“Lupine calves” are an example of what can happen when certain plant toxins are ingested by a pregnant cow during pregnancy.
These toxins cause the developing fetus to be malformed. Usually it’s the leg joints and limbs, but occasionally you’ll see a calf born with a cleft palate.
Native pastures in the West may contain several types of lupine. This hardy plant blooms in early spring, often with blue flowers, but some varieties are yellow, white, blue and white or pink. The blooms stay on for many weeks. Some species of lupine are harmless, but other types contain alkaloids that can cause deformities in calves if eaten by pregnant cows.
Some years there are high numbers of lupine deformities in certain regions. In 1997, in Adams County, Washington, about 20% of the calves born that spring were so seriously affected they were humanely destroyed. This drastic increase was thought to be due to cool, wet weather the preceding summer, which increased the amount of lupine on rangelands, and the incidents of cows eating lupine during critical stages of pregnancy. Lupine deformities can also occur because of a late spring; the grass is not ready yet, but the lupine is growing well, and cows eat more of it.
Most lupine species are perennials. They start growing early in the spring, flowering in May or June, with blooms staying on until seeds are formed in July or August. The poisonous species are dangerous from the time they start growing in early spring until they dry up in the fall. Young plants in spring are more dangerous than mature plants in summer, though the plants are also dangerous again in late summer because of the high alkaloid content in the seeds.
When the fetus of a pregnant cow is affected, often the legs are crooked or the joints are fused and the legs don’t move or bend properly, which can become a problem during birth. Most of these calves can be delivered through the birth canal — unless the deformity is too severe. In those situations, the calf must be surgically removed.
These defects are caused by certain alkaloids, and only between 40 and 70 days’ gestation. The alkaloids affect the brain and act as a sedative, and the sedated fetus isn’t moving. The legs and joints become stiff or fixed in abnormal positions. The fetus may have one or more joints or limbs affected, or the spine. As stated by Dr. David Steffen, a diagnostic pathologist and professor at the School of Veterinary Medicine of the University of Nebraska, most of the body structures are formed during early gestation, so this is when they can be adversely affected.
“The palate closes at about 55 to 60 days of gestation. If the fetus is affected by lupine or another toxic plant alkaloid at that point in time, the tongue isn’t moving so it forms a physical obstruction as the palate plates move in toward one another. When the tongue is in the way and prevents those plates from coming in from the sides and fusing, we know the insult occurred prior to 60 days,” Steffen says. “We see similar defects in geographic regions where there isn’t any lupine; these defects can be caused by other plant toxins such as hemlock.”
Any kind of plant alkaloid or toxin can affect a developing calf’s nervous system. Even some viruses can cause these abnormalities.
“In order for the legs and joints to be mobile and develop normally, there must be an intact nervous system,” Steffen says. “If there is no function, no motion during development, the joints tend to become fixed. When a calf is born with crooked legs or fused joints, we don’t always know why, but in many cases we can suspect plant toxins, especially if the cows were grazing pastures containing lupine during early pregnancy.”