Pre-weaning and post-weaning diarrhea are common in the pig industry. This disease results in significant economic losses due to high mortality and morbidity. In addition, an outbreak of diarrhea leads to a low growth rate after recovery from the illness as a consequence of using antibiotics for treatment, which increases the risk of anti-microbial resistance (Fairbrother et al., 2005). According to Luise et al. (2019), most types of diarrhea in piglets are caused by enterotoxigenic Escherichia coli (ETEC). There are two types of virulence factors that allow ETEC to cause diarrhea, namely enterotoxins and fimbrial adhesins. ETEC expressing F4 fimbriae causes more severe diarrhea in nursery, weaning, and weaned piglets (Vu-Khac et al., 2007; Kim et al., 2010). Nevertheless, not all pigs are susceptible to ETEC F4 infection due to the presence and number of F4 specific receptors in the brush border of the small intestine, which prevent ETEC from adhering and developing diarrhea (Sterndale et al., 2019). The mucin 4 (MUC4) gene, which is located on chromosome 13 and physically mapped to SSC13q41 (Jacobsen et al., 2011), encodes a membrane-bound O-glycoprotein (F4 receptor) in pigs (Fontanesi et al., 2012).
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F4 receptors are present on the surface of gastrointestinal epithelial cells and act as a functional barrier to cover and protect mucosal surfaces. From literature studies, MUC4 has been considered as the most promising candidate gene for F4 receptors (Jørgensen et al., 2003; Joller et al., 2009; Jacobsen et al., 2011). The study by Joller et al. (2009) reported the strong association of the XbaI polymorphism in intron 7 of MUC4 with the susceptibility of the animal, where allele C is associated with resistance while allele G is associated with susceptibility. In the study of Peng et al. (2007), the MUC4 g.243A>G mutation in intron 17 was associated with susceptibility/resistance to ETEC F4ab/ac infection.
The effects of MUC4 on animal resistance to ETEC have been shown repeatedly. Polymorphisms of the MUC4 gene have been used as markers to identify the susceptibility of animals for breeding selection in many countries. However, the frequencies of alleles and genotypes of MUC4 polymorphisms have been shown to vary in different breeds (Fontanesi et al., 2012). In addition, MUC4 polymorphisms may be associated with other production traits of pigs. Therefore, selection focused on candidate genes such as MUC4 to improve disease resistance should consider the impact selection has on other important economic traits. A study of Balcells et al. (2011) showed that the mutation g.243A>G in intron 17 of MUC4 did not affect the total number of piglets born or number born alive. Inversely, a study by Liu et al. (2015) confirmed that the GG genotype, which relates to the resistant genotype, showed a strong association with improvement of IL8, IL10, and age for pigs that reached a bodyweight of 100kg compared with the AA and AG genotypes.
Porcine mucin 4 (MUC4) is a candidate gene for controlling the adhesion of the enterotoxigenic Escherichia coli (ETEC) F4 receptor. Polymorphisms of the MUC4 gene have been used as markers to identify the susceptibility of neonatal diarrhea in piglets for breeding selection. The objective of this study was to evaluate the effects of MUC4 g.243A>G polymorphisms on the production traits of Landrace and Yorkshire pigs in Vietnam. A total of 1,057 Landrace and 1,361 Yorkshire piglets were used to estimate the allelic and genotypic frequencies of the polymorphisms. Body weights at birth, at weaning, at initial fattening (IBW), and at the end of fattening period (FBW), backfat thickness (BFT), and depth of the longissimus dorsi muscle (DLD) were measured and lean meat percentage was estimated. Frequency of the susceptibility allele A to ETEC was higher than the resistance allele G for both breeds based on genotyping piglet tails collected at birth. The AA, AG, and GG genotypes were present in Yorkshire while GG was not found in Landrace. The production traits were not affected (P >0.05) by MUC4 polymorphisms except BFT and DLD (P <0.05). There were interactions between gender and MUC4 genotype (P <0.05) for IBW, FBW, average daily gain, and DLD. These traits of GG males were significantly higher than those of GG females (P <0.05). The results suggest that selecting pigs carrying the GG genotype of MUC4, known as providing resistance to ETEC, do not negatively affect productive performance in Landrace and Yorkshire pigs.
The full paper can be accessed here on Vietnam Journal of Agricultural Sciences (ISSN 2588-1299).
References
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