Abstract
Swine respiratory disease (SRD) causes massive economic losses in the swine industry and is difficult to control and eradicate on pig farms. Here, we employed population genetics and transcriptomics approaches to decipher the molecular mechanism of host adaptation to swine respiratory disease. We recorded two SRD‐related traits, the enzootic pneumonia‐like (EPL) score and lung lesion (LL) levels, and performed four body weight measurements, at ages of 150, 180, 240, and 300 days, in a Chinese Bamaxiang pig herd (n = 314) raised under consistent indoor rearing conditions. We divided these animals into disease‐resistant and disease‐susceptible groups based on the most likely effects of both SRD‐related traits on their weight gain, and performed genetic differentiation analyses in these two groups. Significant loci showing the top 1% of genetic differentiation values, exceeding the threshold of p = 0.005 set based on 1,000‐times permutation tests, were defined as candidate regions related to host resistance or susceptibility to SRD. We identified 107 candidate genes within these regions, which are mainly involved in the biological processes of immune response, fatty acid metabolism, lipid metabolism, and growth factor signaling pathways. Among these candidate genes, TRAF6, CD44, CD22, TGFB1, CYP2B6, and SNRPA were highlighted due to their central regulatory roles in host immune response or fat metabolism and their differential expression between healthy lung tissues and lung lesions. These findings advance our understanding of the molecular mechanisms of host resistance or susceptibility to respiratory disease in pigs and are of significance for the breeding pigs resistant to respiratory disease in the swine industry.
Highlights
Swine respiratory disease (SRD), referred as the swine/porcine respiratory disease complex (SRDC/PRDC), is prevalent in modern intensive pig farms worldwide and can cause poor porcine growth performance, in turn leading to serious economic losses to the swine industry (Opriessnig, Gimenez‐Lirola, & Halbur, 2011)
It was shown that 93.4% of pig lungs exhibited pneumonic lesions among 4,508 pigs at slaughter, and 98.1% of enzootic pneumonia (EP)‐affected lungs showed lesions similar to pneumonic lesions caused by M. hyopneumoniae (Wallgren, Beskow, Fellström, & Renström, 1994), which demonstrated that the pigs had been subjected to an adverse SRD environment
We first investigated the relationship of two SRD‐related traits, enzootic pneumonia‐like (EPL) scores and lung lesion
Summary
Swine respiratory disease (SRD), referred as the swine/porcine respiratory disease complex (SRDC/PRDC), is prevalent in modern intensive pig farms worldwide and can cause poor porcine growth performance, in turn leading to serious economic losses to the swine industry (Opriessnig, Gimenez‐Lirola, & Halbur, 2011). This disease is arguably the most important health concern for swine producers at present (Brockmeier, Halbur, & Thacker, 2002). Bamaxiang pigs are a well‐known Chinese indigenous breed distributed around Bama Yao Autonomous County in Guangxi Province, China These pigs are characterized by two‐end black coat color, small body size, and good meat quality (Wang et al, 2011). Our findings provide novel insights into the genetic architecture of host adaptation to swine respiratory disease, will be beneficial for the breeding of pigs resistant to swine respiratory disease in the swine industry, and may provide a useful reference for revealing the molecular genetic basis of host resistance to chronic refractory diseases in other mammals
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