Effect of Mootral and Forage Amount on Methane Emission, Growth and Carcass Characteristics of Feedlot Steers
thesisposted on 2021-11-22, 18:07 authored by Bryce BitsieBryce Bitsie
Methane (CH4) production from enteric fermentation in ruminant animals is a contributor to global greenhouse gas emissions. Because CH4 has an impact on increasing global temperatures, there is a push for government regulations to reduce CH4 from livestock animals. At 1.9% of U.S. CH4 emissions beef cattle are a large contributor to agricultural CH4 emissions or (EPA, 2020). Enteric CH4 emissions are also a loss of energy for the animal, accounting for 2-12% of energy loss from the ruminant animal (Johnson & Johnson, 1995). This energy loss from the diet is contingent upon forage content, where increasing forages in the diet increases CH4 yield (g/kg of gross energy intake; van Gastelen et al., 2019). Mootral is a feed supplement that contains garlic (Allium sativum) and bitter orange (Citrus aurantium) extracts. The organosulfur compounds in garlic the flavonoids found in bitter orange extracts are known to decrease CH4 production, (Busquet et al., 2005a; Balcells et al., 2012; Seradj et al., 2014). However, it is unclear how the forage content and Mootral inclusion will interact to effect CH4 production and animal performance. Because feedlot cattle are fed a range of forage:concentrate ratios while in the feedlot, it is important to know how effective mitigation strategies are in different forage:concentrate diets. Therefore, the objective of the current study was to quantify CH4 production and determine growth, intake, and carcass characteristics of feedlot steers fed Mootral in diets with a low, medium, and high forage content. Knowing the effect of garlic and flavonoids on methanogenesis, we hypothesized that Mootral would decrease CH4 emissions without impacting growth, intake, and carcass characteristics of feedlot steers. We expect that the CH4 mitigating ability of Mootral will be greatest in the diet with the most forage. For the experiment, 144 Angus x Simmental steers were allotted by body weight (BW; 363 kg, breed composition, and farm origin to a 3 x 2 factorial arrangement of 6 treatments (4 pens per treatment) to determine the effect of Mootral (garlic + citrus extract; 0.25% of the diet DM vs. 0.0%) on methane emissions, growth and carcass characteristics of feedlot cattle. During the first 84 days, cattle were fed three different forage concentrations in the diet (15, 41.5, or 68% corn silage) with or without Mootral. From day 85 to slaughter, corn silage was included at 15% of the diet DM with or without Mootral. Methane emissions were measured on day 42-46 and day 203-207. Data were analyzed using the GLIMMIX procedure of SAS. There was an interaction (P = 0.03) between forage content and Mootral for DMI from d 0 to 84, where Mootral decreased DMI of steers fed 15% corn silage but did not affect DMI of steers fed 41.5 or 68% corn silage. There were no effects (P ≥ 0.22) of forage content or Mootral on BW or average daily gain at any time, or on DMI from d 84 to slaughter and overall. Intake from d 0-84 was lower and gain:feed from d 0-84 and overall was greater (P = 0.04) for steers fed 68% compared to 15 or 41.5% corn silage. On d 42-46, steers fed 41.5 and 68% corn silage had increased (P ≤ 0.02) methane emissions compared to steers fed 15% corn silage. Mootral did not affect methane emissions on day 42-46 (P ≥ 0.47), but there was a forage effect, where steers fed the 41.5 and 68% corn silage diets emitted more methane on a g/d (P = 0.05) and a g/kg of DMI (P = 0.007) basis and tended (P = 0.07) to produce more methane on g/kg BW basis compared to steers fed the 15% corn silage diet. Steers fed Mootral emitted less (P ≤ 0.03) methane on a g/d, g/kg DMI, and g/kg BW basis on d 203-207 compared to steers not fed Mootral. Mootral tended to decrease (P ≤ 0.09) fat thickness and yield grade. In conclusion, increasing forage content increased methane emissions and Mootral decreased methane production in 15% corn silage diets and improved carcass leanness.