The advantage of energy dense fat supplements in lactation rations to enhance performance in modern dairy cows has been cited since the early 1930s but the detrimental effect on rumen fermentation, particularly fibre digestibility, required further research. Compared to triglycerides, free fatty acids, particularly unsaturated, have been shown to have increased digestibility in the small intestine, but depress ruminal microbial metabolism when provided in large enough quantities. Early studies in the 1970s by Galbraith and co-workers showed the formation of calcium soaps of long chain fatty acids (LCFA) and reversal of the anti-bacterial effects of LCFA. However, adding calcium to the diet did not completely reverse the inhibitory effect of unsaturated fatty acids because the fatty acids do not react completely in the aqueous medium. Palmquist and Jenkins (1982) demonstrated the digestibility of pre-formed calcium soaps of fatty acids, their beneficial effect on increased digestibility of all dietary components and increased energy for lactation (Palmquist, 1984). Volac International Ltd worked alongside Palmquist in the early 1980s to develop calcium soaps of palm fatty acid distillate (PFAD) as a commercial protected fat supplement for the ruminant industry.