HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: jas.2008-1083v1 86/11/2862    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 Welsh, T. H. Search for Related Content PubMed PubMed Citation Articles by Lancaster, P. A. Articles by Welsh, T. H., Jr.

Effects of divergent selection for serum insulin-like growth factor-I concentration on performance, feed efficiency, and ultrasound measures of carcass composition traits in Angus bulls and heifers

P. A. Lancaster^*, G. E. Carstens^*,1, F. R. B. Ribeiro^*, M. E. Davis, J. G. Lyons^* and T. H. Welsh, Jr.^*

^* Department of Animal Science, Texas A&M University, College Station 77843; and Department of Animal Sciences, The Ohio State University, Columbus 43210

¹ Corresponding author: g-carstens{at}tamu.edu

Angus bulls and heifers from lines divergently selected for serum IGF-I concentration were used to evaluate the effects of IGF-I selection line on growth performance and feed efficiency in 2 studies. In study 1, bulls (low line, n = 9; high line, n = 8; initial BW = 367.1 ± 22.9 kg) and heifers (low line, n = 9; high line, n = 13; initial BW = 286.4 ± 28.6 kg) were adapted to a roughage-based diet (ME = 1.95 Mcal/kg of DM) for 24 d and fed individually for 77 d by using Calan gate feeders. In study 2, bulls (low line, n = 15; high line, n = 12; initial BW = 297.5 ± 34.4 kg) and heifers (low line, n = 9; high line, n = 20; initial BW = 256.0 ± 25.1 kg) were adapted to a grain-based diet (ME = 2.85 Mcal/kg of DM) for 32 d and fed individually for 70 d by using Calan gate feeders. Blood samples were collected at weaning and at the start and end of each study, and serum IGF-I concentration was determined. Residual feed intake (RFI) was calculated, within study, as the residual from the linear regression of DMI on midtest BW^0.75, ADG, sex, sex by midtest BW^0.75 and sex by ADG. In study 1, calves from the low IGF-I selection line had similar initial and final BW and ADG, compared with calves from the high IGF-I selection line. In addition, DMI and feed conversion ratio were similar between IGF-I selection lines; however, calves from the low IGF-I selection line tended (P < 0.10) to have lesser RFI than calves from the high IGF-I selection line (–0.26 vs. 0.24 ± 0.31 kg/d). In study 2, IGF-I selection line had no influence on performance or feed efficiency traits. However, there was a tendency (P = 0.15) for an IGF-I selection line x sex interaction for RFI. Bulls from the low IGF-I selection line had numerically lesser RFI than those from the high IGF-I selection line, whereas in heifers, the IGF-I selection line had no effect on RFI. In studies 1 and 2, weaning and initial IGF-I concentrations were not correlated with either feed conversion ratio or RFI. However, regression analysis revealed a sex x IGF-I concentration interaction for initial IGF-I concentration in study 1 and weaning IGF-I concentration in study 2 such that the regression coefficient was positive for bulls and negative for heifers. These data suggest that genetic selection for postweaning serum IGF-I concentration had a minimal effect on RFI in beef cattle.

Key Words: beef cattle • carcass composition • divergent selection • insulin-like growth factor-I • residual feed intake

This article has been cited by other articles:

				S. S. Moore, F. D. Mujibi, and E. L. Sherman Molecular basis for residual feed intake in beef cattle J Anim Sci, April 1, 2009; 87(14_suppl): E41 - E47. [Abstract] [Full Text] [PDF]