Six trials involving 888 pigs (Study 1) and three trials involving 360 pigs (Study 2) were conducted at various geographical locations in the U.S. and Canada to evaluate the effect of ractopamine hydrochloride on the performance and carcass characteristics of finishing swine. All trials were conducted using a randomized complete block design. Trial data were pooled within study for statistical analysis. Pigs averaged approximately 64.5 kg (Study 1) and 65.9 kg (Study 2) initially and had ad libitum access to a 16% crude protein corn-soybean meal or barley-soybean meal diet. Ractopamine was included in the diet at 0, 2.5, 5, 10, 20 or 30 ppm (Study 1), or at 0, 5, 10, 15 or 20 ppm (Study 2); diets were fed for an average of 45 d (Study 1) and 50 d (Study 2) to a final weight of about 104.3 kg (Study 1) and 106.6 kg (Study 2). Carcass dissection data were collected in three of the six trials in Study 1 (0, 5 and 20 ppm ractopamine) and in all three trials in Study 2 (0, 5, 10, 15 and 20 ppm ractopamine). All ractopamine levels improved (P less than .05) ADG and feed: gain (Studies 1 and 2) above those of control pigs. Ractopamine levels of 10 to 30 ppm (Studies 1 and 2) improved (P less than .05) dressing percentage over controls. Pigs fed ractopamine at 5 and 20 ppm (Study 1) and 10, 15 and 20 ppm (Study 2) had increased (P less than .05) dissected leanness compared with controls.(ABSTRACT TRUNCATED AT 250 WORDS)

At approximately 68 kg live weight, crossbred barrows and gilts (n = 144) were allocated to be fed to one of two weight end points (107 kg and 125 kg). Pigs from each weight group were treated with Ractopamine (RAC) (0, 10, or 20 ppm; n = 24/ treatment for the last 40 kg of gain. Feed consumption and weight gain were measured. Pigs were slaughtered and carcass measurements made at 24 h postmortem. Carcasses were fabricated into wholesale, trimmed wholesale, and boneless wholesale cuts for cutting yields. Hams were separated into muscle, fat, and bone. The RAC improved growth characteristics and carcass characteristics. Pigs fed RAC had increased (P < .01) average daily gain and improved (P < .01) feed:gain ratio over controls in each weight group. Carcasses from pigs treated with RAC had larger (P < .01) longissimus muscle area and reduced (P < .01) fat at the 10th rib. Cuts from 125-kg pigs were generally heavier than those from 107-kg pigs. The RAC increased (P < .05) the boneless cut weights of both weight groups. Percentage of dissected lean from the hams of RAC-treated pigs was (P < .05) higher than that of controls. Few consistent differences were observed between the 10 and 20 ppm of RAC treatments. Results from this study indicate that RAC had positive effects on the growth characteristics, carcass characteristics, and carcass cutting yields of pigs representative of the broad spectrum of market weights.

One hundred eighty barrows were evaluated to determine the effects of ractopamine hydrochloride (RAC) on lean carcass yields and pork quality. The pens were blocked by weight (six pens per block) with starting block weights of 69.0, 70.7, 73.8, 76.6, 78.4, and 84.3 kg. Pens within a block were assigned randomly to one of three RAC treatments so each treatment in a block was replicated twice. Treatments (as-fed basis) included control diet, 10 ppm of RAC added (R10), and 20 ppm of RAC added (R20) and ranged from 25 to 41 d depending on block. Pigs were slaughtered by blocks when block average live weights were 109 kg. Gain and feed efficiency were improved (P < 0.05) with increasing dietary concentrations of RAC, but feed intake did not differ (P > 0.05). Dressing percentage was higher (P < 0.05) for RAC-treated pigs. Subjective color, firmness, marbling scores, and Minolta L* reflection of the LM were not different (P > 0.05) among treatments. Carcass weights were heavier (P < 0.05) for pigs treated with RAC compared with control pigs and were higher for R20 than for R10. The RAC-fed pigs had greater (P < 0.05) yields (actual and percentage of HCW) of the following Institutional Meat Purchase Specification (IMPS) cuts than control pigs: trimmed, boneless ham (IMPS-402C and IMPS-402G), loin (IMPS-414), sirloin, and Boston butt (IMPS-406A). Pigs treated with RAC had a greater (P < 0.05) percentage of fat-free lean trimmings (IMPS-418) than did control pigs. Pigs treated with the R20 concentration had increased (P < 0.05) water-holding capacity compared with control pigs. Purge loss decreased linearly (P < 0.05) with increasing RAC compared with control for 14-d aged, non-enhanced loins. Warner-Bratzler shear (WBS) force values measured for nonenhanced chops were greater for RAC-treated pigs than for control pigs with a low dose response (P = 0.001). Enhanced chop (salt and phosphate injection) WBS values did not differ (P > 0.05) among dietary treatments. Trained sensory evaluation panel results for tenderness decreased in a low-dose plateau response fashion for nonenhanced chops (P = 0.004). Tenderness of enhanced chops decreased linearly (P = 0.04) with increasing RAC concentrations. No differences (P > 0.05) were found in juiciness or flavor of enhanced or nonenhanced chops. Feeding RAC to late-finishing swine resulted in faster growing, more efficient animals with increased boneless subprimal yields, and it had little effect on pork juiciness and flavor.

This study was designed to evaluate growth performance, carcass cutting yield, and processing characteristics of boneless hams and bellies from finishing pigs fed diets containing 0, 5, 10, or 20 ppm of the phenethanolamine ractopamine hydrochloride (RAC). Sixty pigs were blocked by starting weight and randomly assigned to pens (four pigs/pen) within each of three blocks. Treatments were then randomly assigned to the pens to total six pens of the 0-ppm level and three pens each at the 5-, 10-, and 20-ppm RAC levels. Weight gain and feed consumption were monitored and animals were slaughtered by weight block after approximately 48 d on trial. Slaughter weight, ADG, and feed/gain were improved (P less than .05) for RAC treatments. Dressing percentage was higher and increased linearly (P less than .05) for RAC treatments. Carcass weight, length, leaf fat weight, backfat thickness, loin eye area, and color, marbling, and firmness of the longissimus were evaluated. The RAC-treated carcasses were heavier (P less than .05) and loin eye area increased linearly (P less than .05). One side of each carcass was fabricated using National Association of Meat Purveyors specifications. Trimmed hams and loins from the RAC treatments were heavier (P less than .05) than those from control animals. No differences (P greater than .05) in carcass cutting yield (percentage of trimmed primal cuts) were observed between treatments. However, trimmed hams and loins from the 20-ppm RAC treatment represented a greater (P less than .05) percentage of carcass weight than did those from control animals. Ractopamine did not affect raw belly or bacon characteristics (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)