The effect of Magnesium supplementation on Pork Quality NPB #98-178

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1 Title: The effect of Magnesium supplementation on Pork Quality NPB # Investigator: Institution: Riëtte L.J.M. van Laack University of Tennessee Date Received: 1/3/2000 Abstract The objective of the study was to determine the feasibility of improving pork quality by magnesium supplementation, as magnesium-sulfate. In a pilot study, we determined that the level and duration of magnesium supplementation required to increase blood levels of magnesium (Mg) by 10% was 2 g elemental Mg/kg feed for 5 days before slaughter. The final concentration of Mg in the control and supplemented feed were 1.3 and 3.7 g Mg/kg feed, respectively. Subsequently, 100 halothane-negative pigs were supplemented at this level of magnesium for 5 days before slaughter. One-hundred non-supplemented pigs of the same genetic line were used as control group. Pigs were slaughtered on day 6, after 12 h fasting and transport to the packing plant. Blood, collected immediately after slaughter, was analyzed to determine Mg concentration. Blood Mg concentration in supplemented animals was 10% higher than in the control group (P<0.05). At 30 min, and at 3, 5 and 20 h postmortem, the ph in the loin was 6.43, 6.39, 6.20 and 5.71 respectively. Mg supplementation did not influence the ph decline. Meat quality characteristics at 24 h postmortem (color and water holding capacity) of the loin and ham (semimembranosus muscle) were not influenced by Mg supplementation. Mg supplementation did not influence purge % and shear force of 3 weeks stored loins. We conclude that in normal halothane-negative pigs, short term Mg supplementation does not significantly improve pork quality or reduce purge losses.

2 Introduction Poor water holding capacity (WHC) of pork products costs the swine industry substantial sums of money (Meeker and Sonka, 1994; Kauffman, 1996). These losses encompass not only lost product weight but also indirect costs associated with adverse customer reaction to pork products. PSE (Pale, Soft, Exudative) pork is the result of a rapid postmortem ph-decline, resulting in extensive protein denaturation, and loss of WHC. Much WHC research has focused on PSE prevention. Some pig breeds/lines are stress prone and consequently often yield PSE meat. Stress incurred during transport, ante-mortem handling, and during slaughter may cause PSE in genetically stress-resistant pigs as well. Because preslaughter stress cannot be totally eliminated, other, more practical means of preventing stress-induced PSE are needed. Although most WHC research concerns PSE, normal pork also loses a significant amount of drip. A reduction in this normal drip loss would be of enormous economic benefit for the industry. Magnesium (Mg) is an important cofactor of enzymes involved in energy and protein metabolism. As an antagonist to calcium, magnesium depresses skeletal muscle activity. Also, Mg reduces the secretion of neurotransmitters and, thus, neuromuscular stimulation (Niemack, 1985). Initial work on (injected) Mg showed that it slows glycolysis, and results in a higher ultimate post-slaughter ph (Sair et al., 1970; Lister and Ratcliff, 1971). Later, Niemack et al. (1979) and Kietzman and Jablonski (1985) demonstrated that dietary Mg supplementation of pigs reduced the effects of stress. This led to the suggestion that magnesium supplementation may be a way to improve meat quality (Kuhn et al., 1981). Despite the potential of Mg to improve pork quality, it has received little attention. Although results are variable, available data suggest that Mg supplementation improves meat quality (Otten et al., 1992; Schaefer et al., 1993; Porta et al., 1995; D'Souza et al., 1998; 1999). Differences between experimental results may result from differences in dose (Otten et al., 1992), duration of administration (Porta et al., 1995), and genetics of the pigs used. Recent results by D'Souza et al. (1998) suggest that Mg supplementation not only results in a PSE reduction, it may also reduce drip in normal pigs. Similar to earlier studies (Sair et al., 1970; Otten et al., 1992; Porta et al., 1995), D'Souza et al. (1998) observed that Mg supplementation resulted in an increase in ultimate ph. A higher ultimate ph is associated with higher water holding capacity. Thus, Mg supplementation may increase WHC of normal pork by increasing its ultimate ph. Generally, Mg is administered as Mg-aspartate -- a compound not permitted for use in the US. However, Mg-sulfate seems as effective as Mg-aspartate (D'Souza et al., 1999; Lister and Ratcliff, 1971). Available data suggest that effectiveness depends on the increase in blood Mg levels rather than on the type of salt. In the studies that Mg supplementation was effective, Mg blood levels increased 10% compared to control (no Mg supplementation). Objectives The objective of the study was to determine the feasibility of improving pork quality by Mg supplementation in the form of Mg-sulfate. Specifically, we tested the hypothesis that Mg supplementation improves water-holding capacity (reduces drip losses) in pork.

