Effects of energy density of forage and amount of concentrates on feed intake, rumination behaviour and performance of German Holstein cows during a whole lactation.

Within the nationwide project "optiKuh" a feeding trial was carried out with 48 dairy cows allotted to four experimental groups in the years 2015 and 2016 at the Experimental and Educational Centre for Agriculture 'Haus Riswick', Chamber of Agriculture of North Rhine-Westphalia, Kleve, Germany. The rations fed to cows in the four groups differed in regard to energy density of the forage and energy supply from concentrates. Level of energy supply did not affect total dry matter intake during the entire lactation. With greater energy density of forage, forage dry matter intake decreased in favour of the intake of concentrates. The impact of energy density of forage on yields of energy-corrected milk was greater than the effect of concentrate supply indicating that energy-rich roughage can reduce the amount of concentrates. The energy balance differed between groups with the highest and the lowest energy supply. In-depth data analysis indicated that greater dry matter intake results in a more pronounced decrease in ration digestibility than currently assumed. Considering all response variables together such as dry matter intake, milk yield and composition, ruminating behaviour, it can be stated that all rations of this study can be used for on-farm feeding of dairy herds.