Grinding energy and in vitro gas technique for the assessment of Syrian barley straws: physical and microbial degradation and voluntary feed intake by sheep

Abstract

The extent and rate of in vitro gas production of 40 Syrian barley straws, from various varieties with known dry matter intakes (DMI), were examined. The physical resistance of those straws to particle size reduction was also investigated, by using a grinding method (GER) which measures the electrical energy required to reduce a defined amount of straw to a 1-mm particle size. In vitro gas-production parameters, and the logarithm of GER, were combined in multiple regressions to predict DMI. About 87 % (p < 0.0001) of the variation in DMI was accounted for by the combined measurements, with log GER alone accounting for 83.4 %; in vitro gas-production parameters contributed 2.9 % (p < 0.01) to the variation in DMI explained. The extent and rate of gas production, without log GER, explained 84 % of the variation in DMI, with the rate accounting for 80 % of the variation in DMI. The combination of any gas-volume measurement between 12 and 96 h of incubation and log GER accounted for 86-87 % of the variation in DMI. Log GER was found to be inversely related to the rate (r = -0.93, p < 0.0001) and extent (r = -0.78, p < 0.0001) of in vitro gas production.