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  Toxins: All my sources agree that its principle toxin is ranunculin which releases protoanemonin. This can be an irritant when fresh, potentially causing mouth irritation, excessive salivation and diarrhea. Because portoanemonin is unstable and turns into a yellow oil or volatilizes, Cheeke says that it is non-toxic when dried in hay (Natural Toxicants in Feeds, Forages and Poisonous Plants, Peter R. Cheeke, 2nd Edition pg. 449). Both Cheeke and Knight et al ( A Guide to Plant Poisoning of Animals in North America) say that feeding trials indicate that buttercup does not seriously affect cattle or sheep in most circumstances. However, bur buttercup is responsible for many sheep deaths, so do not teach your sheep to eat this.
      Protoanemonin has a bitter taste which can be passed into the milk of lactating animals, so I would caution dairies against teaching their animals to eat this plant unless they do milk taste tests to determine results.
      If I were to train animals to include this food in their diet I would go forward very cautiously. I would watch them closely for signs of irritation and ensure that they have plenty of other forage to mix with it both during training and in pasture. If I saw any negative signs I would stop at once and provide them with intestinal protectants (see your vet) until the plant has been eliminated from the digestive tract. I would bale it in hay as a way of controlling it.

Canada Thistle

Cows have been trained to eat this weed.
A native of southeastern Eurasia, Canada thistle was originally introduced to Canada as a crop seed contaminant in the 1700s. It spread so rapidly that by 1795 there was legislation in Vermont requiring landowners to control the weed. In addition to reproducing by seed, it can send out lateral roots 3 feet below ground to sprout new plants. It can also regenerate from root fragments less than an inch in length.
     Toxins: The toxin in Canada thistle is nitrate According to A Guide to Plant Poisoning of Animals in North America by Anthony Knight and Richard Walter "There is considerable variation as to what constitutes a safe level of nitrate in animal feeds because of different factors that influence nitrate metabolism. Under normal circumstances nitrate is reduced in the rumen in a series of steps from nitrate to nitrite to ammonia and eventually to microbial proteins. It is the rapid formation and absorption of large quantities of nitrite and not nitrate that causes poisoning." They go on to say that the speed of absorption depends on the rate of adaptation to nitrate of rumen microorganisms the rate and amount of nitrate ingested and the amount of carbohydrates in the rumen. When corn or molasses is present in the rumen nitrate is more rapidly converted to ammonia without the accumulation of nitrite. Rumen microbes are also capable of adjusting to nitrate if given appropriate time. Therefore when starting on training a nitrate accumulating forage, be sure that animals only eat a small amount initially and then increase over time. As always, it's important that your animals have a variety of forages to choose from.
      Grazing Prescription: Research indicates that topping or grazing the plant stimulates new growth. The plant must be grazed repeatedly to weaken nutrient transfer to roots and reduce its ability to regrow. Shoot populations can be reduced to very low levels by regular, short-term, rotational grazing.
      Related Plants: Cows trained to eat Canada thistle chose to add bull and musk thistle to their diets when in pasture. If you don't have Canada thistle, but do have these types of thistle, go ahead and train your animals to eat them.
Additional Resources: U.S. Forest Service databaseNPS Fact Sheet


Scentless Chamomile/ Scentless False May Weed (Anthemis arvensis, Tripleurospermum perforaturm (Merat) or Matricaria perforata )
      Here's the only thing I've been able to find on this plant so far: From "Natural Toxicants in Feeds, Forages and Poisonous Plants," Peter R. Cheeke, 2nd Edition pg. 449  "...does not seem to be toxic to livestock." It does not appear in A Guide to Plant Poisoning of Animals in North America. I would try feeding it to my animals.

