Monosaccharides such as glucose contribute to the development of meat flavor upon heating via the Maillard reaction;
therefore, monosaccharide content is related to beef palatability. Here, we analyzed the effects of genetic and environmental
factors on the content of glycogen, one of the precursors of monosaccharides, in the muscles of 958 fattened
Japanese Black cattle from Yamagata Prefecture. Analysis of variance showed that muscle glycogen content was affected
by the farm and postmortem periods, but not by sex, slaughter age, slaughter month or number of days detained at the
slaughter yard. Additionally, consumption of digestible brown rice feed elevated muscle glycogen levels. Glycogen
heritability was estimated to be 0.34, and genetic correlations between glycogen and carcass weight (CW) or beef marbling
standard (BMS) were weak. The predicted breeding values varied among paternal lines. These results demonstrated that
genetic factors might improve muscle glycogen content and therefore beef palatability, but do not influence CW or BMS.