Plants are the major source of feed for herbivorous animals and also used for the treatment of many diseases. Moreover, plants have vital nutritious importance to animals and providing the normal atmospheric oxygen. As animals majorly feed on plants and these plants comprise a large variety of poisons known [1], poisoning in animals consuming these plants is inevitable. Poisonous plants produce their toxic effects after being ingested and/or absorbed by animals, which include physical upset, loss of productivity and death. A variety of poisonous plants have caused extensive losses to the livestock industry in many parts of the world mainly east Africa including Ethiopia [2].

The possibility of founding poisonous plants in hay and forage poses a serious risk to livestock and other animals. There are several contributing factors, which facilitate the occurrence of animal poisoning. Different sensitive species of animals can ingest or exposed to a poisonous plant at normal conditions. It is also more likely to occur in animals which have been moved from one part of the country to another. Sudden onset of disease in a group of animals is the most obvious case among the many indications of plant poisonings [3].

Factors such as route of absorption, dose, physical and chemical nature of the poison, frequency of exposure, species, body size, sex, and general health status of the animal may influence the action of poisonous substances. In addition, chemical factors such as particle size, solubility, toxicity, absorption and excretion rate, affinity for body tissues or fluids, interaction with other drugs, and lacking development of metabolic pathway can have an impact on its occurrence. Liver or kidney insufficiency may enhance toxicity due to poor metabolism or slow excretion of toxicants. Alteration in gastrointestinal pH can change the ionization of drug or chemicals and influence their absorption; presence or absence of food in the stomach affects the toxicity of certain compounds [4].

Plant poisoning of livestock can be diagnosed based on history, clinical syndrome observed, post mortem lesions, evidence of plant grazing and/or browsing, and remains of poisonous plants in the gastro intestinal tract. If poison principle of the poisonous plants is known, confirmatory laboratory tests can be done [5]. Good pasture management such as keeping the desirable forage species productive throughout the grazing season reduces the possibility of animals grazing on poisonous plants. In this case, most poisonous weeds and cultivated plants can be controlled. It may be practical to simply fence off infested areas so that animals do not have access to particularly hazardous weeds. This is one of the most important steps in preventing animal suffering or loss from poisonous plants. Other alternative methods of controlling poisonous weeds are to spray them with approved herbicides and physically or mechanically remove the poisonous plants [6].

Poisonous plants affecting both large and small animals are a major concern for the practicing veterinarian and livestock producer in every country. In countries with higher plant biodiversity, the problem of plant poisoning to livestock may be greater. Plant biodiversity in Ethiopia is very high, as there are about 7,000 species of vascular plants in which some of it could be poisonous [7].

Plant poisoning in livestock can occur due to either accidental ingestion along with grass or obstinate consumption. Animals can consume poisonous plants when pasture is dry while most poisonous plants remain green all throughout the year [1]. Newly imported or animals migrated from other areas could be at higher risk because they are unfamiliar with the strange ingestion of their fresh surrounding [8].

Overgrazing of pastures and ranges probably the greatest factor in causing losses from poisonous plants. The danger of overgrazing is always greatly increased in periods of moisture deficiencies that reduce forage production. However, plant poisoning essentially is a local problem occurring in areas where poisonous plants may form a large proportion of the herbage species available to grazing animals. Poisonous plants are often naturally refused by animals due to their repulsive smell or irritant juices and are eaten only when other herbage pastures is scarce [9]. Some plants may have the potential to penetrate skin of animals and introduce a poisonous chemical and causes an immediate burning sensation of the skin [10].

Among the factors that expose the livestock to the poisonous plants; shortage of feed, nutritional deficiency and sudden exposure were the major problems [1, 9]. Feed shortage can force animals to browse perennial shrubs and bushes while most of these perennial plants have been known to contain toxic secondary metabolites [5]. These plant poisoning cause health problems in livestock with huge economic loss to the pastoralists due to production loss, morbidity and mortality of their animals. Furthermore, it is not customary among local veterinarians to write plant poisoning case reports, thus most of the plant poisonings that occur in the pastoral areas of Ethiopia are not well documented in the literature. Hence, it is imperative to bring the attention of professionals to the effects of poisonous plants on animal health and productivity [11]. Therefore, this study was conducted to fill this gap by identifying the potential poisonous plants to domestic animals and its veterinary importance in selected districts of Afar region, Northeast Ethiopia.

