In vitro ruminal fermentation of ground and dry-rolled barley grain differing in starch content

• Batch culture study of barley samples varying in starch content was evaluated.
• Starch content had significant effect on the rate of gas production and dry matter disappearance.
• Processing (ground versus dry-rolled) increased the disappearance of dry matter and starch.

In vitro ruminal fermentation of ground and dry-rolled barley samples differing in starch content was evaluated using a batch culture technique. The study was arranged in a 2 (low and high starch) × 2 (ground and dry-rolled) factorial design. Gas production (GP), short chain fatty acids (SCFA), dry matter (DM) and starch disappearance were estimated at 3, 6, 12 and 24 h of incubation using rumen fluid from 3 ruminally fistulated beef cattle. Rate of GP was greater (P<0.05) in both high starch and ground (2 mm) barley samples. Kinetics of DM and starch disappearance were calculated using the equation of a + b (1 − e−c(t−L)). Starch content × processing interactions were noted for the b fraction and rate of DM disappearance. Consistently, both high starch and ground barley samples had greater (P<0.05) a and b fractions, rate constant of disappearance of b fraction and effective degradability versus low starch and dry-rolled samples. Expectedly, molar proportions of individual and total SCFA were greater (P<0.05) in the ground barley samples at all incubation periods. Overall, starch content (high versus low) had significant effect on the rate of GP and constant rate of DM disappearance but no effect on the constant rate of starch disappearance.