I have been to see cattle on 5 properties where the owners were disappointed with weight gains. In all cases my observation was the cattle were being fed less than anticipated. Possibly because the crop yields had been over estimated or the dry matter percentage of the beets was less than expected. Allocating more feed by shifting the breaks more often or giving bigger breaks improved performance. (Beets being left behind, does not mean cattle are fully fed).
On some properties there has been inadequate feed space to allow animals access to the fibre source (straw/bailage) or the feeders have been placed too far from the beet break fence.
Low phosphorus levels were an issue in dairy cows and supplementation with phosphorus is necessary.
High incidences of woody tongue have been encountered, animals with woody tongue probably slobber over the beets as they try to eat and other animals pick up the bacteria in the saliva. Affected animals need to be identified, treated and isolated ASAP.
I remain unconvinced that the protein levels in fodder beet are sufficient to achieve good weight gains in young growing cattle over extended periods.