Toxic/Poisonous to Livestock Plants of Mongolian Rangelands

Toxic/Poisonous to Livestock Plants of Mongolian Rangelands Daalkhaijav Damiran and Enkhjargal Darambazar Eastern Oregon Agricultural Research Center, Union, OR-97883, Oregon, USA Briefly about Mongolian rangelands Mongolian natural rangeland covers 128.8 million ha. There are about 2823 vascular plant species and over 662 genera and 128 families have been recorded (Gubanov, 1996). Mongolian rangeland can be divided into 4-5 zones according to locations that differ in landscape, annual and seasonal climatic conditions, species composition and growth rate: high mountains, forest-steppe, steppe, desert-steppe and desert belt. Desert-steppe and desert belt account for 44.6% of the pastureland and the main domestic herbivores are camels and goats. Forest-steppe and high mountains accounts for 27.4% and the main domestic herbivores are cattle, sheep, horse and yaks. The rest 28% of the pastureland belongs to steppe and is the main stock-raising zone for cattle, sheep, horse, camels and goats. Mongolia is the only country of Eurasia to retain huge areas of steppes vegetation (Gunin et al. 1999). Mongolian rangeland is distributed over the extremely continental climate with harsh continental and extremely unpredictable climatic conditions. North and central part of country’s isohyets of 250-300 mm annual rainfall and over the southern-desert part of the country 50 to 100 mm annual rainfall. In Mongolia, the growing season is short and very dependent on climate, particularly rainfall. New growth in the forest steppe and steppe zones begins in mid- April, whereas elsewhere it may not begin until mid-May. Growth is often very slow, and the grazing of young grass may only be possible after 30-35 days. Livestock, therefore, 1 consume small amount of fresh grass/forage in April/May along with larger amounts of senescent material. From June to September, nearly the entire intake is of fresh forage. Some forage plant species reach their final growth stage in August and show signs of senescence, although other plant species may have vegetative growth till mid-September and some remain green until mid-October. During the growing season some areas remain ungrazed to be harvested and conserved as hay or left to provide standing forage during the winter (Daalkhaijav, 1995; Murray et al., 1998). Therefore Mongolian animals changeover from consumption of dead grass to fresh forage over a period of 10-11 weeks, and from fresh forage to standing dead over 5-6 weeks. This has the advantage in that it allows development of stable activity of rumen microbes on both diets due to gradual changeover (Daalkhaijav, 1995). Thus Mongolian livestock may rely on senescent grasses as its main feed for about 200 days. From the point of the view of toxicology there are some advantages. This gradual changeover prevents animals from diarrhea which is caused by lush spring pasture. Animals’ long time foraging by standing dead has some positive effects, in particular, it reduces possibility of plant poisoning, since plants usually contain more toxicants in their growing (green) season. Mongolian traditional livestock management method such as keeping all types of animals in one grazing together might allow them to avoid plant toxicities, due to a possibility of one type of animal influencing the other beneficially by consuming the plants which might be toxic to others by those which are resistant. Also Mongolian nomadic way of leading animal husbandry that is a selective use of rangeland through year round moving from one pasture to another may have a positive effect to avoiding animals poisoning. 2 Livestock number in Mongolia is increasing significantly in last couple of years. Heavy grazing results in strong vegetation degradation. All plant community indices decline, community structure is simplified, and floristic richness declines (Gunin et al. 1999). Such vegetation degradation will drive to decreasing pasture yield, which eventually would likely to lead to limiting forage choices for animals and increasing animal poisoning incidents from poisonous plants and losses. Thoughts on toxic /poisonous plants of Mongolian rangelands Plants contain toxic substances to protect themselves from herbivore. Animals also have been exposed to toxic constituents of plants during their long period of co- evolution and have developed numerous biochemical strategies for detoxification of poisonous compounds (chemical defenses). Detoxification in the digestive tract is very common and evolved ways of detoxification of invertebrate and vertebrate. These include chemical and microbiological detoxification mechanisms in the gastrointestinal tract, a host of detoxifying enzymes in the liver and similar enzymes in all other tissues (Cheeke, 1998). From ancient times the Mongols have herded five kinds of animals (sheep, goat, cattle/yak, horse, and camel) in the severe Central Asian climate, have grazed them throughout the year on open pastures. Investigation of the relationship between plant toxicants and Mongolian range animals should be of higher scientific and practical as well as theoretical interest since Mongolian range animals have been through a long evolutionary process to build up protection from poisonous plants (Figure 1) and they can obtain over 95% of their annual feed intake requirements from pasture along. 