Sapogenin levels in Narthecium ossifragum plants and Ovis aries lamb faeces during two alveld outbreaks in Møre og Romsdal, Norway, 2001

Content of the Saponin Protodioscin in Brachiaria spp. from the Eastern Plains of Colombia

Protodioscin is used as a marker of saponin content that could cause hepatotoxicity in ruminants. In Brachiaria spp. from two regions of the Colombian Eastern Plains (east mountain range of the Andean-"piedemonte" and Ariari River Valley) were determined this metabolite at 14 and 28 days post-cutting under different climatic conditions. No protodioscin was detected in B. dictyoneura or B. humidicola. In B. brizantha, B. decumbens and B. ruziziensis x B. decumbens x B. brizantha (hybrid), protodioscin content corresponded to an interaction between species, post-cutting time and season. Concentrations ≥1% (minimum toxic level) were recorded in B. decumbens and the hybrid, and to a lesser extent in B. brizantha. The concentration of protodioscin was higher at 28 days, when the pastures are suitable for consumption. B. brizantha accumulated the lowest saponin concentration, whereas the hybrid had the highest levels, particularly in the "piedemonte" and during drought (3.37%). Dry season favored the protodioscin concentration in B. decumbens (in river valley) and in the hybrid (in "piedemonte"). In the latter, there was a positive correlation with temperature and a negative with humidity, which are typical characteristics of dry periods. This is the first report of protodioscin content in the hybrid.

Photosensitisation of livestock grazing Narthecium ossifragum: Current knowledge and future directions

Photosensitisation diseases can cause production and animal welfare losses world-wide. In North-West Europe a photosensitisation disease complex known as 'plochteach', 'yellowses', 'saut' and 'alveld' occurs in lambs on extensive pastures containing bog asphodel (Narthecium ossifragum). Affected lambs develop lesions on the ears, face and sometimes the back, with erythema, oedema, ulceration and necrosis that can be followed by secondary infection and death. Adult sheep appear unaffected, the incidence in lambs varies from year to year and there are variations in susceptibility between- and within-breeds. The definitive cause remains uncertain although ingestion of N. ossifragum, which contains hepatotoxic saponins, has been implicated in the aetiology. However, problems replicating the disease complex by feeding N. ossifragum in a controlled environment have led to alternative hypotheses, including possible intake of toxins from fungal spores and cyanobacteria. Further research is required to assess the putative role of N. ossifragum, the scale of economic and animal welfare losses associated with the disease, how best to identify affected animals before external clinical signs appear and the treatment and management of clinical cases. Given the challenges involved in isolating the causative agent(s) of plochteach, an animal breeding route may be effective if heritability of resistance/susceptibility can be demonstrated.

Detection of singlet oxygen in blood serum samples of clinically healthy lambs and lambs suffering from alveld disease

Alveld is a disease in lambs of domestic sheep (Ovis aries L.), characterized by a combination of photosensitivity and liver damage. Generation of singlet oxygen play a major role in phototoxicity reactions. The compound phylloerythrin (phytoporphyrin) is so far assumed to be the main photodynamic agent in hepatogenous photosensitivity diseases in sheep. Phylloerythrin is a potent photosensitizer and an efficient source of singlet oxygen. The compound accumulates in the peripheral circualtion upon liver damage. Liver dysfunction is also likely to cause an increase in the blood level of bilirubin. Formation of singlet oxygen by bilirubin is reported. In the present work the photosensitizing potential of serum has been measured and related to the bilirubin- and phylloerythrin levels in lambs suffering from alveld and in clinically healthy controls. The singlet oxygen level of the serum was taken as a measure of the photosensitizing potential. The observed singlet oxygen values in serum from alveld lambs were significantly higher than the corresponding values observed in clinically healthy control lambs. This indicates that the serum of the alveld lambs contains an elevated concentration of photosensitizer. The singlet oxygen level was not correlated to the concentration of bilirubin or phylloerythrin. The results indicate that the photosensitizing mechanism is quite complex and may involve other sensitizer(s) than phylloerythrin.