Processing of legume seeds : effects on digestive behaviour in dairy cows

In this study, effects of toasting, expander treatment and pelleting on in situ rumen degradability and intestinal digestibility of legume seeds are described. Toasting decreases protein degradability of peas, lupins, faba beans and soybeans and starch degradability of peas and faba beans, especially when broken instead of whole seeds are processed. Toasting of a mixture of peas, lupins and faba beans resulted in a higher starch degradability than expected on the separately treated feedstuffs. Toasting the mixture decreased protein degradability, whereas pelleting and expander treatment increased protein degradability.The observed effects for the latter two treatments were related to particle size reduction during processing. Combinations of toasting, expander treatment and pelleting resulted sometimes in interactions,but the order of the treatments hardly affected the effects on protein and starch degradability.Peas and faba beans showed great resemblance in chemical composition. This was reflected in their sensititivy to the processing conditions. Likewise, lupins and soybeans showed similar behaviour after toasting. The rumen degradability of amino acids (AAN) in lupins decreased, and showed a curvi-linear response to processing time and temperature. Effects of toasting were similar for all amino acids. Correction for microbial contamination based on diaminopimelic acid resulted in a higher degradability of AAN compared to uncorrected N. Moreover, corrections affected the ranking of treatments with respect to degradability of individual amino acids.Laboratory measurements showed that protein dispersibility index (PDI) and protein denaturation enthalpy, as measured by differential scanning calorimetry (DSC) are useful indicators for protein denaturation, and can be used for evaluation of effects of toasting on intestinal digestible rumen undegraded protein.</p