Submitted to: Journal of Animal Science Supplement
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 6, 2002
Publication Date: March 1, 2003
Citation: FERRELL, C.L., JENKINS, T.G., FREETLY, H.C. INFLUENCE OF PRIOR NUTRITIONAL TREATMENT ON RESIDUAL FEED INTAKE AS AN INDICATOR OF EFFICIENCY. JOURNAL OF ANIMAL SCIENCE. 2003. v. 81(Suppl. 2): Abstract p. 99. Technical Abstract: Objectives were to evaluate prior treatment effects on residual feed intake (RFI), an indicator of efficiency in beef steers. Average daily gain (ADG), daily dry matter intake (DMI), feed/gain (FPG), and residual ADG (RADG) were also evaluated as indicators of efficient steers. Simmental × MARC III steers (358±3.0 kg) were individually fed a diet (80% corn, 13.61% corn silage, 4.40% soybean meal, 0.78% urea, 0.67% limestone, 0.43% dicalcium phosphate, 0.09% salt, 0.008% trace mineral premix, and 0.015% monensin premix; dry basis) in pens of six. Twelve steers were assigned to each of eight preliminary treatments: 40, 50, 60, 70, 80, 90, 100, or 110 g × kg-0.75 × d-1 for 112 d. Steers were weighed at 14 d intervals, and feed allotments were adjusted at those times. All steers were fed ad libitum until slaughter during the ensuing experiment which consisted of 74 d for steers fed at the 40-70 levels and 39 d for steers at the 80-110 levels during the prior period. Steers were slaughtered at a commercial facility and carcass data was collected. Initial weight (IWT), final weight (FWT) and ADG were calculated from regressions of weight on time for each steer. Similarly, DMI was calculated from cumulative feed consumed on time for each steer, and FPG was calculated. Residual feed intake was determined as the residual from the regression of DMI on IWT and ADG, and RADG was determined as the residual from the regression of ADG on IWT and DMI. Prior treatment influenced IWT (P<0.001), FWT (P<0.001), ADG (P<0.001), DMI (P=0.047), FPG (P<0.001), RFI (P=0.041), and RADG (P=0.053). Means (± SD) for these traits were 469 (55), 566 (39), 1.69 (0.33), 10.00 (1.31), 6.15 (1.52), 0.00 (1.04), and 0.00 (0.27), respectively. Five steers (of 93) identified as efficient based on low RFI had 14 kg greater IWT, 1.86 kg/d lower DMI, 0.32 kg/d lower ADG than the mean, whereas steers identified by RADG had 18 kg greater IWT, 0.04 greater DMI, and 0.41 kg/d greater ADG. These results suggest potential negative consequences of selecting solely on RFI and that RADG may be a viable alternative.