The levels of delta-valerobetaine were by far higher in ruminant than in non-ruminant meat and, among ruminants, cattle present higher levels of the substance than sheep and goat. The levels of delta-valerobetaine in milk of ruminants are much lower than in their meat. However, delta-valerobetaine content in milk of ruminants is noticeably higher than that observed in non-ruminant milk. It is showed that incubation of ruminal fluid with labeled N-trimethyllysine leads to a rapid formation of labeled delta-valerobetaine.