3 There were not so much available published sources, specifically focused on toxic plants on Mongolian rangelands. We’ve screened some key review books related to rangeland and forage plant investigation (Yunatov 1954, Tserendulam 1980, Jigjidsuren 1984, and Ulziikhutag 1984, 1985, Grubov 2001) of Mongolia. Special chapters or parts defined to plant toxicity/poison were not found (toxic dose, toxicity rating, dangerous parts of plant, signs, first aid, and etc.,) in those reference materials, although when they give descriptions about nutritive significance they mentioned, which plant is the most toxic, when, and its species susceptibility. However, this information (Table1) about plant toxicity was based mostly on folk sources obtained from herdsmen, which present difficulties to make “inferences”. Information on species susceptibility, for example, which type of animal how much (consumed amount animal body weight ratio) is toxicated was not clearly determined; it was stated that Senecio jacobaea is toxic for sheep and goats, which was not similar in North American studies (Cheeke 1998) about this species toxicity. It should be noted that there were included only those plant species which cause significant toxicity, but were not mentioned moderately or mild toxic plants at all. So the table presented here is made by gathering and abstracting the information from various kinds of sources and summarizing it to make a brief report. Recently a research was done about a toxic plant called Ammopiptanthus mongolicus (Mongol monkh khargana) and the scientists from the Research Institute of Animal Husbandry, Mongolia have derived a component of alkaloid type and found it effective for promoting animal growth, which is now being introduced to practice. 4 Historically, the Mongols have accumulated wide experience of treating of poisoned animals. Medicinal preparation used by the Mongols can be divided into three groups: of animal, vegetable and mineral origin. They include sour milk, airag (fermented mare’s milk), dairy home-brew, meat and bone broth, bile, blood, horns and bones of various wild animals, soot and ashes of individual tree species, various plants, natural salts, agates, sulphur, copper, silver and others (Dash 1990), either in natural form or as components of compound prescriptions. Bloodletting is very widely used on poisoned animals. For horse alone, herders use more than 30 points for bloodletting. Though traditional methods of poisoned animal treatment gradually ignored for years in Mongolia. Toxic/poisonous plants and human health concerns Like other nations, the Mongols have number of ways of avoiding natural toxicants. One example is the Mongols drink green tea, prepared with some milk and a pinch of salt, brewed by boiling it for couple of minutes. Generally, consumption of high tannins is the cause of high incidences of esophageal cancer. Tannins in tea have also been implicated. According to Cheeke (1998) addition of cream or milk to tea eliminates this effect, because of formation of a protein-tannin complex. Sodium of salt would be also useful, because it will form metal-tannin complex. Low incidence of esophageal cancer among the Mongols might be explained by this, by adding milk and salt to green tea. There are number of such kind of examples. The Mongols should be more concerned, however, about natural toxins, especially plant toxins due to their preferences to animal originated food, which is related to the traditional nomadic way of life. There is some incidence of mental or neurological 5 diseases mainly among people in some parts of semi-desert and desert zones of the country who make their living by raising goats, which might be partly related to their consumption of raw milk from goats grazed on arid land plants which tend to have elevated contents of toxic chemical substances. Goats would be a more likely source of contaminated milk than cattle, because of their tendency to eat many poisonous to other animals plants, since they are more resistant to many plant toxins. For example, they readily consume Senecio spp. which contain pyrrolizidine alkaloids (Cheeke 1998). Also, herders’ children spend all day long on pasture land herding

Load more