Feeding systems and implant strategies for calf-fed Holstein steers

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C. T. Milton , R. T. Brandt, Jr. ,and E. C. Titgemeyer 1 1
Summary Two hundred sixty-four Holstein steer improved feed efficiency and a compensatory calves (308 lb) were used in a 2×3 factorially gain response during the latter phase of the designed experiment to compare the effect of feeding period. However, the gain restriction two feeding systems and three implant strate-over the first 200 days in this study probably gies on performance and carcass characteris-was too severe to allow program-fed steers tics. Steers were allowed ad libitum access to to finish at a similar weight with a similar a conventional, high-grain diet for the entire number of days on feed those feeding ad feeding period or were program-fed a high-libitum. Implanting calf-fed Holstein steers grain diet to gain 2.2 lb/d for 109 days and with a low dose of estrogen and then increas-2.6 lb/d for 92 days and then allowed ad ing implant potency step-wise optimized libitum access to feed for the remainder of the performance and carcass quality. feeding period. Steers were fed to a common weight endpoint (1260 lb). Implant strategies (Key Words: Holstein, Calf-Fed Steers, were: 1) Synovex -S on days 1, 109, and 201 Feeding Systems, Implants, Carcasses.) ® (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).
Holstein steers placed on feed as young Over the entire feeding period, steers finished calves (300 to 400 lb) often are fed highon the ad libitum system consumed 7% grain diets for 280 to 350 days. These steers (P<.01) more feed daily and gained 7.2% often display reduced feed consumption (P<.01) faster than those in the programmed during the final 80 to 100 days on feed. The feeding system. Steers in the programmed cause of this "stalling out" phenomenon feeding system required an additional 24 days remains unknown but may be related to to achieve similar finished weights and had extended ruminal acidic conditions, metabolic smaller (P<.05) ribeye areas and less (P<.01) signals associated with physiological maturity backfat than steers feeding ad libitum or body composition, and(or) boredom with throughout. Feed efficiency and total feed the diet. Managing calf-fed Holsteins in a consumed were similar between feeding two-step programmed feeding system before systems. Compared to S-S-S, feed efficiency placing them on full feed may improve feed was improved 4.3% by C-S-R and 6.7% efficiency, take advantage of compensatory (P<.05) by C-R-R. The C-R-R implant strat-growth, and minimize "stall out" from continegy reduced marbling (P<.01) and percentage uous ad libitum feeding. of USDA Choice carcasses (P=.01) com-pared with S-S-S or C-S-R. A two-phase, programmed feeding system can result in Introduction Implant programs that optimize performance and carcass characteristics for calffed Holsteins remain elusive. Implants too potent early in the feeding period may downregulate receptors and reduce responses to subsequent implants.
Our objectives were to 1) compare a twophase programmed feeding system followed by full feeding a high-grain diet to a conventional, full-fed system and 2) evaluate three implant programs using products varying in hormonal compounds and concentration.

Experimental Procedures
Two hundred sixty-four Holstein steer calves (308 lb) were stratified by weight into one of four weight replicates. Within each replicate, steers were allotted randomly to one of six pens (11 head/pen) in a 2x3 factorially arranged experiment. Factors were two feeding systems and three implant strategies. Steers in 12 pens were allowed to feed ad libitum on a conventional high-grain finishing diet for the entire feeding period. Steers in the other 12 pens were limit-fed a high-grain diet and programmed to gain 2.2 lb/day for 108 days, 2.6 lb/day for 92 days, and then allowed ad libitum access to a finishing diet for the remainder of the feeding period. Programmed rates of gain represented approximately 65% and 85% of maximal rate of gain for the respective periods. Four pens within each feeding system received one of three implant strategies: 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 followed Revalor-S on days 109 and 201 (C-R-R).
During the first 200 days of the experiment, the finishing diet (Finisher 1) was based on dry-rolled corn and contained (dry basis) 10% corn silage (Table 1). Because feed intake was restricted in the programmed feeding system, corn silage was increased to 25% of the diet. When programmed steers were changed to ad libitum intake (day 201), all steers were fed a common diet based on high-moisture and dry-rolled corn (Finisher 2; and 2.6 lb/day had higher (P<.01) feed intake, Table 1). All diets provided 275 mg of gained 15% (P<.01) faster, and were 7% Rumensin and 90 mg of Tylan per head (P<.05) more efficient than those having ® ® daily. Initial and final weights were the continuous access to feed. Increased feed averages of two consecutive, early morning, intake and daily gain and improved feed full weights taken before feeding. Steers efficiency are characteristic of compensatory were slaughtered by feeding system at a growth. Steers reimplanted with Revalor-S weight-constant endpoint (1260 lb). Steers in gained faster (P<.05) and more efficiently the ad libitum system were fed for 326 days, (P<.05) than those reimplanted with whereas those on the programmed feeding Synovex-S and those receiving their first system were fed for 350 days. Revalor-S.

