Effects of type and treatment of grain and protein source on dairy cow performance

The effects of different types of energy or protein supplementation on perf ormance of cows given grass silage-based diets were studied. The possibilit y of maintaining high energy intakes by using different grain sources, barl ey or maize, or by the use of the physical processing of the barley was inv estigated. In addition, the relative quality of rapeseed meal as a protein supplement compared with alternative protein supplements was examined. In e xperiment 1 16 Finnish Holstein-Friesian cows were used in a cyclic change- oner design experiment with eight diets and four 21- day periods. The conce ntrate supplements comprised a 2 X 2 X 2 factorial arrangement of two grain sources (barley (B) and maize (M)) given either ground (T-) or steam-rolle d (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 an d concentrates at a rate of 11.2 kg DM per day. M supplements increased mil k, milk protein and lactose output (P < 0.05) and decreased milk urea conce ntration (P < 0.01) compared with B supplements. Blood beta -hydroxybutyrat e (BHB) and plasma urea concentrations were higher (P < 0.01) for B than M diets. R supplements increased silage intake, energy-corrected milk yield a nd milk protein output and concentration (P < 0.05) compared with GS supple ments. Steam-rolled grain decreased food intake, blood BHB (P < 0.05) and p lasma and milk urea concentrations (P < 0.001). Steam rolling improved orga nic matter digestibility (grain X processing interaction, P < 0.05) with M but not with B supplements. In experiment 2 four Finnish Holstein-Friesian cows fitted with rumen cannu la were used in a balanced complete change-over design to evaluate ground o r steam-rolled barley (T- v. T+) and two protein treatments (rapeseed expel ler, R or a mixture of maize gluten/soya-bean meal/sugar beet solubles, CSS ). Cows were given concentrates at 11.2 kg dry matter (DM) per day and offe red grass silage ad libitum. There were no differences (P > 0.05) in food i ntake, 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 X compared with GSS supplements. The results showed that replacing B with M grain resulted in minor increas es in milk production. Steam rolling of grain did nor influence animal perf ormance. Among the protein supplements R increased animal performance compa red with GS supplement.