COMPARISON OF THE NATIONAL RESEARCH COUNCIL ENERGY SYSTEM FOR LACTATING COWS WITH 4 EUROPEAN SYSTEMS

The structure, prediction steps, and accuracy of the US (NRC), United Kingdom (ARC), Dutch (VEM), French (UFL), and German (NEL) systems for feeding high producing cows were compared. Simulations were made usin g 15 feeds ranging from hays to cereals. Agreement was satisfactory am ong European systems for the prediction of metabolizable energy and ne t energy for lactation (NEL) contents of feeds and the quantities of f eeds in balanced diets necessary to meet the energy requirements of la ctating cows. The metabolizable energy and NEL contents of feeds seeme d overestimated by the US system compared with results using the Europ ean systems, and the ratio of NEL to total digestible nutrients was al most constant, unlike the other systems. Estimating the NEL content of feeds for a level three times maintenance intake allowed satisfactory rationing for the production of 20 to 25 kg of fat-corrected milk/d. However, feed allowances seemed underestimated for higher milk product ion, especially with diets based on hay, probably because of the overe stimation of feed NEL content, the underestimation of level of feeding , and the effects associated with feeding levels > 3 and high concentr ate diets.