No abstract

Formic acid (FOR) is a silage additive used to suppress growth of undesired bacteria. However, its effects on silage quality and dairy cattle performance have not yet been systematically reviewed. The objectives of this study were to conduct a systematic review and meta-analysis (1) to evaluate the efficacy of FOR as a silage additive on fermentation quality and (2) to evaluate the effects of silage preserved with FOR on dairy cattle performance. One hundred and fifty-three and twenty-eight research articles were reviewed for silage quality and dairy cattle performance. The data were analyzed using a mixed model, with random effects of study and fixed effect of treatment (formic acid) The raw mean difference (RMD) for each response variable, with 95% confidence interval, was calculated as the difference between FOR and control diets. The additives increased (P < 0.01) dry matter intake (RMD = 0.540 kg/d), milk yield (RMD = 0.453 kg/d), fat (RMD = 0.115 %) and protein (RMD = 0.075 %) concentrations. Milk urea nitrogen (RMD = -0.813 mg/dL) and lactose (RMD = -0.018 %) were reduced (P < 0.01) with the use of additives. Formic acid increased (P < 0.01) silage dry matter (DM) concentration (RMD = 6.06 g/kg DM), recovery (RMD = 2.30 % of DM), and in vitro digestibility (RMD = 19.1 g/kg DM), and water-soluble carbohydrates (RMD = 16.5 g/kg DM) concentration. The addition of FOR reduced (P < 0.001) silage pH (RMD = -0.226), ammonia-N (RMD = -37.3 g/kg of total nitrogen), lactic (RMD = -13.4 g/kg DM), acetic (RMD = - 11.5g/kg DM) and butyric (RMD = - 1.92 g/kg DM) acids. Formic acid-based additives ( >50% of FOR) improved silage quality and dairy cattle performance.