J.E. Rossi and S.C. Loerch1
The Ohio State University Department of Animal Sciences
Abstract
Steer calves (n = 106; initial body weight (BW) = 604 ± 4 lb) were allotted by BW to 12 pens and fed in three periods as described in Rossi and Loerch, 2001. Four feeding regimens were investigated: 1) AL; steers were offered a 15% corn silage diet ad libitum in all three periods; 2) PI; dry matter intake (DMI) was restricted to achieve a predicted gain of 2.5 lb/day in Period 1, 3.0 lb/day in Period 2, and feed was offered ad libitum in Period 3; 3) CS-HLL; prescription intake as described above except diets contained 85, 15, and 15% corn silage in Periods 1, 2, and 3, respectively; and 4) CS-HIL; same feeding regimens as CS-HLL, except diets were 85, 50, and 15% corn silage in Periods 1, 2, and 3, respectively. Steers were offered feed ad libitum in Period 3. Overall average daily gain (ADG) was lower (P < 0.05) for steers in the CS-HLL and CS-HIL feeding regimens compared with steers in the AL and PI regimens. Feed efficiency was greatest for steers in the PI regimen similar between steers in the AL and CS-HLL regimens, and lowest for steers in the CS-HIL regimen (0.206, 0.194, 0.191, and 0.183 lb gain/lb feed, respectively; P < 0.01). Effects of feeding regimen on carcass characteristics were minimal.
Introduction
Feeding cattle to achieve stepwise increases in rate of gain has been shown to result in similar performance and carcass characteristics as steers offered feed ad libitum throughout the feeding period (Knoblich et al., 1997; Rossi et al., 2000).
Cattle consuming roughage-based diets have greater gastrointestinal tract weights than cattle consuming concentrate-based diets (Rompala et al., 1988), which may increase maintenance requirements and negatively affect rate of gain during compensatory growth. Diets consisting of high proportions of corn silage (Loerch, 1990) or hay (Gunter et al., 1998) have been used to limit rate of gain in the first half of the feeding period with little effect on subsequent rate of gain during the finishing phase. However, no information is available on optimal roughage levels in feeding systems that restrict DMI to achieve stepwise increases in growth rate. Further, effects of proportion of dietary roughage on performance responses to subsequent increases in DMI are unknown. Objectives were to determine effects of proportion of corn silage during periods of feed restriction on performance and carcass characteristics of steers fed to achieve stepwise increases in rate of gain.