Evaluation of the net energy for lactation system and estimation of the energy requirements of dairy cows based on a comprehensive analysis of feeding trials

摘要

Respiration experiments with high-yielding dairy cows in Northern Ireland have shown higher energy maintenance requirements than those used in the requirements standards of, e.g. France, UK, USA and Germany. Therefore, the current net energy for lactation (NEL) system of Germany was tested by comparing measured NEL intake with calculated NEL requirements based on a comprehensive dataset from feeding trials conducted at nine research institutions in Germany, Austria and Switzerland. The relationship between NEL requirements and NEL intake is described by the equation: NEL requirements 1/2 MJ=d. 1/4 26:6o.0:4THORN thorn 0:82o.0:004THORN. NEL intake 1/2 MJ=d. with Coefficient of Determination R2. 1/4 0:677; Root Mean Square Error oRMSETHORN 1/4 15:9 MJ NEL: The equation indicates a systematic over-estimation of NEL requirements in the lower performance range and an under-estimation at higher energy intake levels. A multiple regression analysis was conducted by calculating metabolisable energy (ME) requirements [MJ/d] using metabolic body size (MBS) [kg0.75], milk energy performance (LE) [MJ/d] and body weight change (BWC) [kg/d]: ME intakeoMEITHORN 1/2 MJ.1/4 0:651o.0:004THORN. MBS thorn 1:37o.0:006THORN. LE thorn 16:6o.0:31THORN. BWC with R2 1/4 0:717; RMSE 1/4 24:0 MJ: