197. Effect of Barley Grain Processing Method in Finishing Feedlot Diets on Enteric Methane Emissions, Growth Performance, and Ruminal Fermentation in western Canadian Beef Heifers.

Abstract The objective of this study was to determine the impact of barley grain processing in western Canadian finishing feedlot rations fed to heifers on enteric methane (CH4) and carbon dioxide (CO2) emissions, growth performance, and ruminal fermentation characteristics. Nintey-seven Angus crossbred heifers were randomly assigned to a pen (n = 4), and were fed 87% barley grain, 8% corn silage, and 5% vitamin and mineral supplement (dry matter basis). Treatments included barley grain rolled to a processing index of 80% (RL) or steam flaked to a processing index of 70% (FL). The experiment was conducted over three consecutive 28 day measurement periods for a total of 84 days on feed. Enteric emissions were measured using GreenFeed Emissions Monitoring Systems (GEMS, C-Lock, SD, USA) located in two of the four pens. Heifers and their respective treatments were rotated between pens once a week to ensure access to each GEMS unit (n = 2) each period. Body weight was measured on two consecutive days at the beginning and end of each period. Feed was provided ad libitum and feed intake was individually measured using GrowSafe feed bunks (GrowSafe System Ltd, Edmonton, AB, Canada). Ruminal fluid was collected by esophageal tubing at the end of each period for the determination of volatile fatty acid (VFA) and ammonia (NH3) concentrations. Statistical analysis was performed using the GLIMMIX procedure of SAS (SAS Institute Inc., Cary, NC, USA) as a completely randomized design with period as a repeated measure, treatment as a fixed effect, and heifer as the experimental unit. Heifers fed FL had lower (P < 0.001) dry matter intake (DMI) and higher (P < 0.01) gain to feed ratio than RL; however, average daily gain was not different (P = 0.46) between treatments. Enteric CH4 (g/d, g/kg DMI) and CO2 (g/d) were not impacted (P ≥ 0.08) by barley processing method. There was no impact of barley processing method on total VFA or NH3 concentration in rumen fluid; however, FL resulted in greater (P < 0.001) propionate, and lower (P ≤ 0.04) isobutyrate, isovalerate, and valerate proportions. The results of this study suggest that the increased starch availability of steam flaked barley grain may have increased energy availability of the diet reducing DMI required to meet requirements and improving feed conversion without impacting enteric gaseous emissions.