Distaff thistle (Carthamus lanatus)

I've trained cows to eat this weed
Other Common name(s): saffron thistle, false star thistle, woolly safflower, woolly star thistle, downy safflower
       This native of the Mediterranean region is a spiny annual that can grow up to 3 1/2 feet tall. We know that efforts to control the thistle began as early as 1871 in Australia, but in spite of their ongoing efforts, it is still reported in every Australian state (1). For more on the plant itself, download this Fact Sheet from Oregon.
        Nutrients: Peggy Rathmann harvested a late-growing distaff thistle in October and had it tested for nutritional value at Utah State University. It compared favorably with the nutritional value of Alfalfa, and contained 17% crude protein, 34% NDF and 57% TDN.
       Toxins: There are no known incidents of poisoning due to distaff thistle. Based on a report by San Feliciana, et al. (2) the plant contains sesquiterpene glycosides. This is similar to what is found in spotted knapweed which cows were successfully trained to eat at Grant-Kohrs Ranch national historic site. In general, animals are more successful eating terpene-containing plants when they have adequate protein.

Field Scabious (Knautia arvensis)

Cows in Canada have been trained to eat this weed using my process.
      I've found nothing about this plant in any of my toxin books. I did find this in, a European project to "Realize the Economic Potential of Sustainable Resources - Bioproducts from Non-Food Crops: "It is now regarded as a potential oilseed crop: the seeds contain about 25 percent oil, of which some 33-40 percent is in the form of the saturated caprylic and capric acids. These acids are being increasingly used in high-performance oils for jet engines and
other lubricants of high quality, and also in the preparation of some valued dietary fats. At present, the only directly available sources of these acids are coconut and palm kernel oil, which are imported principally for their content of lauric acid, used in soap and detergent manufacture. A locally grown source of these acids would be welcomed by the oleochemical industry; preliminary agronomic studies have been undertaken at Sonning during recent years."
      My one caution would be about timing of grazing. I found a fact sheet from Alberta that said that wildlife and cattle nip the flowers off which could facilitate seed spread and another piece that said that seeds were viable almost as soon as the flower blooms. If that's true, I'd want to graze it early.

Gorse (Ulex europaeus)

This is a spiny, perennial, evergreen shrub in the Pea Family growing to over 2 metres. It has small leaves terminate in rigid spines, bright yellow flowers surrounded by a velvety calyx. Flowers develop into black seedpods with dark hairs.
Our November sample of gorse indicated that it is lower in protein than alfalfa and has moderate total digestible nutrients.
       Toxins: There are no known incidents of this plant causing animal poisonings.
       Timing of Grazing: Those in Australia who have had success using grazing to control gorse note that it is best to graze young plants that have not yet grown the large spines common on the mother plants. Since younger plants are generally protected by the mother plants, fire has been used to rid the area of the large plants and then animals have eaten young sprouts.

Orange Hawkweed (Hieracium aurantiacum)

I've found nothing that indicates this plant can not be eaten. Thanks to Geneve Dagenais who found this information regarding a native hawkweed species:
Handbook on grazing values of range plants of BC by research station, Kamloops Canada dept of Ag 1964 by Alastair McLean, ER Smith and WL Pringle. Grazing Preference: High for all stock in summer. Flowers in mid-July and august, soon becoming harsh. Nutritive Value: medium protein in spring, low when mature. Crude Fiber medium in spring, medium to high later in season. Indicator Values: Presence on grazed range indicated proper use. Special remarks: A preferred forage plant but of low yield due to sparse growth and basal leaves. Does not stand up to heavy grazing.

Italian thistle (Carduus pycnocephalus L.)

I've trained cows to eat this weed.
       This is a vigorous annual thistle that originated in western and southern Europe. It arrived in California during the 1930s and has since become a serious weed problem. It occurs in a variety of disturbed habitats and germinates rapidly and in large numbers. It is most abundant in coastal areas and occurs as a weed of pastures, ranges, roadsides, rural areas, fallow cropland, railroad rights-of-way, field margins, and ditchbanks (Goeden and Ricker 1978). A variety of herbicides have been used on C. pycnocephalus, but they give only temporary control (Wheatley and Collett 1981). Ranchers report that if they cut the thistle, cows will eat it after it wilts.
        Nutrients: We have not tested for nutrient content.
       Toxins: Though some Carduus species are known to accumulate nitrates in toxic quantities, C. pycnocephalus has not been incriminated as a toxic weed (Goeden 1974).

