Through experience and experimentation, most folks have a feeding formula they believe helps them manage shrink. And, that’s a good thing, because research results are all over the board on what type of ration offers the most positive results.
For instance, in one KSU trial (Table 4) evaluating pre-fast diets the amount of shrink, relative to the makeup of roughage and concentrate in the ration, varied with the transportation time, as well as how and when the cattle were fed before fasting. In one case, steers fed a 50% concentrate diet shrunk less than those fed only hay. In another, steers fed hay shrunk less than those fed a 55% concentrate ration. You get the idea. Bottom line based on this and other data researchers conclude that it is questionable whether or not feeding concentrate prior to shipment will reduce shrink.
Likewise, research serves up varying results of the impact that feed additives may have on shrink (Table 5). For instance, suckling calves hauled 120 miles shrank 45% less when Lasalocid was included in creep feed prior to shipment, compared to calves fed creep without the additive. Stocker heifers hauled 300 miles shrank 8.3% when fed lasalocid in a mineral mixture, compared to heifers fed only mineral, or mineral with oxytetracycline. Those receiving lasalocid shrank a total of 5.5%, compared to 5.9% for those receiving oxytetracycline and 6.0% for the heifers receiving mineral without an additive. All told, indications are that feeding an ionophore for extended periods before shipment may help reduce shrink.
For that matter, as logical as it may be to assume that preconditioned cattle should shrink less, there is no definitive evidence either way so far.
Source: Beef Stocker USA