3 Procedures The study consisted of a pilot experiment to establish the required level of Mg supplementation and a meat-quality study. In the pilot experiment, we only analyzed Mg blood values. The pilot study results guided choice of Mg supplementation level and duration in the meat quality study. The meat quality study consisted of two identical trials with two groups of pigs: a control and a supplemented group. Establishment of supplementation level The purpose of the pilot study was to establish the supplementation level. Based upon data of D'Souza et al. (1998) and Schaefer et al. (1993), a 10% increase in blood Mg concentration is required. Results by D Souza et al. (1998) suggest that supplementation with about 1 g elemental Mg per kg feed (final Mg concentration in feed about 2.3 g/kg), for 5 days before slaughter, will raise Mg levels by 10%. Because those data are based on Mg-aspartate and -fumarate, we needed to determine whether a similar dose of Mg-sulfate would increase blood levels by 10%. A group of 45 pigs (15 control, 15 at 1 g Mg/kg feed and 15 at 2 g Mg/kg feed) was used. After 5 days supplementation blood samples were taken and analyzed for Mg content. Mg supplementation continued for another 5 days. Then, pigs were fasted for 12 h. Following fasting and before transport for slaughter, blood samples were taken and analyzed for Mg. This pilot experiment was repeated The Mg content of the control and supplemented feeds was assessed. Meat quality as affected by Mg supplementation After establishing the duration and level of supplementation, we tested the effect of Mg supplementation on meat quality. In two identical trials, 200 halothane-negative pigs were studied. One hundred pigs served as control, and 100 were supplemented. Supplementation at 2 g elemental Mg/kg feed stared five days before slaughter. In each trial, 50 pigs were supplemented while the other 50 pigs served as controls. After 5 days treatment, the pigs were transported to the slaughter plant (Premium Standard Foods). All pigs were slaughtered at day 6. Blood of each pig was collected immediately after slaughter. Loin ph was assessed at 30 min, 3, 5 and 24 h postmortem. It was not possible to measure ph between 30 min and 3 h because the carcasses were in the blast chiller and the surface was frozen. The longissimus muscle (LM) was excised and deboned and ph, color L*, a*, b* values, drip loss, color score, and marbling were determined at 24 h postmortem. The remaining section of the longissimus was weighed, packaged and stored for 21days at 0-2C. After 21 days storage, purge was determined, and samples for cooking and shear force measurement were cut. In 5 animals of each group, Mg concentration in the LM was assessed. At 24 h postmortem, the ham was excised, and color and ph of the face of the semimembranosus (SM) was determined. Biochemical and pork quality measurement Plasma and feed magnesium concentrations were determined using atomic absorption spectrophotometry. All analyses were done in duplicate. The ph between the 12 th and 13 th rib was determined using a portable ph meter (Orion Model 250 A, Orion Research Inc., Boston, MA 02129) with a Mettler-Toledo combination ph electrode (Mettler-Toledo Process Analytical Inc. Wilmington, MA 91887). The percentage drip loss was measured using the 24 h tube method. Surface L*, a* and b* values were measured using a Minolta Chromameter CR-200 (Minolta Camera Co., LTD., Japan), using D65 lighting, a 2 standard observer and a measuring aperture of 8mm. The machine was calibrated to 4 color plates as described by Warner (1994). Visual color was determined using the Japanese color scale as a standard (1=pale, 6 = dark). Marbling score (1=devoid, 5=abundant) was determined according to NPPC guidelines. Purge was

