The effect of method of conserving grass herbage and the frequency of feeding on digestion in and passage from the rumen was studied in growing cattle. A single sward of perennial ryegrass (Lolium perenne cv. Endura) was cut on 1 d and conserved as silage or hay. These forages were offered as the only feed to twelve rumen-cannulated Friesian steers (average initial live weight (LW) 128 kg) either at a restricted level of intake (20 g dry matter (DM)/kg LW; Expt 1) or ad lib. (Expt 2). In Expt 1 the forages were offered either once or eight times daily. When fed once or eight times daily, in vivo digestibility of DM was very similar for hay and silage (0.771 and 0.783 respectively), while the fractional rate of digestion measured by incubation in Dacron bags was significantly (P less than 0.05) higher for silage (0.069) than hay (0.057). The rate of passage of mordanted feed out of the rumen was significantly (P less than 0.01) faster for silage when determined from concentrations of marker in the rumen (0.034 v. 0.028/h). The volume of liquid in the rumen was lower (P less than 0.01) for animals consuming silage (27.51) compared with hay (37.11), while the fractional rate of passage of liquid from the rumen was higher (0.141 v. 0.098/h, P less than 0.05). The volume of liquid in the rumen was also lower (P less than 0.05) in steers offered feed eight times daily (29.5 l), compared with once daily (35.1 l), but frequency of feeding had no significant effect either on total digestibility or on rate of digestion in the rumen. The ad lib. intake of silage was significantly (P less than 0.01) lower than that of hay (4.53 v. 5.16 kg DM/d) in Expt 2.
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Thiago et al. (1992) studied this question.