Higher dry matter intakes (DMI) have been reported in dairy cows fed maize silage than in dairy cows fed grass silage. The objective of this experiment was to investigate this phenomenon by the measurement of digestibility and the determination of rumen outflow rates for both forages. The response in milk production of late lactation dairy cows to grass or maize silage was also measured.
Fourteen late lactation multiparous dairy cows (n = 7) were fed diets containing either grass silage (GS) (DM: 197g/kg; pH: 4.05; NDF: 642g/kg DM) or high starch maize silage (MS) (DM: 339g/kg; pH: 3.94; starch: 360g/kg DM; NDF: 442g/kg DM) ad-libitum plus 4kgs/hd/day of a dairy concentrate (233g CP/kg DM). Urea (460g N/kg DM) was used as a source of degradable protein (10g/kg DM) for the MS diet which also included straw (40g/kg DM). Dietary NDF equalled 542 and 423g/kg DM for the GS and MS diet.