Several studies have shown increased silage dry-matter intake (SDMI) and improved milk fat concentrations in dairy cows offered restricted fermented grass silages compared to more extensively fermented silages. A recent study suggested that differences in silage intake per se rather than an alteration in rumen fermentation may be responsible for the changes in milk composition observed in the previous studies (Doherty and Mayne, 1993). The aim of the present study was to examine the effect of changes in concentrate composition on milk production parameters in dairy cows offered grass silages of contrasting fermentation type.

Two direct cut grass silages were prepared using either an inoculant, containing a single strain of Lactobacillus plantarum, (Ecosyl, 3 1/t fresh weight, Zeneca Products Ltd) or a mixture of aliphatic carboxylic acids (Maxgrass, 6 1/t fresh weight, BP Chemicals Ltd). Two concentrates (high starch or high fibre) were formulated containing either: barley, 300; wheat, 355; and soyabean-meal, 270 g/kg (high starch) or unmolassed sugar-beet pulp, 555; citrus pulp, 100; and soyabean-meal, 270 g/kg (high fibre).