In the present study, from the total respondents (245), about 70.2% (172) of the interviewee were livestock owners and 15.5% (38) and 14.3% (35) were animal health practitioners and traditional healers, respectively. The majorly described predisposing factors for the occurrence of plant poisoning were feed shortage, nutritional deficiency and excessive consumption. The common poisoning seasons indicated were at the end of rainy season (August to September) and during drought time (February to May) but at the beginning of the rainy Season (June to July) was low (Table 1).

According to the present study, a total of 21 plants were identified and documented to have a poisonous effect on livestock. The poisonous plants frequently complained by the respondents were Capparis tomentosa, Prosopis juliflora, Parthenium hysterophorus, Lantana camara, Acacia absynica, Sorghum bicolar, Datura stramonium, Plantago lanceolata, Grass species, Bracken fern (Pteridium aquilinum) and Solanum incanum (Figs. 1-8). The major plant parts that caused poisoning were leaves. This study also revealed that bloating and other GIT disturbances, salivation, bloody urine and inappetence were among the frequently manifested signs by poisoned livestock. Moreover, this study showed that caprine and bovine followed by camels and ovine were the most frequently poisoned animals (Table 2).

The poisonous plants with higher botanical frequency complained by respondents were Capparis tomentosa (156) and Prosopis juliflora (133). The clinical sign with leading veterinary frequency was bloating. Moreover, majority of the poisonous plants mainly occur at the rainy season and causes poisoning after repeated exposure (Table 3).

Poisonous Plants Collected from the study areas.

Fig. (1). Picture of Capparis Tomentosa (‘Andela’)

Fig. (2). Picture of ‘Asihara’

Fig. (3). Picture of ‘Boboe’ita’

Fig. (4). Picture of Solanum incanum

Fig. (5). Picture of Parthenium hysterophorus

Fig. (6). Picture of Lantana Camara

Fig. (7). Picture of ‘Adihara'

Fig. (8). Picture of Prosopis juliflora (‘Datihara’)

Animal poisoning due to plants constitutes one of the most important health problems to livestock in countries with extensive production system [2]. In this study, the respondents have showed that livestock health disorders due to phytopoisoning cause a significant morbidity and mortality in animals in their areas.

The major predisposing factors for the occurrence of plant poisoning in the study areas were feed shortage, nutritional deficiency and excessive consumption. Afar region is one of the pastoral areas of Ethiopia with lower rainfall and limited plant coverage but rich in livestock production potential. This condition showed that there is long dry period and feed shortage in the region. Hence, due to feed shortage, animals are enforced to feed on poisonous perennial shrubs and bushes surviving the environment which are known to contain poisonous metabolites. In addition, there is a sudden consumption of new plants while migrating and excessive consumption of plants grown following short rainy season which contributed to phytopoisoning. Accordingly, the common poisoning seasons complained were at the end of rainy season (August-September) and during drought time (February-May). This finding is in agreement with the similar reports from Wollega, Ethiopia [14, 15].

According to this study, a total of 21 plants were identified and documented to have a poisonous effect on livestock. The poisonous plants frequently described by the respondents were Capparis tomentosa, Prosopis juliflora, Parthenium hysterophorus, Lantana camara, Acacia abyssnica, Sorghum bicolar, Datura stramonium, Plantago lanceolata, Grass species such as Panicum species, Bracken fern (Pteridium aquilinum) and Solanum incanum. Reports from Adama, Ethiopia [16] and from Wolllega, Ethiopia [14, 15] have documented Parthenium hysterophorus, Lantana camara, Sorghum bicolar, Datura stramonium, Plantago lanceolata, Panicum grass species and Bracken fern (Pteridium aquilinum) as the most frequently implicated poisonous plants which are in agreement with the current finding.

