Earlage versus silage
Comparing the two as roughage, grain source in finishing diets
By Garret Lemon, Alfredo DiCostanzo, Galen Erickson and Pablo Loza
High-moisture ear corn (HMEC) is another endpoint of harvesting corn for cattle feed that would occur between the harvest of corn silage and high-moisture corn (HMC) that produces a high-energy feed but also includes a source of roughage in the diet. An ear of corn is made up of approximately 80% grain and 20% roughage that consists of the ear, husk and shank.
High-moisture ear corn encompasses earlage which is the harvest of just the grain and cob that is kernel processed for ensiling, and snaplage which contains the entire ear, husk and shank. Earlage and snaplage are more common terms for HMEC and are frequently used interchangeably although having different compositions.
Feedlot finishing diets are formulated to maximize the amount energy being consumed by the animal to contribute to gain and roughage is included to optimize the health and function of the rumen and stimulate feed intake. Neutral detergent fiber (NDF) of roughage sources is often used to balance the amount of roughage included in the diet and previous literature indicates that roughage sources can be used interchangeably when balanced on an NDF basis and yield similar amounts of dry matter intake between roughage sources.
The objective of this study was to determine the effects on performance and carcass characteristics of cattle fed earlage or corn silage as the source of roughage in the diet while balancing these on an equal NDF basis at two inclusion levels.
ProcedureA finishing trial was conducted at the University of Nebraska Panhandle Research, Education and Extension Center (PREEC) research feedlot near Scottsbluff, Nebraska. Crossbred yearling steers (n=216; initial BW = 1037 lb. ± 69 lb.) were fed one of four experimental diets in a 2×2 factorial treatment arrangement. This trial was designed as a randomized block design with pen as the experimental unit.
In the current experiment, inclusions of roughage were determined with the assumptions in mind that corn silage is composed of 50% grain and 50% forage while earlage is 80% grain and 20% forage. Therefore, using NDF from forage, inclusion rates were obtained with corn silage representing “normal” dietary roughage inclusion (i.e., corn silage at 15% to supply 7.5% forage in the diet) and then a diet using earlage as the roughage source to match that amount of forage NDF provided by corn silage.
The other inclusion of roughage was based on the amount of roughage supplied if earlage was the only grain source in the diet. As a result, forage NDF was approximately doubled, providing 14.8% forage NDF (using that approach 74% earlage compared to 30% corn silage) these two treatments were designated as 2X normal forage NDF inclusion.
Treatments were designed to evaluate the feeding performance (ADG, DMI and feed efficiency) and carcass characteristics of cattle fed corn silage or earlage as the sole roughage source, with diets matched in NDF content. Treatments included corn silage at normal NDF inclusion, corn silage at 2X normal NDF inclusion, earlage at normal NDF inclusion DM, and earlage at 2X normal NDF inclusion (Table 1).
Corn silage was harvested, packed and stored in an uncovered bunker prior to the initiation of the experiment, and contained an average starch content of 34% and averaged 38.0% NDF. Earlage was purchased and delivered to the feedlot as needed throughout the trial. The earlage was stored unpacked and uncovered in a bunker and had an average starch content of 55% and averaged 20.2% NDF. High moisture corn was stored in an uncovered bunker, and dry rolled corn was supplied in both corn silage diets and the low inclusion (7.5%) earlage diet as a 50:50 blend on a DM basis.
Wet distillers grains plus solubles were included at 20% (DM basis), reflecting the most commonly used diet inclusion levels in the industry. A liquid supplement was included at 6% and was formulated to provide 360 mg/steer of monensin (Rumensin, Elanco Animal Health) and 90 mg/steer of tylosin® (Tylan Elanco Animal Health) daily. Feed was offered once a day to target ad libitum intake.
A Revalor-200 (Merck Animal Health) implant was administered to all animals on day 0 Initial BW was determined by an average of weights collected on day 0 and 1 while consuming a corn silage diet targeting 2.2% of BW for 30+ days prior to trial initiation to equalize gut fill.
Twenty-four pens with 9 steers/pen were used in this trial. Cattle were stratified by weight from day 0 and were subjected to blocking criteria based on initial body weight and to reduce BW variation. All blocks started on the same day and were fed for 120 days. Three body weight blocks were used (light, medium and heavy), with two treatment repetitions within each block. Live body weights were collected one day prior to cattle shipment to a commercial abattoir.
