Determining the sex of store-bought beef to distinguish between endogenous and exogenous hormone residues

Establishing the sex-of-origin for beef products is an important consideration for distinguishing between endogenous and exogenous hormone sources. A quantitative polymerase chain reaction (qPCR) assay was developed to determine the sex of store-bought beef products, which detected as little as 0.003% male in a female sample. Of the 213 store-bought beef steak and organ samples, 56% originated from males and 44% from females. Among ground beef samples (n = 108), 78.7% were mixed male/female, 16.7% were male, 3.7% were female contaminated with a low-level of male, and 0.9% were female. Liquid chromatography tandem-mass spectrometry was used to quantify 12 endogenous or synthetic hormones/hormone growth promotants (HGP) in 517 beef samples. Meat, organs and adipose from steers implanted with HGP served as positive controls for sex genotype and hormone-treatments. Among all samples tested, two HGP (trenbolone, n = 2; and melengestrol acetate, MGA, n = 78) were detected. Two endogenous hormones that potentially originated from HGP, namely progesterone (P4; n = 140) and testosterone (n = 23), were also detected. MGA and P4 were highest in female samples (P < 0.0001), testosterone was highest in male samples (P < 0.05), while testosterone levels correlated with epitestosterone in male samples (R² = 0.33). Based on the sexing of samples, all P4 and testosterone detections were almost certainly from endogenous sources. MGA was detected in seven male samples, two organic samples and six samples marketed as "Hormone Free", which was inconsistent with product usage guidelines or label claims. These results demonstrate the efficacy of qPCR for determining the sex of store-bought beef for identifying the origin of residual hormones.