[Single nucleotide polymorphism analysis in sow mu opioid receptor gene exon III]

Stereotypies are the most common abnormal behaviours in sows. Stereotypies are repeated, relatively invariable sequences of movements which have no obvious purpose. Mu opioid receptor is a member of G protein-coupled receptor family, distributed in the pain transduction region in the brain and related emotion and behavior regions where influence the animal neural reaction and behavior. The possibility of the MOR gene as the candidate gene to affect the stereotyped behavior traits in sows was discussed in this study. The primer of sow MOR gene exon III partial sequence was designed to analyze single nucleotide polymorphisms by PCR -SSCP in Landrace, Yorkshire and Duroc breeds. Two polymorphisms were found, which was caused by a single nucleotide mutation of C to T and C to A at the positions of 1169 and 1226, respectively compared with the sequence in GenBank, but it was the silence mutation. The results of chi 2 test showed that the frequencies of genotypes resulted in different breeds were significantly different (P < 0.01). The least square analysis between the nucleotide acid mutant induced three genotypes and the stereotyped behavioral traits in Yorkshire showed that individuals with BB genotype have significant higher (P < 0.01) sham-chewing behavior than those with AA genotype, but not for bar-biting and standing. According to the above results, we can putatively draw the conclusion that MOR gene is probably the major gene affecting the sham-chewing behavioral traits or linked to the major gene.