PSIX-10 - Effect of different levels of DMI on O2 consumed, CO2 released, growth and carcass characteristic in feedlot cattle

Our objective was to determine the effect of different levels of dry matter intake (DMI) on O₂ consumption, CO₂ emission, growth, and carcass characteristic in feedlot cattle. The experiment used 60 individually fed backgrounded Angus × SimAngus-crossbred steers (n = 30) in a randomized complete block design. Steers (paired blocked by body weight and gain to feed ratio (G:F) were randomly allocated to one of the following treatments: ad-libitum (AI) or restricted intake (RI; the same diet fed at 85% of the AI) finishing diet. The diet contained 61% cracked corn, 9% corn silage, 15% DDGS, 5% soyhulls, and 10% of a protein-mineral-vitamin premix. Measurement of CO₂ emission, and consumption of O₂, were taken using the Greenfeed system (n = 15/treatment) once the steers were fed for 140 days. Plasma and gas samples were collected 10 d before slaughter, 1 h before and 2 h after feeding. Plasma glucose and insulin concentration and gasses (O₂ and CO₂) were analyzed using the MIXED procedure of SAS evaluating the fixed effect of treatment, time (repeated measurement) and their interaction. Growth and carcass characteristics were analyzed with a similar model, without the time statement and its interaction. Compared with RI, AI steers had greater (P < 0.01) DMI and average daily gain (ADG). Steers on AI tended to have greater final body-weight (BW) (P = 0.07) and ribeye area (P = 0.09) (Table 1). There was no effect of treatment (P ≥ 0.11) on G:F, subcutaneous (BF) and intramuscular (IM) fat, O₂ consumption and CO₂ emission. Plasma glucose concentration of AI steers were greater before and after feeding than RI (P < 0.05; Table 2). In conclusion, feeding steers ad-libitum increased DMI, ADG, and plasma glucose concentration, but does not affect G:F, BF, IM fat, CO₂ emission, and consumption of O₂.