An examination of the effect of method and level of concentrate feeding on milk production in dairy cows offered a grass silage-based diet

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Abstract
An experiment was conducted to examine the effect of method and level of concentrate feeding on milk production characteristics in dairy cows offered a grass silage-based diet. Twelve treatments were used with 24 Holstein/Friesian dairy cows in a four-period change-over design experiment. Treatments consisted of three methods of concentrate feeding (twice daily, four times daily or complete diet) and four levels of concentrate feeding (2, 4, 6 or 8 kg/day). Offering a complete diet significantly reduced silage substitution rate (0·28 kg silage dry matter (DM) per kg concentrate DM) compared with concentrates offered twice daily (0·50 kg silage DM per kg concentrate DM;P< 0·01). Method of concentrate feeding had no significant effect on milk yield or milk fat concentration (P> 0·05), although the response in milk protein concentration to increased concentrate food level was significantly greater with twice and four times daily concentrate feeding than with complete diet feeding (0·59, 0·56 and 0·44 g/kg per kg increase in concentrate food level;P< 0·05). Increasing concentrate inclusion level significantly reduced silage DM intake (P< 0·001) but significantly increased (P< 0·001) total DM intake. Milk yield and milk protein concentration were significantly increased (P< 0·001) and milk fat concentration significantly reduced (P< 0·02) with increasing concentrate inclusion level. Total ration apparent digestibility coefficients were unaffected (P> 0·05) by either method of feeding or concentrate inclusion level. However, modified acid-detergent fibre apparent digestibility decreased significantly with increasing concentrate inclusion (P< 0·01). Results suggested that offering complete diets, with concentrates comprising on average 0·33 of total DM intake, increased both silage and total DM intake although this was not reflected in either increased milk yield or improvements in milk composition.