Nutritional Effects on Pork Quality in Swine Production

A number of factors affect pork quality, with swine genetics, preslaughter handling, harvest, and pork carcass chilling having the greatest impacts. However, there is considerable evidence indicating that manipulating the nutrient composition of swine diets may offset the negative effects of genetic predisposition and/or pig handling on pork quality, and may actually enhance pork quality traits of well-handled pigs of good quality genotypes. Pork quality traditionally refers to the measurement of muscle pH, color, firmness, marbling or intramuscular fat (IMF) content, shelf-life, and cooked pork palatability. Yet, domestic and international consumers may define pork quality in terms associated with environmental, ethical, and animal welfare aspects of pork production, whereas pork processors typically include fat color, firmness, and composition, as well as nutrient composition and microbiological safety in their definition of pork quality. The purpose of this review is to provide an overview of the effects of dietary modifications on: 1) postmortem muscle metabolism and technological quality attributes (i.e., pH, color, and water-holding capacity); 2) pork IMF content; 3) pork fat quality; 4) color and lipid stability during refrigerated storage/display; and 5) cooked pork palatability.


Dietary Effects on Postmortem Metabolism and Pork Quality


When blood is lost during exsanguinations, oxygen availability to muscles is eliminated, thereby shifting muscle metabolism from aerobic metabolism of lipids to anaerobic metabolism of muscle glycogen reserves. The end-product of anaerobic postmortem muscle metabolism is the accumulation of lactic acid, which, in turn, causes postmortem muscle pH to decline from approximately 7.1 to 7.3 to an ultimate pH value of 5.4 to 5.7. There are three basic pork quality defects associated with abnormal postmortem pH decline (Figure 1): pale, soft, and exudative (PSE) pork; dark, firm, and dry (DFD) pork; and red, soft, and exudative pork (RSE).


When muscle pH declines rapidly (falls below 5.8 to 6.0 within the first hour postmortem) due to excessive lactic acid accumulation, the high intramuscular acidity coupled with high muscle temperature results in muscle protein denaturation and the development of PSE pork. The rapid decrease in muscle pH can be attributed to the genetic predisposition (halothane or ryanodine receptor genotype in particular), preslaughter stress, or both acting in concert. Conversely, when muscle glycogen reserves are low, the accumulation of lactic acid is greatly curtailed; leading to ultimate pH values in excess of 6.0 being established early in the postmortem period and development of DFD pork. The low preslaughter muscle glycogen reserves are typically the synergistic effect of a combination of stressors increasing energy demands prior to slaughter. Lastly, there is a swine genotype, generally referred to as the Rendement Napole (RN-) gene that has abnormally high concentrations of muscle glycogen; therefore, excessive intramuscular lactic acid accumulation can cause ultimate muscle pH to decline to values less than 5.5. Even though the color of RSE pork is virtually normal, the extremely low pH causes muscle proteins to lose their affinity for water, which leads to excessive moisture losses (i. e., decreased water-holding capacity).

Figure 1. The association between postmortem pH decline and pork quality. Along with the typical pH decline (Normal), the three basic quality defects are presented, including: pale, soft and exudative (PSE) pork, dark, firm and dry (DFD), and red, soft and exudative (RSE) pork.

Figure 1. The association between postmortem pH decline and pork quality. Along with the typical pH decline (Normal), the three basic quality defects are presented, including: pale, soft and exudative (PSE) pork, dark, firm and dry (DFD), and red, soft and exudative (RSE) pork.


Preslaughter Feed Withdrawal. Obviously, manipulating preslaughter muscle glycogen reserves could lead to improvements in fresh pork color and water-holding capacity (WHC). In fact, there is considerable evidence that withholding feed from pigs for 16 to 36 h before slaughter effectively reduces longissimus muscle (LM) glycogen concentrations and elevates initial and ultimate muscle pH values, which, in turn, leads to the production of darker, more desirable colored pork with improved WHC of fresh pork [86]. However, short-duration feed withdrawal periods of 16 h or less have no appreciable effects on muscle glycogen reserves, postmortem pH decline, or fresh pork quality [39]. Moreover, it appears that withholding feed from RN- pigs for as long as 60 h prior to slaughter does not alter LM glycogen levels, indicating that preslaughter fasting, alone, is not an effective method of manipulating the abnormally high muscle glycogen reserves in pigs with this genetic mutation [18]. In addition to the beneficial effects on pork quality, preslaughter feed withdrawal also decreases pig mortality during transportation and lairage, reduces carcass contamination with pathogenic bacteria in response to puncture of the gastrointestinal tract, and produces less waste to be rendered and/or disposed [71].


