Utilization of corn silage grown by conventional and sustainable methods fed with different nitrogen supplements

Abstract

A metabolism trial and a feedlot finishing trial were conducted with silage made from corn (Zea mays L.) forage grown by conventional and sustainable methods. For the metabolism trial, 24 wether lambs were allotted to four diets: 1) conventional corn silage supplemented with urea, 2) conventional corn silage supplemented with soybean meal (SBM), 3) sustainable corn silage supplemented with urea, and 4) sustainable corn silage supplemented with broiler litter. Apparent DM digestibilities were 65.9, 69.3, 63.8, 66.2%, for the respective diets. Apparent digestibilities of NDF, ADF, and cellulose were lower (P < .05) for the urea-supplemented diets than the SBM and broiler litter supplemented diets. Sheep fed sustainable silage supplemented with broiler litter had the highest (P < .05) fecal N excretion, due to at least partly to the highest (P < .05) N intake. Total N excretion was similar (P > .05) among sheep fed all diets. Sheep fed conventional and sustainable silages supplemented with urea were in negative N balance (-1.04, and -.38, respectively). Sheep fed the conventional silage supplemented with SBM and sustainable silage supplemented with broiler litter had similar (P > .05) positive N retention.

Conventional and sustainable silages were fed to feedlot steers and supplemented with either SBM or broiler litter. Conventional steers had a higher (P < .05) live weight (421 kg) upon entering the feedlot than the steers fed the sustainable diet (390 kg). Difference in ADG did not become apparent until the second-to-last 28-d period, at which time the conventional steers had a higher (P < .05) ADG than the steers fed the sustainable diet. Cattle fed the sustainable diet tended to consume more feed (P > .05) and had lower gain/feed (P < .05) than those fed the conventional diet. At slaughter, cattle fed the conventional diet were heavier (P < .05), (596 vs 541kg). Carcass maturity, marbling, backfat, percent kidney, pelvic and heart (KPH) fat, and quality grade were similar (P > .05) for the cattle fed the two diets. Carcass weight, ribeye muscle area, yield grade and dressing percentage were higher for the cattle fed the conventional diet, reflecting higher liveweight than cattle fed the sustainable diet.