Plant poisoning in goats
Abstract
As herbivores goats are at risk of plant poisoning. Poisoning may occur if goats are accidentally fed plant cuttings or through contamination of feed, but as goats are agile and inquisitive they can escape from their enclosure and encounter poisonous plants in gardens or woodland. They may also eat plants they would normally avoid if other forage is unavailable. Poisoning with plants containing grayanotoxins (Pieris and Rhododendron species) or cyanogenic glycosides (e.g cherry laurel, Prunus laurocerasus) is very common in goats. Other plants that have caused poisoning in goats include yew (Taxus species), oak (Quercus species), hemlock (Conium maculatum), leylandii (× Hesperotropsis leylandii), box (Buxus sempervirens) and plants containing cardiac glycosides such as oleander (Nerium oleander) or pyrrolizidine alkaloids such as ragwort (Jacobaea vulgaris). Sudden death is frequently the first sign of plant toxicosis in livestock. Management of plant poisoning in goats is supportive including removal from exposure, and providing analgesia, rehydration and potentially a rumenotomy for plant exposure in valuable animals.
Goats are browsers and may eat a variety of plants. They are also agile and inquisitive animals so may gain access to toxic plants if they escape from their enclosure into an ornamental garden or woodland, for example. If plant poisoning is suspected it is important to investigate potential sources such as plants growing in the vicinity, contaminated feed or cuttings to which they may have had access (e.g. been accidentally fed or left in their enclosure). A site investigation may be more useful and quickly identifies possible suspects compared with attempting to identify chewed plant fragments in the rumen or regurgitated rumen content (Harwood, 2021).
Grayanotoxin poisoning is very common in goats (and sheep). Numerous cases are reported in the literature involving Rhododendron spp. (Figure 1a) (which includes azaleas, Figure 1b) (Casteel and Wagstaff, 1989; Puschner et al, 2001; Pereira et al, 2008; Vargas et al, 2014; Kim et al, 2017) and Pieris species (Figure 1c) (Smith, 1978; Smith, 1979; Hollands and Hughes, 1986; Plumlee et al, 1992; Baert et al, 2005; Eo and Kwon, 2009; Bischoff et al, 2014). Kalmia species (evergreen ornamental shrubs) also contain grayanotoxins. Mortality can be high in goats with grayanotoxicosis; in the 60 field cases described above 22 goats died, a mortality rate of 36.6%.
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