Effects of Dietary Zinc Level and Ractopamine on Pork Chop Tenderness and Shelf-Life Characteristics

Feeding pigs 10ppm ractopamine HCl (RAC) altered the pig muscle fibre types, as did additional dietary zinc, which affected meat colour characteristics, according to research presented at the 2013 Kansas Swine Industry Day.
calendar icon 3 April 2014
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Researchers at Kansas State University, including first-named author, C.B. Paulk, presented their study examining the effects of dietary zinc level and RAC on the tenderness and shelf-life of pork chops.

A total of 320 finishing pigs (PIC 327 × 1050; initially 216 lb) were utilised to determine the effects of adding zinc to diets containing RAC on muscle fibre type distribution, fresh chop colour and cooked meat characteristics.

Dietary treatments were fed for approximately 35 days and consisted of: a corn- and soybean meal–based negative control (CON); a positive control diet with 10ppm of RAC (RAC+); and the RAC+ diet plus 75, 150 or 225ppm added zinc from either zinc oxide or Availa-Zn (Zinpro, US).

Loins from 80 barrow and 80 gilt carcasses were evaluated.

No zinc source effect or zinc source × level interactions were observed during the study (P>0.10).

Pigs fed the RAC+ had increased (P<0.02) percentage type IIX and a tendency for increased percentage type IIB muscle fibres. Increasing added zinc decreased (linear, P=0.01) percentage type IIA and tended to increase (P=0.09) IIX muscle fibres.

On days 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 the CON.

On days 0 and 3 of display, increasing added zinc tended to decrease (quadratic, P=0.10) L* values and decreased (quadratic, P<0.03) L* values on days 1, 2, 4 and 5.

Pigs fed RAC+ had decreased (P<0.05) a* values (less red) on days 1 and 4 of display and tended to have decreased (P<0.10) a* values on day 0 and 2 compared with CON pork chops. RAC+ decreased (P<0.001) metmyoglobin reducing ability (MRA) of pork chops on day 5.

Chops from pigs fed added zinc had increased (quadratic, P<0.03) MRA on days 3 and 5 of the display period.

There was a trend for increased (linear, P=0.07) cooking loss as added zinc increased in RAC diets.

Paulk and colleagues concluded that RAC+ diets produced chops that were lighter and less red but maintained a higher percentage of surface oxymyoglobin throughout a five-day simulated retail display. RAC+ reduced MRA at the end of the display period but supplementing zinc to RAC diets restored MRA to near CON treatment levels at the end of the display period.


Paulk C.B., M.D. Tokach, J.L. Nelssen, D.D. Burnett, M.A. Vaughn, K.J. Phelps, S.S. Dritz, J.M. DeRouchey, R.D. Goodband, T.E. Houser, K.D. Haydon and J.M. Gonzalez. 2013. Effects of dietary zinc level and ractopamine HCl on pork chop tenderness and shelf-life characteristics. Proceedings of 2013 Kansas Swine Day, p145-159.

Further Reading

You can view the full paper by clicking here.
Read other papers presented at the 2013 Kansas Swine Day by clicking here.

April 2014

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