NUTRITIVE VALUE OF GROUND AND/OR AMMONIATED CORN STOVER

Abstract

Corn stover stacks were harvested and a portion of these were treated with anhydrous ammonia at a level of 3% of dry matter (DM) and left covered with plastic for at least 30 days during the fall of 1977. In the spring, both treated and untreated corn were chopped through a forage harvester. A portion of each was then ground through a 1.3-cm screen. Treatments were: untreated chopped, untreated ground, ammoniated chopped, ammoniated ground. Treatments were evaluated with eight Hereford-Angus yearling steers in a double 4 × 4 latin square design. In addition to the stover, rations contained 10% molasses, 6% soybean meal, and 2.3% mineral mix. Urea was added to the untreated rations at the level of 1.6% to make rations isonitrogenous. Steers were injected with vitamins A, D and E at 90-day intervals. With both control and ammoniated rations, grinding increased (P < 0.001) intake on a body weight raised to the 0.75 power basis (MBW) of DM, digestible energy (DE) and digestible DM by 47%, 39%) and 39%), respectively. With both chopped and ground stover rations, ammoniation increased (P < 0.001) intake of digestible DM and DE and increased (P < 0.01) intake of DM all on a MBW basis by 22%, 31% and 12%), respectively. However, grinding decreased digestibilities of DM and neutral detergent fibre (NDF) (P < 0.001) and of organic matter (OM) (P < 0.01) by 5%, 10% and 5%, respectively. With both chopped and ground stover rations, ammoniation increased (P < 0.001) digestibility of DM, OM, and NDF by 9%, 9% and 14%, respectively. Ammoniation plus grinding increased (P < 0.01) intake (MBW) of DM, digestible DM and DE by 64%), 71% and 85%), respectively, over untreated chopped rations. Grinding increased (P < 0.01) rumen acetate 0.5 h preprandially but did not significantly affect other rumen parameters measured preprandially or 2 h postprandially. Ammoniation increased (P < 0.01) rumen propionate 0.5 h preprandially but did not significantly affect the remaining rumen parameters. Before versus after feeding levels of rumen metabolites did not differ except for an increase (P < 0.01) in ammonia-N and total VFA postprandially. No significant treatment interactions were present.