Du könntest `dcolumn` verwenden. Damit kann man Spalten an einem beliebigen Zeichen ausrichten.
\documentclass{article}
\usepackage{caption} % for \caption*
\usepackage{dcolumn}
\newcolumntype{d}{D{+}{\,\pm\,}{-1}}
\begin{document}
\begin{table}
\caption{Shows growth performance parameters of the four treatments C-, C+, A-, A+. All values are calculated means of corresponding group body weights (n=7) with corresponding standard deviation.}
\begin{tabular*}{\textwidth} {@{\extracolsep{\fill} } l d d d d}
\hline
\multicolumn{1}{c}{\textit{bla}}
& \multicolumn{1}{c}{\textit{C-}}
& \multicolumn{1}{c}{\textit{C+}}
& \multicolumn{1}{c}{\textit{A-}}
& \multicolumn{1}{c}{\textit{A+}}\\
% & & C- & & C+ & &A- & &A+ \\
\hline
Initial IBM [g] & 17.3 + 0.4 & 17.3 + 0.2 & 17.2 + 0.2 & 17.4 + 0.3 \\
Final IBM [g] & 33.6 + 2.2 & 33.5 + 1.1 & 33.1 + 1.0 & 32.0 + 1.3 \\
BMG [g] & 16.3 + 1.9 & 16.1 + 1.0 & 16.0 + 1.0 & 14.4 + 1.1 \\
BMG [\%] & 93.9 + 11.5 & 93.0 + 6.4 & 93.0 + 6.1 & 82.8 + 7.4 \\
Feed [g] & 24 + 0.8 & 24 + 0.66 & 23.6 + 0.61 & 23 + 0.69 \\
FCR [$ \frac{g} {g}$] & 1.48 + 0.13 & 1.49 + 0.06 & 1.48 + 0.06 & 1.58 + 0.07 \\
SGR [$ \frac{\%} {day}$] & 1.57 + 0.12 & 1.56 + 0.07 & 1.56 + 0.07 & 1.45 + 0.07 \\
PER [$ \frac{g} {g}$] & 1.49 + 0.13 & 1.47 + 0.06 & 1.54 + 0.06 & 1.4 + 0.07 \\
ANPU [\%] & 23.8 + 2.0 & 23.8 + 0.9 & 24.0 + 1.5 & 23.6 + 1.1 \\
ANLU [\%] & 58.1 + 4.2 & 61.7 + 1.9 & 59.4 + 2.1 & 56.2 + 2.2 \\
\hline
\end{tabular*}
\caption*{Mean $\pm$ SD; IBM = individual body mass; BMG = body mass gain; FCR = feed conversion ratio; SGR = specific growth rate; PER = protein efficiency rate, ANPU = apparent net protein utilization; ANLU = apparent net lipid utilization.}
\label{table:growthperformance}
\end {table}
\end{document}
[![alt text][1]][1]
---
Eine andere Möglichkeit wäre den `\extracolsep` immer abwechselnd an- und abzuschalten.
\documentclass{article}
\usepackage{caption} % for \caption*
\begin{document}
\begin{table}
\caption{Shows growth performance parameters of the four treatments C-, C+, A-, A+. All values are calculated means of corresponding group body weights (n=7) with corresponding standard deviation.}
\begin{tabular*}{\textwidth}{
@{\extracolsep{\fill}} l
@{\extracolsep{\fill}} r@{\extracolsep{0pt}$\pm$}l
@{\extracolsep{\fill}} r@{\extracolsep{0pt}$\pm$}l
@{\extracolsep{\fill}} r@{\extracolsep{0pt}$\pm$}l
@{\extracolsep{\fill}} r@{\extracolsep{0pt}$\pm$}l
}
\hline
\multicolumn{1}{c}{\textit{bla}}
& \multicolumn{2}{c}{\textit{C-}}
& \multicolumn{2}{c}{\textit{C+}}
& \multicolumn{2}{c}{\textit{A-}}
& \multicolumn{2}{c}{\textit{A+}}\\
% & & C- & & C+ & &A- & &A+ \\
\hline
Initial IBM [g] & 17.3 & 0.4 & 17.3 & 0.2 & 17.2 & 0.2 & 17.4 & 0.3 \\
Final IBM [g] & 33.6 & 2.2 & 33.5 & 1.1 & 33.1 & 1.0 & 32.0 & 1.3 \\
BMG [g] & 16.3 & 1.9 & 16.1 & 1.0 & 16.0 & 1.0 & 14.4 & 1.1 \\
BMG [\%] & 93.9 & 11.5 & 93.0 & 6.4 & 93.0 & 6.1 & 82.8 & 7.4 \\
Feed [g] & 24 & 0.8 & 24 & 0.66 & 23.6 & 0.61 & 23 & 0.69 \\
FCR [$ \frac{g} {g}$] & 1.48 & 0.13 & 1.49 & 0.06 & 1.48 & 0.06 & 1.58 & 0.07 \\
SGR [$ \frac{\%} {day}$] & 1.57 & 0.12 & 1.56 & 0.07 & 1.56 & 0.07 & 1.45 & 0.07 \\
PER [$ \frac{g} {g}$] & 1.49 & 0.13 & 1.47 & 0.06 & 1.54 & 0.06 & 1.4 & 0.07 \\
ANPU [\%] & 23.8 & 2.0 & 23.8 & 0.9 & 24.0 & 1.5 & 23.6 & 1.1 \\
ANLU [\%] & 58.1 & 4.2 & 61.7 & 1.9 & 59.4 & 2.1 & 56.2 & 2.2 \\
\hline
\end{tabular*}
\caption*{Mean $\pm$ SD; IBM = individual body mass; BMG = body mass gain; FCR = feed conversion ratio; SGR = specific growth rate; PER = protein efficiency rate, ANPU = apparent net protein utilization; ANLU = apparent net lipid utilization.}
\label{table:growthperformance}
\end {table}
\end{document}
Die Ausgabe sieht ungefähr gleich aus.
[1]: https://texwelt.de/wissen/upfiles/test_468.png
