Results and Discussion
Performance data are presented in Table 2. In Period 1, ADG was greatest for steers in the AL regimen, intermediate for steers in the PI regimen, and lowest for steers in the CS-HLL and CS-HIL feeding regimens (P < 0.01). In previous programmed gain studies (Knoblich et al., 1997; Rossi et al., 2000), ADG was similar to predicted ADG when steers were fed to gain 2.5 lb/day. Although actual ADG was greater than predicted, the relative differences in ADG between steers consuming the PI and AL diets in the present experiment were similar to those described in the experiments cited above. Feed efficiency was increased (P < 0.01) 22% in steers consuming the PI versus the CS-HLL and CS-HIL diets. Feed efficiency of steers in the AL feeding regimen was lower (P < 0.01) compared with steers in the PI regimen, but greater compared with steers in the CS-HLL and CS-HIL regimens. Feed efficiency of steers fed the 85% corn silage diet was lower than that of steers fed the AL diet. In Period 2, ADG was not different among feeding regimens (P = 0.84). Daily DMI was similar (P = 0.43) between steers in the AL and CS-HIL feeding regimen, and both were greater (P = 0.06) than steers in the PI and CS-HLL regimens. Feed efficiency was similar (P = 0.49) between steers in the PI and CS-HLL feeding regimens and was increased (P = 0.08) compared with that of steers in the AL regimen. Steers in the CS-HIL feeding regimen had a comparable (P = 0.49) feed efficiency to steers in both the AL and PI regimens but a lower (P = 0.08) feed efficiency than for steers in the CS-HLL regimen. Concentration of corn silage in diets fed in Period 1 had little carryover effects on ADG, DMI, and feed efficiency in Period 2 when steers were switched to the same diet (PI vs CS-HLL). In Period 3, ADG of steers was not different among treatments (P = 0.44). There was a trend for steers consuming corn silage-based diets (CS-HLL and CS-HIL) early in the feeding period to have lower ADG in Period 3. Reasons for these differences are not clear. However, stomach and large intestine weights were reported to be larger for animals consuming high roughage diets (Rompala et al., 1988), which may have increased maintenance requirements of steers consuming corn silage-based diets. Because of the short duration of Period 3, any delay in the compensatory growth response would negatively affect performance in this period. Overall ADG was lower (P < 0.01) for steers in the CS-HLL and CS-HIL feeding regimens compared with steers in the AL and PI regimens. A portion of the lower overall ADG of steers in the CS-HLL and CS-HIL feeding regimens compared with steers in the PI regimen was a result of lower ADG in Period 1. When ADG was analyzed from the beginning of Period 2 until harvest, ADG was not different between steers in the PI and CS-HLL regimens, but was lower (P < 0.05) for steers in the CS-HIL regimen (3.51, 3.77, 3.64, and 3.53 lb/day for steers in the AL, PI, CS-HLL, and CS-HIL feeding regimens, respectively). Overall daily DMI was greatest for steers offered feed ad libitum, intermediate for steers in the CS-HIL regimen, and lowest for steers in the PI and CS-HLL regimens (P < 0.05). Feed efficiency was greatest for steers in the PI regimen, similar between steers in the AL and CS-HLL regimen, and lowest for steers in the CS-HIL regimen (P < 0.01). Total DMI was lower (P < 0.05) for steers in the PI feeding regimen than for steers in the CS-HLL and CS-HIL regimens. In addition, total DMI of steers in the PI feeding regimen was similar to that of steers in the AL feeding regimen. Compared with steers in the AL feeding regimen, days fed were 9, 22, and 28 greater (P < 0.01) for steers in the PI, CS-HLL, and CS-HIL feeding regimens, respectively. No differences were observed for carcass characteristics (P > 0.22; Table 3).