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Effect of dietary zinc and Ractopamine-HCl on pork chop tenderness and shelf-life characteristics
Finishing pigs (n=160; PIC 327 × 1050; initially 98 kg) were used to determine the effects of adding Zn to diets containing ractopamine HCl (RAC; Elanco Animal Health, Greenfield, IN) on muscle fiber type distribution, chop color, and cooked meat characteristics. Eight dietary treatments were fed for approximately 35-d and consisted of: a corn-soybean meal control (0.66% SID Lys), a diet (0.92% SID Lys) with 10 ppm RAC, 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. No Zn source effects or Zn source × level interactions were observed. Pigs fed RAC had increased (P<0.02) percentage type IIX and a tendency for increased (P<0.10) percentage type IIB muscle fibers compared to pigs not fed RAC. Increasing added Zn decreased (linear, P=0.01) type IIA and tended to increase (P=0.09) IIX muscle fibers. On d 1, 2, 3, 4, and 5 of display, pork chops from pigs fed the RAC treatment had greater (P<0.03) L* values (lighter) compared with those fed the control diet. On d 0 and 3 of display, increasing Zn tended to decrease (quadratic, P=0.10) L* values and decreased (quadratic, P<0.03) L* values on d 1, 2, 4, and 5. Pigs fed RAC had decreased (P<0.05) a* values (less red) on d 1 and 4 of display and tended to have decreased (P<0.10) a* values on d 0 and 2 compared with control pork chops. RAC decreased (P<0.001) metmyoglobin reducing ability (MRA) of pork chops on d 5 compared to chops from pigs fed the control diet. Chops from pigs fed added Zn had increased (quadratic, P<0.03) MRA on d 3 and 5 of display. There were no differences in chop pH, cooking loss, or shear force. There was a trend for increased (linear, P=0.07) cooking loss as Zn increased in RAC diets, but no difference in pH or shear force. In conclusion, RAC diets produced chops that were lighter and less red. At the end of the display period, RAC reduced MRA, but adding Zn to RAC diets mitigated this reduction in MRA.
Keywords: Ractopamine HCl, shelf-life, zinc
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ppm Zn |
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Fiber Type,% |
Control |
RAC |
75 |
150 |
225 |
SEM |
I |
8.89 |
8.77 |
8.40 |
8.24 |
8.49 |
0.77 |
IIA |
12.37 |
14.74 |
14.14 |
12.93 |
11.05 |
1.48 |
IIX |
32.57 |
25.51 |
26.23 |
29.13 |
29.24 |
2.36 |
IIB |
46.12 |
50.94 |
51.18 |
49.65 |
51.14 |
2.56 |