Meat quality is evaluated according to quality parameters such as pH, colour or intramuscular fat content. Meat colour is one of the main quality properties which influence consumer's acceptance, but also reflects the quality of meat (Estévez, Morcuende and Cava, 2003; Alonso et al., 2009). Within the qualitative parameters of meat, evaluating percentage of intramuscular fat seems to be the best way to separate indigenous pigs from commercial breeds (Pugliese and Sirtori, 2012), because it is usually observed that intramuscular fat content in important cuts of pork is less than 1.5% in pig meat breeds (Hamill et al., 2012). Jeong et al. (2010) indicated that intramuscular fat content is important factor that contribute to eating quality and it is influenced by genotype, gender, age and diet. Some reports indicate that when intramuscular fat content increases from 1% to 3%, the qualitative parameters increase at high rate. However as intramuscular fat content increase from 3% to 6%, the qualitative traits also improve, but at the lower levels.

The indigenous breeds such as Iberian and Mangalitsa are known to have desirable quality properties of meat that could be of interest to farm, giving the possibility to produce unique high-quality meat products. These indigenous breeds have a high intramuscular fat content (Straadt, Aaslyng and Bertram, 2013). Mangalitsa is one of the most popular rustic pig breeds in Europe, because the meat has excellent properties, such as taste, marbling and low cholesterol content (Pârvu et al., 2012). This breed is also characterized by dark colour of meat, robust constitution and slower growth rate with higher content of fat in carcass (65% – 70%) and reduced content of meat (30% – 35%) in carcass compared to commercial breeds (Egerszegi et al., 2003; Stanišić et al., 2013).

In the intensive pig production, the most common crossbreeding program is to use breeds such as Large White, Duroc, Pietran, to improve some production parameters as well as qualitative traits in meat (Alonso et al., 2015). In the last several decades, pigs have been crossed for the rapid production of lean meat and to increase the slaughter yield. According to this, most recent pig breeds have less than 2% of intramuscular fat in meat with exception of Duroc breeds (Suzuki et al., 2003; Sheard et al., 2005; Alonso et al., 2009).

Literature is controversial if the percentage of meat intramuscular fat in affects several quality traits. With this purpose, the objective of this experiment was to evaluate the effect of intramuscular fat content on physical parameters and proximate composition in musculus longissimus dorsi (MLD) from Mangalitsa breed and their Slovak Large White x Mangalitsa crossbreed.

The results of physical and chemical parameters of MLD from genotypes are presented in Table 3 and Table 4. The pH 45 min and 24 h post mortem was not influenced by genotypes. The values of pH decreased after 24 hours post mortem, what agrees with studies of Lindahl et al. (2006) and Young, Bertram and Oksbjerg (2009). MLD of Mangalitsa pigs had slightly higher values of pH 45 min and 24 h post mortem than crossbreeds SLW x Ma. Similarly, Tomović et al. (2016) confirmed that MLD of Mangalitsa had higher values of pH compared to their crossbreed (ph_45min 6.37 vs. 6.26; pH_24h 5.72 vs. 5.53). Sirtori et al. (2011) indicate that indigenous breed Cinta Senese had higher value of pH in MLD compared to crossbreed Italian Large White x Cinta Senese. The indigenous pig breed Chato Murciano had also higher value of pH in MLD than their crossbreed Chato Murciano x Iberian pig, what is obtained by Galián et al. (2007).

