Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: March 10, 2003
Publication Date: July 1, 2003
Citation: FERRELL, C.L., JENKINS, T.G., FREETLY, H.C. INFLUENCE OF SIRE BREED ON RESIDUAL FEED INTAKE AS AN INDICATOR OF EFFICIENCY IN STEERS. JOURNAL OF ANIMAL SCIENCE. 2003. v. 81(SUPP.1): ABSTRACT P. 107-108. Technical Abstract: The objective was to evaluate residual feed intake (RFI) as an indicator of efficiency. Steers (107) sired by Angus (A), Hereford (H), Belgian Blue (B), Piedmontese (P), Boran (Bo), Brahman (Br), and Tuli (T) and from A, H, or MARC III dams were used. Eight additional steers of each sire breed were used as initial slaughter animals. Steers were individually fed (half near maintenance and half at ad libitum) a high-concentrate diet (83.8% corn) in pens of eight for 140 d. Steers were weighed at 14 d intervals, and feed allotments were adjusted at those times. Steers were slaughtered at the MARC abattoir and retained energy (RE) was determined by comparative slaughter procedures. Initial weight (IWT), final weight (FWT) and ADG were calculated from regressions of weight on time for each steer. Similarly, DMI and MEI was calculated from regressions of cumulative feed consumed on time for each steer. Residual feed intake (RFI) was determined as the residual from within feed level regressions of MEI (kcal/kg0.75/d) on retained energy (kcal/kg0.75/d), and residual retained energy (RRE) was determined as the residual from the regression of RE (kcal/kg0.75/d) on MEI (kcal/kg0.75/d). Increased feed level increased intake and retained energy (P<0.01), RRE (P=0.06), but not RFI (P=0.99). Sire breed influenced all traits (P<0.01), but feed level X sire breed did not influence RRE (P=0.25) or RFI (P=0.35). Mean RRE and RFI for A, B, H, Bo, P, Br, and T sire breeds were: 2.17, 0.52; -10.04, 7.3; 3.28, 6.25; 3.65, -16.34; -8.68, 24.95; 4.83, -10.74; and 3.34, -11.77, respectively. The five of 107 steers identified as most efficient based on RFI were from the ad libitum group and averaged 4.95 kg DMI/d and 5.02 Mcal RE/d (means for ad libitum were 7.11 kg/d and 5.67 Mcal/d) suggesting potential negative consequences of over emphasizing RFI as a means to improve efficiency. These results suggest important differences exist among sire breeds in efficiency as measured by RRE or RFI.