Static plant for preparing feed mixes for ruminant livestock, having a conveyor unit for conveying the feed mix ingredients, chain and/or screw feeders, feeders with weight sensors and supplementary conveyor belt, silos of solid ingredients, and silos of liquid ingredients, independently supplying two or more high-capacity mixers, via the conveyor unit by a dual flow, the mixers including weight control means, laser sensors and strain gauges. The invention allows for mixing to be controlled with increased accuracy and, consequently, improving the quality of the mix, using fully automated continuous operating cycles, the resulting mix being discharged onto any type of known device using discharging means, for its distribution.