Rumen microbial degradation of allyl cyanide as a possible explanation for the tolerance of sheep to brassica-derived glucosinolates

The possible role of allyl cyanide (ACN), the nitrile breakdown product of prop-2-enyl glucosinolate, in reducing the voluntary food intake (VFI) of a dried grass pellet diet in sheep was examined in a ruminal infusion experiment. Voluntary food intake of Scottish Blackface wether lambs, infused intraruminally with allyl cyanide (0 mmol day⁻¹, C; 4.8 mmol day⁻¹ L; 9.6 mmol day⁻¹, H) for 9 weeks was significantly depressed (P < 0.05) on H and L treatments compared with the C treatment. Clinical indicators of liver function (plasma gamma glutamyl transpeptidase (GGTP) activity) and kidney function (plasma urea and creatinc concentrations) indicated minor liver damage but no effects on renal function. Plasma GGTP activity was significantly (P < 0.05) higher in the H than in the C group. Liver cytochrome oxidase activity at the end of the infusion period was significantly lower (P < 0.05) in the H than in the C group indicating effects on cellular respiration. In general, sheep showed considerable tolerance to administration of ACN in comparison with previously demonstrated toxicity in monogastrics.