J. E. Rossi and S.C. Loerch1
The Ohio State University Department of Animal Sciences
This experiment evaluated effects of different growth rates in steers fed to achieve step-wise increases in growth rate during the feeding period. Steers (n = 96; 679.6 lbs) were either offered feed ad libitum (AL) throughout the feeding period or intake was restricted to achieve gains of 2.5 (prescription intake; low rate of growth; PIL) or 2.75 lb/day (prescription intake; high rate of growth; PIH) for the first 170 lb of gain; 3.0 (PIL) or 3.25 lb/day (PIH) for the next 280 lb of gain; and offered feed ad libitum for the final 127 lb of gain before slaughter (at 1,260 lb). Steers programmed to gain 0.25 lb/day more (PIH) during Periods of restricted intake actually gained 0.42 and 0.34 lb/day more than PIL steers during Periods 1 and 2, respectively. Steers in both PIL and PIH treatments gained 36% more than predicted during Period 2. However, during Period 3, PIL steers gained 0.72 lb/day more than PIH steers. Feed efficiency was improved (P < 0.10) for PIH (0.230) vs. PIL steers (0.213) during Period 1, was similar (P > 0.10) for Period 2 (0.219 and 0.230 for PIL and PIH, respectively), and was improved (P < 0.05) for PIL (0.200) vs. PIH (0.165) steers during Period 3. Days fed for PIH were reduced eight days during Period 1 and five days during Period 2 compared with PIL steers. Overall ADG was similar (P > 0.37) between treatments. Dry matter intake per day was greatest (P < 0.05) for AL steers (19.6 lb/day), intermediate for PIH steers (18.4 lb/day), and lowest for PIL steers (17.5 lb/day). Feed efficiency tended to be improved for PIL (0.212) and PIH (0.211) steers compared with AL steers (0.198). Total intake was reduced 158 lbs for PIL and 167 lbs for PIH steers compared with AL steers. Total days fed were the same for AL and PIH steers and nine days greater for PIL steers. No differences (P > 0.22) were observed for carcass characteristics.
1 For more information, contact at: The Ohio State University, Ohio Agricultural Research and Development Center, 1680 Madison Avenue, Wooster OH 44691, 303-263-3900, e-mail: loerch.1@osu.edu