Evaluation of Enteric Methane from Cattle Adapted to the Same Finishing Diet Using RAMP Versus Forage

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 139-day finishing experiment evaluating the effects of feeding RAMP (Cargill Corn Milling, Blair NE) during diet adaptation compared to a traditional forage program on methane and carbon dioxide emissions was done to corroborate a previous study (2025 Nebraska Beef Report, pp. 55-58). 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 a common finishing diet. Feeding RAMP had no statistical reduction in methane or carbon dioxide production during step 1. When cattle were fed the same finishing diet, there was a 7% reduction in methane due to possible carry over effects from feeding RAMP. These data suggest there was a likely reduction in methane during finishing by feeding RAMP during adaptation compared to using a conventional program, which corroborates previous work, but a significant decrease in methane was not observed during step 1.

Introduction

The agricultural industry is increasingly focused on strategies to reduce methane (CH₄) emissions, with beef cattle as a key contributor due to enteric fermentation. RAMP (Cargill Corn Milling) is a complete starter feed, comprised of high levels of Sweet Bran, low levels of forage, minerals, and vitamins, used for starting and adapting cattle to finishing diets in the Southern Plains. Sweet Bran is a highly digestible feed product that contains more energy than traditional forages. Replacing forage with RAMP during the adaptation period may decrease CH₄ due to lower fiber and higher energy content. A previous study suggested cattle fed RAMP decreased CH₄ by 12% compared to using 43% forage in step 1 (2024 Nebraska Beef Rep, pp. 55-58). In that study, cattle also produced 9% less CH₄ while fed the finishing diet despite being fed the same diet. As a result, this study was conducted to corroborate the impact of using RAMP on CH₄ production during step 1 but also the ‘carryover’ effect when fed the same finishing diet.

Procedure

A finishing experiment using the calorimetry emission barn at the Eastern Nebraska Research, Extension, and Education Center near Mead, NE tested enteric CH₄ emissions. Sixty-four steers (initial BW = 932 lb ± 14 lb) were used to evaluate the effects of feeding RAMP during diet adaptation versus 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 before to determine initial BW. Steers were then blocked by BW into four weight blocks (4 paired replicates), stratified by BW, and assigned randomly to pens (n = 8 pens; 8 steers/pen). The paired replicates consisted of two treatments which were fed either 100% RAMP or 43% forage during step 1 (Table 1). The cattle fed RAMP contained 100% during step 1 and were then adapted to a common finisher diet consisting of 65.5% steam-flaked corn (SFC), 25.5% Sweet Bran, 8% corn stalks, and 4% supplement (DM basis). The second treatment was a traditional forage adaptation diet (CON) where cattle were fed 30.5% SFC, 22.5% Sweet Bran, 8% corn stalk, 35% alfalfa hay, and 4% supplement (DM basis) during step 1 and adapted to the same common finishing diet (Table 1). All cattle were fed 4 step-up diets over 22 d, with step 1 fed 7 d and steps 2, 3, and 4 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 140 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 before 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 (12 weeks after first entering barn).

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 through 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 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, and 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 ≤ 0.10.

Results

No differences in DMI were observed during step 1 of grain adaptation phase (P = 0.73; Table 2). Feeding RAMP during step 1 had no difference in CH₄ as g/d (P = 0.66). There was a numerical but small reduction in CH₄/lb DMI but this difference was not significant (P = 0.52). Theoretically, feeding less forage by feeding RAMP should decrease CH₄ in g/d as observed in a previous study where 21 g/d (12%) less methane was produced (2024 Nebraska Beef Report, pp.55-58) but was only 6 g/d numerically less in this study and not statistically different. Steers fed RAMP had no difference in CO2 production when measured as g/d (P = 0.92) or as CO2 in g/lb DMI (P = 0.60), resulting in no differences in CH₄:CO2 ratio (P = 0.71). 

During the finishing phase when both treatments received the same diet, cattle fed RAMP had no difference in observed DMI compared to those stepped up with the control (P = 0.70; Table 3). Feeding RAMP compared to the control adaptation programs resulted in a 7% reduction in CH₄ expressed as g/d (P = 0.10). A similar 9% decrease in CH₄ was observed during finishing when adapted with RAMP compared to forage, despite being fed the same diet during finishing (2024 Nebraska Beef Report, pp. 55-58). In this study, CH₄ was reduced by 15 g/d and by 16 g/d in previous work (2024 Nebraska Beef Report, pp. 55-58). There was a decrease in the CH₄:CO2 ratio for the RAMP treatment (P = 0.03), which was driven by the decrease in CH₄. The decrease in methane in the finishing diet was due to a possible carryover effect from the grain adaptation phase as both treatments were fed the same finishing diet for 8 weeks before measurement.

There were no differences in initial BW between treatments as designed (P = 1.00; Table 4). During the entire 139 d trial, DMI (P = 0.73) did not differ among treatments, but ADG (P = 0.05) was significantly decreased for cattle fed RAMP. Feeding RAMP had a significant difference in carcass adjusted final BW compared to control treatment (P = 0.05). Cattle adapted with RAMP had 15 lb lighter hot carcass weights (P = 0.06) which is opposite to the 11 to 19 lb increases observed in other studies designed to better assess  performance changes (2012 Nebraska Beef Cattle Report, pp 85-86). A small number of replications and cattle adapted across different weeks limits any inference about performance due to dietary treatments in this study. No differences were observed between cattle adapted with RAMP compared to forage during the adaptation phase for carcass traits (P > 0.39). Liver abscess prevalence tended to be 14% lower for cattle adapted with RAMP compared to control adaptation treatment (P = 0.10).

Conclusions

These data suggest that using the complete starter diet, RAMP, had no reductions in methane emissions when fed during the initial adaptation diet. But, methane was reduced by 7% during the finishing phase possibly due to carryover effects once on the same finishing diet. 

Acknowledgment

Funding provided by Cargill Corn Milling, Blair, NE; products provided by Elanco Animal Health and Merck Animal Health.

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