FEEDING VALUE OF COMPLETE DIETS BASED ON GRASS-SILAGE FOR DAIRY-COWS

Feeding value of complete diets based on grass silage for dairy cows. Three trials (I, II and IV) were executed with dairy cows to determine , by means of animal performance, the feeding value of complete diets based on grass silage, compared with the same diets in which roughage and concentrate were fed separately. With complete diets the cows ate on average 1.8 kg more Of total DM (+2.3 kg of roughage, because the s upply of concentrate was reduced experimentally by 0.5 kg). This intak e increment was mainly caused by the chopping of the silage in the mix ing vessel. This was shown by a reduced chewing time per kg DM of sila ge. The increased intake was probably also caused by the regularity of concentrate intake during the day. Compared with the classical diet, the complete diet did not significantly modify milk production, despit e a decrease of 0.5 kg FCM/day caused by a non-significant decrease of 1 g/kg in the milk fat content. The animals increased five-weight by 100 g per d extra for the complete diet, when the supply of concentrat e was not modified (trials I and II). Taking into account the observed results, it can be calculated that the energetic value of the complet e diets is lower than that of the control diet, for the same proportio n of concentrate. A further trial (III) was executed to measure the ef fect of chopping in the mixing vessel and the consequences of a reduct ion in the proportion of concentrate in the complete diet on chewing t ime for the diets.