Higher expression of acyl-CoA dehydrogenase genes in adipose tissues of obese compared to lean pig breeds.

The balance between biosynthesis and oxidation of fatty acids determines adipose deposition in mammals. Obese and lean pigs show obvious differences in total adipose mass and therefore offer an attractive model for comparative studies. We found that obese Rongchang pigs, when compared with lean Landrace pigs, exhibited significantly higher mRNA levels for five genes encoding acyl-CoA dehydrogenases involved in mitochondrial fatty-acid ß-oxidation in eight different adipose tissues. These changes in gene expression were positively correlated with adipocyte volume in the eight adipose tissues. Based on these results, we hypothesize that acyl-CoA dehydrogenase genes participate in the regulation of fat mass in pigs.

Distribution of H-FABP and ACSL4 gene polymorphisms and their associations with intramuscular fat content and backfat thickness in different pig populations.

Here, we analyzed the distribution of H-FABP/(HinfI, MspI, and HaeIII) and ACSL4/RsaI polymorphisms, and the associations of these 4 polymorphic loci with intramuscular fat (IMF) content and backfat thickness (BFT) in Yanan, Jinhua, Duroc, Landrace, Yorkshire, and Duroc x (Landrace x Yorkshire) (DLY) pigs. H-FABP/HinfI polymorphisms were present in all the 6 populations. At the ACSL4/RsaI locus, sows had 3 genotypes, whereas boars only had haplotype A or G, in Duroc, Landrace, Yorkshire, and DLY pigs. H-FABP/(MspI and HaeIII) and ACSL4/RsaI polymorphisms were absent in Yanan and Jinhua pigs. Linkage disequilibrium analysis indicated that the 3 loci (HinfI, MspI, and HaeIII) were separated. Association analysis showed that the H-FABP/HinfI locus significantly affected IMF content in DLY (P < 0.05) and Yanan (P < 0.001) pigs. The highest IMF content was recorded in the adH haplotype of the 3 H-FABP polymorphic loci (2.59%, P < 0.05) in DLY pigs. At the ACSL4/RsaI locus, higher IMF content was recorded for sows with a GG genotype or boars with a G haplotype compared to those with an AA genotype (2.53 vs 2.10%, P < 0.05) or A haplotype (2.48 vs 1.73%, P < 0.01) in DLY pigs. Significant differences were not obtained among these 4 polymorphic loci and BFT (P > 0.05). The results indicate that H-FABP and ACSL4 genes might serve as markers to improve IMF content (but not BFT) in the pig breeding system.

Inbreeding and genetic diversity in three imported Swine breeds in china using pedigree data.

The accumulation of inbreeding and the loss of genetic diversity is a potential problem in the modern swine breeds in China. Therefore, the purpose of this study was to analyze the pedigrees of Chinese Duroc (CD), Landrace (CL) and Yorkshire (CY) swine to estimate the past and current rates of inbreeding, and to identify the main causes of genetic diversity loss. Pedigree files from CD, CL and CY containing, 4529, 16,776 and 22,600 records, respectively, were analyzed. Pedigree completeness indexes of the three breeds, accounting for one generation back, were 83.72, 93.93 and 93.59%, respectively. The estimated average annual inbreeding rates for CD, CL and CY in recent three years were 0.21, 0.19 and 0.13%, respectively. The estimated average percentage of genetic diversity loss within each breed in recent three years was about 8.92, 2.19, and 3.36%, respectively. The average relative proportion of genetic diversity loss due to unequal contributions of founders in CD, CL and CY was 69.09, 57.95 and 60.57%, and due to random genetic drift was 30.91, 42.05 and 39.43%, respectively. The estimated current effective population size for CD, CL and CY was 76, 117 and 202, respectively. Therefore, CD has been found to have lost considerable genetic diversity, demanding priority for optimizing the selection and mating to control future coancestry and inbreeding. Unequal contribution of founders was a major cause of genetic diversity loss in Chinese swine breeds and random genetic drift also showed substantial impact on the loss of diversity.

Carcass and meat quality traits of four commercial pig crossbreeds in China.

We evaluated carcass and meat quality traits of two Chinese native crossbreeds Landrace x Meishan (LM) and Duroc x (Landrace x Meishan) (DLM) and two foreign crossbreeds Duroc x (Landrace x Yorkshire) (DLY) and PIC (an imported five-way crossbreed). One hundred and twenty weaned pigs (half castrated males and half females) were reared and slaughtered at a predestinated slaughter age. The general carcass and meat quality traits were measured and analyzed. The DLY and PIC crosses had significantly heavier live weights (93.39 and 96.33 kg, P < 0.01), significantly higher dressing percentages (80.65 and 79.39%, P < 0.05), significantly bigger loin areas (42.69 and 43.91 cm(2), P < 0.001), and significantly more lean carcasses (65.78 and 66.40%, P < 0.001) than LM and DLM. On the other hand, LM had a significantly lower live weight (70.29 kg, P < 0.01), significantly thicker back fat (3.54 cm, P < 0.001), significantly less lean carcasses (46.82%, P < 0.001), and significantly less ham and breech (26.53%, P < 0.05) than the other crossbreeds. Among meat quality parameters, LM had the highest intramuscular fat content (5.02%, P < 0.001) and the smallest fiber area (3126.45 µm(2), P < 0.01). However, PIC showed the lowest pH(1) (5.82, P < 0.01) and pH(2) (5.63, P < 0.01), the highest drip loss (2.89%, P < 0.01), and the lowest intramuscular fat (1.35%, P < 0.001). We concluded that LM and DLM had good meat quality traits but poorer carcass traits than DLY and PIC; DLY had good carcass and meat quality traits; PIC had good carcass traits, but it had less intramuscular fat, lower pH and higher drip loss.

Evaluation of endogenous control genes for gene expression studies across multiple tissues and in the specific sets of fat- and muscle-type samples of the pig.

To normalize a set of quantitative real-time PCR (q-PCR) data, it is essential to determine an optimal number/set of housekeeping genes, as the abundance of housekeeping genes can vary across tissues or cells during different developmental stages, or even under certain environmental conditions. In this study, of the 20 commonly used endogenous control genes, 13, 18 and 17 genes exhibited credible stability in 56 different tissues, 10 types of adipose tissue and five types of muscle tissue, respectively. Our analysis clearly showed that three optimal housekeeping genes are adequate for an accurate normalization, which correlated well with the theoretical optimal number (r ≥ 0.94). In terms of economical and experimental feasibility, we recommend the use of the three most stable housekeeping genes for calculating the normalization factor. Based on our results, the three most stable housekeeping genes in all analysed samples (TOP2B, HSPCB and YWHAZ) are recommended for accurate normalization of q-PCR data. We also suggest that two different sets of housekeeping genes are appropriate for 10 types of adipose tissue (the HSPCB, ALDOA and GAPDH genes) and five types of muscle tissue (the TOP2B, HSPCB and YWHAZ genes), respectively. Our report will serve as a valuable reference for other studies aimed at measuring tissue-specific mRNA abundance in porcine samples.