184
Effects of Added Zn in Diets with Ractopamine HCl on Growth Performance, Carcass Characteristics, Zn Concentrations in Plasma, Loin, and Liver, and Ileal Mucosal Inflammation mRNA Expression of Finishing Pigs
A total of 320 pigs (PIC 327 × 1050; 98 kg BW) were used in a 35-d study to determine the effects of added Zn on growth performance, carcass characteristics, plasma and tissue Zn concentrations, and ileal mucosal mRNA expression of finishing pigs fed ractopamine HCl (RAC; Elanco Animal Health, Greenfield, IN). Pens were randomly allotted to diets with 2 pigs per pen and 20 pens per treatment. Treatments included a corn-soybean meal diet (0.66% SID Lys), a diet (0.92% SID Lys) with 10 ppm RAC, or the RAC diet plus 75, 150, and 225 ppm added Zn from ZnO or Availa-Zn (Zinpro, Eden Prairie, MN). All diets contained 55 ppm Zn from ZnSO4. Mucosal swabs were collected (16 pigs/treatment) to determine mRNA expression of inflammatory cytokines . Pigs fed the RAC diet had increased (P<0.05) ADG, G:F, HCW, loin depth, percentage lean, and liver weights compared with pigs fed the control diet. No Zn level or source effects or level × source interactions were observed for growth performance. However, pigs fed RAC diets with added Zn from ZnO had numerically heavier (P=0.09) liver weights than pigs fed added Zn from Availa-Zn. A Zn level × source interaction (quadratic, P=0.02) was observed in liver Zn concentrations, resulting from liver Zn concentrations plateauing at 150 ppm of added Zn from ZnO, but a linear increase when adding Zn from Availa-Zn. There was no difference in Zn concentrations in the loin. The only difference for plasma Zn was that pigs fed RAC diets with added Zn had increased (linear, P<0.02) plasma Zn levels on d 18 and 32. The expression of IL-1β was increased (P=0.01) in mucosa of pigs fed the RAC diet compared to those fed the control diet. Expression of IL-1β decreased (linear; P=0.03) in the mucosa of pigs fed increasing levels of added Zn. There were no differences in IL-8 or TNF-α relative expression. In conclusion, additional Zn increased plasma Zn and reduced IL-1β, but did not improve growth performance of pigs fed diets containing RAC.
Keywords: finishing pigs, Ractopamine HCl, zinc
|
|
|
ZnO, ppm Zn |
Availa-Zn, ppm Zn |
|
||||
Item |
Control |
RAC |
75 |
150 |
225 |
75 |
150 |
225 |
SEM |
ADG, kg |
1.04 |
1.15 |
1.16 |
1.17 |
1.17 |
1.15 |
1.14 |
1.12 |
0.03 |
G:F |
0.311 |
0.365 |
0.373 |
0.371 |
0.369 |
0.373 |
0.365 |
0.367 |
0.014 |
HCW, kg |
99.0 |
101.7 |
102.5 |
101.7 |
102.8 |
101.9 |
101.7 |
101.0 |
1.3 |