Holstein–Friesiancowsasaconsequenceofprolongedgenetic
selectionforincreasedmilkproduction(Veerkampetal.,
2001). Inseasonalgrass-basedsystemssuchasinIreland,
the relativeimportanceofhighproductivityefficiencyis
greaterthaninyearroundconfinementsystemsbecauseof
the needforacompactcalvingpatterninspringsothatgrass
growthmatchesfooddemand(Veerkampetal.,2002).