Leafy Spurge (Euphorbia Esula)

I have trained cows to eat this weed.
This is another Eurasia native that arrived in North America as a seed impurity around 1827. A perennial it reproduces by roots and seeds. Seeds may be viable for up to 8 years. It is commonly believed that cattle will not eat leafy spurge. However, there is anecdotal evidence to the contrary. For example, a rancher in North Dakota fenced his cattle into a small pasture with grass and leafy spurge. His plan was that once the cows had eaten all the grass. he would move them and then use an herbicide on the leafy spurge. When he returned to move the cows they had eaten all the leafy spurge. Other ranchers say that their cattle will eat it when it is not a monoculture. Terpenes appear to be the aversive toxin in the plant. Experiments with both sheep and goats have shown that protein increases their ability to consume terpene-containing foods. Click here for more informatin on leafy spurge.

Multiflora rose (Rosa multiflora)

Cows have eaten this plant.
This plant was introduced from Japan as rootstock for ornamental roses. In the 1930s the U.S. Soil Conservation Service promoted it for erosion control and living fences and in the 1960s the Virginia Highway Department planted it in interstate medians to reduce headlightglare and provide a crash barrier. One multiflora rose can produce as many as 500,000 seeds per year and seeds can remain viable in the soil for 10 to 20 years.
Toxins: I have found none listed, and I have found no information indicating problems with animals eating this plant.   However, since all plants contain toxins I would be sure that animals have a variety of forages to mix with this plant.
Grazing Prescription: According to the National Park Service, frequent, repeated cutting or mowing at the rate of three to six times per growing season, for two to four years, has been shown to be effective in achieving high mortality of multiflora rose. So, if eradication is you goal, put your four-legged mowers to work on your multiflora rose at that rate. If that's more fencing and labor than you care to invest, think of it as forage.

Oxeye Daisy

I've found nothing about this plant in any of my toxin books. As part of the Asteraceae family it likely contains sesquiterpene lactones. I have found numerous references to sheep, goats, horses and cattle eating it. I've also found notes that the flavor of milk may change when dairy animals eat this plant.
Ox-eye daisy spreads through abundant seed production and vegetatively by rooting underground stems (rhizomes) (Griswold 1985). Georgia (1914 found that seeds can bcome viable 10 days after the flower opens, and according to Salisbury (1942) an oxeye daisy plant may produce over 2,500 offspring per year. The plant can also resprout if the roots and rhizomes are not completely removed. Seeds can also remain viable for long periods of time. In a rial conducted by Toole and Brown (1946), 82% of the seeds were still viable after 6 years and 1% of the seeds were viable after 39 years.
The effects of intensive cattle grazing on oxeye daisy were assessed in southwestern Montana by B.E. Olson and R.T. Wallander. They found that two years of intensive grazing reduced densities of oxeye seedlings and rosettes. Though the study showed no effect on densities of adult plants compared with densities in adjacent, ungrazed exclosures during the two year period of the study, they believed that by reducing densities of the seedlings and rosettes, densities of adult plants would have decreased in subsequent years had the study been able to continue. They also found that the intensive grazing had minimal impact on perennial grasses in the pastures. Further, they found that overall use on the daisy was similar to use on the other vegetation, so there was no strong avoidance to the plant.
It's important to note that biting off the flowers promotes the rapid development of many lateral stems. In addition, Howarth and Williams found that of the seeds passing through the cow somewhat less than 40% are still viable. Considering that each flower can produce 1,300 to 4,000 seeds (Dorph-Petersen 1925), a 40% seed survival rate means you should be careful how you manage your animals if your goal is not to spread the plant to unaffected areas.
References - Drawn from "The Identification, Distribution, Impacts, Biology and Management of Noxious Rangeland Weeds," Roger Sheley, an October 14, 1994 report for the Interior Columbia Basin Ecosystem Management Project Scence Integration Team Terrestrial Staff Range Task Group
Dorph-Petersen, K. 1925. Examinations of the occurrence and vitality of various weed seed species under different
conditions, made at the Danish State Seed Testing Station during the years 1896-1923. Rep. 4th Int. Seed Test. Congr.
Howarth, S.E., and J.T. Williams. 1968. Biological flora of the British Isles. J. Ecol. 56:585-595.
Georgia, A. 1914. A manual of weeds. MacMillan, NY. 593 p.
Salisbury, E.J. 1942. The Reproductive Capacity of Plants. G. Bell and Sons Ltd, London.
Toole, E.H., and E. Brown. 1946. Final results of the Duvel buried seed experiment. J. Agri. Res. 72:201-210.

