Alkaloids in Australian rye ergot (Claviceps purpurea) sclerotia: implications for food and stockfeed regulations

Abstract

Rye ergot (Claviceps purpurea) occasionally causes toxicity (chiefly expressed as hyperthermia) in Australian livestock, either as a result of grazing infected annual (Lolium rigidum) and perennial (L. perenne) rye grasses, or if the ergot sclerotia produced in rye grasses contaminate grain crops used as stockfood. Alkaloids in 30 samples of Australian rye ergot sclerotia taken from rye grasses and grain screenings, and some feed samples contaminated with rye grass ergot sclerotia, were assayed by high performance liquid chromatography. Samples originated from across southern Australia. Ergotamine was the dominant alkaloid in all samples, followed by a-ergocryptine, ergocornine, ergosine and their respective -imine epimers. Ergotamine concentrations in sclerotia ranged up to 2257 mg/kg (as received basis). Ergocristine was a very minor component (<50 mg/kg) in all samples. Total alkaloids in freshly collected sclerotia ranged from 1003 to 3321 mg/kg (0.10 to 0.33%), and up to 3766 mg/kg with epimers included, although lower concentrations were found in samples stored for some time. Alkaloid profiles in sclerotia were all very similar, and concentrations did not appear to be related to size of sclerotia, source region, nor to the rye grass or grain from which they were taken. Previous cases of toxicity in livestock are reviewed and several new cases are reported. The implications of variable alkaloid contents of rye ergot sclerotia are discussed in terms of Australian food and stockfeed regulations.

A review of potential contaminants in Australian livestock feeds and proposed guidance levels for feed

“…For practical purposes it is preferred to propose a low level rather than a zero tolerance and a level of 0.01% ergot sclerotia in the total diet of cattle, goats and sheep is proposed, with an equivalent alkaloid content limit of 0.2 mg/kg. This limit is lower than that suggested by Blaney et al (2009), and lower than current state regulations, but given the very low frequency of contamination of bulk grain in Australia, it appears achievable by industry and consistent with the principle of as-low-as-reasonably-achievable.…”

“…A large proportion of the alkaloid content of sclerotia is represented by these epimers and it is unclear how much is present in developing sclerotia and how much is a result of isomerisation during storage. While relatively inactive in laboratory animal models (Stoll 1952;Goodman et al 2011) there is insufficient information on the potential for the epimers to be converted back to active isomers in the rumen and risk assessment should consider the total alkaloid content of feed (Blaney et al 2009). …”

“…Infection of cereal crops, including rye, oats, wheat and barley is rare in Australia mainly due to the dry conditions prevailing during flowering of these crops but occurs in Europe and North America (Blaney et al 2009). Consequently poisoning of livestock occurs only occasionally and in a few localities either as a result of grazing infected rye grass or if rye grass is not controlled in wheat or barley crops and grain becomes contaminated with ergot sclerotia during harvest (Blaney et al 2009). Management of contamination of stock food might need to consider levels in grain and in hays prepared from infected pastures.…”

“…The alkaloid profiles of ergot sclerotia from south-western and eastern Australia are very similar. Ergotamine and ergocryptine are the major components with lesser concentrations of ergocornine and ergosine (Blaney et al 2009). Ergot alkaloids may be converted to their C8 epimers on storage (i.e.…”

“…In the few Australian cases of livestock poisoning severe hyperthermia was observed in ruminants fed 1-3 mg alkaloids/ kg. To avoid severe poisoning it was suggested (Blaney et al 2009) that the total alkaloid content of feed should be restricted to <0.4 mg/kg, which for sclerotia with an alkaloid content of 0.2% equated to the existing 0.02% limit for ergot sclerotes in stock food in Queensland (Qld 1997).…”