Effects of barley silage of different theoretical cut length on digestion kinetics in ruminants

Abstract

Two studies were conducted to determine the effects of two theoretical lengths of cut (TLC) (short = 4.7 mm and long = 18.8 mm) on the feeding value of barley silage to steers fed an all-forage diet. In the first study, six steers were used to determine intake of dry matter, total tract digestibility of dry matter (DMD), neutral detergent fiber (NDFD), and acid detergent fiber (ADFD) in a replicated switchback design. In the second study, six steers equipped with rumen cannulas were used to determine the effects of barley silage particle size on ruminal kinetic and fermentation parameters. Feeding short barley silage to steers increased (P < 0.05) dry matter intake (DMI), DMD, NDFD, and ADFD compared with feeding long barley silage. The results of the second study showed that reducing barley silage particle size decreased (P < 0.05) ruminal retention time and increased (P < 0.05) passage rate of particulate matter. Ruminal pH was lower (P < 0.05) at 1000, 1200, 1800, 2000, and 2200 h for steers fed the short barley silage compared with those fed the long barley silage. However, the effects of barley silage particle size on ruminal ammonia nitrogen and volatile fatty acid (VFA) concentrations were minimal. Eating rate was similar in both dietary treatments (average 40.3 g min-1). However, steers fed the long silage produced more (P < 0.05) saliva per kg DMI compared with those fed the short barley silage diets. It was concluded that reducing TLC of barley silage increased feed intake and improved total tract utilization of cell wall components by steers. Results of the metabolism study also showed changes in fermentation parameters, but no adverse physiological changes were noted when cattle were fed all forage diets. Key words: Barley silage, particle size, fermentation patterns