Location: Nutrition, Growth and Physiology
Project Number: 3040-31000-102-005-I
Project Type: Interagency Reimbursable Agreement
Start Date: Feb 27, 2024
End Date: Aug 31, 2028
Objective:
The objectives of this research are two fold. First we will assess the impact of rate of gain during backgrounding on enteric and environmental methane production during finishing of beef steer calves. Second, we will determine the impacts of advancing season on enteric methane emissions of grazing beef ruminants.
Approach:
Following training, 27 calves (6 primary and 3 alternates per treatment) will be selected for use in the experiment and begin receiving 1 of 3 treatments: 1) 1.5lb/d rate of gain, 2) 2.25lb/d rate of gain, and 3) 3.0lb/d rate of gain for a total of 84d. Rate of gain will be attained by manipulating the quantity of feed provided. Following the 84-d growing period, all calves will be transitioned to and receive ad libitum access to a finishing ration for the remainder of the study. The 18 primary steers selected for use in the experiment will be transferred to Building 48 on 1 occasion during the backgrounding phase for 5-d sample collection periods. To facilitate collections one-half of each treatment group will be moved at a time (Group A in Week 1; and Group B in Week 2). This headbox collection will be accomplished between d70-84 for collection of methane emmissions via indirect calorimetry. Following these collections, all steers will be adapted to a final finishing diet with three subsequent collection periods occurring when the average weight of each treatment group reaches 900, 1100, and 1300lbs, respectively.
For this study two cohorts of beef cows of similar age will be grazed under different grazing management strategies. Two treatment grazing systems will be evaluated 1) a system where irrigated forage is the primary source of grazing (IRG) and 2) a system where non-irrigated pastures are the primary source of forage (Non-IRG). Cattle, approx. 40hd per treatment, will be used in this study. Cattle access to greenfeed will be limited to those demonstrating a propensity for use of the machine, however these cattle will co-graze with cattle without greenfeed access. Measurements of methane and forage maturity will be collected throughout the grazing season to determine if any relationship exists between forage maturity and methane emissions.
