Enhanced Retinol Extraction From Bovine Whole Blood Using n-Hexane and Phosphate-Buffered Saline

Ensuring optimal blood retinol levels of cattle during fattening is essential for achieving high-quality marbling in beef production. We previously developed a rapid analytical method for measuring blood retinol concentration that eliminates the process of blood cell separation. However, achieving a strong correlation with actual retinol levels proved challenging due to the requirements of vigorous agitation of blood and n-hexane using a vortex mixer. Consequently, in this study, we developed a modified method that does not require intense agitation by adding phosphate-buffered saline (PBS) to the blood and n-hexane mixture. The addition of PBS facilitated the dispersion of whole blood in n-hexane, although the augmented interface between the two enhanced extraction efficiency. Furthermore, we conducted field tests using blood samples collected from 98 fattening cattle from six different farms, each using distinct feeding methods and rearing environments, to reflect the diverse feeding practices in Japanese Black beef production. Their retinol concentrations were analyzed using the developed method and compared with values obtained by HPLC. A correlation coefficient of 0.94–0.96 was obtained, indicating that blood retinol levels can be reliably measured even among farms with different feeding methods.