Meta-analysis of the effects of ionophores supplementation on dairy cows performance and ruminal fermentation

A meta-analysis of 52 peer-reviewed papers was conducted to investigate the effects of ionophores (IOP) supplementation on the performance and ruminal fermentation of lactating dairy cows. We used random-effects models to examine the raw mean difference (RMD) between the IOP group (diets with IOP) and the control group (diets with no additives), weighed by inverse of the variance. We also evaluated the effects of the covariates IPO supplementation level dose groups ( 25 mg/kg dry matter (DM) diet), IOP type (monensin or lasalocid), feeding system (total mixed ration or pasture) and days in milk (DIM) on RMD, by meta-regression and subgroup analysis. Overall, IOP supplementation (21.3 ± 8.3 mg/kg DM) reduced DM intake (DMI; RMD = - 0.39 ± 0.22 kg/d; P N (P = 0.63) and acetate concentrations (P = 0.08); however it enhanced the rumen concentration of propionate (P