A total of 253 finishing pigs (PIC 327 × 1050; initial BW 204 lb) were used in a 28-d
study to determine the effects of added Zn (Availa-Zn; Zinpro Corp., Eden Prairie,
MN), Cu (Availa-Cu; Zinpro Corp.), or both to diets containing ractopamine HCl
(RAC; Paylean; Elanco Animal Health, Greenfield, IN) on growth performance and
carcass characteristics. Pens of pigs were randomly assigned to 1 of 5 treatments and
balanced on average pig weight with 7 to 8 pigs per pen. Treatments included a control
diet without RAC (negative control) and 4 diets containing 9 g/ton RAC with or without
added Zn (50 ppm) or Cu (125 ppm) in a 2 × 2 factorial.
Overall, pigs fed RAC had increased (P < 0.01) ADG and improved F/G, which
resulted in approximately a 15.5-lb heavier (P < 0.01) pig compared with those fed the
negative control diet. Pigs fed added Zn had decreased (P < 0.05) ADG and tended
to have decreased (P < 0.09) ADFI. Pigs fed added Cu also tended (P < 0.10) to have
decreased ADG. No differences were observed in F/G when Zn or Cu was added to the
diet.
Hot carcass weight, carcass yield, loin depth, and percentage lean increased (P < 0.01)
in pigs fed the positive control diet containing RAC compared with those fed the
negative control diet, whereas backfat was unaffected. Carcass characteristics were not
affected by added Zn or Cu.
Feed cost and revenue increased (P < 0.01) for pigs fed the positive control diet
containing RAC by approximately $9.63 and $10.08, respectively, compared with pigs
fed the negative control diet; however, no difference was observed in feed cost per lb of
gain. Income over feed cost (IOFC) did not differ in pigs fed the negative or positive
control diet. Adding Zn decreased (P < 0.05) revenue per pig, and adding Cu tended to
increase (P < 0.06) feed cost per lb of gain and reduce (P < 0.10) revenue per pig. There
were no differences in IOFC between diets containing added Zn and no added Zn.
Added Cu reduced (P < 0.05) IOFC.
In summary, growth and carcass characteristics improved in pigs fed dietary RAC as
expected, but adding Zn, Cu, or both to diets containing RAC did not improve growth
performance, carcass characteristics, or IOFC. Adding copper actually reduced IOFC
due to the added expense.
