). In the 2nd trial, perennial ryegrass was cut on either 25 May (in vitro D-value 73) or 19 June (in vitro D-value 59) and ensiled with either formic acid (3.0 l/t) or equal volumes of formic acid and formalin (6.5 l/t, 3.1 g HCHO/100 g CP). The silages were given alone or with rolled barley