Hepatogenous photosensitisation in cows grazing turnips (Brassica rapa) in South Africa.

Holstein cows on a farm in the Humansdorp district, Eastern Cape province, South Africa, developed reddened, painful teat skin 3 days after grazing a mixed forage crop dominated by bulb turnip (Brassica rapa, Barkant cultivar). The crop was grazed 45 days after planting and 10% of the herd developed symptoms. More characteristic non-pigmented skin lesions started manifesting 1-2 days after the appearance of the teat lesions. Affected cows had elevated serum activities of gamma-glutamyl transferase, glutamate dehydrogenase and aspartate aminotransferase. These blood chemistry findings confirmed a secondary (hepatogenous) photosensitivity. As a result of the severity of the teat and skin lesions, seven cows were slaughtered and tissue samples from five of them were collected for histopathological examination. Liver lesions in cows that were culled 3 or more weeks after the onset of the outbreak showed oedematous concentric fibrosis around medium-sized bile ducts and inflammatory infiltrates in portal tracts. Characteristic lesions associated with other known hepatobiliary toxicities were not found. No new cases were reported 5 days after the cattle were removed from the turnips. The sudden introduction of the cows, without any period of transitioning or adaptation to grazing turnips, as well as the short latent period, clinical signs of photosensitisation, blood chemistry and histopathology, confirmed a diagnosis of Brassica-associated liver disease, a condition seen in New Zealand but not previously described in South Africa. Brassica forage crops are potentially toxic under certain conditions and farmers must be aware of these risks.

Corrigendum: Hepatogenous photosensitisation in cows grazing turnips (Brassica rapa) in South Africa.

No abstract available.

Investigating the cause of Brassica-associated liver disease (BALD) in cattle: Progoitrin-derived nitrile toxicosis in rats.

A large outbreak of liver toxicity in dairy cows that were consuming swede (rutabaga, Brassica napus ssp. napobrassica) crops in Southland and Otago, New Zealand in 2014 prompted the search for the toxin(s) responsible for brassica-associated liver disease (BALD). Analysis of swede plant material showed that the ultra-dominant glucosinolate was progoitrin. The two nitrile derivatives of progoitrin, 1-cyano-2-hydroxy-3-butene (CHB, also known as crambene) and 1-cyano-2-hydroxy-3,4-epithiobutane (CHEB), were custom-synthesised. In this pilot trial, individual progoitrin nitriles were administered by gavage to rats in order to establish a "subtoxic" dose, i.e. the dose where apparently clinically normal rats show liver injury based on altered serum biochemical indicators and histological lesions. We found that consecutive daily doses of 1 mmol/kg CHB produced severe pancreatic and mild liver histological lesions in the absence of notable biochemical changes in clinically normal rats. No evidence of a cumulative effect was seen. Single doses of 1 mmol/kg of CHEB caused elevated concentrations of serum creatinine and distinctive renal and stomach histological lesions in apparently clinically normal rats. Consecutive daily 1 mmol/kg doses of CHEB had a considerable cumulative effect and proved severely hepato- and nephrotoxic with creatinine concentrations peaking after three daily doses. Three other commercially available nitriles (3-butenenitrile, 4-pentenenitrile and 5-hexenenitrile) derived from minor glucosinolates in the swedes were also investigated in this pilot trial. Single combined 1 mmol/kg doses of both progoitrin nitriles as well as these two nitriles plus small doses of the other three failed to demonstrate any synergism, however, the characteristic and apparently dominant effects of CHEB were consistently demonstrated. The results of this pilot study confirmed the previously reported pancreatotoxicity of CHB and nephrotoxicity of CHEB. CHEB also caused intraepithelial pustules, submucosal oedema, erosions and ulcers in the squamous portion of the stomach. These stomach lesions, as well as the renal lesions, appear identical to those caused by another epithionitrile, 1-cyano-3,4-epithiobutane, derived from gluconapin, which was a minor glucosinolate in the swedes. Because of the fact that cyanide can be released with the metabolism of some nitriles, we analysed cyanide in the livers of treated rats. The liver of a rat dosed with 1 mmol/kg of 3-butenenitrile contained 0.5 µg/g of cyanide. The hypothesis that BALD is due to nitrile toxicity requires further testing.

Photosensitisation diseases of animals: Classification and a weight of evidence approach to primary causes.

