THE EFFECT OF THE ADDITION OF CELL-WALL DEGRADING ENZYMES AT ENSILING ON THE RESPONSE TO POSTRUMINAL SUPPLEMENTATION OF PROTEIN IN DAIRY-COWS RECEIVING A SILAGE-BASED DIET

Two silages were prepared from the same sward of perennial ryegrass. One was ensiled without additive and the other was ensiled with the addition of a mixture of cellulase and hemicellulase enzymes. Silage intake and milk production responses to the infusion of 230 g day-1 into the abomasum were examined in four dairy cows in a 4 x 4 latin square design experiment with 14-day periods. The four treatments were (i) no-additive silage without casein, (ii) no-additive silage with casein, (iii) enzyme-silage without casein, and (iv) enzyme-silage with casein. Both silages were given ad libitum with 5 kg day-1 of a barley-soya bean meal mixture. Casein infusion tended (0. 10 < P > 0.05) to increase the intake of the no-additive silage but the intake of the enzyme silage was unaffected. When casein was not given, the yields of milk and milk constituents were greater (P < 0.05) for the enzyme-silage than for the no-additive control. Casein infusion increased (at least P < 0.05) the yields of milk and milk protein with both silages but the increases were substantially greater with the no-additive silage; values were for milk yield (kg day-1) 14.4 and 16.6 (no-additive), 15.9 and 16.8 (enzyme); and for milk protein yield (g day-1) 464 and 558 (no-additive), 499 and 566 (enzyme) for the unsupplemented and casein treatments, respectively. The amino acid profile suggested that the supply of amino acids from the small intestine was greater with the enzyme-silage.