Abstract
Two hundred sixty-four Holstein steer calves (308 lb) were used in a 2x3 factorially designed experiment to compare the effect of two feeding systems and three implant strategies on performance and carcass characteristics. Steers were allowed ad libitum access to a conventional, high-grain diet for the entire feeding period or were program-fed a high-grain diet to gain 2.2 lb/d for 109 days and 2.6 lb/d for 92 days and then allowed ad libitum access to feed for the remainder of the feeding period. Steers were fed to a common weight endpoint (1260 lb). Implant strategies were: 1) Synovex® -S on days 1, 109, and 201 (S-S-S); 2) Synovex® -C on day 1, Synovex-S ® on day 109, and Revalor -S on day 201 (C-S-R); and 3) Synovex-C on day 1 and Revalor-S on days 109 and 201 (C-R-R). Over the entire feeding period, steers finished on the ad libitum system consumed 7% (P<.01) more feed daily and gained 7.2% (P<.01) faster than those in the programmed feeding system. Steers in the programmed feeding system required an additional 24 days to achieve similar finished weights and had smaller (P<.05) ribeye areas and less (P<.01) backfat than steers feeding ad libitum throughout. Feed efficiency and total feed consumed were similar between feeding systems. Compared to S-S-S, feed efficiency was improved 4.3% by C-S-R and 6.7% (P<.05) by C-R-R. The C-R-R implant strategy reduced marbling (P<.01) and percentage of USDA Choice carcasses (P=.01) compared with S-S-S or C-S-R. A two-phase, programmed feeding system can result in improved feed efficiency and a compensatory gain response during the latter phase of the feeding period. However, the gain restriction over the first 200 days in this study probably was too severe to allow program-fed steers to finish at a similar weight with a similar number of days on feed those feeding ad libitum. Implanting calf-fed Holstein steers with a low dose of estrogen and then increasing implant potency step-wise optimized performance and carcass quality.
Highlights
Holstein steers placed on feed as young calves (300 to 400 lb) often are fed highgrain diets for 280 to 350 days
Steers were fed to a common weight endpoint (1260 lb)
Over the entire feeding period, steers finished on the ad libitum system consumed 7% (P
Summary
Holstein steers placed on feed as young calves (300 to 400 lb) often are fed highgrain diets for 280 to 350 days. These steers often display reduced feed consumption during the final 80 to 100 days on feed. The cause of this “stalling out” phenomenon remains unknown but may be related to extended ruminal acidic conditions, metabolic signals associated with physiological maturity or body composition, and(or) boredom with the diet. Managing calf-fed Holsteins in a two-step programmed feeding system before placing them on full feed may improve feed efficiency, take advantage of compensatory growth, and minimize “stall out” from continuous ad libitum feeding. Implants too potent early in the feeding period may downregulate receptors and reduce responses to subsequent implants
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