Spring is a time of new birth, green growth, and uplifted spirits. But it can also be a time of devastation and discouragement if special attention is not paid by the goat-keeper to toxins and poisonous plants that may be lurking in pen and pasture, due to early spring greening. There are a multitude of plants containing materials toxic to dairy goats if eaten in sufficient quantity. Some of those plants are well known and some not, some are useful, and still others are enjoyed as ornamentals.
Deadly conditions for dairy goats related to spring rains and greening pastures include: poisoning, grass tetany (mainly caused by low magnesium), thiamin (B1) deficiency, and parasitic overloads.
The USDA and the State Departments of Agriculture, through local extension offices and Internet, offer informational bulletins for recognizing poisonous plants in local areas. I sometimes peruse them, but mostly depend on my Merck Veterinary Manual, and my Audubon field texts with photos. I recommend North American Trees and North American Wildflowers for anyone interested in further identification and in-depth information about plants not mentioned here.
Although it is important to note that it usually takes more than one of the following factors to contribute to the deadly poisoning of goats during spring green-up, death comes more often than some like to acknowledge. Severity of the poisoning is often related to the quantity of material ingested, the portion and condition of the plant eaten, the level of ground moisture, and the general health, age and weight of the goat. Some goats can eat some of the bad plants without incident. At other times death occurs even after the slightest ingestion.
Factors that can contribute to the propensity of poisoning in the goat herd include the following.
- Starvation: Most woodland or perpetually wet pastures contain many species of poisonous plants, but are generally ingested only when the goats have no choice due to lack of other feedstuffs
- Accidental browsing: Water hemlock is one main culprit, as it emerges in wet areas which are first to green-up in spring. Animals often accidentally bite off the crown of this plant in their excitement of green pastures, with fatal results.
- Boredom: Some animals on good feed in a dry lot situation or even on excellent pasture, become bored with predictable diets. In spring they are usually quite anxious to eat greening, unpalatable weeds and ornamental plants growing along, or outside of their fences. Goats, especially, are programmed to prefer variety in their diets with ‘‘browse.”
One metabolic disorder related to spring greening and possible goat poisoning is called grass tetany. The sickness is characterized by low blood magnesium levels. The causes of low blood magnesium levels are varied, and are likely to occur when the forage in early spring pastures causes an imbalance which interferes with magnesium metabolism. Grass tetany happens most frequently to mature heavy milkers who are nursing kids less than two months old. Mature goats are more susceptible because their ability to utilize magnesium from body stores to correct low magnesium blood level, decreases with age. The result is often death. Cattle and goat producers lose over several million dollars yearly to grass tetany deaths, while steers, calves, goat kids and breeding bucks are rarely affected.
Symptoms of the disorder include: grazing away from the herd, irritability, twitching of the flank, wide-eyed stare, clumsiness, convulsions, and coma prior to death. These symptoms may occur in as little as two to three hours, making early detection difficult. The first observed symptom may simply be a dead goat, showing evidence of thrashing in the area around the body.
There are some prevention tactics to be utilized which prohibit or lesson the incident of grass tetany in the goat herd. Grazing bucks, dry goats and kids over four months old, can be placed on higher risk pastures, because these groups are less likely to develop grass tetany. Another option is to feed hay to goats prior to turning out on lush pastures for the first 10 to 14 days after kidding in spring.
Poor nutritional practices combined with less than desirable conditions of low-magnesium forage often have lethal results. These situations can be prevented with proper supplementation and timing of pasture fertilization. Immature grasses and cereal grains are already magnesium-low, but cool wet soil reduces their ability to assimilate magnesium. High nitrogen and potassium levels from chemical fertilizers or manure can also inhibit magnesium absorption by the plants. Early spring fertilization presents more risks to goats than pastures fertilized in the fall or late spring. However, high phosphorus levels interfere with a plant’s ability to absorb magnesium, so foregoing fertilization is not the answer.
Studies have shown that inadequate salt intake can also increase the risks of grass tetany. Simultaneous consumption of salt and magnesium may be critical to increasing magnesium absorption. It might help in prevention of grass tetany to avoid supplementation of high levels of potassium, which can affect magnesium absorption. Provide magnesium to freshened goats in the form of free-choice minerals in order to maintain adequate blood magnesium.
