity (especially lupine) and stage of pregnancy of the cow. Lupine toxicity problems can be lessened by making sure there is adequate forage available at turnout in the spring, especially in pastures that contain higher levels of lupine plants. Cattle tend to select grass and avoid lupine forbs, especially if there is adequate grass available.
Perhaps the larger concern is managing grazing late in the summer when lupine plants have developed seedpods, which contain the highest levels of alkaloids. This seedpod development tends to occur when the quality and availability of native range is beginning to decline, and the management concern is that cattle on native grass in August and September may begin searching for higher protein plants to supplement their diet. In many cases, lupine plants tend to remain green longer, and have a considerably higher protein content late in the summer grazing season, making the lupine plant more desirable for grazing selection.
The day 40 to 100 “gestational window” of pregnancy is also important to keep in mind. This is the developmental period when the fetus is most susceptible to the toxic effects of lupine. For March 1 calving herds, this time period is July 2 through Aug. 31. The critical period for April 1 calving herds is Aug. 2 through Oct. 1. Finally, for May 1 calving herds, the critical window is Sept. 1 through Oct. 31.
Traditionally, the direct effects and symptoms of lupine toxicity tend to happen in the spring. Cattle that consume the lush, actively growing lupine vegetation may exhibit signs such as nervousness, excitability and excessive salivation and frothing. Severe symptoms include difficulty breathing, loss of muscle control, blindness and convulsions. The secondary, or delayed, tetragenic effects tend to be associated with livestock consuming the more mature plant, pods and seeds during mid- to late-summer.
Managing livestock to minimize lupine toxicity may mean adjusting grazing periods to avoid the early vegetative stage, and/or late seedpod stage. Additional management may mean adjusting calving dates to avoid grazing lupine during the very susceptible 40- to 100- day gestational window. If chemical control is an option, there are several products that are effective in controlling lupine, but keep in mind that spraying would impact all forbs in the plant community. Working with your local range specialist or weed and pest personnel will help in selecting the correct product, application method and timing.