Purple starthistle (Centaurea calcitrapa)

This is a biennial that sometimes acts as an annual or a short-lived perennial. Mature plants are 1 to 4 feet tall, have a stout taproot, and are densely and rigidly branched. Purple starthistle is native to Asia Minor from a region between the Black and Caspian seas. It was first detected in California near Vacaville in 1886 (1). Similar in some respects to yellow starthistle, this is an aggressive Centaurea, that is a problem on annual rangelands in the San Francisco Bay area. it tends to occur on sites more mesic (moist) than those occupied by yellow starthistle. When the two species occur together, purple starthistle grows on heavier bottomland soils. Grazing animals generally avoid purple starthistle, but may eat the young rosettes if other feed is not available.
        Nutrients: We sampled purple starthistle with and without spines and its roots and found that in all cases, it is comparable to alfalfa in nutritional value. As the root was being dried it gave off an aroma similar to a sweet baked potato. A 2002 study showed that ethnic Albanians living in Italy gather and eat the plant's young whorls. Researchers have also found that extracts from the plant do a better job of degrading milk caseins and suggest that these extracts should be used as an alternative to commercial animal rennets in the manufacture of cheese.
        Toxins: There are no known cases of poisoning of animals eating purple starthistle.

Russian Thistle (Tumbleweed - Salsola kali, Salsola tragus)

I have not trained animals to eat this plant, but it has been used in the past as a forage during drought. This 2003 North Dakota State University Fact Sheet describes how to use it as a feed for sheep and cattle. They note that "Russian thistles, cut in the blossom stage and carefully cured as hay, contain about the same amounts of protein as alfalfa. The total digestible nutrients have been estimated at 10 to 15 percent less than those in alfalfa hay."
      This plant is a Eurasian native. The confusion in the latin name for this species is due to a variety of thistles that look very similar. Be prepared to look up information under both names for the best results. Currently the plant growing in coastal zones is known as S. kali, while the more prevalent species is called S. tragus. Because this plant is very salt tolerant and flourishes in conditions that would cause problems for most other plants, "it is an arid-lands forage of considerable value. When young and green, it is palatable and nutritous for sheep and cattle, but not necessarily for horses." (Toxic Plants of North America, Burrows and Tyrl, first edition, pg. 357.) Most resources suggest that as the plant matures, the spines harden, and they attribute the spinyness to the plant's reduced palatability. In fact, it may simply be because nutritional value declines.
      Toxins: This plant can be a nitrate accumulator, and nitrate levels increase as the salinity of the soil it is growing in increases. Although diarrhea may be a consequence when sheep subsist on Salsola for several weeks, more important is a rare, acute neurological/metabolic problem following ingestion of large quantities of Salsola in only a few hours. This problem is a result of the oxalates in the plant. (Toxic Plants of North America, Burrows and Tyrl, first edition, pg. 357.) According to A Guide to Plant Poisoning of Animals in North America (Knight and Walter 1st edition, pg. 265-266), "Supplementary dicalcium phosphate in the diet before and during high-risk oxalate exposure is an efective means of reducing losses. High levels of dietary calcium bind oxalate in the rumen as insoluble, nonabsorbable calcium oxalate. Calcium may be provided to the animals in a salt mix (75 lb salt, 25 lb. dicalcium phosphate) or in pelleted alfalfa at a 5 % concentration and fed at the rate of .5 lb. per sheep/day. Livestock diets can also be supplemented with hay to help reduce the total intake of oxalate-containing plants."
      Grazing Prescription: You can graze this plant with the following, normal precautions:

