Evaluation of Enteric Methane from Cattle Adapted Using RAMP vs. A Traditional Forage Program Stepped Up to Different Finishing Diets

Authors:  Jack Fort, Graduate Student; Isaque Vicci, Graduate Student, ENREEC; Josh Benton, Beef Feedlot Unit Director, ENREEC; Rebecca McDermott, Research Technician; Jim MacDonald, Professor, Animal Science, Lincoln; Maggie Youngers, Cargill Corn Milling, Blair, NE; Galen Erickson, Professor, Animal Science, Lincoln.

Summary with Implications

A 93-day finishing experiment evaluated feeding RAMP (Cargill Corn Milling, Blair NE) during diet adaptation and finishing diet containing 20% Sweet Bran compared to a traditional adaptation program using forage with a finishing diet without Sweet Bran on methane and carbon dioxide production, animal performance and carcass characteristics in beef steers. Cattle were measured using a calorimetry emission barn to quantify the production of methane and carbon dioxide during step 1 of adaptation and 1 time during finishing diet. Feeding RAMP did not significantly reduce methane but did reduce the ratio of methane to carbon dioxide during step 1 compared to adapting with 45% forage. No differences in methane production during the finishing phase was observed when either 0 or 20% Sweet Bran were fed. Adapting cattle with RAMP instead of forage likely reduces methane and carryover effects suggest that feeding Sweet Bran is similar to steam-flaked corn in finishing diets if cattle were adapted with RAMP.

Introduction

Greenhouse gas emissions from beef cattle, particularly methane (CH₄) produced during enteric fermentation, are a concern due to their contribution to climate change. Methane is a natural byproduct of microbial fermentation in the rumen, and more is generally produced per unit of intake when cattle consume high-forage diets compared to concentrates. RAMP (Cargill Corn Milling), a high-energy complete starter feed, is commonly used in the Southern Plains to receive cattle and subsequently adapt cattle to finishing diets. Traditionally, cattle are stepped up by gradually decreasing forage and increasing grain in the diet. Using RAMP reduced CH₄ emissions compared to a traditional forage-based adaptation due to its greater energy density and lower fiber content (2024 Nebraska Beef Report, pp. 55-58). In two previous studies, adapting cattle using RAMP versus forage to the same finishing diet resulted in lower CH₄ even during the finishing phase when cattle were fed the same diet (2024 Nebraska Beef Report, pp. 55-58; 2026 Nebraska Beef Report, pp. 78-80, Fort-RAMP-Methane Same Finishing Diet). The objective was to determine how adaptation strategy and Sweet Bran inclusion in the finishing diet affects CH₄ and CO2 emissions from finishing cattle. Most feedyards that adapt cattle with RAMP are going to use Sweet Bran in the finishing diet whereas feedyards adapting with forage may not use Sweet Bran in the finishing diet. Therefore, in this study, steers were adapted using either RAMP to a finishing diet containing 20% Sweet Bran compared to steers adapted using a traditional forage-based program to a finishing diet without Sweet Bran. Measurements were made while cattle were on the first step of adaptation and again once on the finishing diets for 8 weeks.

Procedure

A 93-day finishing experiment was conducted using the calorimetry emission barn at the Eastern Nebraska Research, Extension, and Education Center near Mead, NE to test greenhouse gas emissions. Sixty-four steers (initial BW = 1140 lb ± 18 lb) were used to evaluate the effects of feeding RAMP during diet adaptation instead of a traditional forage diet on methane (CH₄), carbon dioxide (CO2), animal performance, and carcass characteristics. Cattle were limit-fed a common diet of 50% alfalfa hay and 50% Sweet Bran on a DM basis at 2% body weight (BW) for 5 days to equalize gut fill. Weights were taken for two consecutive days to determine initial BW. Steers were stratified by BW and blocked by BW into four weight blocks (4 paired replicates), and assigned randomly to pens within block (n = 8 pens; 8 steers/pen). The paired replicates (BW block) consisted of two treatments which were fed either 100% RAMP or 45% forage during step 1 (Table 1). The first treatment consisted of cattle adapted using RAMP to a finishing diet with 20% Sweet Bran (RAMP-SB) and the second treatment consisted of cattle adapted with forage to a finishing diet containing 0% Sweet Bran (CON). The cattle fed 100% RAMP during step 1 and were adapted to a finishing diet consisting of 51% steam-flaked corn (SFC), 20% Sweet Bran, 10% corn silage, 4% corn stalk, 10% modified distiller grains plus solubles (MDGS), and 5% supplement (DM basis). The CON treatment was a traditional forage adaptation diet (CON) where cattle were fed 35% SFC, 36% alfalfa hay, 10% corn silage, 4% corn stalk, 10% MDGS, and 5% supplement (DM basis) during step 1. Cattle on CON treatment were adapted to a finishing diet consisting of 71% SFC, 10% corn silage, 10% MDGS, 4% corn stalks, 5% supplement (Table 1). All cattle went through 4 step-up diets over 22 d, with step 1 fed 7 d while steps 2, 3, and 4 were fed for 5 d each. 

