Cereal grains are important components in diets for high producing dairy cows and fast growing beef cattle. The most important feed fraction in cereals is starch, which constitutes the major portion (70-80%) of cereal grains. In ruminant nutrition different starch sources are characterized by their physical and chemical properties and might be ranked as highly and poorly degrading starch after their extent and rate of degradation in rumen (Nocek and Tamminga, 1991). It is hypothesized that rumen fermentation rate of cereal starch varies considerably and that this might affect fibre digestibility, forage intake, and animal performance (Nocek and Tamminga, 1991; Mills et al., 1999). It would, therefore, be useful to reliably determine the differences in rumen fermentation characteristics of cereals. Part of the variation can be attributed to the methods used for evaluation (Stensig et al., 1998b; Huhtanen and Sveinbjörnsson, 2006 ). The in sacco technique has been used extensively in the recent past (Stensig et al., 1998a; Larsen et al., 2009) and is still an important analytical method in modern feed evaluation systems (Volden et al., 2011) even though the method has several limitations. Particle loss and microbial contaminations during incubations are associated with this technique, consequentially, leading to over- or under-predictions (Huhtanen and Sveinbjörnsson, 2006). The in vitro gas production (GP) technique, on the other hand, has some advantages over the in sacco method. The GP technique is characterized with negligible primary and secondary particle-losses (Huhtanen and Sveinbjörnsson, 2006), minimizing the risks of over- or under-predictions. In addition, it can be automated to generate and record a large number of data points and can be potentially used to study the fermentation characteristics of soluble and insoluble fractions of forages (Hetta et al., 2004).
Proceedings of the 2nd Nordic Feed Science Conference, 2011, p. 29-33