豬大腸桿菌F4ab/ac抵抗力相關基因單核苷酸多態型對藍瑞斯、約克夏及杜洛克豬生長性能與屠體性狀之影響

Abstract

下痢是仔豬最普遍的疾病，大腸桿菌則為常見的腸道病原，會導致新生仔豬下痢及離乳豬水腫病。腸毒素大腸桿菌是否能在小腸上繁殖，主要受到在小腸絨毛刷狀緣是否有受體所影響，若小腸刷狀緣有受體，菌體表面的菌毛會與小腸黏膜上皮細胞的刷狀緣黏合而致病。豬腸毒素大腸桿菌F4ab/ac抵抗力相關基因已被定位於第13號染色體長臂41區，mucin 4 (MUC4)、mucin 13 (MUC13)和transferrin receptor (TFRC)基因已被證實為腸毒素大腸桿菌F4ab/ac抵抗力的候選基因，唯選拔F4ab/ac抵抗力對豬隻生長性能與屠體性狀是否有負面影響則尚未有報告，因此，本研究之目的在探討杜洛克、藍瑞斯和約克夏純種豬腸毒素型大腸桿菌F4ab/ac抵抗力相關基因單核苷酸多態型(single nucleotide polymorphisms, SNPs)及其與生長性能和屠體性狀之關係。生長性能部分研究共使用1480頭以隔離早期離乳進豬之種豬性能檢定公豬(1057頭杜洛克、317頭藍瑞斯和106頭約克夏)，測量性狀包括背脂厚度、隻日增重、飼料效率、到達110kg日齡、150日齡體重等生長性狀，並計算其選拔指數；屠體性狀部分研究則使用159頭來自同一民間豬場之純種豬(100頭杜洛克、47頭藍瑞斯和12頭約克夏)，公豬與母豬分別為74頭與85頭，測量性狀包括屠宰率、第一肋背脂厚度、最後肋背脂厚度、最後腰椎背脂厚度、屠宰後45分鐘與24小時里肌及後腿部位之pH值；以聚合酶連鎖反應限制片段長度多態型分析法進行各候選基因SNPs分析 。研究結果顯示台灣藍瑞斯、約克夏和杜洛克之TFRC無多態型。MUC4-C8227G具易感性之G對偶基因頻率於種豬性能檢定之杜洛克、藍瑞斯和約克夏豬分別為0.02、0.46和0.51，於民間豬場母豬者為0.04、0.50和0.60，公豬為0.05、0.42和0.07；MUC13-A908G基因具易感性之G對偶基因頻率於種豬性能檢定之杜洛克、藍瑞斯和約克夏豬分別為0.50、0.71和0.62，於民間豬場者母豬為0.53、0.80和0.50，公豬為0.42、0.77和0.50，不同品種間MUC4和MUC13基因型頻率具顯著差異(P<0.0007)。MUC4及MUC13基因多態型對杜洛克和約克夏生長性狀均無顯著影響(P>0.05)，MUC4基因多態型會影響藍瑞斯豬到達110公斤日齡及150日齡時體重，MUC13基因多態型則會影響其背脂厚度；屠體性狀方面，對F4ac易感之MUC13 GG基因型有較高的屠後pH值。綜合本研究結果可知以MUC4及MUC13基因SNPs選拔腸毒素型大腸桿菌F4ab/ac抵抗病力將不會影響約克夏和杜洛克豬隻之生長性能，但選拔帶有MUC4抗病基因型藍瑞斯純種豬可能會影響其到達110公斤日齡和150日齡時體重，而MUC13基因SNPs對屠體性狀之效應則需更進一步驗證。

Diarrhea of neonatal and weaning pigs is a serious disease in pig industry. Enterotoxigenic E. coli (ETEC) expressing F4 fimbriae is a common porcine enteric pathogen, causing diarrhea in new born and weaning pigs, and edema disease in pigs after weaning. The F4 fimbriae are filamentous surface appendages that allow the bacteria to attach to F4 variant specific receptors on brush borders of enterocytes, and then to colonize the small intestine of piglets. The locus controlling susceptibility towards ETEC F4ab/ac has been mapped to SSC13q41. The mucin 4 (MUC4), mucin 13 (MUC13) and transferrin receptor (TFRC) genes have been proposed as candidate genes for the disease resistance to ETEC F4ab/ac. However, there was still no report on the possible effect of selecting resistance to ETEC F4ab/ac on the growth performance and carcass traits in pigs. The purpose of this study was to investigate the effect of single nucleotide polymorphisms (SNPs) in ETEC F4ab/ac resistance-related genes on the growth performance and carcass in purebred pigs in Taiwan. For evaluating the effect of selecting SNPs on growth performance, 1480 centrally performance tested purebred boars (1057 Duroc, 317 Landrace, and 106 Yorkshire) were used. The performance traits included average daily gain, feed conversion ratio, backfat thickness, age at 110 kg of body weight, and body weight at 150 days of age. The selection index of each individual was also calculated. For carcass traits, a total of 159 purebred pigs (100 Duroc, 47 Landrace and 12 Yorkshire) from a commercial farm were used. There were 74 males and 85 females. The carcass traits included dressing percentage, backfat thickness at the first-rib, the last-rib, and the last lumbar backfat and pH value of ham and loin muscle at 45 minutes and 24 hours postmortem. The genotypes of MUC4, MUC13 and TFRC SNPs were determined by polymerase chain reaction based restriction fragment length polymorphism. The results indicated that there was no polymorphism in TFRC. The allelic frequencies of the ETEC F4ab/ac susceptive G allele in MUC4-C8227G in centrally performance tested Duroc, Landrace, and Yorkshire pigs were 0.02, 0.46, and 0.51, respectively. The allelic frequencies in the pigs from the commercial farm in female were 0.04, 0.50, and 0.60. In males, the allelic frequencies were 0.05, 0.42, and 0.07. The allelic frequencies of G allele in MUC13-A908G in the centrally performance tested boars were 0.50, 0.71, and 0.62 in the three breeds of pigs. The allelic frequencies of MUC13-A908G in female pigs of the three breeds from the commercial pig farm were 0.53, 0.80, and 0.50. In males, the allelic frequencies were 0.42, 0.77, and 0.50. Results of statistical analysis revealed that there was no significant effect of the SNPs in MUC4 and MUC13 on the growth performance in Duroc and Yorkshire (P>0.05). The SNP in MUC4 showed significant effect on days of age arrive 110 kg body weight and body weight at 150 days of age of Landrace boars. For carcass traits, the susceptible GG type in MUC13 showed higher pH value than other genotypes. The results of this study suggested that selecting disease resistance to ETEC F4ab/ac by SNPs in MUC4 and MUC13 may not affect the growth performance in Duroc and Yorkshire pigs, but may affect the growth of Landrace pigs. However, the effect of SNP in MUC13 on carcass traits requires further validation.