Glycogen-Reducing Diets. Research has shown that feeding high-fat (17 to 19%), high-protein (19 to 25% CP) diets formulated with very low levels (< 5%) of digestible carbohydrates will reduce muscle glycogen concentrations in pork LM at slaughter [15]. More importantly, 45-min, but not 24-h, postmortem muscle pH was elevated, and WHC was increased, in response to feeding these glycogen-reducing diets [81, 82]. The effects of glycogen-reducing diets on pork color are inconsistent, and there is little information to suggest cooked pork palatability is altered by feeding pigs high-protein/high-fat/low-carbohydrate diets prior to slaughter [15, 82].


Other Dietary Modifications to Alter Postmortem Metabolism. It is generally accepted that preslaughter stress affects muscle glycogen reserves and, ultimately, pork quality; so, it is plausible that modifying the pig’s response to a stressor could also modify muscle glycogen reserves. Supplementing swine diets with the amino acid tryptophan increases serotonin production, which has been shown to alleviate aggression in pigs and reduce circulating cortisol concentrations [47], and, more importantly, reduced the incidence of PSE pork [1]. Even though most of the recent research has failed to detect beneficial effects of dietary L-tryptophan supplementation on pork quality, Guzik and co-workers [47] demonstrated that pork from pigs fed 0.5% supplemental tryptophan for 5 d prior to slaughter received greater color scores and lower L* values than pork from minimally-handled pigs.


Magnesium (Mg) supplementation has also been shown to effectively reduce the stress response of pigs prior to slaughter and reduce the incidence of PSE pork [32]. More importantly, it has been regularly demonstrated that supplementing swine diets with Mg for as little as a week before slaughter will improve the WHC of fresh pork, regardless of Mg source [3]. Furthermore, research has shown that fresh pork color can be improved by either long- [5] or short-duration [32] Mg supplementation.


Within the body, creatine increases the bioavailability of phosphocreatine for cellular ATP production, especially in active muscle. This fact led researchers to test the supplementation of swine diets with creatine monohydrate to increase antemortem muscle phosphocreatine levels, thereby sparing muscle glycogen, and reducing the incidence of PSE pork. Initial pork LM pH values were increased by 5 d of supplementing swine diets with creatine monohydrate [107], and both James et al. [51] and Young et al. [107] reported that supplementing swine diets with creatine monohydrate reduced LM drip losses. Conversely, creatine supplementation does not appear to alter fresh pork color, marbling, or cooked pork palatability [16, 17, 51].


Dietary Effects on Intramuscular Fat Content


Intramuscular fat (IMF) content of pork plays an important role in consumers’ perceptions of cooked pork palatability [61], and it has been suggested that an IMF content between 2.5 and 3.0% is necessary for consumer acceptability of cooked pork [28]. Moreover, the majority countries importing U. S. pork prefer IMF contents of at least 4%; however, the adoption of leaner swine genotypes by U. S. pig producers over the past two decades has reduced IMF contents to as low as 1.0%. Even though there are a number of swine genetic lines with the propensity for higher IMF deposition, there is a growing effort to increase the marbling/IMF content in today’s pork by manipulating swine nutrition.


Dietary Protein and Amino Acid Effects on Pork IMF. One strategy shown to effectively increase the IMF content of pork is reducing the crude protein (CP) and/or lysine content of swine diets (Table 1). When dietary CP levels were reduced in grower and finisher diets, IMF was increased 13.7 to 176.5% [42, 105], whereas reducing the dietary lysine content in diets of growing-finishing pigs elevated IMF content 66.7 to 136.8% [19, 21]. Obviously, long-term exposure of pigs to CP- and/or lysine-deficient diets will affect gain and feed conversion efficiency detrimentally, but feeding lysine-reduced diets over the last 5 to 6 weeks of the finishing period had virtually no impact on performance and still IMF concentrations were increased in the LM [18, 24]. On the other hand, increasing CP and/or lysine levels in swine diets has been repeatedly shown to reduce IMF content of fresh pork. In fact, Johnston et al. [52] and Friesen et al. [40] observed linear reductions in LM marbling scores as the dietary lysine content increased from 0.54 to 1.4%.


