New Zealand White Rabbits

1 School of Veterinary Science, Massey University, Private Bag 11-222, Palmerston North 4442, New 5 Zealand; m.g.collett@massey.ac.nz (M.G.C.); z.matthews@hotmail.com (Z.M.M); k.parton@massey.ac.nz 6 (K.H.P.) 7 * Correspondence: m.g.collett@massey.ac.nz 8 9 Abstract: Cattle occasionally develop brassica-associated liver disease (BALD) and 10 photosensitisation when grazing turnip or swede (Brassica spp.) forage crops. The liver toxin in these 11 brassica varieties has yet to be discovered. Progoitrin is the dominant glucosinolate in incriminated 12 crops. Apart from goitrin, progoitrin hydrolysis yields the nitrile, 1-cyano-2-hydroxy-3-butene 13 (CHB), and the epithionitrile, 1-cyano-2-hydroxy-3,4-epithiobutane (CHEB). The two compounds 14 were custom-synthesised. In a small pilot trial, New Zealand White rabbits were given either CHB 15 or CHEB by gavage. Single doses of 0.75 mmol/kg of CHB or 0.25 mmol/kg of CHEB were subtoxic 16 and elicited subclinical effects. Higher doses were severely hepatotoxic causing periportal to massive 17 hepatic necrosis associated with markedly elevated serum liver biomarkers often resulting in severe 18 illness or death within 24 h. The possibility that one or both of these hepatotoxic nitriles causes BALD 19 in cattle requires further investigation. 20