Comparison of steroid hormone concentrations and mRNA levels of steroid receptor genes in longissimus dorsi muscle and subcutaneous fat between bulls and steers and association with carcass traits in Korean cattle

Castration of Korean cattle improves quality grade, and it reduces production of testosterone. Carcass traits, steroid hormone concentrations, aromatase activities, and expression levels of androgen receptor (AR) and estrogen receptor α (ERα) genes were compared in longissimus dorsi (LD) muscle and subcutaneous fat tissues between bulls and steers, and association of carcass traits with steroid hormone concentrations and mRNA levels of AR and ERα genes was estimated in order to identify factor(s) that contribute to improvement of beef meat quality. Steer showed better marbling score and better quality grade. Bulls showed higher testosterone concentrations in LD muscle than steers. mRNA levels of the androgen receptor (AR) gene in LD muscle were higher (p < 0.001) in bulls compared to steers, and those were negatively correlated with marbling score and quality grade. Steers showed higher concentrations of both 17α-estradiol (p < 0.05) and estrone (p < 0.1) in both LD muscle and fat tissues than bulls. Both 17α-estradiol and estrone concentrations and mRNA levels of estrogen receptor α (ERα) gene were higher in the muscle and fat tissues of steers than those in bulls. The 17α-estradiol and estrone concentrations and mRNA levels of the ERα gene in LD muscle were positively correlated with quality grade.