The effects of different types of energy or protein supplementation on performance of cows given grass silage-based diets were studied. The possibility of maintaining high energy intakes by using different grain sources, barley or maize, or by the use of the physical processing of the barley was investigated. In addition, the relative quality of rapeseed meal as a protein supplement compared with alternative protein supplements was examined. In experiment 1 16 Finnish Holstein-Friesian cows were used in a cyclic change-over design experiment with eight diets and four 21- day periods. The concentrate supplements comprised a 2 ✕ 2 ✕ 2 factorial arrangement of two grain sources (barley (B) and maize (M)) given either ground (T–) or steam-rolled (T+), each supplemented with either rapeseed expeller (R) or a mixture of maize gluten and soya-bean meal (GS). Grass silage was given ad libitum and concentrates at a rate of 11·2 kg DM per day. M supplements increased milk, milk protein and lactose output (P < 0·05) and decreased milk urea concentration (P < 0·01) compared with B supplements. Blood β-hydroxy-butyrate (BHB) and plasma urea concentrations were higher (P < 0·01) for B than M diets. R supplements increased silage intake, energy-corrected milk yield and milk protein output and concentration (P < 0·05) compared with GS supplements. Steam-rolled grain decreased food intake, blood BHB (P < 0·05) and plasma and milk urea concentrations (P < 0·001). Steam rolling improved organic matter digestibility (grain ✕ processing interaction, P < 0·05) with M but not with B supplements.
In experiment 2 four Finnish Holstein-Friesian cows fitted with rumen cannula were used in a balanced complete change-over design to evaluate ground or steam-rolled barley (T– v. T+) and two protein treatments (rapeseed expeller, R or a mixture of maize gluten/soya-bean meal/sugar beet solubles, GSS). Cows were given concentrates at 11·2 kg dry matter (DM) per day and offered grass silage ad libitum. There were no differences (P > 0·05) in food intake, digestibility or milk production and composition between treatments. Plasma urea concentrations (P < 0·01) and molar proportion of butyrate (P < 0·05) in rumen fluid were decreased with R compared with GSS supplements. The results showed that replacing B with M grain resulted in minor increases in milk production. Steam rolling of grain did not influence animal performance. Among the protein supplements R increased animal performance compared with GS supplement.