4 Magnesium and pork quali determined by weight loss during three weeks storage. For cooking loss and tenderness, AMSA 1996 guidelines were followed (AMSA, 1996). In an impingement oven (Wear-Ever Professional by Lincoln Impinger II, Lincoln Foodservice Products, Inc., Fort Wayne, IN 46801, USA), a chop of approximately 3.8 cm thickness was cooked to an internal temperature of 70C. Cooked pieces were stored overnight at 4C and cooking loss was determined. On seven to ten cores (1.25 cm diameter) per chop, Warner Bratzler shear force was assessed with a TA-XT2 Texture Analyzer (Texture Technologies Corp., Scarsdale, NY 10583, USA). Results were subjected to ANOVA using the GLM procedures, with treatment by replication as the error term (SAS, 1996). A probability level of 5% was used. Results and discussion Mg supplementation level We tested 2 different levels of Mg supplementation, 1 and 2 g elemental Mg/kg feed. Initial Mg levels varied from animal to animal. However, in the pilot study, each animal could serve as its own reference. The 5-day supplementation at 2 g Mg/kg feed consistently resulted in a 10% increase in Mg blood levels. Longer supplementation did not result in a further increase of Mg blood levels. We decided to use 2 g Mg/kg feed for 5 days for the meat quality study. Meat quality of Mg supplemented pigs Blood Mg values were higher than those found in the pilot studies. We do not know what caused this increase. Probably, blood composition immediately after slaughter is different from that of a life animal. The stress during stunning and slaughter results in total hemolysis, therefore, it is impossible to collect plasma samples after slaughter. Mg blood values were 10% (first trial, 3.95 vs 3.55 mg/100 ml) and 14% (second trial; 3.77 vs mg /100 ml) higher (P<0.05) in the supplemented group than in the control group. Mg concentration of the muscle from supplemented and control pigs did not defer. Blood content of muscle is relatively low and the difference in muscle may be expected to be smaller than in the blood. Mg analysis techniques are not sensitive enough to detect small difference in Mg concentration in the muscle. Others (for review see Pettigrew and Esnaolo, 1999) did not determine Mg concentration on the muscle. Postmortem ph values and meat quality characteristics of the LM and SM from control and supplemented pigs are included in Table 1. Mg supplementation did not significantly affect any of the variables. For 24 h postmortem ph in LM and SM and for L*, b* value of the SM, there was an interaction between trial and treatment, the effect of Mg supplementation in the first trial was significantly different from that in the second trial (Table 2). These results indicate that the effect of Mg supplementation was small or not existent. Our results contradict those of D Souza et al. (1998; 1999). We used the same level and duration of Mg supplementation and Mg blood levels were comparable in both studies. The pigs used by D Souza et al. (1998; 1999) were not from a commercial line. The halothane-status of those pigs is not known. Possibly, the more stress-prone halothanepositive pigs are more responsive to stress reducers like Mg. Also, the PSE incidence in the studies by D Souza et al. (1998; 1999) was higher than in our study. Thus, there was more room for improvement in their study compared to ours.

