Evaluation of the chemical composition and the particle size of maize silages produced in north-west of Portugal

The chemical composition and the particle size distribution of 37 maize silages produced in north-west of Portugal were determined. Mean dry matter (DM), crude protein (CP), neutral detergent ®bre (NDF) and starch were 288 33, 81 9, 502 45 and 229 54 g kgÿ1 DM, respectively. Particle size was determined by manual separation of fresh silage into three fractions: material >30 mm in length; material between 30 and 10 mm in length; and material <10 mm in length. Linear interpolation and extrapolation calculated median particle size. The effects of chopping±harvesting machine type and percentage of blades used to chop maize plants were also analysed. The results of this study suggested that most farmers chopped the maize plants very coarsely prior to storage. In fact, the type of chopping±harvesting machine had no effect on median particle size, but the percentage of blades used affected signi®cantly (p<0.001) this parameter. This can prevent maximisation of voluntary intake and high milk yields. Therefore, extension work is necessary to implement the ®ne chop of maize plants and to correctly choose as well harvest date and the maize varieties that are most adapted to local production conditions. # 2000 Published by Elsevier Science B.V. All rights reserved.