Effect of rapeseed-mustard cake from genotypes with varying glucosinolate levels as supplements on in vitro fermentation variables and substrate degradability

The feeding value of rapeseed-mustard cakes (RMC) from six genotypes with varying levels of glucosinolates (∼20–100 μmol/g) was evaluated by in vitro gas production technique. The chemical composition of different genotypes of RMC was similar except acid detergent fibre (ADF) content that was lower in TERI (OE) EN O3 than other five genotypes. Except for genotype TERI-LGM 08 and Varuna of B. juncea containing >40% erucic acid (% of oil, w/w), rest of the genotypes used in this experiment had erucic acid level below 2%. The gas production was lower (P<0.01) at <20 μmol/g glucosinolate level in B. napus [TERI (OO) R9903] relative to remaining cultivars of either B. napus or B. juncea. However, the level of glucosinolates in RMC did not exert any significant effect (P>0.05) on in vitro truly degradable organic matter in rumen (TDOMR). Mean microbial biomass production (%TDOMR or per 200mg substrate) and PF (mg TDOMR/ml gas) were significantly higher for canola quality B. napus [TERI (OO) R9903] containing lowest level of glucosinolates (<20 μmol/g) relative to other genotypes. It may be concluded that variability in the glucosinolates content of various genotypes of RMC may not exert any significant effect on substrate degradability; however, microbial biomass production could be varied in different cultivars.