By Cassandra Schroeder AAg, Range Management Extension Specialist, Kindersley
Dry conditions in many areas across Saskatchewan have meant low forage supplies and expensive feed for many ranchers. Given these conditions, producers might be considering turning cattle out early onto pastures with limited forage carryover and growth. However, such conditions increase the risk of animals consuming some toxic plants. Normally, cattle avoid most toxic plants, but with a lack of other forage there is an increased risk of consuming toxic plants. Some plants are more toxic in the spring or more likely to be consumed in the spring because of their earlier growth. Although poisonings are not common, it is important to be aware of these risks so that steps can be taken to prevent unnecessary losses. Some toxic plants to watch out for this spring include death camas, water hemlock, and seaside arrowgrass.
Death camas is a small perennial plant in the lily family. It has v-shaped, grass-like leaves and cream coloured flowers. It is common in southern Saskatchewan most often in upland draws and depressions. Death camas has early growth that might be grazable before surrounding vegetation, which increases the risk of poisonings in the spring. All parts of this plant are poisonous, but the bulbs usually have the highest concentration of toxins. The bulbs are also more likely to be consumed in the spring when they can be pulled out of the soft ground with the rest of the plant. Sheep are more commonly poisoned than cattle, but death camas is also poisonous to cattle. Death camas contains steroidal alkaloids that reduce blood pressure and cause symptoms like excessive salivation, vomiting, staggering, and collapse prior to death.
Water hemlock is considered the most poisonous plant in Canada. The root of a single water hemlock plant can kill a cow. It is the roots of water hemlock that are most poisonous, although the rest of the plant is also toxic. The toxicity of above ground growth is highest in the spring and the dangerous roots are more likely to be consumed in the spring when they are more easily removed from the ground. The oily toxic substance can be seen in the root chambers if the roots are cut open. The oils exuded by the roots are also very toxic to humans so use gloves and be extremely cautious when handling water hemlock. The oily toxin directly impacts the central nervous system causing extreme convulsions and death within a few hours of ingestion. Water hemlock, a member of the carrot family, prefers wet areas such as those along sloughs and streams, and in wetland areas. Water hemlock is a large plant, usually a few feet tall, with umbrella-shaped clusters of small white flowers at the top. There are several non-poisonous plants, including cow parsnip, that are very similar to water hemlock. The Ministry of Agriculture video "Identifying Water Hemlock" highlights some distinguishing features.
Although their fruit is well enjoyed by most prairie people, chokecherry and saskatoon trees can cause livestock poisonings. These are usually only of concern when lack of suitable forage results in cattle consuming significant amounts of leaves and twigs. Both plants have a compounds that break down into hydrogen cyanide which affects cellular respiration and causes symptoms such as rapid breathing, muscle spasms, and convulsions. If large amounts are consumed in a short period of time death occurs with little time for intervention. Toxicity of these trees varies, but as little as three pounds of fresh twigs and leaves can cause the death of a mature cow. Generally speaking, both trees have higher concentrations of toxins earlier in the spring and chokecherry branches are more toxic than saskatoon branches.
Seaside arrowgrass is a perennial grass-like plant that grows in saline or alkaline marshes and flats. It is relatively common across Saskatchewan and most of Canada. Seaside arrowgrass starts to grow earlier than other grasses, rushes and sedges, thus increasing the risk of consumption in the spring. Highest concentrations of toxins also occur early in the season in the young leaves and developing flower spikes. Stresses such as drought and physical damage can also increase toxin levels within the plant. Depending on toxin levels, six pounds of fresh seaside arrowgrass can be lethal to a mature cow. Similar to chokecherry and saskatoon, the toxin in seaside arrowgrass results in rapid hydrogen cyanide poisoning. Unlike many other toxic plants that are generally avoided by cattle, cattle can be attracted to seaside arrowgrass when the plant accumulate salts. Hence it is important to ensure cattle have access to an adequate supply of salt to prevent them from searching for alternative sources.
General tips to avoid livestock poisonings include ensuring that animals have good available forage, salt, and water. Unsatisfied animals are more likely to eat things that they should not. Managing pastures to keep vigorous stands of desirable vegetation helps to reduce the chances of poisonous plants being consumed. Scouting for poisonous plants in high-risk situations and areas is advisable. Depending on the quantity and distribution of any poisonous plants identified, the plants could be removed, the area fenced off, or the time of grazing could be changed to reduce the risk of consumption. Herbicides are rarely an option to target poisonous plants. Images of most plants are easily searched, but it can still be challenging to positively identify some poisonous plants.
For help identifying poisonous plants contact your local Regional Services office.