Table 1. Effect of reduced crude protein (CP) and/or lysine on the intramuscular fat content (IMF) of fresh pork.

Reference Dietary CP (lysine) content, %a IMF change (%)b
Control Reduced
Essen-Gustavsson et al. [38] 18.5 (0.96) 13.1 (0.64) + 66.7*
Castell et al. [22] 17.6 (0.81) 11.9 (0.48) +150.0*
Goerl et al. [42] 25.0 10.0 +176.5*
Kerr et al. [53] 16.0 (0.82) 12.0 (0.55) +103.6*
Cisneros et al. [24] 14.0 (0.56) 10.0 (0.40) + 50.0*
Blanchard et al. [19] 20.5 (1.05) 16.6 (0.70) +100.0*
Cameron et al. [21] 26.2 (1.57) 15.7 (0.56) +136.8*
Nold et al. [73]c 13.0 to 19.0 12.0 to 18.0 + 19.6*
Bidner et al. [18] (0.64) (0.48) + 25.7*
Wood et al. [105]d 20.0 (1.14) 16.0 (0.68) +13.4 to +54.6*
Teye et al. [91]e ~ 21.0 ~18.0 +64.7*

aOn an as-fed basis.
bRepresents the percent change from the IMF content of pork from pigs fed the control diet (an asterisk [*] indicates a statistically significant [P < 0.05] difference from the control).
cDifference between control and treated diets was 1.0% CP in diets for boars, barrows, and gilts.
dThe IMF change range is across all genders.
eApproximate CP levels because of the three different fat sources altered the CP content less than 0.5%.


Research out of the University of Illinois has shown that the addition of an extra 2.0% leucine in swine finishing diets increased pork marbling scores (20 to 30%) and IMF content in the LM (25 to 42%) and SM (18%), without altering pig performance [24]. It could be argued, however, that the increases in IMF were an indirect response to reductions in lysine intake caused by an amino acid imbalance incurred with the high levels of supplemental leucine rather than a direct effect of increasing dietary leucine levels 200%.


Feed and energy intake. Even though restricting feed intake of finishing pigs doesn’t affect muscle pH [59] or fresh pork color [86], feed restrictions of 75 to 80% ad libitum have been repeatedly shown to reduce IMF content between 8 and 27% [26, 59]. Interestingly, reducing the energy density of swine finishing diets does not alter IMF, or any other fresh pork quality attribute [60], nor is there evidence that the grain source incorporated in the diet affects marbling scores [87].


Fats and oils. Fats and oils have been used for decades to increase the caloric density of swine diets, but the effects of dietary fat levels and/or sources on pork IMF content are inconsistent. Feeding diets formulated with sunflower or canola oil has been shown to reduced LM marbling scores [68, 72]; however, Apple and others [12] observed that LM IMF content increased with increasing dietary corn oil, whereas LM IMF content was increased by approximately 25% in pigs fed diets containing 5% beef tallow [35]. For the most part, however, few studies have demonstrated an effect of dietary fats/oil on pork marbling scores [8, 37] or IMF content [69].


Conjugated linoleic acid (CLA) refers to a mixture of positional and geometric conjugated isomers of linoleic acid. Most synthetic CLA sources contain approximately 65% CLA isomers, and, since July, 2009, CLA is being marketed in the U. S. under the trade-name of Lutalin® (BASF SE, Ludwigschafen, Germany) for inclusion into swine and broiler diets. More importantly, there is substantial evidence that supplementing swine diets with CLA can increase LM marbling scores and/or IMF content (Table 2). Sun et al. [88] and Martin et al. [64] reported increases in IMF content ranging from as little as 12% to as much as 44%, whereas Wiegand et al. [100] demonstrated that incorporating 0.75% CLA in diets increased the IMF content in the LM of halothane-negative, halothane-carriers, and halothane-positive pigs by 17.8, 19.2, and 16.6% respectively.


Table 2. Effect of dietary conjugated linoleic acid (CLA) level on the intramuscular fat content (IMF) of fresh pork.

