Feed conversion (FC) is key to understand income over feed costs in dairy farms; however, FC is highly variable in commercial farms due to the multiple management factors involved. A 5-year (2012 to 2016) data set from 4 pens (early and mid-lactation multiparous cows, early and mid-lactation primiparous cows; n = 7300) from a commercial dairy farm (Chiavassa Dairy Farm, Argentina; −32° 02′ 60″ S, −61° 47′ 59″ W) was used to investigate which performance and feed management variables affect FC variability. Variables were recorded daily and included: milk yield (MY, kg/d), dry matter intake (DMI, kg/d), FC (kg milk/kg DM), and TMR DM content (%TMRDM). For the complete set of 5-year, coefficient of variation (CV) between days (i.e., from previous to current day or −1 d vs. 0 d) was then estimated for each of those variables. Individual MY was recorded by ALPROTM (DeLaval) and averaged by pen. DMI was estimated by difference between feed offered and refused, divided by the number of cows per pen. Offered TMR and orts DM content was determined in a forced-air oven for 2 h at 135°C. Holstein cows were milked 3x/d and fed 2x/d with a TMR (corn silage, alfalfa silage, alfalfa hay, corn grain, soybean meal, mineral premix; 49.8 ± 1.1% DM, 15.8 ± 0.9% CP, 29.9 ± 5.3% NDF, 3.9 ± 0.3% ether extract, and 2.89 ± 0.15 Mcal ME/kg DM; mean ± SD). Partial correlations (r; calculated using the MANOVA / PRINTE commands of PROC GLM of SAS version 9.3, SAS Institute Inc., Cary, NC) evaluated association between CV of FC and the other variables. The model included year, month, and pen. Coefficient of variation of FC was highly and positively correlated (P < 0.01) with CV of DMI (r = 0.90) and CV of MY (r = 0.34). It was also positively correlated (P < 0.01) but to a lesser extent with FC (r = 0.25), CV of %TMRDM (r = 0.08), and %TMRDM (r = 0.04). On the other hand, CV of FC was negatively correlated (P < 0.01) with DMI (r = - 0.24) and MY (r = - 0.07). Our data show that FC variability could be reduced by reducing daily variation in DMI and increasing DMI.