Effects of programmed growth rate and days fed on performance and carcass characteristics of feedlot steers

Two-experiments were conducted to investigate a feeding regimen in which a programmed amount of feed was offered daily to control growth rate of steer s. In Exp. 1, steers (n = 107, 309 +/- 3 kg) were used to determine effects of offering ad libitum access to feed (AL) vs a programmed intake feeding regimen (PI) and the number of days steers were fed (168 vs 203) on perform ance and carcass characteristics. Steers in the programmed intake feeding r egimen were fed to achieve a predicted gain of 1.13 kg/d for the first 78 k g of gain, 1.36 kg/d for the next 124 kg of gain, and were given ad libitum access to feed for the final 54 or 103 kg of gain before slaughter (for st eers fed for 168 d or 203 d, respectively). Feed efficiency was greater (P < 0.02) for steers in the PI than for those in the AL feeding regimen (0.19 3 vs 0.183 kg gain/kg feed, respectively). From d 169 to 203, steers in the PI feeding regimen had greater (P < 0.06) ADG (1.60 vs 1.38 kg/d) and simi lar (P = 0.38) feed efficiency than steers in the AL regimen. In Exp. 2, st eers (n = 96; 308 +/- 3 kg BW) were offered feed ad libitum throughout the experiment (AL) or were programmed to gain at a high (PI-H) or low (PI-L) g rowth rate. For the first 78 kg of gain, intake was restricted to achieve p redicted gains of 1.13 kg/d (PI-L) or 1.25 kg/d (PI-H). For the next 124 kg of gain, intake was restricted to achieve predicted gains of 1.36 kg/d (PI -L) or 1.47 kg/d (PI-H), Feed was offered ad libitum for the final 58 kg of gain. Overall ADG was similar (P > 0.37) among feeding regimens despite lo wer DMI for the steers in the PI-L and PI-H feeding regimens than for those in the AL regimen. Feeding regimen did not affect (P < 0.22) carcass chara cteristics. Programmed intake feeding regimens sustained growth rate and fe ed efficiency for an extended period of time without detrimental effects on carcass characteristics.