In addition, the importance of Snowdenia polystarchia, and Sorghum bicolar as causes of livestock poisoning have been reported [17]. Similarily, Lantana camara causes similar effect in Columbia [18] and in Swaziland [19]. Bracken fern is also widely distributed in many parts of the world including Ethiopia. Its existence and importance as a cause of bloody urine has been previously shown in different regions [20] and it has also been reported in South Africa [21]. Various studies conducted on this issue indicated that poisonous plants may grow together with forage plants; therefore, readily accessible to grazing animals. Under normal conditions only a few poisonous plants can be considered sufficiently palatable. But during shortage of pasture and forage animals may be forced to browse these poisonous plants [16, 22, 23].

The respondents of this study showed that when camels and small ruminants feed on ‘Andela’ (Capparis tomentosa) the leaf causes bloating but its seed pod is fatal to both animals. A leaf of ‘Adihara’ causes bloating in goats but it is a good feed to other large animals. The leaf and fruit of ‘Asihara’ causes bloating in animals especially camels and goats but after repeated exposure it becomes edible without serious effects. It grows at the end of rainy season or any time in irrigation fields. A leaf of ‘Bobe’eita’ is fatal to goats but it is a common feed to camels and it is commonly found in high hills. The seedling stage of ‘Basinga’ (Sorghum bicolar) can cause bloating in all animals but it may kill animals if it is overtaken at the same time. A leaf of ‘Datihara’ (Prosopis juliflora) is not palatable by animals due to its repellant nature but during drought times animals may be enforced to consume some as it is ever green and it causes bloating. Although its seed pod is palatable by animals, it can cause lower jaw dislocation when it is consumed after it is dropped and decayed in the ground and when it is not consumed together with other feed types [1]. Any type of grass especially Panicum grass species emerging at the beginning of rainy season have the potential to cause bloating and/or diarrhea as the animals consume much of it at a time following long dry periods.

The major plant parts that caused poisoning were leaves as these parts are easily accessible and repeatedly fed by animals. This study also revealed that bloating and other GIT disturbances, salivation, bloody urine and inappetance were among the frequently manifested signs by poisoned livestock. This finding is in agreement with the reports in Wollega, Ethiopia [14, 15]. Furthermore, this study showed that caprine and bovine followed by camels and ovine were the most frequently poisoned animals which did not agree with the reports from Wollega. This could be due to the difference in livestock species abundance in which small ruminants and camels constitutes majority of livestock population in the current study area.

The clinical sign with leading veterinary frequency was bloating as the poisonous plants primarily affect the digestive system of animals. Moreover, majority of the poisonous plants mainly occur on the rainy season because following the rainfall a lot of plants will grow up and causes poisoning after repeated exposure. This finding is in line with the findings in Wollega, Ethiopia [14, 15]. The poisonous plants with higher botanical frequency identified by respondents were Caparis tomentosa and Prosopis juliflora which differed from the above reports because of the difference in climatic conditions and plant coverage in the current study areas.

This study identified and documented a total of 21 plants having a poisonous effect on livestock. The poisonous plants with higher botanical frequency were Capparis tomentosa and Prosopis juliflora. Feed shortage, nutritional deficiency and excessive consumption were the major predisposing factors for the occurrence of plant poisoning. The common poisoning seasons were at the end of rainy season and during drought time. This study also revealed that bloating and other GIT disturbances were among the frequently manifested signs by poisoned livestock. Moreover, this study showed that caprine and bovine followed by camels and ovine were the most frequently poisoned animals. Hence, phytopoisoning is commonly occurring and challenging health of livestock in the area. Therefore, proper range management should be practiced to decrease the danger of plant poisoning to animals and all concerned bodies should collaborate on pasture and water development programs to minimize the risk of enforced consumption of livestock on poisonous plants due to feed shortage.