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\hypersetup{pdftitle={Digestibility and Metabolisable Energy Concentrations of Tropical Feeds as Estimated \textit{in vitro} or by Prediction Equations},pdfauthor={Alice Onyango, Uta Dickhoefer, Klaus Butterbach-Bahl, John Goopy},pdfsubject={Tropentag 2016: Abstract},pdfkeywords={Digestibility, in vitro, metabolisable energy, prediction, tropical feedstuff},pdfpagemode=None,colorlinks=true}
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\parbox[b]{13.4cm}{\centering \large{\textbf{Tropentag, September 18-21, 2016, Vienna, Austria}}\\[1ex] \Large{``Solidarity in a competing world ---\\fair use of resources''\\[2ex]}}
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\Large{\textbf{Digestibility and Metabolisable Energy Concentrations of Tropical Feeds as Estimated \textit{in vitro} or by Prediction Equations\footnote{\textbf{Contact Address:} Uta Dickhoefer, University of Hohenheim, Inst. of Agricultural Sciences in the Tropics (Hans-Ruthenberg-Institute), Fruwirthstr. 31, 70599~Stuttgart, Germany, \mbox{e-mail}: \email{Uta.Dickhoefer@uni-hohenheim.de}}\\[0.8ex]}}
\normalsize{\textsc{Alice Onyango$^{1}$, Uta Dickhoefer$^{1}$, Klaus Butterbach-Bahl$^{2,3}$, John Goopy$^{3}$}}
\end{center}
\begin{itemize*}
\item[]{\small{\textit{$^{1}$University of Hohenheim, Inst. of Agricultural Sciences in the Tropics (Hans-Ruthenberg-Institute), Germany}}}
\item[]{\small{\textit{$^{2}$Karlsruhe Institute of Technology, Institute for Meteorology and Climate Research, Atmospheric Environmental Research, Germany}}}
\item[]{\small{\textit{$^{3}$International Livestock Research Institute (ILRI), Kenya}}}
\end{itemize*}
\index[author]{Onyango, Alice}
\index[author]{Dickhoefer, Uta}
\index[author]{Butterbach-Bahl, Klaus}
\index[author]{Goopy, John}
\begin{center}
\vspace{1.1cm}
\textbf{Abstract}
\begin{abstract}
\normalsize{
\textit{In vivo} determination of digestible organic matter (dOM) and metabolisable energy (ME) concentrations of feeds is laborious and expensive, whereas analysis of their nutrient contents is routinely performed. Prediction equations based on the chemical composition of feeds can be a compromise. This study compared dOM and ME estimates of tropical feeds derived from selected equations (Yan and Agnew, 2004; Stergiadis et al., 2015a; Stergiadis et al., 2015b; AFRC, 1993) with those determined by the \textit{in~vitro} gas production method (Menke and Steingass, 1988). Samples of supplement feedstuffs (n = 12) and the herbaceous and ligneous vegetation on native pastures (n = 12) were collected in Lower Nyando, Kenya, over two seasons of one year. Samples were analysed for dry matter (DM; in \% of fresh matter), crude ash, crude protein, ether extract, neutral and acid detergent fiber (NDF, ADF) (all in \% of DM). Gross energy was determined by calorimetry. 



Nutrient concentrations varied across all samples with 8.5 -- \mbox{87.9\,\%} DM, 5.2 -- \mbox{16.8\,\%} crude ash, 36.7 -- \mbox{74.1\,\%} NDF, 25.5 -- \mbox{39.4\,\%} ADF, 3.2 -- \mbox{14.2\,\%} crude protein, and 0.6 -- \mbox{4.5\,\%} ether extract. The gross energy, \textit{in~vitro} dOM, and ME concentrations were 14.5 -- 18.8\,MJ\,kg\textsuperscript{-1} DM, 26.3 -- 54.5\,\%}, and 3.8 -- 8.4\,MJ\,kg\textsuperscript{-1} DM, respectively. Compared with the \textit{in~vitro} method, all nutrient"=based equations overestimated dOM ($p < 0.001$), whereas ME estimated from \textit{in~vitro} gas production was similar to that derived from the AFRC equation ($p > 0.5$). Nutrient"=based equations do not sufficiently account for differences in nutrient availability, an aspect better simulated \textit{in~vitro}. Further development and/or validation of nutrient"=based equations might be needed to more accurately predict dOM and ME of tropical feeds.



AFRC. 1993. Wallingford: CAB International.




Stergiadis et al. 2015a. J Dairy Sci, 98(5), 3257--3273



Stergiadis et al 2015b. Brit J Nutr, 113(10), 1571--1584. 



Yan and Agnew. 2004. J Anim Sci., 82, 1367--1379.
}

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\end{abstract}
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\noindent \textbf{Keywords:} Digestibility, metabolisable energy, prediction, tropical feedstuff
\index[key]{Digestibility}
\index[key]{In~vitro@\textit{In~vitro}}
\index[key]{Metabolisable energy}
\index[key]{Prediction}
\index[key]{Tropical feedstuff}
\end{document}
