Daily gain among wheat pasture stockers was increased by nearly ½ lb./day with the use of Rumensin® in a mineral supplement or block, and an implant. The net return of these technologies is substantial in today’s market and shouldn’t be overlooked.

University of Arkansas (UA) beef researchers studied the effects of growth-promoting implants and Rumensin fed via a free-choice mineral supplement or a pressed-protein block supplement in 525-lb. stocker steers. The steers were grazed on wheat pasture in northeast Arkansas over two, 75-day combined fall- and spring-grazing seasons.

Steers in separate pastures were given access to:

  • A non-medicated free-choice mineral,
  • A free-choice Rumensin-containing mineral or
  • A pressed-protein Rumensin block.

Stocking rate was one steer/acre in the fall-grazing season, and two steers/acre in the spring-grazing season.

The Rumensin free-choice mineral supplement and block contained 1,620 and 300 grams/ton of Rumensin, respectively. The supplements were fed in covered mineral feeders and intake was recorded weekly. Half the steers in each pasture were implanted with a Component® TE-G implant, while the other half was not implanted.

Daily gain was increased by 0.18 lb./day for the steers fed either the Rumensin free-choice mineral or the Rumensin block, compared to the non-medicated mineral-fed steers. Daily gain wasn’t different for the cattle consuming Rumensin by either of the delivery methods. Implanted steers gained 0.32 lb./day faster than non-implanted steers. The responses to implanting and feeding Rumensin are in close agreement with research from other university trials.

Oklahoma State University (OSU) beef researchers found it was beneficial to feed a free-choice mineral supplement to steers grazing wheat pasture. Gain was increased by 0.24 lb./day in the cattle offered a free-choice mineral compared to cattle fed no mineral. However, daily mineral consumption was determined to often be higher than the level needed to meet nutritional requirements of grazing steers.

Meanwhile, daily consumption of the non-medicated mineral in the UA study averaged 5.8 oz./head/day and was 38% greater than the targeted intake of 4 oz./head/day. Daily intake of the Rumensin mineral was 3.7 oz./day, which was more in line with the desired mineral consumption.

Free-choice mineral intake of cattle grazing wheat pasture often exceeds the intended daily consumption level, and over consumption can become quite costly. Mineral intake can be held in check by including Rumensin in the free-choice mineral mixture; an unforeseen, but economically favorable benefit.

Several OSU studies have shown that Rumensin-fed wheat pasture stockers consume up to 60% less mineral mix containing Rumensin, while gaining up to 0.2 lb./day more weight than non Rumensin-supplemented cattle consuming greater amounts of mineral. Mineral consumption of cattle grazing wheat pasture should be closely monitored to ensure that adequate, but not excessive, quantities are being consumed.

OSU studies have also shown that Rumensin can reduce the incidence of bloat in stockers grazing wheat pasture. The level of control is likely related to the quantity and consistency of Rumensin consumed and growth characteristics of the wheat forage.

The use of growth-promoting and feed-additive technologies can have profound effects on grazing cattle returns without increasing feeding costs. Utilizing Rumensin and implants together was calculated to reduce cost of gain by 25%. UA researchers projected a return from implanting of $60/head, and a $50/head return from feeding Rumensin. Use of these and other technologies must always be considered.

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