Effects Of Conjugated Linoleic Acids On Meat Quality And Muscle Fiber Types In Growing-finishing Pigs

This paper was conducted to investigate the effect of Conjugated linoleic acids (CLA) on growth performance, carcass characteristics, meat quality and muscle fiber types (MyCHs) in growing- finishing pigs, and analysis the correlation between muscle fiber types and meat quality.160 Landrace×Rongchang pigs were selected while body weight at 30 kg and randomly divided into 5 groups, each group had 8 duplicates, each duplicate had 4 pigs. The basal diet reference to feeding standard for Chinese pigs (NY/T 65-2004) was prepared, treatment groups diet were based on the basal diet and replaced soybean oil by-0.5%,1.0%,1.5% and 2% CLA-60 respectively. Weighed all the pigs while average body weight of group at 60 kg and 90 kg, calculated average daily gain (ADG), average daily feed intake (ADFI), feed/·gain (F/G). After that, the one which was most approaching to group average weight was slaughtered in each duplicate, determined carcass characteristics and meat quality. Sampling thoracolumbar longissimus dorsi, extracted RNA and reverse transcription. The mRNA expression of MyHC muscle fiber subtype were determined by quantitative PCR, and analysised the correlation between muscle fiber types and meat quality.Results were as follows:(1) CLA had no significant influence on ADG. During 30-60 kg body weight, F/G of 1%CLA group lower than control group (P<0.05). During 60-90 kg body weight, ADFI of 2%CLA group was lower than control group (P<0.01).(2) At 60 kg body weight, the dressing percentage of 0.5% and 2%CLA group were higher than control group (P<0.05). At 90 kg body weight, the carcass weight and dressing percentage of 1%,1.5%, and 2% CLA group were lower than control group (1%, p<0.01; 1.5% and 2%, p<0.05). The lean percentage of 1% CLA group was higher than control group (p<0.01). As to the backfat thickness,0.5%CLA decreased the fatthickness of 10th and last rib (P<0.05).1% and 2%CLA decreased the average backfat thickness (P<0.05), fatthickness of 10th and last rib (P<0.05), and the fatthickness of 6th rib (1%, P<0.01; 2%,p<0.05).(3) At 60 kg body weight, b value of 1% CLA group was lower than control group (P<0.05). The pH1 of 1% and 2% CLA group were lower than control group (P<0.05), the pH decline of 2% CLA group was slower than control group (P<0.05). Intramuscular fat of 0.5%-2% CLA groups were more than control group (1%, P<0.01; 0.5%,1.5% and 2%, P<0.05). Marbling score of 0.5%, 1.5%,2% CLA groups were higher than control group (0.5% and 2%, P<0.01; 1.5%, P<0.05). Water-holding capacity of 0.5% and 2% CLA group wefe better than control group (P<0.05). At 90 kg body weight,0.5%-2%CLA increased the tenderness of psoas (1%, P<0.01; 5%,1.5% and 2%, p<0.05).The b value of 1% and 2%CLA group were lower than control group (1%, P<0.01; 2%, P<0.05). The a value of 2%CLA group was higher than control group (P<0.05). Marbling score of 1.5% and 2% CLA groups were higher than control group (P<0.01).(4) At 60 kg body weight, the mRNA expression of MyCH I and 2a of 1.5%CLA group were increased compared with control group (P<0.05). At 90 kg body weight, the mRNA expression of MyCH 2x of 0.5%CLA group were decreased compared with control group (P<0.05), the mRNA expression of MyCH I and 2a of 2%CLA were increased compared with control group (P<0.05).(5) At 60 kg body weight, MyHC I mRNA expression were positive correlation with intramuscular fat (r=0.901, P=0.037), and negative correlation with water-loss rate (r=-0.916, P=0.014). MyHC 2x mRNA expression were positive correlation with L value (r=0.949, P=0.014). At 90 kg body weight, MyHC I mRNA expression were positive correlation with pH decline (r=0.917, P=0.028). MyHC 2a mRNA expression were positive correlation with a value, pH decline and marbling score (r=0.936, P=0.019; r=0.889, P=0.044; r=0.946, P=0.015). MyHC 2b mRNA expression were negative correlation with marbling score and intramuscular fat (r=-0.947, P=0.015; r=-0.953, P=0.012).In this study, the CLA could improved pork quality by regulated muscle fiber types; the CLA improved carcass characteristics in 90kg growing-finishing pigs, and 1% CLA was most effective; the CLA enhanced growth performance in growing-finishing pigs at both 60kg and 90kg body weight, and 1% CLA was most effective; the CLA had no significant effect on average daily gain.