Implant program effects on performance and carcass quality of steer calves finished for 212 days.

We compared the effects of seven implant treatments combining use of Ralgro (RAL), Synovex-S (SYN), and Revalor-S (REV) on performance and beef quality traits of crossbred steer calves (n = 560) finished for 212 d. A randomized complete block design was used to compare treatments consisting of 1) non-implanted control (CON); 2) RAL on d 0, SYN on d 60, and REV on d 130 (RALSYNREV); 3) RAL on d 0, REV on d 60, and REV on d 130 (RALREVREV); 4) SYN on d 30 and REV on d 130 (SYNREV); 5) REV on d 30 and REV on d 130 (REVREV); 6) REV on d 0, REV on d 75, and REV on d 150, 12.5% crude protein diet (REV3X-12.5); and 7) REV on d 0, REV on d 75, and REV on d 150, 14.5% crude protein diet (REV3X-14.5). All implant groups had higher ADG and gained more efficiently (ADG: feed intake) than the CON group. No distinct performance advantages were noted for particular implant schemes. Implant treatments did not (P > .05) affect dressing percentage, carcass weight, or KPH fat percentage. Fat thickness did not differ (P > .05) for implanted vs CON steers; however, REVREV, SYNREV, and RALREVREV steers produced fatter carcasses than did REV3X-12.5 and RALSYNREV steers. The REV3X-12.5 and REV3X-14.5 treatments increased longissimus muscle area compared with CON; longissimus muscle areas for all other treatments did not differ (P > .05) from CON. No reduction in percentage of Choice and Prime carcasses occurred with use of SYNREV or REVREV; however, all treatments receiving three successive implants had lower (P < .05) percentages of Choice and Prime carcasses than the CON group. Increasing dietary crude protein seemed to lessen the detrimental effect of three successive REV implants on percentages of Choice and Prime carcasses. Loin steaks from REVREV, REV3X-12.5, and REV3X-14.5 steers had higher (P < .05) shear force values than steaks from CON steers.

Effects of dietary virginiamycin on performance and liver abscess incidence in feedlot cattle.

The effects of dietary virginiamycin level on performance and liver abscesses in feedlot cattle were evaluated in seven dose-response studies. Steers and heifers were fed finishing diets ranging in energy content from 1.34 to 1.51 Mcal of NEg/kg of DM. In all studies, virginiamycin added to the diet improved average daily gain and(or) feed conversion, with no substantial effect on dry matter intake. Pooled analyses of four studies providing virginiamycin at 11.0, 19.3, and 27.6 mg/kg of DM in the complete diet indicated that growth and feed conversion were linearly improved (P < .05); feeding 19.3 mg/kg improved these measurements by 3.0 and 3.8%, respectively. Overall incidence (score 0 vs score 1, 2, and 3) and severity (score 0, 1, and 2 vs score 3) of liver abscesses were reduced (P < .01) by feeding virginiamycin at either 19.3 or 27.6 mg/kg. Linear plateau modeling indicated that the effective dose range for virginiamycin in feedlot diets (DM basis) was 19.3 to 27.3 mg/kg for increasing average daily gain, 13.2 to 19.3 mg/kg for improving feed conversion, and 16.5 to 19.3 mg/kg for reducing liver abscess incidence.

Efficacy of laidlomycin propionate for increasing rate and efficiency of gain by feedlot cattle.

One thousand twenty steers and heifers were used in six feeding trials to examine the influence of laidlomycin propionate on feedlot performance and to determine the most efficacious dietary concentrations of that ionophore. Cattle were fed diets ranging in energy content from 1.08 to 1.49 Mcal NEg/kg of DM. Laidlomycin propionate improved rate of gain and feed conversion in both steers and heifers. Improvements in performance were not evident when laidlomycin propionate was fed at only 3 mg/kg. However, both average daily gain and feed conversion were improved by laidlomycin propionate within the range of 6 to 12 mg/kg of DM (P less than .001). Feed consumption was not substantially affected by inclusion of laidlomycin propionate in the diet. Improvements in ADG and feed conversion were greater on lower-energy diets than on higher-energy diets, but both these performance characteristics were improved regardless of the type of diet fed. Average daily gain was maximized with laidlomycin propionate at 6 mg/kg, whereas improvements in feed conversion were sustained through 12 mg/kg. Carcasses of cattle fed diets containing 6 to 12 mg/kg of laidlomycin propionate weighed 7.3 kg more (P less than .001) than carcasses of cattle fed the control diets. Yield grade and quality grade were not affected by laidlomycin propionate (P greater than .05).

