Conjugated salt of potassium formate and formic acid. Feed additive for pigs; promotes growth and controls microbial activity by decreasing the pH of the digestive tract. Prepn: E. Groschuff, Ber. 36, 1783 (1903). X-ray crystal structure: G. Larsson, I. Nahringbauer, Acta Crystallogr. B24, 666 (1968). Electron density study: K. Hermansson, R. Tellgren, ibid. B45, 252 (1989). Growth-promoting effects in pigs: B. R. Paulicks et al., Agribiol. Res. 49, 318 (1996); M. Kirchgessner et al., ibid. 50, 1 (1997). Antimicrobial effects in pig digestive tracts: N. Canibe et al., J. Anim. Sci. 79, 2123 (2001).