Relationships between muscle fibre characteristics and physico-chemical properties of longissimus lumborum muscle and growth rate in pig fatteners of three breeds*

In 40 Polish Landrace, 38 Polish Large White and 14 Pietrain fatteners the longissimus lumborum (LL) muscle fibres were characterized and LL quality indicators determined. The correlation was estimated between the LL fibres traits and daily live weight gain, muscle pH and texture parametres. Muscle fibres were identified as I, IIA and IIB types based upon their dehydrogenase (NADH) activity. The daily live weight gain of fatteners and their muscle pH45, pH24, Warner-Bratzler shear force and texture properties were determined. Breed was found related neither to meat quality traits, nor fibre type per cent and fibre relative area, but it affected the size of fibres. The LL from Pietrain fatteners had larger diameter of fibres within each fibre type compared to fatteners of remaining two breeds (P≤0.01). The phenotypic correlations between histological and physico-chemical traits were generally low. The content (%) and relative area of type IIB fibres, unlike those of type I, positively correlated with daily live weight gain (P≤0.01). Moreover, increase in the daily live weight gain was related to increased size of type IIB fibres. Shear force was negatively related to type IIA muscle fibre size. A similar tendency was found between pH24 and diameter of type IIA fibres.