Effect of monensin on the performance of cattle on pasture or fed harvested forages in confinement.

Three series of trials were conducted to evaluate the effect of monensin on the growth performance of cattle. Twenty-four trials were conducted to evaluate the addition of monensin at 200 mg/d to limited quantities of supplemental concentrate for growing cattle grazing pastures. The pastures ranged from dormant end-of-the-season grasses and crop residues to lush green pastures, and were located in several different states. Pasture plus supplement supported gains of control cattle (without monensin) of .24 to .96 kg, with an average of .56 kg/d. The addition of 200 mg monensin to the supplement increased daily gain in all 24 trials by an average of .09 kg daily (+16.3%). Eleven trials were conducted with monensin and energy supplements fed at .907 kg.- head-1 X d-1 to growing cattle grazing growing, nondormant pastures for an average period of 117 d. Each trial was designed to compare the performance of unsupplemented cattle, cattle fed a supplement and cattle fed a supplement with monensin. Cattle on pasture gained .50 kg daily. Supplement feeding increased average daily gain by .09 kg and the addition of monensin to the supplement further increased gain by .09 kg, for a total increase of .18 kg (34.2%). The efficiencies with which supplemental feed was converted to extra gain (kg supplement/kg gain) for the supplement-only and the monensin treatment groups were 10.1:1 and 5.0:1, respectively. In a series of 12 trials, monensin was added at a level of 33 mg/kg air-dry diet to limited quantities of supplemental feed for cattle fed harvested forages in confinement. All trials compared monensin feeding with a nonmedicated control treatment. Hay was fed in 8 of the 12 trials, fresh-cut green-chop in two trials and ensiled corn stover and ensiled milo stover in one trial each. Monensin reduced feed intake by -3.1%, improved average daily gain by .09 kg (+14.4%) and improved feed efficiency by 15.3%.

Administration of monensin in self-fed (salt limiting) dry supplements or on an alternate-day feeding schedule.

Two series of trials were conducted to evaluate alternative methods of administering monensin to pasture cattle. In a series of five trials, monensin was incorporated into supplements at 440 mg/kg to provide an average intake of 200 mg X head-1 X d-1 for growing cattle on pasture. Comparisons were made between daily and alternate-day feeding of the supplements. A control treatment consisting of unmedicated supplement fed daily also was included. Monensin at 200 mg/d and 400 mg on alternate days increased gain by .077 (P less than .01) and .082 (P less than .01) kg/d above control-cattle gains (.54 kg daily). Nine pasture trials were conducted to compare the effectiveness of monensin in increasing the daily gain of growing cattle when hand-fed daily in a supplement or self-fed in supplements that contained salt to regulate supplement intake. Desired supplement intakes were approximately .454 kg X head-1 X d-1 in six trials, .68 kg/d in one trial and 1.81 kg/d in two trials. Monensin produced gain increases of .09 kg daily (P less than .01) with both feeding systems. The daily gains of cattle that were hand-fed and self-fed were equal (P greater than .10). Self-fed treatments containing monensin required fewer changes in salt level than self-fed treatments not containing monensin, and the salt levels required to limit intake were generally 25 to 50% lower when monensin was in the supplement.

Effect of monensin and tylosin on average daily gain, feed efficiency and liver abscess incidence in feedlot cattle.

Fourteen trials were conducted to evaluate the effects of feeding monensin at 33 ppm alone, tylosin at 11 ppm alone and the two feed additives in combination on the average daily gain, average daily feed intake, feed:gain ratio and the incidence of liver abscesses in feedlot cattle. Monensin reduced feed intake and improved feed efficiency (P less than .05), and had no effect on average daily gain. Tylosin improved average daily gain (P less than .05) and had no effect on daily feed intake. The effect of tylosin on feed efficiency approached significance. The interaction of monensin and tylosin was nonsignificant for daily gain, daily feed intake and feed:gain ratio. Monensin had no effect on liver abscess incidence, while tylosin reduced abscess incidence from 27 to 9%.