Electric conductivity (EC) 45 min post mortem was lower in MLD of Mangalitsa pigs compared to crossbreeds SLW x Ma. The EC increased after 24 hours post mortem, whereby Mangalitsa pigs had lower EC₂₄ than crossbreeds SLW x Ma, Electric conductivity (EC) 45 min post mortem was lower in MLD of Mangalitsa pigs compared to crossbreeds SLW x Ma. The EC increased after 24 hours post mortem, whereby Mangalitsa pigs had lower EC₂₄ than crossbreeds SLW x Ma, indicating statistical significance (p <0.05). In the same way, values of drip loss were lower in MLD of Mangalitsa in relation to crossbreeds SLW x Ma. Most commonly, pH and electrical conductivity are used as indicators for pale, soft, exudative (PSE) meat (Warriss et al., 1998; Josell, Von Seth and Tornberg, 2003; Altmann et al., 2005). Mörlein et al. (2007) applied strict levels for determination of PSE meat, when pH₄₅ <6.0 – 5.8 are used as threshold levels. Then, EC₂₄ values above 9 – 7 mS.cm^-1 were applied as PSE meat. Threshold parameters for drip loss were above 7 – 9% within 48 h post mortem. On the basis of this fact, it was found in our study PSE of meat from Mangalitsa pigs fed by LFM. According to Lee et al. (2000) exist linear relationship between drip loss and electric conductivity, what is in consistent with our results. In our study was not determined pale, soft and exudative (PSE) meat. As regards Warner-Bratzler shear force (W-B), the MLD from Mangalitsa showed lower values of shear force (2.63 kg.cm^-2) compared to crossbreed SLW x Ma (3.14 kg.cm^-2; p <0.05). The values were notably lower than those obtained by Stanišić et al. (2015) in Mangalitsa breed and Landrace as well as by Tomović et al. (2016) in MLD of Mangalitsa and Large White. Data confirmed that Mangalitsa has more tender meat than Landrace and Large White.

As regards the instrumental colour of MLD measured 45 min post mortem, the value CIE L* was higher in MLD from crossbreed SLW x Ma (p <0.01) compared to MLD from Mangalitsa. Similarly, the value CIE b* was higher in MLD from crossbreed SLW x Ma (p <0.01) and the value CIE a* was lower compared to MLD from Mangalitsa. However, no significant differences were found in CIE a* value due to genotype after 24h. The colour parameters (CIE L*, a*, b*) in MLD increased after 7 days post mortem, which is common due to the maturation process of the meat. This fact agrees with studies of Estévez, Morcuende and Cava (2003), Lindahl et al. (2006) and Stanišić et al. (2016). The CIE L* and CIE a* values were significantly influenced by genotype where Mangalitsa exhibited darker (CIE L*; p <0.001) and redder (CIE a*; p <0.05) MLD compared to crossbreed SLW x Ma. Although were not found significant differences for CIE b* in MLD, Mangalitsa had lower values than crossbreed SLW x Ma. It is in accordance with Stanišić et al. (2016).

Comparing our results with those obtained by Franci et al. (2005), we found that their results for CIE L* and CIE b* were lower, but CIE a* value was higher. In their study pure breed Cinta Senese exhibited darker (CIE L*) and redder (CIE a*) meat, but lower value of index b* compared to crossbreed Large White x Cinta Senese. Similarly, Szulc et al. (2012) obtained that pure breed Zlotnicka spotted had higher values of CIE L*, CIE a* as well as CIE b* compared to crossbreed Zlotnicka spotted x Polish Large White. On the contrary Poto, Galián and Peinado (2007) worked with Spanish indigenous breed Chato Murciano and they found lower values of colour parameters in MLD from crossbreed Chato Murciano x Large White than in indigenous breed Chato Murciano. On the other hand, Renaudeau and Mourot (2007) studied differences on meat quality between indigenous pigs Creole and Large White, where Creole pigs had lower colour parameters in relation to Large White. Bednářová et al. (2014) analyzed samples of pork 72 hours post mortem from different supliers. L* value from m. semimenbranosus was found from 46.13 to 48.53

