Enhancing the feeding value of corn crop residues to improve beef cattle production

Corn has been used in cattle diets for more the 50 years in the United States. However, since 2005 when the “Ethanol Era” started, the demand for corn to be converted in to ethanol has been increasing. The increased demand for corn to be converted into ethanol, led to increased corn prices. When corn prices peaked, alternative feeds for beef cattle become more popular, particularly co-products from corn industry. For many years, distillers grains and solubles (DGS) were used in order to replace corn in cattle diet. However, DGS prices followed corn prices, and soon became an expensive energy source in cattle diets as well. Another byproduct that can be included in cattle diets is corn stover. Corn stover is one of the most abundant crop residues in the United States. Corn stover is the material (husk, leaf, and stem) left on the field following a combine, after traditional corn harvest. However, corn stover is a poor quality forage, limiting energy and protein, and has functioned mainly as a source of bedding or as a fiber source in cattle diets. In recent years, more research has been conducted in order to increase the inclusion of corn stover in growing cattle diets. Most of that research has been focused on treating corn stover chemically or physically in order to improve the feeding value by breaking lignin-hemicellulose bonds to increase digestibility. However, there are extra costs and hazards to manage when chemically treating corn stover. These costs and hazards, in addition to the extra labor involved in both physical and chemical processing, create challenges when applying these techniques in small scale operations. Harvesting less mature plants yields a material that has less lignin, thus, less bonding with hemicellulose, and tends to improve digestibility and cattle feedlot performance. However, feeding immature corn crop residues to cattle has not been heavily investigated. Feeding immature residues lends itself to harvesting these residues wet and storing them as silages. The use of forage additives, such as lactobacillus and propionic acid, improve the quality of ensiled whole corn plants and small grains; however, they have not been investigated as means to improve ensiling of corn crop residues. Therefore, the objectives of this study were to test the feeding value of corn plant residues, harvested at 2 maturities, and the effects of additives, Silage SAVOR Plus (propionic acid-based additive) or Silo-King (lactobacillus-based additive), on in situ fiber disappearance, economic traits, and growth performance and carcass characteristics of growing feedlot cattle. Steers were fed 1 of 4 treatments: 1) corn stover wetted to 40% DM and ensiled (SVT), 2) corn stalklage, harvested at 40% DM and ensiled (STK), 3) corn stalklage plus Silo-King (STKL; Silo-King, Agri-King, Inc., Fulton, IL at 0.25 kg/ton), or 4) corn stalklage plus Silage SAVOR Plus (STKP; Silage SAVOR Plus, Kemin Industries, Inc., Des Moines, IA at 0.5 kg/ton). Corn stover (71.5% NDF, 6.12% CP, and 5.88% lignin) was harvested 186 d post planting, after dry corn (88% DM). Corn stalklage (68.3% NDF, 6.24% CP, and 5.39% lignin) was harvested 158 d post planting, after harvesting high moisture corn (HMC; 77% DM). Diets were fed for 85 d (growing phase of the feedlot), and contained 25% corn plant residue, 30% modified wet distillers grain with solubles (MWDGS), 35% HMC, and 10% supplement (DM basis). From d 86 to 186 (finishing phase of the feedlot), all steers were fed a common finishing diet that contained 20% silage, 20% MWDGS, 50% HMC, and 10% supplement (DM basis). In order to characterize corn stover composition a chemical, physical and in situ analysis were conducted. The in situ analysis was conducted in order to determine in situ DM disappearance (DMD) and NDF disappearance (NDFD). Corn plant residue samples (SVT, STK, STKL and STKP) were incubated in 2 ruminally fistulated steers for 12, 24, 36 and 48 h. There were no effects of treatment on DMD (P = 0.40) and NDFD (P = 0.34) over time. Average NDFD at 48 h were 27.39, 30.59, 32.50, and 29.45% for ST, STK, STKL, and STKP, respectively. Feeding wetted corn stover resulted in similar ruminal fiber degradation, and steer growth and carcass performance as feeding corn stalklage. There was a treatment effect (P ≤ 0.03) on corn stover particle size (0.8 to 1.9 cm and >1.9 cm) for SVT and STKP treatments, which was not expected since all of the materials went through the same harvesting process; however, the difference in particle size did not impact another measurements on the current trial. During the first 85 d, when fed 25% of corn residue, there were no difference in ADG during the first 85 d on feed, steers gained on average 1.69, 1.80, 1.74, and 1.67 kg/d when fed SVT, STK, STKL, and STKP, respectively. There were no carry-over effects (P ≥ 0.66) of treatment from d 86 to 186; thus, there were no effects (P ≥ 0.78) of treatment on overall steer performance for the entire 186 d. Yield and quality grade distributions, HCW, marbling, back fat, ribeye area and dressing percentage also did not differ (P ≥ 0.14) among treatments. Due to the similar results on performance and carcass characteristics, there were no effect (P ≥ 0.44) of treatments on economics traits (feedlot cost, cost of gain, return per head, and break-even price to pay on stover) for any of the feeding phases (growing phase, finishing phase, and overall). However in the current trial, a 3 pass harvesting and bagging corn stover system was used for all of the treatments. Previous research suggests the use of a 3-pass method saves cost by not having to grind and treat corn stover previous to feeding (Vadas and Digman, 2013). Moreover, when this system is used for cattle feed, cattle growth performance improves when compared to cattle fed a conventional baled corn stover (Russell et al., 2011). The lack of differences in animal performance and corn residue characteristics in the current trial may be explained by the short window (28 d) between the 2 harvesting days, due to the weather issues faced on the fall of 2014, the harvest of HMC was delayed which impacted the fiber fractions of the plant more than was expected. However, is important to notice that all animals gained 12% more than predicted, suggesting a greater feed value of corn plant residues when fed in combination with DGS than NRC (1996) claims. Corn plant residues create another option to replace some corn in a feedlot diet during the growing phase