## 3 Results and Discussion
\begin{table}
\begin{tabular}{l c c c} \hline \hline  & \multicolumn{4}{c}{**Muscle Fibre Type Percentages**} \\ \cline{2-4}
**Genetic Groups of Fatteners** & **IIB** & **IIA** & **I** \\  & \(\overline{\pi}\pm\)**SD** & \(\overline{\pi}\pm\)**SD** & \(\overline{\pi}\pm\)**SD** \\ \hline \hline  & \multicolumn{4}{c}{Breed} \\ \hline ZS & 57.38 a \({}^{\text{a}}\) \(\pm\) 4.92 & 21.57 a \({}^{\text{a}}\)\(\pm\) 2.38 & 21.05 a \({}^{\text{a}}\)\(\pm\) 4.01 \\ ZS \(\times\) D & 61.46 b \({}^{\text{b}}\)\(\pm\) 1.13 & 19.38 b \({}^{\text{b}}\)\(\pm\) 2.31 & 19.62 a \({}^{\text{a}}\)\(\pm\) 1.82 \\ (ZS \(\times\) ZS) \(\times\) D & 64.94 c \({}^{\text{c}}\)\(\pm\) 6.25 & 20.83 a,b \({}^{\text{b}}\)\(\pm\) 1.58 & 14.24 b \({}^{\text{b}}\)\(\pm\) 6.14 \\ ZS \(\times\) PLW & 69.45 d \({}^{\text{d}}\)\(\pm\) 1.57 & 15.15 c \({}^{\text{c}}\)\(\pm\) 1.23 & 15.40 b \({}^{\text{b}}\)\(\pm\) 0.95 \\ \(p\)-value & 0.0008 & 0.0000 & 0.0003 \\ \hline  & \multicolumn{4}{c}{Barrows} \\ \hline ZS & 52.80 a \({}^{\text{a}}\)\(\pm\) 1.24 & 22.63 a \({}^{\text{a}}\)\(\pm\) 0.62 & 24.57 a \({}^{\text{a}}\)\(\pm\) 1.70 \\ ZS \(\times\) D & 61.27 b \({}^{\text{b}}\)\(\pm\) 1.08 & 19.92 b \({}^{\text{b}}\)\(\pm\) 1.18 & 19.72 b \({}^{\text{b}}\)\(\pm\) 1.75 \\ (ZS \(\times\) ZS) \(\times\) D & 64.81 c \({}^{\text{c}}\)\(\pm\) 5.52 & 20.29 b \({}^{\text{b}}\)\(\pm\) 1.52 & 14.20 c \({}^{\text{c}}\)\(\pm\) 5.24 \\ ZS \(\times\) PLW & 68.67 d \({}^{\text{c}}\)\(\pm\) 1.23 & 15.43 c \({}^{\text{c}}\)\(\pm\) 1.46 & 15.90 c \({}^{\text{c}}\)\(\pm\) 0.85 \\ \(p\)-value & 0.001 & 0.0000 & 0.0006 \\ \hline  & \multicolumn{4}{c}{Gilts} \\ \hline ZS & 61.96 a \({}^{\text{a}}\)\(\pm\) 1.73 & 20.50 a \({}^{\text{a}}\)\(\pm\) 3.01 & 17.53 a,b \({}^{\text{a}}\)\(\pm\) 1.85 \\ ZS \(\times\) Du & 61.64 a \({}^{\text{a}}\)\(\pm\) 1.26 & 18.85 a \({}^{\text{a}}\)\(\pm\) 3.14 & 19.51 a \({}^{\text{a}}\)\(\pm\) 2.09 \\ (ZS \(\times\) ZS) \(\times\) Du & 65.06 a \({}^{\text{a}}\)\(\pm\) 7.58 & 21.36 a \({}^{\text{a}}\)\(\pm\) 1.62 & 13.58 b \({}^{\text{a}}\)\(\pm\) 7.49 \\ ZS \(\times\) PLW & 70.23 b \({}^{\text{b}}\)\(\pm\) 1.58 & 14.88 b \({}^{\text{b}}\)\(\pm\) 1.04 & 14.89 b \({}^{\text{b}}\)\(\pm\) 0.81 \\ \(p\)-value & 0.005 & 0.0003 & 0.038 \\ \hline Average for genetic groups and sex & 62.12 \(\pm\) 6.25 & 19.69 \(\pm\) 3.13 & 18.27 \(\pm\) 4.74 \\ \hline x \(\pm\) SD—mean and standard deviation, mean values in the same columns designated by the different letters differ significantly at: a,b,c,d—\(p\)\(\leq\) 0.05, ZS—Zlotnicka Spotted \(\times\) Zlotnicka Spotted; ZS \(\times\) D—Zlotnicka Spotted \(\times\) Durco; (ZS \(\times\) ZS) \(\times\) D—Zlotnicka Spotted \(\times\) Zlotnicka Spotted/Durco; ZS \(\times\) PLW—Zlotnicka, Spotted \(\times\) Polish Large White. & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The muscle fibre type percentage (%) of the _m.longissimus thoracis_ for male and female fatteners of the Zlotnicka Spotted (ZS) breed and the hybrid crosses. In the case of experiments conducted by [PERSON] and [PERSON] [48], the diameter of IIB fibres was 57.43 \(\upmu\)m, for IIA fibres--41.56 \(\upmu\)m and for Type I--47.85 \(\upmu\)m. In our studies, the diameter of muscle fibres derived from the _longissimus thoracis_ muscle of the Zlotnicka Spotted breed (ZS \(\times\) ZS) amounted to 64.71 \(\upmu\)m (IIB), 52.58 \(\upmu\)m (IIA) and 57.11 \(\upmu\)m (I) and was greater in comparison with hybrids of Duroc and Polish Large White breeds as shown in Table 3. The crossing of Zlotnicka Spotted with Duroc and Polish Large White breeds led to a significant decrease of the muscle fibre diameter in hybrids. [PERSON] et al. [25] reported that the increased diameter of muscle fibres in heavy fatteners exerted a favourable impact on meat processing properties because muscles made up of thicker fibres are more sensitive to massaging treatment. However, according to [PERSON] and [PERSON] [49], a smaller thickness of the fibres favourably affects meat quality, and it might be considered an indicator of a delicate structure of the meat.