Regarding the proximate parameters, water content was significantly higher in MLD from Mangalitsa than in MLD from crossbreed SLW x Ma (p <0.05). The MLD from Mangalitsa had lower protein content (p <0.05), but higher percentage of intramuscular fat than MLD from crossbreed SLW x Ma, where the difference did not reach the significance. Franci et al. (2005) observed that pure breed Cinta Senese had lower water content as well as protein content compared to their crossbreed Large White x Cinta Senese and the percentage of intramuscular fat was higher. Data are in accordance with our results except to water content in MLD. Our results showed higher values of water content and protein content, but lower percentage of intramuscular fat than in study of Sirtori et al. (2011) and Parunović et al. (2013). In their study, the indigenous breeds such as Cinta Senese, compared to Mangalitsa, had lower percentage of water as well as protein content and higher percentage of intramuscular fat in meat compared to commercial breeds. According to Serra et al. (1998), the pure breed Iberian had lower water and protein content, while the percentage of intramuscular fat was higher than Landrace pig meat. The results of cholesterol content were in accordance with percentage of intramuscular fat content in MLD, however no significant differences were found due to genotype. As regards the cholesterol content, Pârvu et al. (2012) determined, that Large White pig meat had higher cholesterol content with lower percentage of intramuscular fat (cholesterol content 41.64 mg.100g^-1; IMF 23.21%) compared to Mangalitsa (cholesterol content 61.24 mg.100g^-1; IMF 10.69%). These results are in contrast with ours. The cholesterol content of MLD was in the study of Parunović et al. (2013) and Parunović et al. (2015) higher than in our results, but they confirmed that Mangalitsa had higher value of cholesterol compared to Swedish Landrace pig meat. Similarly, Salvatori et al. (2008) found that indigenous pigs Casertana had higher cholesterol content in MLD than their crossbreeds Casertana x Large White. On the other hand, Stajić et al. (2011) indicated that Mangalitsa had lower cholesterol content in meat in relation to Landrace. Although it is saying that Mangalitsa pigs had lower cholesterol content in the meat, it can be confirmed by our study that Mangalitsa had higher cholesterol content than their crossbreeds.

Table 5 shows coefficients of Pearson's correlation between physico-chemical parameters and intramuscular fat content in musculus longissimus dorsi. The percentage of intramuscular fat (IMF) in MLD was positively correlated (p <0.05) with CIE a* 7 days post mortem (r = 0.324) and also with cholesterol content (r = 0.656; p <0.001). The relationship between percentage of intramuscular fat and cholesterol content in meat is shown by Figure 1. In contrast, the IMF in MLD was negatively correlated with percentage of water (r = 0.399; p <0.05) and with protein content in MLD (r = -0.812; p <0.001). These results are in accordance with study of Vranic et al. (2015) and Tomović et al. (2016). Figure 2 represents the relationship between intramuscular fat content and protein content in meat by linear regression. As regarding the Warner-Bratzler shear force, no significance was found between intramuscular fat and tenderness of meat. The results are in accordance with Jeong et al. (2010). On the contrary, Barlocco et al. (2006) found positive correlation between Warner-Bratzler shear force and intramuscular fat content in the meat. In other parameters, no significant correlations were found.

Chemical analysis showed that MLD from Mangalitsa had lower protein content (24.15, resp. 24.56%) and higher content of intramuscular fat (1.93, resp. 1.66%) compared to Slovak Large White x Mangalitsa crossbreed. As regards the Warner-Bratzler shear force, the meat from Mangalitsa was tenderer than in crossbreeds (p <0.05). Intramuscular fat in the meat positively correlated with colour parameter CIE a* (r = 0.324; p <0.05) as well as cholesterol content (r = 0.656; p <0.001). Cholesterol content was found statistically non-significant difference (Mangalitsa 43.01 and SLW x Ma 38.91 mg.100 g^-1).

It can be concluded that the percentage of intramuscular fat significantly influenced the physical and the chemical parameters of pork. As regards the differences between genotypes, Mangalitsa has darker, redder and tenderer meat with lower moisture content and higher intramuscular fat content compared to crossbreeds Slovak Large White x Mangalitsa. The meat from Mangalitsa is more suitable for production of special meat products (fermented and smoked).