Effects of single nucleotide polymorphisms in leptin and pro-opiomelanocortin on peripheral eucocyte counts in beef cattle

Abstract

Single nucleotide polymorphisms (SNP) in leptin (LEP) and pro-opiomelanocortin (POMC) have been associated with beef carcass quality and yield respectively. Both hormones also play a role in immune performance. Since both of these genes are pleiotrophic, it was important to determine whether selection based on these SNPs would negatively affect immune cell numbers. A SNP in each of these hormones was assessed for effects on immune cell counts and antibody titres in twenty-seven beef cattle herds (n = 556). A commercial rabies vaccine was administered to these animals. Prior to being vaccinated, the types of lymphocytes evaluated included B cells, gamma delta cells, regular and activated CD4 and CD8 cells and numbers of lymphocytes as well as baseline serum antibody titres. On day 21, antibody titres were measured and a booster vaccine was administered. Finally on day 42, antibody titres and lymphocyte types were again counted. Several cell types were significantly associated with the LEP genotype however, no consistent pattern of correlation was observed between LEP genotype (TT, CT or CC) and peripheral blood lymphocyte populations. The number of different lymphocytes significantly associated with LEP genotype increased from two on day 0 to four on day 42. Animals with CT and CC genotypes had significantly higher increased rabies antibody titres in the first 21 days after vaccination than those with TT genotypes. The POMC SNP also did not show a clear pattern of association between lymphocyte subtypes and genotype. There was no difference in response to the rabies vaccination associated with the POMC genotype. Our results suggested that selection at either of the SNPs examined in this research would not detrimentally impact immune function in beef cattle.