Upon harvest, hot carcass weights (HCW), and liver abscess scores were recorded. Carcass adjusted final body weights were calculated using a common 63% dressing percentage. Following a 48-hr chill, Longissimus muscle (LM) area, 12th rib fat thickness, marbling score, and USDA quality and Yield grades were collected. Net energy values were calculated using DMI and ADG data with the heaviest pen average as the target end weight for each block and choice as the target finishing quality grade.
ResultsUpon lab analysis for NDF content of earlage and corn silage, NDF content of corn silage was 38.0%, which is on the lower end of NDF values presented in the NRC (43 ± 5.50). This provided 5.3% NDF from corn silage at the normal inclusion and 10.4% NDF at the matched 2X normal inclusion of forage. Earlage was 20.2% NDF which reflects NRC values for earlage NDF (21 ± 5.6) and provided 7.5% NDF at the matched normal inclusion of forage and 14.9% NDF at the 2X normal inclusion. Differences in NDF content of these two roughage sources led to greater differences in forage NDF at both inclusions.
When evaluating the interaction between roughage source and inclusion (Table 2), no interaction was observed for gain, intake, feed conversion or carcass characteristics (P ≥ 0.13) except for a tendency for marbling score (P = 0.05). Cattle fed corn silage at 15 or 30% of the diet had equal (P > 0.33) marbling scores (523 and 527 respectively) which was equal to the lower inclusion of earlage (529). When the only grain source was earlage, marbling was lowest (493); P ≤ 0.09).
A tendency for an interaction was also observed for percentage of animals with liver abscesses (P = 0.09). When examining forage type, liver abscess percentage did not differ (P = 0.27) among inclusion levels of dietary NDF. Liver abscess prevalence was greater (P = 0.19) for cattle fed earlage compared to corn silage when fed at the normal inclusion of forage but was not different between roughage sources at the 2X normal forage inclusion (P = 0.43). The prevalence of A+ liver abscesses among all animals was 8%, and of animals with a liver abscess, A+ liver abscess accounted for 15% of those. No other interactions were observed so the main effects of roughage type and inclusion level will be discussed.
When evaluating effects due to inclusion of roughage, feed conversion was impacted. Cattle that were fed the 7.5% forage NDG were 6% more efficient (P <0.01) when compared to the 14.8% forage NDF and tended to have greater ADG (P = 0.10) treatments while DMI between inclusion was similar (P = 0.11). Hot carcass weight was also greater in steers fed the normal inclusion of dietary NDF (P = 0.03). Reductions in gain and efficiency would be expected as the roughage proportion increases in the diet which would replace corn grain, lowering the available net energy to be put towards growth (NEg).
When analyzing the main effects for roughage source, greater intakes were observed in cattle fed corn silage which led to those cattle also having greater ADG (P ≤ 0.01) than those fed earlage. The steers fed corn silage consumed more which allowed them to gain more, resulting in similar F:G (P = 0.36) between the two roughage sources. Hot carcass weights were significantly greater when cattle were fed corn silage as the roughage source (P = 0.02).
Net energy utilization for maintenance (NEm), gain (NEg), and metabolizable energy were also analyzed using calculations with values derived from the NRC. Significant differences were present for all net energy calculations (P <0.01). The normal forage inclusion (7.5%) for both roughages showed greater energy concentrations for NEm, NEg, and ME compared to 2X inclusion. However, these calculations that are based on feed conversion are not good reflections of intake and gain responses, and usually favor lower intakes.
Cattle fed less roughage had greater calculated energy concentrations, similar to the F:G response. Cattle fed silage were equivalent to cattle fed earlage for calculated energy concentration, which also is similar to the F:G responses observed. Using net energy calculations from performance illustrates that the responses are similar to F:G observations. Cattle fed silage as a roughage source consumed more and gained more than cattle fed earlage, which is not accounted for in these calculations of energy concentration.
Lemon is a graduate student, DiCostanzo is a beef systems Extension educator, Erickson is a professor in ruminant nutrition and Loza is an assistant professor in feedlot management and a nutrition Extension specialist, all in the Animal Science Department at the University of Nebraska-Lincoln.