Results and Discussion
finished using the conventional, ad libitum Because no interactions between feeding system consumed 7% (P<.01) more feed per system and implant strategy occurred for day and gained 7.2% (P<.01) faster comfeedlot performance or carcass characteris-pared with steers in the programmed feeding tics, only the main effects are presented. system. Feed efficiency was similar between Nine steers either died or were removed from feeding systems, and equal amounts of feed the experiment for reasons not related to were required to achieve similar finished treatment. They were distributed approxi-weights. Although steers finished on the mately equally across treatments.
programmed gain system expressed compen-During the first implant period (day 1 to feed, an additional 24 days were required to 108), programmed feeding resulted in lower achieve a finished weight similar to that of (P<.01) daily gain, but feed efficiency was steers in the continuous ad libitum system. improved 3.7% (P<.10) compared with ad The length and(or) severity of restriction libitum feeding (Table 2). Daily gain of likely increased the time required to achieve programmed steers (2.4 lb/day) was slightly the desired finished weight. Steers implanted higher than the 2.2 lb/day predicted. Implant-with C-S-R or C-R-R gained faster (P<.05) ing steers with Synovex-C tended (P=.13) to than steers implanted with S-S-S. Steers improve feed efficiency compared with implanted with C-S-R or C-R-R were 4.3 and Synovex-S. 6.7% (P<.05) more efficient, respectively, During the second implant period (Day 109 to 200), programmed feeding resulted in Hot carcass weights were heavier (P<.05) lower (P<.01) daily gain, but feed efficiency for steers implanted with C-S-R or C-R-R was improved 5.4% (P<.05) compared with than S-S-S (Table 3). Carcass weights were ad libitum feeding. Steers implanted with similar between feeding systems. However, Synovex-S that had initially received fat thickness (P<.01), ribeye area (P<.05), Synovex-C gained faster (P<.05) and more marbling (P<.10), and percentage of Choice efficiently (P<.05) in this period than steers carcasses (P<.01) were greater for steers in initially implanted with Synovex-S. the ad libitum than the programmed feeding During the third implant period (day 201 restriction during the programmed feeding to 326 or 350), all steers were allowed ad was severe enough to alter body composition. libitum access to a common finishing diet.
Dressing percentage, kidney, pelvic, and Steers previously programmed to gain 2.2 heart fat, yield grade, and the incidence of Over the entire feeding period, steers satory growth during the final 150 days on than steers implanted with S-S-S.
system. These data indicate that the level of abscessed livers were unaffected by feeding compensatory growth response later in the system or implant strategy. The C-R-R finishing period compared with continuous ad implant strategy reduced marbling (P<.01) libitum feeding. However, the duration and and percentage of Choice carcasses (P=.01) level of restriction that is needed to improve compared with S-S-S or C-S-R. Compared overall feed efficiency remains elusive. to S-S-S, implanting with C-S-R had no Implanting steers with a low dose of estrogen effect on marbling or percentage of Choice initially and then increasing implant potency carcasses.
step-wise optimized animal performance and A two-phase programmed feeding system followed by full feeding produced a carcass quality in calf-fed Holstein steers.