5 Conclusions We conclude that short term (5 days) Mg supplementation (2 g Mg /Kg feed) does not significantly improve the quality of pork from halothane-negative pigs. Longer term supplementation with Mg did not result in further increase of Mg blood levels. We cannot exclude that longer term supplementation will result in increased Mg levels in the muscle and thus influence quality. Other procedures to improve water holding capacity of normal pork need to be investigated. Acknowledgments This study was supported by a grant from the National Pork Producers Council. Without the cooperation and help of PIC, Franklin, KY and Premium Standard Foods, Milan, MO this research would not have been possible The assistance of Weon-Seog Choe, Emayet Spencer, and Linda Miller is greatly appreciated. References D'Souza, D.N., Warner, R.D., Leury, B.J. and Dunshea, F.R J. Anim. Sci. 76: D Souza, D.N., Warner, R.D., Dunshea, F.R. and Leury, B.J Meat Sci. 51: Kauffman, R.G Muscle Biology Lab. Univ. Wisconsin-Madison. Kietzman, M. and Jablonski, H Praktische Tierz. 661: Kuhn, G., Nowak, A., Otto, E., Albrecht, V., Gassman, B., Sandner, E., Przylbiski, H. and Zahn, L Arch. Tierz. Berlin 24: Lister, D. and Ratcliff, P.W Proc. 2nd Int. Symp. Condition Meat Quality Pigs. Meeker, D. and Sonka, S NPPC Publication, Des Moines IA. Niemack, E.A Schweiz. Arch. Tierheilk. 127: Niemack, E.A., Stockli, F., Husmann, E., Sanderegger, J., Classen, H.G. and Helbig, J Magnesium Bull. 3: Otten, A., Berrer, S., Hartman, S., Bergerhoff, T. and Eichinger, H.M Proc. Int. Congr. Meat Sci. Technol., Clermont-Ferrand, p Pettigrew, J.E. and Esnaola, M.A National Pork Producers Council, Des Moines, IA. Porta, S., Ehrenberg, A., Helbig, J., Classen, H.G., Egger, G., Weger, M., Zimmerman, P. and Weiss, U Magnesium Bull. 17: Sair, R.A., Lister, D., Moody, W.G., Cassens, R.G., Hoekstra, W.G. and Briskey, E.J Am. J. Physiol. 218: SAS, Cary, NC SAS Institute Inc. Schaefer, A.L., Murray, A.C., Tong, A.K.W., Jones, S.D. and Sather, A.P J. Anim. Sci. 73: Warner, R.D PhD thesis, Univ. Wisconsin-Madison.

6 Table 1: Quality characteristics, and ph at various times postmortem, in pork from control and Mg supplemented (2 g Mg/kg feed 1, as Mg sulfate, for 5 days before slaughter) pigs; two trials, n=50 per trial, per treatment. Control Mg supplemented SEM ph in the loin 30 min postmortem h postmortem h postmortem h postmortem h postmortem ph in the semimembranosus Visual color score loin 2 ( 1= pale, 6= dark) Marbling score loin 2 (1=devoid, 5=abundant) Loin color 2 L*-value a* -value b*-value Semimembranosus color 2 L*-value a*-value b*-value Drip % loin Purge % loin Cook loss % Shear force kg Elemental Mg concentrations in feed were: control 1.3 and supplemented 3.7 g Mg/kg feed. 2 Measurements at 24 h postmortem, in muscle excised from carcass. 3 Measurements after 21 days storage at 0-2 C. 4 For these variables, there was an interaction between trial and treatment, see Table 2. None of the differences were significant (P<0.05).

7 Table 2: Significant (P<0.05) interaction between trial and treatment (Mg supplementation at 2 g Mg/kg feed for 5 days vs. control, no Mg supplementation) for various pork quality characteristics; two trials n=50 per treatment per trial. Trial 1 Trial 2 Control Supplemented Control Supplemented ph loin 20 h postmortem 5.70ab 5.68b 5.69b 5.75a ph loin 24 h postmortem 5.60b 5.57b 5.61ab 5.67a ph SM 24 h postmortem 5.79b 5.74b 5.80b 5.88a Semimembranosus color L*-value 46.4bc 50.5a 48.5ab 45.9c b*-value 4.0bc 4.7a 4.1b 3.5c abc: values without a common letter are significantly different (P<0.05)