Effects of dietary protein level on intramuscular fat content and its fatty acid composition in lean and obese genotype finishing pigs

Effects of dietary protein level on intramuscular fat content and its fatty acid composition in lean and obese genotype finishing pigs were studied. Twenty four Crossbred (DurocxLandracexLarge White) barrows (49.1 +/- 4.9kg of BW) and eighteen Ningxiang barrows (61.6 +/- 4.1kg of BW) were equally randomly assigned to two groups and fed diets I (13.89% CP) and II (15.33% CP), respectively. The pigs were slaughtered after 46 days. Longissimus dorsi muscle (LD) and semitendinosus muscle (ST) samples were taken and the intramuscular fat (IMF) content as well as its fatty acid composition were determined. There was no significant difference in IMF content both in LD and ST between breed, within breed or between muscles, when Diet I was fed. The percentage of oleic acid (C18:1) and linoleic acid (C18:2) in LD of Crossbred was significantly lower (p<0.01) and higher (p<0.01) than that of Ningxiang, respectively, when Diet I was fed. There was no significant difference (p>0.05) in fatty acid composition in ST between breeds when Diet! was fed. When Diet II was fed, the IMF amount of LD in Crossbred was significantly lower (p<0.01) than that in Ningxiang and significantly lower (p<0.05) than that of its own ST. Ratio of stearic acid (C18:0), C18:1 and C18:2 in LD of Crossbred was significantly higher (p<0.01), lower (p<0.01) and higher (p<0.01) than that of Ningxiang pig, respectively. Ratio of palmitic acid (C16:0), C18:0, C18:1 and C18:2 in ST of Crossbred was significantly lower (p<0.01), higher (p<0.01), lower (p<0.01) and higher (p<0.01) than that of Ningxiang pig. Ratio of C18:1 in LD of Crossbred was significantly lower (p<0.01) than that of its own ST while ratio of C18:0 and C18:1 in LD of Ningxiang pig was significantly higher (p<0.05) and lower (p<0.05) than that of its own ST, respectively. These results indicate that breed, protein level of diet and muscle types have effects on IMF content and its fatty acid composition and different muscle types of different breeds responded differently in IMF content and fatty acid composition to the small change in dietary protein level.