Here the flowers and leaves of the water hemlock are apparent. Some confuse this plant with yarrow or elderberry, but it is important to identify it correctly. It shows up early in spring when goats are hankering for variety.
The use of free-choice, high-magnesium supplements on a consistent basis is paramount in preventing herd loss due to spring greening poisoning. Magnesium is naturally unpalatable to livestock so the use of supplements that have been enhanced for palatability to encourage daily consumption is of utmost importance. Blood magnesium levels may fall as quickly as 48 hours after cessation of supplementation!
Another spring greening disease some goat breeders encounter is Polioencephalomalacia (thiamine, B1 deficiency). This neurological disease is caused by thiamine deficiency and can quickly take a goat’s life, if not recognized by the owner. Thiamine is produced by normal bacteria in the rumen but goats on high carbohydrate diets may have disturbed rumen flora resulting in either thiamine deficiency, or over-production of an enzyme that inhibits thiamine. Other cases have resulted from the overuse of the drug Amprolium as a treatment for coccidia eradication. Polioencephalomalacia, which literally means "the softening and necrosis" of the brain’s grey matter, can also be caused by high levels of sulphur in the diet (possibly from iron-eating bacteria in well water), or by goats grazing on mare’s tail (equisetum).
Early on in the course of the disease, the goat may present with a stiff-legged gait, head held high and anxious behavior, but early polio cases often respond partially, if not completely, to thiamine administration within a few hours of initial symptoms.
As the disease progresses, sometimes within six hours, the goat becomes blind and the head may be pulled straight back towards its shoulders. The front legs get stiffer and the goat might fall down, making the abnormal head and neck stance more evident. The pupils will constrict to light, but the eyes cannot react to hand movements. Other rule-outs are tetanus, but those animals will not be blind. One case may not necessarily mean a herd problem, as some "problem" herds routinely require thiamine supplementation.
There are many more nutritional diseases related to land and plant deficiencies, but the previously reviewed diseases are the most likely to affect goats during spring-greening. A plant to watch out for is the water hemlock and/or poison hemlock as it is highly toxic for both humans and animals. Poisoning rarely occurs as it is quite unpalatable. But in early spring, when young plants might get accidentally eaten, the roots, stems, leaves and flowers are always poisonous. The avid goat breeder should look for and learn to identify these plants in the summer when they are large and showy. They are members of the carrot family, and have white umbrella-like flower heads.
Water hemlock is a perennial that begins growth in early spring, and is frequently found in wet, fertile soil. This particular hemlock is five-feet-tall, with thick rootstocks, double compound leaves, (not unlike ferns), and small white flowers in umbrella-like clusters. Its green foliage appears earlier than most other plants, tempting goats to pull at the tender leaves, uprooting the whole plant from still soft soil due to late-winter rains. The roots are the most poisonous part of water hemlock. If the plant is cut open lengthwise you can see air cavities separated by partitions of solid tissue. It is this yellow, odorous, resinous fluid that contains the poisonous alkaloid, which appears at the cuts.
As a preventative, water hemlock plants should be pulled from the soil during the summer when they can readily be found and destroyed. The combination of foliage and roots in considerable quantity is what causes fatalities, while the leaves and seeds alone contain little of the toxic substance.
There are several look-alike plants that are not poisonous but can be mistaken for water hemlock. They include the water parsnip (similar ecology to western water hemlock except that there are no chambers in the roots), cow parsnip (grows in upland and riparian areas, distinguished by large maple-like leaves and upwards growth of two feet), and Angelica arguta (grows in the uplands and lowlands with the bases of its leaf stalks inflated and tubular).
In my own goat herd, I sadly have experienced some devastating goat deaths due to the plant-related spring maladies. These were due to nutritional imbalances, metabolic problems, as well as some high toxicity levels. I found that offering free-choice minerals met the needs of my goats, reduced their attraction to poisonous plants and lowered the incidence of such losses in my herd.