Abstract：CAST gene plays an important role in muscular protein degradation, muscle cell proliferation and post-slaughter calpain activation. Study on interaction effects of polymorphisms of CAST gene and nutrition levels has an essential role in the regulation of pig carcass quality. Interaction effects of polymorphisms of CAST gene at HinfⅠ, MspⅠand RsaⅠsites and three nutrition levels on meat carcass traits were studied among four pig population including Duorc, Daweizi, Durocⅹ(LandraceⅹLarge White) and Larege White ⅹDaweizi. The results showed that the three RFLP markers of gene CAST were all polymorphic in the four pig populations. These RFLPs are bi-allelic, with alleles A and B at HinfI, alleles C and D at MspI, and alleles E and F at RsaI. Genotype AA was significantly associated with reduced cooking percentage and drop loss in the high nutrition group, and with augmented drop loss in the moderate nutrition group (P<0.05). Genotype AB was associated with significantly decreased carcass length and loin eye area, and with increased drop loss in the high nutrition group, and with significantly decreased dressing percentage, back-fat thickness, and cooking percentage in the moderate nutrition group. Genotype CD showed significant interaction with high nutrition level on all traits. Genotype CC significantly increased drop loss (P<0.05). The performance of pigs of genotype EF overcame the average by 10% in some traits, when fed with high nutrition diets (P<0.05). The interaction between genotype EE and moderate nutrition level was significant on back-fat thickness.
