Chenghua (CH) pig and Qingyu (QY) pig are typical Chinese native fatty breeds.  CH pig is mainly distributed in Chengdu Plain, while QY pig is widely distributed throughout the mountain areas around the Sichuan Basin.  There are significant differences in their phenotypic traits, including body image, growth performance, and meat quality.  This study compared several meat quality traits of CH and QY pigs and conducted a genome-wide DNA methylation analysis using reduced representation bisulfite sequencing (RRBS).  It was observed that the pH at 45 min (pH_45min, P=5.22e–13), lightness at 45 min (L*_45min, P=4.85e–5), and lightness at 24 h (L*_24h, P=3.57e–5) of CH pigs were higher than those of QY pigs.  We detected 10 699 differentially methylated cytosines (DMCs) and 2 760 differentially methylated genes (DMGs) associated with these DMCs.  Functional analysis showed that these DMGs were mainly enriched in the AMPK signaling pathway, Type II diabetes mellitus, Insulin signaling pathway, mTOR signaling pathway, and Insulin resistance.  Furthermore, 15 DMGs were associated with fat metabolism (ACACA, CAB39, CRADD, CRTC2, FASN, and GCK), muscle development (HK2, IKBKB, MTOR, PIK3CD, PPARGC1A, and RPTOR), or meat quality traits (PCK1, PRKAG2, and SLC2A4).  The findings may help to understand further the epigenetic regulation mechanisms of meat quality traits in pigs and provide new basic data for the study of local pigs.

To develop a modified live vaccine (MLV) against porcine reproductive and respiratory syndrome virus (PRRSV), virulent CH-1a strain was attenuated by serial passages up to 130 passage (P130) in Marc-145 cells. The virulence and immune efficacy of the attenuated CH-1a were evaluated in pigs. The results showed that animals inoculated with P130 did not develop any clinical sign of the disease, but produced rapid and effective humoral immune responses against PRRSV challenge, indicating that attenuated CH-1a P130 is the candidate as the effective vaccine against PRRSV. To define the potential mutations in the attenuated CH-1a genome, we sequenced and analyzed the ORF5 gene of CH-1a strain of different passages (P39, P55, P65, P70, P85, P100, P115, P120, P125, and P130) and found that three mutations (C5Y, H38Q and L146Q) which may be related with the attenuation of CH-1a. In addition, we also found a unique restriction enzyme site (TspEI) in the ORF5 gene of attenuated CH-1a, which can be used as a genetic marker to distinguish original and attenuated CH-1a.