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Three experiments were conducted to evaluate the effect of adding salts of formic acid to diets for growing-finishing pigs. In Exp. 1, 72 pigs (23.1 kg and 104.5 kg initial and final BW) were used to evaluate the effect of Ca/Na-formate and K-diformate on performance and carcass traits. Treatments were organized in a 2 x 3 factorial arrangement with two feeding regimens (limit and semi-ad libitum feeding) and three diets (control, .85% Ca/Na-formate, and .8% K-diformate). No significant feeding regime x diet interaction was found. The K-diformate diet increased overall ADG of pigs compared with the control and Ca/Na-formate diets, but had no effect on ADFI or gain/feed (G/F) ratio. Neither K-diformate nor Ca/Na-formate had any effect on carcass lean or fat content. In Exp. 2, 10 limit-fed pigs (24.3 kg and 85.1 kg initial and final BW) were used to study the effect of K-diformate on performance and sensory quality of pork. Adding .8% K-diformate to diets increased ADG (P < .13) and G/F (P < .04), but had no effect on sensory quality of the pork or content of formate in liver, kidney, or muscle tissue of pigs. In Exp. 3, 96 limit-fed pigs (27.1 kg and 105 kg initial and final BW) were used to determine the effect of adding K-diformate to diets on performance, carcass traits, and stomach keratinization and(or) lesions. Adding K-diformate (0, .6, or 1.2%) to diets increased ADG and ADFI (linear P < .01). The K-diformate reduced the percentage of carcass fat (linear P < .03) and fat area in the cutlet (linear P < .09) and increased percentage lean in the ham (linear P < .01), flank (linear P < .02), loin (linear P < .09), and neck and shoulder (linear P < .09). The K-diformate had no negative effect on stomach alterations. In Exp. 3, the concentration of coliform bacteria in the gastrointestinal tract was evaluated in eight control and eight 1.2% K-diformate-fed pigs. The K-diformate reduced the number of coliforms in the duodenum (P < .03), jejunum (P < .02), and rectum (P < .10) of pigs. In conclusion, K-diformate improved growth performance and carcass quality of growing-finishing pigs, whereas Ca/Na-formate had no effect. K-diformate had no adverse effect on sensory quality of pork or on stomach alteration scores.

The faecal concentration of substances responding to the chemical test for N-nitroso compounds (apparent total N-nitroso compounds, ATNC) was investigated in human subjects consuming their normal free-choice diet. Concentrations ranged from 40 to 590 micrograms (N-NO)/kg faeces. To ascertain the likely relative contributions of endogenous ATNC formation and preformed, dietary ATNC, the subjects consumed a diet low in nitrate and ATNC for 8 days. At the end of this period, ATNC had decreased substantially with concentrations ranging from below the 40 micrograms (N-NO)/kg detection limit up to 143 micrograms (N-NO)/kg, mean 82 micrograms (N-NO)/kg. On supplementing this diet with 300 mg nitrate/day, faecal ATNC levels increased markedly. On the third day of this regime, values were in the range 73-714 micrograms (N-NO)/kg with a mean of 307 micrograms (N-NO)/kg. The results, together with the known limited occurrence of ATNC in the majority of foodstuffs so far tested, generally non-detectable or less than 100 micrograms (N-NO)/kg, suggest that endogenous formation via species derived from dietary nitrate is likely to be an important source of ATNC in human faeces.

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