Corn Moisture, Protein Concentration and Rumensin and Digestion by Feedlot Steers

Sixteen steers (650 Ib) were used to determine the effects of corn moisture, protein concentration and monensin (Rumensin) on ration digestibility and nitrogen retention. The steers were placed in metabolism stalls and fed rations of high moisture corn (HMC) or dry rolled corn at two protein levels (9.3 and 12.3 percent) with two monensin levels (0 and 30 g per ton of feed). Monensin addition decreased feed intake and increased digestibility of dry matter, organic matter, starch and nitrogen. The higher protein concentration increased nitrogen retention and digestibility of dry matter, organic matter, nitrogen, starch and ash. HMC had greater digestibility of dry matter, starch and organic matter than dry corn but produced lower dry matter intake and nitrogen retention. Although no monensin-protein interaction was apparent, addition of either protein or monensin to the low protein ration enhanced digestibility. Consequently, monensin may "spare" protein by this action. Responses to monensin supplementation were greater for dry rolled than high moisture corn suggesting that monensin benefits may be greater with less processing of the grain.