Effects of Dietary Protein Level and Supplementation of Conjugated Linoleic Acid on Growth Performance and Meat Quality Parameters in Finishing Pigs

This study was conducted to investigate effects of dietary crude protein (CP) level and supplementation of conjugated linoleic acid (CLA) on growth performances and meat quality parameters in finishing pigs. The experiment was designed using protein levels (11.3%, 16.0%) and CLA levels (0%, 2.5%) according to 2×2 factorial design. A total of forty-eight pigs [(Landrace×Yorkshire)×Duroc] with an average initial weight of 79±1 kg were allotted to one of four dietary treatments. Each treatment had four replications of three pigs per replicate. Final body weight (P less than 0.05) and average daily gain (P less than 0.01) were lower in 11.3% CP treatments than in 16.0% CP treatments, while feed/gain was high (P less than 0.01) in 11.3% CP treatments compared with 16.0% CP treatments. Carcass weight was lighter in 11.3% CP treatments (P less than 0.001) and CLA 2.5% treatments (P less than 0.01) than in 16.0% CP and CLA 0% treatments, respectively. A significant interaction between CP and CLA on carcass weight was observed (P less than 0.01), where supplementation of 2.5% CLA to finishing diets decreased carcass weight in 16.0% CP treatments, while no difference was found in 11.3% CP treatments. Backfat thickness was thinner in 11.3% CP treatments and CLA 2.5% treatments than in 16.0% CP and CLA 0% treatments, respectively (P less than 0.05). A significant interaction between CP and CLA on backfat thickness was observed (P less than 0.001), where supplementation of 2.5% CLA to finishing diets decreased backfat thickness in 16.0% CP treatments, while no difference was found in 11.3% CP treatments. Marbling score and intramuscular fat contents were higher in 11.3% CP treatments than in 16.0% CP treatments (P less than 0.01). In conclusion, feeding of protein-deficient diets in finishing pigs could produce favorable pork with high marbling score and thinner backfat. On the other hand, supplementation of CLA was considered to decrease backfat thickness when diets with optimal level of crude protein were fed to finishing pigs.