Clare's (1952) classification system for photosensitisation diseases (types I, II, III and Uncertain) has endured many years of use despite some confusion regarding his secondary, or type III, category, as well as the more recent discovery of two mechanisms (types I and II) of phototoxicity. Therefore, to reduce confusion in terminology, I propose that Clare's four groups be known as primary (or direct), secondary (indirect or hepatogenous), endogenous (aberrant porphyrin synthesis), and idiopathic. The use of the word type can then be reserved for the mechanisms of phototoxicity. Clare's (1952, 1955) papers listed three plants as primary photosensitisers and three as idiopathic. In the literature, several other plants have been associated with photosensitisation in farm animals. Most of these are likely to have a primary pathogenesis; however, the weight of evidence for all but a few is sparse. With respect to plants (and certain mycotoxins and insects) implicated in primary photosensitisation outbreaks, McKenzie's "toxicity confidence rankings" (Australia's Poisonous Plants, Fungi and Cyanobacteria, 2012) has been adapted to "phototoxic agent confidence rankings". Thus, plants, mycotoxins or insects can be categorised regarding phototoxicity, i.e. definite (A); some evidence (B); suspected (C); or phototoxin isolated but no field cases known (D), and weight of evidence, i.e. field cases (1); experimental feeding produces photosensitisation (2); phototoxin isolated (3); phototoxin produces photosensitisation experimentally (4); and/or correlation of the action spectrum/chromatogram in blood or skin with the absorption spectrum/chromatogram of the phototoxin (5). As a result, confidence rankings ranging from A5 to D1 can be allocated. From the available literature, at least seventeen plant species can be ranked as A5 (definite phototoxicity with a maximum weight of evidence). The relatively recent breakthrough regarding the discovery of phototoxic anthraquinones in Heterophyllaea spp. has led to the serendipitous association of the same and similar anthraquinones as the most likely phototoxins in alligator weed (Alternanthera philoxeroides).

Wild parsnip (Pastinaca sativa)-induced photosensitization.

Wild parsnip (Pastinaca sativa) has been associated with livestock and human photosensitization. An investigation of a natural occurrence of photosensitization of grazing horses identified wild parsnip as a possible cause. HPLC-MS and MS/MS analysis of this plant identified five furanocoumarins i.e., xanthotoxin, bergapten, isopimpinellin, imperatorin and a putative methoxyimperatorin. Goats fed this wild parsnip were largely unaffected. Xanthotoxin was not detected in the serum of parsnip-fed goats or in the serum of goats dosed orally or intravenous with purified xanthotoxin. Cutaneous application produced severe photodermatitis in goats and a horse consistent with topical exposure as the likely route to produce wild parsnip-induced photosensitivity. Wild parsnip-induced superficial necrotizing dermatitis was consistent with photodermatitis with no evidence of other allergic or inflammatory components.

Serum metabolomics using ultra performance liquid chromatography coupled to mass spectrometry in lactating dairy cows following a single dose of sporidesmin.

INTRODUCTION: Photosensitization is a common clinical sign in cows suffering from liver damage caused by the mycotoxin sporidesmin. This disease, called facial eczema (FE), is of major importance in New Zealand. Current techniques for diagnosing animals with subclinical sporidesmin-induced liver damage (i.e. without photosensitization) are nonspecific. In addition, little is known of the mechanisms involved in sporidesmin resistance, nor the early effects seen following low-dose sporidesmin intoxication. OBJECTIVE: The objective of this study was to identify individual metabolites or metabolic profiles that could be used as serum markers for early stage FE in lactating cows. METHODS: Results are presented from a 59-day sporidesmin challenge in Friesian-cross dairy cows. Serum metabolite profiles were obtained using reversed phase ultra-performance liquid chromatography (UPLC) electrospray ionization mass spectrometry (MS) and UPLC tandem MS. Multivariate and time series analyses were used to assess the data. RESULTS: Statistical analysis, both with and without the temporal component, could distinguish the profiles of animals with clinical signs from the others, but not those affected subclinically. An increase in the concentrations of a combination of taurine- and glycine-conjugated secondary bile acids (BAs) was the most likely cause of the separation. This is the first time that MS methods have been applied to FE and that bile acids changes have been detected in cattle exposed to sporidesmin. CONCLUSIONS: It is well known that BA concentrations increase during cholestasis due to damage to bile ducts and leakage of the bile. This is the first study to investigate metabolomic changes in serum following a sporidesmin challenge. Further work to establish the significance of the elevation of individual BAs concentrations in the serum of early-stage sporidesmin-poisoned cows is necessary.

