Crambe meal: digestibility in pigs and rats in comparison with rapeseed meal

Seed meals from decorticated Crambe abyssinica (CM) and modern variety rape (RSM) were compared for composition and digestibility. The structural elements of the whole seeds (pericarp, seedcoat and endosperm) were measured through hand-separation. In the digestion trial the decorticated and defatted meals were fed to four pigs (liveweight 35 kg) fitted with ileocaecal valve cannulas. Digestibility data were obtained from a change-over experiment in which both meals were included at 300 g kg−1 in the diet. Then the energy digestibility and nitrogen utilization of the meals were determined in a balance trial with rats. ole crambe seeds contained 300 g pericarp kg−1. After decortication, the seeds possessed 89 g seedcoat kg−1, significantly lower than in rapeseed (160 g kg−1). Compared with RSM, CM contained a considerably higher level of protein (504 vs. 367 g kg−1) and a lower level of fibre constituents (e.g. 65 vs. 139 g kg−1 for crude fibre). Apparent total-tract digestibilities of gross energy for CM and RSM in pigs were 78.3 and 73.2% (P < 0.05), of organic matter 78.7 and 73.2% (P < 0.05), and of protein 76.8 and 79.1%, respectively. However, the apparent ileal digestibility of protein in CM was lower than in RSM (63.0 vs. 71.7%, P < 0.01); that of lysine and cystine was also lower (61.1 and 62.5% for CM vs. 75.3 and 71.2% for RSM, P < 0.01). The difference in protein digestibility was presumably due to overheating of CM during the detoxification treatment. Phosphorus total-tract digestibility was 43.4% for CM and 22.5% for RSM (P < 0.01). In the balance trial, rats received diets in which all nitrogen originated from either CM or RSM. The results showed that CM had clearly higher apparent energy digestibility than RSM (93.4 vs. 79.6%, P < 0.01). Apparent protein digestibility was similar (78.4 vs. 78.8%). However, the biological value and net protein utilization of CM were low, i.e. 46.8 and 41.7%, compared with 87.1 and 77.6% for RSM (P < 0.01). The differences were presumably due to the high level of glucosinolates in CM. It is thus concluded that CM is highly digestible, and that there is large scope for enhancement in protein utilization by optimizing the detoxification treatment.