Evaluation of the German net energy system and estimation of the energy requirement of cows on the basis of an extensive data set from feeding trials

Publikations-Art

Kongressbeitrag

Autoren

Gruber L., A. Susenbeth, F.J. Schwarz, B. Fischer, H. Spiekers, H. Steingass, U. Meyer, A. Chassot, T. Jilg, A. Obermaier

Erscheinungsjahr

2007

Veröffentlicht in

EAAP Publication

Herausgeber

European Association for Animal Production (EAAP)

Verlag

Wageningen Academic Publishers , Wageningen (Niederlande)

Band/Volume

124/

Serie/Bezeichnung

Proceedings of the 2nd EAAP International Symposium on Energy and Protein Metabolism and Nutrition

ISBN / ISSN / eISSN

978-90-8686-041-8

Seite (von - bis)

563-564

Tagungsname

Energy and protein metabolism and nutrition

Tagungsort

Vichy (France)

Tagungsdatum

09.09.2007

Schlagworte

dairy cow, energy requirements, German net energy system

Introduction
The maintenance energy requirement (NEm) of the dairy cow is assumed to be 0.300-0.350 MJ net energy (NEL)/kg metabolic live weight (LW0.75) in the systems established in Europe and the USA (INRA, 1989; AFRC 1993; GfE 2001; NRC 2001). The efficiency of utilisation of metabolisable energy (ME) for milk production (k1) is in the range of 0.60-0.63 in these systems. Recent results of Agnew et al. (2003) indicate both a higher NEm and a higher k1.
Material and methods
A comprehensive data set (n=24 583; means of 2 lactation wk of individual cow measurements) obtained from long term feeding experiments with lactating dairy cows carried out in 9 research Institutes in Germany, Austria and Switzerland (Gruber et al., 2005) was used to evaluate the current German feeding standards (GfE, 2001). The experiments were carried out with Holstein Friesian, Brown Swiss and Simmental cows and the data showed a wide variation in animal parameters [(mean±SD, range); d in milk (138±78, 2-459), milk yield (24.3±8.1, 2.2-60.6 kg/d), feed intake (18.5±3.5, 5.4-31.6 kg dry matter (DM)/d)] as well as nutritional factors [NEL content (5.9±0.5, 4.1-7.4 MJ/kg DM), proportion of concentrate in the dies (25.6±17.9, 0.0-81.1% of DM)]. The NEL system was validated by regressing NEL requirement, calculated on the basis of its assumptions [0.293 MJ NEL/kg LW0.75 for maintenance, NE in milk=0.38xfat+0.21 xprotein+ 0.95 (Tyrrell and Reid, 1965), 25.5 MJ NEL for gain and 20.5 MJ NEL for loss of 1 kg LW, NEL pregnancy = (0.044x exp(0.0165xd of gestation/0.175x0.6)], on actual NEL intake (MJ), considering the decrease of dietary energy content with feeding level in the requirements (GfE, 2001). ME requirement in this study was estimated using multiple regression analysis with LW0.75 (kg), milk energy output (LE, MJ/d) and live weight change (LWC, kg/d) as independent variables.