Silage intake and milk production in cows given barley supplements of reduced ruminal degradability

Three change-over experiments were conducted to determine the effect on ad libitum silage intake and milk production in dairy cows of treatment of barley supplements with an acid-formaldehyde reagent designed to reduce the rate of starch and protein digestion in the rumen. In Experiment 1 there were six dietary treatments consisting of silage with supplements of 4·0,6·5 and 9·0 kg d^-1 of barley given untreated or treated with formaldehyde reagent (8·1 t^-1). In Experiment 2 there were four dietary treatments consisting of silage with supplements of barley (7·0 kg d^-1) or barley and fishmeal (6·0 kg d^-1 plus 1·0 kg d^-1), with the barley untreated or treated with formaldehyde reagent (15·1t^-1). In Experiment 3 there were four dietary treatments consisting of silage given alone or with supplements of barley (9·0 kg d^-1). Treated barley (15·1 t^-1, 9·0 kg d^-1) and barley plus sodium bicarbonate (9·0 kg d^-1 plus 25·0 g d^-1). Treatment of the barley supplement with formaldehyde reagent had no effect on silage intake or milk production in Experiment 1 where the rate of application of the reagent was low and the basal silage-barley diet was limiting in rumendegradable nitrogen. However, in Experiments 2 and 3 treated barley supplements were associated with improvements in silage intake and milk production. As compared with corresponding control diets containing untreated barley, increases in silage intake ranged from 0 to 0·16 of the control value, whilst associated increases in the yields of milk, milk fat, milk protein and lactose were 0·077–0·089, 0·016–0·026, 0·092–0·118 and 0·080–0·092 of the control value. These responses are discussed in relation to the increases in silage intake and milk production observed with fishmeal supplementation of the diet in Experiment 2 and inclusion of sodium bicarbonate in Experiment 3.