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\hypersetup{pdftitle={Growth and Yield of \textit{Oreochromis niloticus} treated by Immersion in 17$\alpha$-methyltestosterone },pdfauthor={Abdussalam Abumhara, Salah Yadem, Richard Sovjak},pdfsubject={Tropentag 2010: Abstract},pdfkeywords={Androgen, fish production, growth performance, Methyltestosterone, Oreochromis niloticus, tilapia},pdfpagemode=None,colorlinks=true}
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\parbox[b]{13.4cm}{\centering \large{\textbf{Tropentag, September 14-16, 2010, Zurich}}\\[1ex] \Large{``World Food System  ---\\A Contribution from Europe''\\[2ex]}}
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\begin{center}
\Large{\textbf{Growth and Yield of \textit{Oreochromis niloticus} treated by Immersion in 17$\alpha$-methyltestosterone \footnote{\textbf{Contact Address:} Abdussalam Abumhara, Czech University of Life Sciences, Animal Science and Food Processing in IT, Kamycka129165 21 Praha 6-Suchdol, CZ~Prague, Czech Republic, \mbox{e-mail}: \email{aabumhara@hotmail.com}}\\[0.8ex]}}
\normalsize{\textsc{Abdussalam Abumhara$^{1}$, Salah Yadem$^{2}$, Richard Sovjak$^{1}$}}
\end{center}
\begin{itemize*}
\item[]{\small{\textit{$^{1}$Czech University of Life Sciences, Animal Science and Food Processing in IT, Czech Republic}}}
\item[]{\small{\textit{$^{2}$University of Alexandria, Dept. of Animal Husbandry, Egypt}}}
\end{itemize*}
\index[author]{Abumhara, Abdussalam}
\index[author]{Yadem, Salah}
\index[author]{Sovjak, Richard}
\begin{center}
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\textbf{Abstract}
\begin{abstract}
\normalsize{
This research was conducted to evaluate the effect of immersion treatment of different levels of 17$\alpha$-methyltestosterone (100,200 and 400 $\mu$g\,l\textsuperscript{-1}) for different immersion periods (3, 6 and 12 hours) on the growth performance and production characteristics of \textit{Oreochromis niloticus}.



The highest final body weight of \textit{Oreochromis niloticus} after 112 days of rearing period and the highest average daily gain (36.58 $\pm$ 0.37\,{g}\,{fish} \textsuperscript{-1}and 0.32 $\pm$ 0.09\,{g}\,{fish}\,day\textsuperscript{-1}, respectively) were obtained by immersion of fry in 17$\alpha$- methyltestosterone at the level of 400$\mu$g\,l\textsuperscript{-1} for 6 h. However , the highest specific growth rate (4.66 $\pm$ \mbox{0.64\,\%} per day) was recorded by using the hormonal level of 400$\mu$g\,l\textsuperscript{-1} for 12h immersion period. The highest total fish yield, net fish yield and the best feed conversion ratio (357.44 $\pm$ 3.47\,{kg}\,{ha}\textsuperscript{-1}, 3.17 $\pm$ 0.18\,{kg}\,{ha}\textsuperscript{-1} / day and 1.52 $\pm$ 0,08 , respectively ) were obtained by using the hormonal level of 400$\mu$g\,l\textsuperscript{-1} for 3h immersion period.




All"=male populations are used in tilapia culture. One of the most common techniques for producing all"=male populations of tilapia is androgen- induced"=sex-reversal. Veracuz and Mair (1994) fed \textit{Oreochromis niloticus} (\textit{O.~niloticus}) fry with powdered feed containing 40\,{mg}\,{kg}\textsuperscript{-1} diet of 17$\alpha$- methyltestosterone (17$\alpha$-MT) for 25 days. After 112 days grow"=out period, they found significant differences in growth rates, hormone"=treated fish having  faster growth than untreated control . Little \textit{et al.} (2003) found that mono"=sex \textit{O.~niloticus} grew faster than mixed"=sex \textit{O.~niloticus} . Little \textit{et al.} (2003) reared \textit{O.~niloticus} fry in fertilised earthen ponds for 168- days. They found that mono"=sex fish reached a larger final individual size than mixed- sex. However, daily weight gain and specific 
growth rate were not significantly different ($p>0.05$) between mono-sex and mixed-sex tilapia.



}

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\end{abstract}
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\noindent \textbf{Keywords:} Androgen, fish production, growth performance, methyltestosterone, \textit{Oreochromis niloticus}, tilapia
\index[key]{Fish!production}
\index[key]{Tilapia!growth performance}
\index[key]{Methyltestosterone}
\index[key]{Oreochromis niloticus@\textit{Oreochromis niloticus}}
\index[key]{Tilapia}
\end{document}