Provided is the use of a feed supplement, produced by reacting an organic acid containing precursor and a multivalent cation source, to improve food utilisation in ruminants. The organic acid containing precursor is an undried fermentation by-product, an undried fermentation product, an acidic plant material or an undried pomace. The organic acid containing precursor contains C3 or C4 organic acids. Exemplified precursors include distillers condensed solubles syrup and red grape marc. The multivalent cation source is preferably calcium, magnesium, iron, copper, cobalt, chromium, molybdenum or manganese. The source of the multivalent cation is preferably an oxide, carbonate, hydroxide, phosphate, halide or sulphate.