Toxicity of white snakeroot (Ageratina altissima) and chemical extracts of white snakeroot in goats.

White snakeroot (Ageratina altissima) is a sporadically toxic plant that causes trembles in livestock and milk sickness in humans that drink tainted milk. The putative toxin in white snakeroot is tremetone and possibly other benzofuran ketones, even though it has not been demonstrated in vivo. Toxic white snakeroot was dosed to goats, and they developed clinical signs of poisoning, exercise intolerance, significant increases in serum enzyme activities, and histological changes. Tremetone and the other benzofuran ketones were extracted with hexane; the extracts and residues were analyzed for tremetone and dosed to goats at tremetone and benzofuran ketone concentrations similar to the original plant material. However, none of the dosed goats developed the disease. The results demonstrate for the first time that white snakeroot is a potent myotoxin in goats and that other compound(s), which may be lost or modified during the extraction process, could be involved in causing trembles and milk sickness.

Could nitrile derivatives of turnip (Brassica rapa) glucosinolates be hepato- or cholangiotoxic in cattle?

Turnip (Brassica rapa ssp. rapa) and rape (Brassica napus ssp. biennis) and other brassica forage crops are regarded as "safe" feed for cattle during late summer and fall in the North Island of New Zealand when high Pithomyces chartarum spore counts in pastures frequently lead to sporidesmin toxicity (facial eczema). Sporadic acute severe cases of turnip photosensitization in dairy cows characteristically exhibit high γ-glutamyl transferase and glutamate dehydrogenase serum enzyme activities that mimic those seen in facial eczema. The two diseases can, however, be distinguished by histopathology of the liver, where lesions, in particular those affecting small bile ducts, differ. To date, the hepato-/cholangiotoxic phytochemical causing liver damage in turnip photosensitization in cattle is unknown. Of the hydrolysis products of the various glucosinolate secondary compounds found in high concentrations in turnip and rape, work has shown that nitriles and epithionitriles can be hepatotoxic (and nephro- or pancreatotoxic) in rats. These derivatives include ß-hydroxy-thiiranepropanenitrile and 3-hydroxy-4-pentenenitrile from progoitrin; thiiranepropanenitrile and 4-pentenenitrile from gluconapin; thiiranebutanenitrile and 5-hexenenitrile from glucobrassicanapin; phenyl-3-propanenitrile from gluconasturtiin; and indole-3-acetonitrile from glucobrassicin. This perspective explores the possibility of the preferential formation of such derivatives, especially the epithionitriles, in acidic conditions in the bovine rumen, followed by absorption, hepatotoxicity, and secondary photosensitization.

Cystitis, pyelonephritis, and urolithiasis in rats accidentally fed a diet deficient in vitamin A.

Female Sprague-Dawley rats (n = 100; age, 3 wk) were fed diets that included a vitamin premix and either albumin or milk powder. Rats fed the albumin diet gained weight more slowly than did the other group. Between 19 and 28 wk of being fed the albumin diet, 12 rats died of bacterial cystitis and pyelonephritis. In addition, 2 more rats from the same dietary group developed peritonitis after ovariohysterectomy. Examination of the 44 rats fed the albumin diet that completed the 34-wk experiment revealed pyelonephritis in 68%, cystitis in 66%, urolithiasis in 27%, and nephrolithiasis in 5%. Squamous metaplasia of the transitional epithelium was present in all 44 rats, although other epithelia were histologically normal. Vitamin A deficiency was diagnosed after analyses of blood and liver samples. Analysis of the vitamin premix revealed approximately 25% of the expected amount of vitamin A. Because the milk powder contained sufficient vitamin A, deficiency did not occur in rats fed the milk powder diet. The major consequences of vitamin A deficiency in the rats were squamous metaplasia, bacterial infection, and calculus formation within the urinary tract. This report illustrates the importance of careful formulation and storage of vitamin premixes used in experimental diets. Vitamin A deficiency should be considered in rats with decreased weight gain and urinary tract disease even if ocular lesions are not present.