    1. Make sure hungry animals are not sent into large stands of this plant.

    2. Make sure they have a variety of forages to choose from

Additional Resources: U.S. Forest Service database

Spotted Knapweed (Centaurea Maculosa)

I have trained cows to eat this weed.
This plant is a native of Central Europe, Russia, Caucasia and western Siberia. It was accidentally imported in the 1800s and since then has spread to every state but Arizona, Georgia, Mississippi, Oklahoma and Texas. An average plant lives 3 to 7 years and is capable of producing 500 - 4000 seeds per square foot per year. Seeds remain viable for 5 to 8 years.  
Toxins: Sesquiterpene lactones are found in Spotted Knapweed. They do not cause any harm to animals grazing them in pasture with a mixture of other forages and cows ate it with gusto.
Grazing Prescription: Plants are less likely to regrow if allowed to form flower stalks before grazing. I found that plants sent up secondary flower stalks after being grazed once. So if eradication is your goal and you won't harm your preferred forage, send animals back for a second try. Still, you'll have to work for several years. Research indicates that it takes three to six years of consecutive grazing to see a reduction in stems, smaller plants and lower seed production.
See this NPS Fact Sheet for More Info

Sulfur cinquefoil (Potentilla recta)

According to reviews by Powell [60] and Werner and Soule [91], sulfur cinquefoil has a tannin content of 17-22% dry weight that likely lowers its palatability relative to many other forage and browse species. Even when forage and browse choice is limited, cattle have been reported to graze the bitter-flavored spotted knapweed preferentially over sulfur cinquefoil [66]. There are no reports of sulfur cinquefoil toxicity to animals that consume it. I have not trained cows to eat this plant, but I have seen those I trained to eat spotted knapweed graze it with gusto.

Additional Resources: U.S. Forest Service database

Dalmatian (linaria dalmatica) and Yello
w (linaria vulgaris)

I have trained cows to eat Dalmatian toadflax and will be training them to eat Yellow Toadflax in 2009.
These "weeds" were brought to the United States as ornamental, medicinal, magical and dye plants. For those of you who find these plants a pain in the rear, you might like knowing that they were once used as a poultice for hemmorhoids. To make your own, chop the whole plant, boil it in lard until crisp then strain it to get a fine green ointment. I don't guarantee any results, I just found the information on the internet.
     Toxins: According to Toxic Plants of North America (Burrows and Tyrl, 1st edition, pg. 1098), both plants contain a series of quinazoline alkaloids, vasicine, vasicinone, and deoxyvasicinone. They also contain several flavonoid glycosides...including linarin and linarisan. Intoxication problems have not been reported; however, vasicine causes bronchodilation, hypotension, and uterine stimulation.
      Grazing Prescription: I will be trying this plant slowly. Sheep and goats show no ill affects from eating either plant and I anticipate no negative effects for the cows.
      Additional Resources: U.S. Forest Service database

Yellow starthistle (Centaurea solstitialis)

Cows have eaten this weed in pasture in California
Yellow starthistle is annual that grows 2 to 3 feet tall. The weed probably arrived as a contaminant in alfalfa seed in the mid-1800s to early 1900s. They are "allelopathic" meaning they produce chemicals in the soil which reduce the ability of other plants to grow in their vicinity. For additional information visit this UC Davis sponsored website about Yellow star thistle.
        Nutrients: Based on what we know about how animals choose what to eat and the fact that cattle have successfully eaten it in research projects it is fair to assume that this plant will have good nutritional value.
        Toxins: There are no known cases of poisoning of cattle eating yellow star thistle. In fact, cows goats and sheep have been successfully used to control the plant in research done at UC Davis. However, Yellow star thistle does contain an unidentified compound that causes chewing disease in horses. The compound damages the area of their brains that controls fine motor movements, including mouth and lip movements. According to Burrows and Tyrl "There seems to be cumulative storage of the toxins rather than cumulative effect or damage. Thus amounts of the plant that migh otherwise produce disease - .... 100% of body weight - may be eaten without deleterious efect if not consumed on a continuous basis."

Plant Information

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