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This Article Full Text (PDF) All Versions of this Article: jas.2008-1352v1 87/4/1528    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Lancaster, P. A. Articles by Crews, D.H. Search for Related Content PubMed PubMed Citation Articles by Lancaster, P. A. Articles by Crews, D.H., Jr.

Characterization of Feed Efficiency Traits and Relationships with Feeding Behavior and Ultrasound Carcass Traits in Growing Bulls

P. A. Lancaster^*, G. E. Carstens, F. R. B. Ribeiro, L. O. Tedeschi and D.H. Crews, Jr.

^* Department of Animal Science, Oklahoma State University, Stillwater 74078 , Department of Animal Science, Texas A&M University, College Station 77843 Department of Animal Sciences, Colorado State University, Fort Collins 80523

g-carstens{at}tamu.edu

Abstract

Objectives of this study were to characterize feed efficiency traits and to examine phenotypic correlations with performance and feeding behavior traits, and ultrasound measurements of carcass composition in growing bulls. Individual DMI and feeding behavior traits were measured in Angus bulls (n = 341; initial BW = 371.1 ± 50.8 kg) fed a corn silage-based diet (ME = 2.77 Mcal/kg DM) for 84 d in Trials 1 and 2 and for 70 d in Trials 3 and 4 using a GrowSafe feeding system. Meal duration (min/d) and meal frequency (events/d) were calculated for each bull from feeding behavior recorded by the GrowSafe system. Ultrasound measures of carcass 12^th rib fat thickness (BF) and longissimus muscle area (LMA) were obtained at the start and end of each trial. Residual feed intake (RFIp) was computed from linear regression of DMI on ADG and mid-test BW^0.75 with trial, trial by ADG and trial by mid-test BW^0.75 as random effects (base model). Overall ADG, DMI and RFIp were 1.44 (SD = 0.29), 9.46 (SD = 1.31), and 0.00 (SD = 0.78) kg/d, respectively. Stepwise regression analysis revealed that inclusion of gain in BF and LMA in the base model increased R² (0.76 vs. 0.78), and accounted for 9% of the variation in DMI not explained by MBW and ADG (RFIp). Residual feed intake (RFIp) and carcass-adjusted RFI (RFIc) were moderately correlated with DMI (0.60 and 0.55, respectively) and FCR (0.49 and 0.45, respectively), and strongly correlated with partial efficiency of growth (PEG; -0.84 and -0.78, respectively), but not with ADG or MBW. Gain in BF was weakly correlated with RFIp (0.30), FCR (-0.15), and PEG (-0.11), but not RFIc. Gain in LMA was weakly correlated with RFIp (0.17) and FCR (-0.19), but not PEG or RFIc. The Spearman rank correlation between RFIp and RFIc was high (0.91). Meal duration (0.41), head down duration (0.38), and meal frequency (0.26) were correlated with RFIp, and accounted for 35% of the variation in DMI not explained by MBW, ADG and ultrasound traits (RFIc). These results suggest that adjusting RFI for carcass composition will facilitate selection to reduce feed intake in cattle without affecting rate or composition of gain.

Key Words: Angus bulls • carcass composition • feeding behavior • residual feed intake

This article has been cited by other articles:

				P. A. Lancaster, G. E. Carstens, D. H. Crews Jr., T. H. Welsh Jr., T. D. A. Forbes, D. W. Forrest, L. O. Tedeschi, R. D. Randel, and F. M. Rouquette Phenotypic and genetic relationships of residual feed intake with performance and ultrasound carcass traits in Brangus heifers J Anim Sci, December 1, 2009; 87(12): 3887 - 3896. [Abstract] [Full Text] [PDF]

				G. M. Bingham, T. H. Friend, P. A. Lancaster, and G. E. Carstens Relationship between feeding behavior and residual feed intake in growing Brangus heifers J Anim Sci, August 1, 2009; 87(8): 2685 - 2689. [Abstract] [Full Text] [PDF]