PSIII-4 - Estimation of dry matter intake in finishing steers using greenhouse gas flux and performance

Abstract: Accurate estimations of individual animal dry matter intake can be challenging to obtain without specially designed equipment, which does not resemble traditional feedlot management settings. Our objective was to generate a prediction equation for dry matter intake (DMI) using gas flux (carbon dioxide (CO₂) or methane (CH₄) production) and growth performance data to demonstrate an estimated DMI can be calculated based on direct measurements of body weight and gas flux. Data was collected on Angus crossbred steers [n=44; initial body weight (BW) 447 ± 30kg]) for 119 days, during which time individual animal intake, and CO₂ and CH₄ gas flux were recorded daily. Individual animal feed intake was measured using an Insentec monitoring system (Insentec Marknesse, Netherlands). The ration fed to the animals consisted of rolled corn (70.5% of DM), wet sweet bran (15.1% of DM), corn silage (6.1% of DM), and a mineral supplement (8.3% of DM). Two GreenFeed gas emission measurement systems (C-Lock Rapid City, SD) were used to measure individual steer CH₄ (0.13 kg/d ± 0.04 kg/d) and CO₂ (9.66 kg/d ± 1.12 kg/d) production. Individual animal body weights (BW) were collected every 28 days and used to calculate average daily gain (ADG). A linear mixed model was used to regress ADG or metabolic body weight (BWadj) and CO₂ or CH₄ production on dry matter intake (DMI) of feedlot cattle. Individual animal ID was included as a categorical random variable in the model. Pearson’s correlation coefficient between DMI and CO₂ or CH₄ was 0.42 and 0.33, respectively. The final model leveraged CO₂ rather than CH₄ due to improved model fit, which could possibly be attributed to the composition of the high grain finishing diet. Pearson’s correlation coefficient between DMI and ADG or BWadj was 0.24 and 0.71, respectively. The final model used BWadj and daily CO₂ production (kg) to describe 67% of the variation in DMI according to the marginal R². The model also demonstrated positive relationships of DMI with CO₂ production and BWadj. The results suggest that beef cattle DMI can be predicted using performance data and CO₂ measurements in the feedlot. This prediction equation will allow for the estimation of individual animal intakes in traditional bunk fed feedlot facilities when equipped with gas flux measurement technology.