Cattle were implanted with Revalor-XS on d 1 of the trial (Merck Animal Health, Summit, NJ). Cattle were harvested on d 94 at Greater Omaha (Omaha, NE). Liver abscesses and hot carcass weights (HCW) were collected on the day of slaughter. The carcass adjusted final BW was calculated using a common dressing percent of 63%. Longissimus muscle (LM) area, 12th rib back fat, and USDA marbling scores were recorded after a 48-hr chill.

Each of the paired replicates started one week after the previous replicate to allow a one-week rotation through the calorimetry barn. This means replications 2, 3, and 4 were each limit-fed one-week longer than the previous replication. Starting with the lightest weight block (replication 1) until the heaviest weight block (replication 4) for a total of 21 d between the start of replicate 1 and replicate 4. Replications were limit-fed 8 lb of grass hay and 8 lb of Sweet Bran (DM Basis) until 5 d before starting step 1 diets and entering the emissions barn. Cattle were fed their treatment diets for 1 d prior to entering the barn on step 1. Cattle were monitored for CH₄ and CO2 emissions during two phases; step 1 of adaptation phase and later during the finishing phase (8 weeks after starting on the finishing diet).

Emissions were measured with the pen scale emissions barn (2019 Nebraska Beef Cattle Report, pp 60-62). The barn uses a negative air pressure system equipped with LI-COR 7700 and LI-COR 7500 analyzers (LI-COR, Lincoln NE) that quantify concentrations of CH₄ and CO2. The barn contains two separate enclosed pens with air flow controlled and are designed so no emissions can crossover between pens within the barn. Paired replications remained paired throughout the duration of the experiment. Cattle entered the chambers at 0800 on d 1 (Wednesday) and remained in the chamber until d 5 (Monday) at 0700, then returned to their respective home pen. Each day was approximately 24 hours, from feeding to feeding. Methane and carbon dioxide from manure from the previous five days while cattle were in the barn were measured from 0700 h on d 5 (Monday) to 1200 h on day 6 (Tuesday) to adjust for only enteric emissions and exclude any from manure. After approximately 36 h of manure collection, the manure was removed via skid steer on d 6 (Tuesday). After the manure was removed, CO2 and CH₄ were measured until the next morning to get a baseline measurement, which was considered d 7, which was the final day in one rotation through the emissions barn. Manure emission levels of CO2 and CH₄ were subtracted from baseline emission levels of CO2 and CH₄ to determine actual cattle production of CO2 and CH₄ without manure contributions.

Data were analyzed using the MIXED procedure of SAS (SAS Institute, Inc., Cary, NC) as a randomized complete block design. Pen was the experimental unit. For performance data and for emissions for step 1 of the step-up diet and finishing phase, treatment and BW block were fixed effects. Significance was declared at P ≤ 0.05 and a tendency at P ≤ 0.10.

Results

No differences in DMI were observed during step 1 of grain adaptation phase (P = 0.26; Table 2). Feeding RAMP during step 1 did not lead to a difference in CH₄ as g/d (P = 0.37) compared to using forage. There was a 9% reduction in CH₄/ lb DMI for cattle fed RAMP versus step 1 from CON, but this was not statistically different (P = 0.18). Steers fed RAMP had similar CO2 production as g/d (P = 0.59) and g/lb DMI (P= 0.56) to CON steers.  The CH₄:CO2 ratio was lower for cattle fed RAMP compare to steers fed step 1 for CON (P = 0.05) which shows a reduction in enteric CH4 for RAMP compared to higher forage diet.

During the finishing phase, the diets evaluated for the RAMP treatment contained 20% Sweet Bran and the CON treatment contained 0% Sweet Bran. Feeding the RAMP treatment which contained Sweet Bran and lower levels of SFC in the finishing diet compared to the control resulted in no difference in DMI (P = 0.85). On a g/d basis, CH₄ was not different between treatments (P = 0.51) which is interesting as feeding 20% Sweet Bran by replacing steam-flaked corn would normally increase enteric methane. When comparing treatments on CO2 emissions, production in g/d and g/lb DMI were not different between treatments, (P = 0.43) and (P = 0.57) respectively. There was no difference in the CH₄:CO2 ratio between treatments as well when fed the finishing diet (P = 0.25). 

There were no differences in initial BW between treatments as designed (P = 0.99; Table 4). During the entire 93 d trial, DMI (P = 0.18) and ADG (P = 0.11) did not differ among treatments. Cattle fed RAMP and 20% Sweet Bran in the finishing diet had a significantly lighter carcass adjusted final BW compared to CON (P = 0.02). Cattle adapted with RAMP had an 11 lb lighter hot carcass weight (P = 0.02) which is opposite to the 11 to 19 lb increases observed in other more replicated studies designed to assess performance changes (2012 Nebraska Beef Cattle Report, pp 85-86). No differences were observed between treatments for marbling scores (P = 0.73), LM area (P = 0.76) or fat depth (P = 0.77). Liver abscess prevalence was also not different for cattle fed RAMP during adaptation phase then 20% Sweet Bran compared to the CON adaptation and finishing treatment. 

Conclusions

These data suggest that using the complete starter diet, RAMP, reduced methane emissions during step 1 based on the ratio of carbon dioxide to methane. There were no differences in enteric methane when evaluating cattle on the finishing diets with 20% Sweet Bran (adapted with RAMP) compared to 0% Sweet Bran.

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