Effect of length of cut on quality of stack silage and milk production

Abstract

Wilted grass at moisture contents ranging between 62 and 76% was chopped at 6.3, 12.7, 25.4 and 38.1 mm theoretical length of cut (TLC) and conserved in large stack silos during 2 consecutive years (1986, 1987). Average real lengths of cut were 11, 21, 37 and 47 mm for the four TLC, respectively. Dry matter losses in the silos containing forage cut at 12.7 and 25.4 mm TLC (15.6 and 16.2%, respectively) were higher (P = 0.016) than losses in the silos containing forage cut at 6.3 and 38.1 mm TLC (12.1 and 12.9%, respectively). Within the range of TLC used, there was no evidence of improved silage quality to favor shorter chop length in stack silos. In both years, silage of each TLC was mixed with high-moisture barley and protein supplement and fed to a group of 16 dairy cows. There was no consistent effect of TLC on dry matter intake. The shortest length produced slightly more milk which was offset by a slightly lower percentage of milk fat. A TLC of 6.3–38.1 mm is adequate for silage fed to dairy cows producing between 20 and 28 kg of milk per day. Key words: Particle length, stack silos, silage, grass, dairy