A new Food and Drug Administration (FDA) approval of an old feed ingredient allowed researchers to get feedlot cattle on top finisher ration faster and improved overall feedlot operational efficiency by reducing manure production.

Kansas State University beef feedlot researchers were able to transition feedlot steers from the starter ration to the final finisher ration in 10 days compared to a more traditional 21 days with the aid of Rumensin® fed at the new dose of 44 g/ton of ration dry matter (DM). Recently the FDA approved an expanded dosing range for Rumensin, allowing cattle feeders to feed up to a maximum of 44.4 g/ton of ration DM. The previously allowed maximum dose was 33.3 g/ton of ration DM.

The research compared starting yearling steers on a traditional four-ration, step-up program with diet changes occurring on days 6, 11, 16 and 21 days on feed vs. an accelerated step-up with changes made on days 4, 6, 8 and 10 days on feed.

Rumensin was fed at 30.0 vs. 40.0 g/ton of ration DM in the two step-up programs beginning on day one and throughout the entire 153-day feeding trial. The final ration contained 7% wheat straw, 58% dry-rolled corn, 30% wet distillers grains and 5% supplement, dry matter basis.

Steers started on the 10-day accelerated step-up program had identical feedlot performance and carcass traits, as did the steers started on the traditional 21-day step-up program. Total roughage consumption of steers started on the accelerated step-up program and fed 40 g/ton Rumensin was 59 lbs./head less over the entire feeding period than for steers started on the 30 g/ton Rumensin-traditional step-up program. The researchers calculated that this level of reduction in roughage consumption would equate to an annual reduction of about 3,000 tons of manure production in a 10,000-head feedyard.

Over the entire feeding period, steers fed Rumensin at 44 g/ton converted feed to gain 2.3% more efficiently than steers fed 33 g/ton of Rumensin. Daily gain and carcass weight weren’t different between the two Rumensin levels. Steers fed the higher level consumed 3.5% less feed – the expected response in cattle being fed Rumensin.

Meanwhile, Oklahoma State University feedlot researchers concluded that feedlot cattle can be adapted to the finishing diet by using a daily combination of the starter and finishing rations, thus eliminating step-up rations.

The researchers compared a traditional step-up program of five rations with a two-ration step-up program comprised of feeding differing proportions of the starter and finishing ration over a 28-day diet adaptation period.

The starter ration for both programs contained 70% concentrate fed for 7 days. The final finisher ration contained 94% concentrate. The three step rations of the traditional step-up program contained 76, 82 and 88% concentrate, respectively; and when fed, each was fed for 7 days. All rations contained Rumensin at 30 g/ton of ration DM; all cattle were fed twice daily.

Beginning on day 8, cattle in the two-ration step-up program were fed the daily feed call based on a predetermined schedule that decreased the proportion of the 70% concentrate starter diet fed in the a.m. feeding by about 5%, and increased the proportion of the 94% concentrate finisher diet fed in the p.m. feeding by about 5%. All cattle were fed the 94% finisher from day 29 until slaughter.

Feedlot performance and carcass traits were not different in cattle stepped-up by the different ration adaptation programs. Elimination of step-up rations will improve feedlot operational efficiencies. A two-ration step-up program may require some additional bunk management, the researchers note.

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– pages 112 and 99.

Scott B. Laudert, Ph.D., is a beef cattle technical consultant and former Kansas State University Extension livestock specialist based in Woodland Park, CO. Contact him at 719-660-4473.