Collings, L. K. M., Proudfoot, K. L. and Veira, D. M. 2011. The effects of feeding untreated and formic acid treated colostrum ad libitum on intake and immunoglobulin levels in dairy calves. Can. J. Anim. Sci. 91: 55–59. Newborn dairy bull calves were fed 4 L of colostrum by esophageal feeder or offered untreated or formic acid-treated colostrum ad libitum for 24 h; effects on intake, serum immunoglobulin G (IgG) levels and behavior were measured. The untreated ad libitum group consumed more colostrum (6 vs. 4 L) but had comparable serum IgG levels to the control (27.8 vs. 28.1 mg mL^-1). Adding formic acid to colostrum successfully reduced total bacteria and coliform counts; however, it reduced 24 h ad libitum consumption. Formic acid is not a practical preservation agent for colostrum offered ad libitum to newborn calves.