## 3 Results
### Model of the Development of the Gastrointestinal Tract of broiler Chickens at Day 35  
Based on an analysis of the individual variables using a multiple regression model (Table 7), a significant effect of the independent variables on jejun length was found (\(p=\) 0.002, R\({}^{2}=\) 0.59). The length of the large intestine and liver weight have significant effects on the value of the dependent variable.  
\begin{table}
\begin{tabular}{l c c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**DV**} & \multirow{2}{*}{**Intercept**} & \multicolumn{6}{c}{**Coefficients for Independent Variables as Constituents of Equation with Sign**} \\ \cline{3-13}  & & **IDF** & **IDF** & **SDF** & **PW** & **GW** & **DW** & **JL** & **LL** & **CL** & **LL** & **HW** & **LW** & **\(p\)-Value** & **R\({}^{2}\)** \\ \hline PW & 3.855 & 0.000 & -0.043 & 0.025 & - & 0.029 & 0.160 & 0.068 & 0.054 & \(-\)0.173 & \(-\)0.229 & 0.130 & \(-\)0.033 & 0.125 & 0.24 \\ \hline GW & 45.687 & 0.436 & \(-\)0.101 & \(-\)0.186 & 0.787 & - & \(-\)0.399 & \(-\)0.065 & 0.000 & \(-\)0.044 & 1.398 & \(-\)0.134 & 0.357 & 0.073 & 0.30 \\ \hline DW & 26.527 & 0.016 & \(-\)0.045 & 0.000 & 0.732 & \(-\)0.068 & - & \(-\)0.267 & 0.002 & 0.503 & 0.818 & \(-\)0.270 & 0.202 & 0.144 & 0.22 \\ JL & 31.861 & \(-\)0.061 & 0.072 & 0.082 & 0.748 & \(-\)0.026 & \(-\)0.640 & - & 0.299 & 0.236 & 1.533* & \(-\)0.578 & 0.500* & 0.002 & 0.59 \\ \hline LL & 8.718 & \(-\)0.084 & 0.138 & \(-\)0.127 & 1.065 & 0.000 & 0.010 & 0.539 & - & 0.585 & \(-\)0.643 & 0.638 & 0.108 & 0.002 & 0.58 \\ \hline CL & 3.550 & \(-\)0.097 & 0.082 & 0.079 & \(-\)0.378 & \(-\)0.004 & 0.239 & 0.047 & 0.064 & - & 0.066 & \(-\)0.108 & 0.159 & 0.002 & 0.43 \\ \hline LL & \(-\)0.499 & \(-\)0.016 & 0.014 & \(-\)0.018 & \(-\)0.232 & 0.053 & 0.181 & 0.141* & \(-\)0.033 & 0.030 & - & 0.094 & \(-\)0.093 & 0.099 & 0.27 \\ \hline HW & 11.913 & 0.045 & \(-\)0.002 & \(-\)0.104 & \(-\)0.443 & \(-\)0.017 & \(-\)0.200 & \(-\)0.179 & 0.109 & \(-\)0.166 & 0.316 & - & 0.186 & 0.127 & 0.19 \\ \hline LW & \(-\)32.160 & 0.157 & \(-\)0.128 & \(-\)0.077 & \(-\)0.335 & 0.135 & 0.448 & 0.641* & 0.056 & 0.739 & \(-\)0.530 & 0.555 & - & 0.037 & 0.51 \\ \hline \hline \end{tabular}
* Coefficients with an asterisk mean significant effects (\(p<\) 0.05) for the independent variable in the entire model. R2—fit of the model to the data. Abbreviations in the header: DV—dependent variable; IDF—total dietary fibre; IDF—insoluble dietary fibre; SDF—soluble dietary fibre; PW—proventicus weight; GW—gizzard weight; DL—dudecoman length; IL—jitum length; LL—jitum length; CL—sceta length (average); LL—large intestine length; HW—heart weight; LW—liver weight.  
\end{table}
Table 7: Multiple regression equations taking into account the effect of dietary fibre and the measurements analysed in this experiment.  
In addition, the independent variables also had an effect (\(p\) = 0.002) on the dependent variables with respect to the ileal and caecal length (R\({}^{2}\) = 0.58 and R\({}^{2}\) = 0.43, respectively), but none of the individual variables had a more significant effect than the others (\(p\) > 0.05). A significant effect of the independent variables was also found in the case of liver weight (\(p\) = 0.007, R\({}^{2}\) = 0.51), and in this case, jejun length was a significant component of the regression equation (\(p\) < 0.05). A similar trend was also found in the case of equations describing the parameters of the muscular stomach weight and large intestine length (0.073 and 0.099, respectively). However, no significant influence of the independent variables on the dependent variables, such as the weight of the glandular stomach, heart weight, or duodenum length, was observed (\(p\) > 0.05).