Reference CLA dose (%) IMF change (%)a
Dugan et al. [33] 2.00 + 22.2*
O’Quinn et al. [77] 0.50 + 13.7
Wiegand et al. [100] – NN 0.75 + 17.8*
Wiegand et al. [100] – Nn 0.75 + 19.2*
Wiegand et al. [100] – nn 0.75 + 16.6*
Averette Gatlin et al. [14] 1.00 + 18.8*
D’Souza & Mullan [30] – Gilts 0.50 + 24.0*
D’Souza & Mullan [30] -Barrows 0.50 + 8.0
Tischendorf et al. [94] 2.00 + 8.8
Wiegand et al. [102] 0.75 + 25.9*
Migdał et al. [67] 2.00 + 8.5
Sun et al. [88] 2.00 + 12.5*
4.00 + 29.2*
Martin et al. [64] 1.0 + 30.8*
2.0 0.0

aRepresents the percent change from the IMF content of pork from pigs fed the control diet (an asterisk [*] indicates a statistically significant [P < 0.05] difference from the control).
Vitamin A Supplementation. A derivative of vitamin A, retinoic acid, is involved in the regulation of adipose cell differentiation and proliferation, and, in theory, a retinoic acid deficiency may directly increase IMF content [29]. In fact, feeding cattle vitamin A-deficient diets increased LM marbling scores and/or IMF content without affecting performance or carcass composition ([45]. D’Souza et al. [31] also demonstrated that feeding vitamin A-restricted diets during the grower and finisher phases increased IMF content by almost 54%, whereas Olivares et al. [76] noted that feeding diets supplemented with 100,000 IU of vitamin A actually increased IMF in pigs with the genetic propensity for IMF, but not in high-lean genotypes. The evidence indicating that both vitamin A deficiencies and supranutritional dietary inclusion of vitamin A can increase pork IMF/marbling is promising; however, dietary inclusion levels, feeding durations, and interactive effects with other feedstuffs and feed additives are largely unknown, especially when fed to growingfinishing pigs.


Dietary Effects on Pork Fat Quality


The fatty acids in pork muscle and fat may be obtained from de novo synthesis from non-lipid substrates and the direct absorption of fatty acids from the pig’s diet. Glucose from the digestion of corn and barley, for example, will increase the proportion of saturated fatty acids (SFA) at the expense of polyunsaturated fatty acids (PUFA) absorbed from the oil fraction of concentrates [57]. However, as indicated previously, fat is routinely incorporated in swine diets to increase the energy density of the diet and reduce the content of dietary cereal grains, especially corn.


Dietary fat source and pork fat quality. The quality of the dietary fat source included in swine diets is dependent upon a number of factors, including iodine value (IV; a measure of the chemical unsaturation of the fat), titre (temperature at which a fat is completely solid), and melting point (temperature at which a fat is completely liquefied). Highly saturated fat sources, like tallow and lard, will have IV of 30 to 70 g of I/100 g of fat, titres of 32 to 47°C, and melting points of 45 to 50°C. Conversely, unsaturated oils from soybeans, canola, corn, sunflower, and safflower seeds will typically have IV greater than 100 g of I/100 g of fat, titre of less than 30°C, and melting points of 20°C, or less. Therefore, the fatty acid composition of pork fat depots will typically reflect the quality (i.e., fatty acid composition) of the fat and/or oil formulated into the diets.


Although there are apparent health benefits associated with the consumption of PUFA, increasing the polyunsaturation of pork fat leads to the development of soft fat. According to Whittington and co-workers [98], pork fat with a linoleic acid (C18:2n-6) content greater than 15% is classified as soft; thus, it is not surprising that feeding pigs fat sources high in C18:2n-6 content will also cause soft fat [68, 72] and pork bellies [9, 12]. Soft fat and pork bellies cause carcass handling and fabrication difficulties; reduced bacon yields; oily, almost opaque-appearing, unattractive products; reduced shelf-life; and, more importantly, discrimination by domestic consumers and export partners. Research has shown that belly thickness and firmness increased as the IV of the dietary fat source decreased from 80 to 20 [13]; so, feeding animal fats does not appear to depress fat and belly firmness/hardness [37] as severely as feeding plant oils. Interestingly, Shackelford et al. [85] reported that bacon from pigs fed sunflower, safflower or canola oil received much lower sensory scores for crispiness, chewiness, saltiness, flavor, and overall palatability than bacon from pigs fed diets devoid of added fat and diets formulated with tallow. Moreover, Teye and others [92] observed that pigs fed soybean oil-formulated diets product soft bacon and a greater number of low-quality, soft bacon slices. There is growing evidence that between 50 and 60% of the change in the fatty acid composition of pork fat caused by manipulating the dietary fat source, inclusion level, or both, occurs during the first 14 to 35 d on the particular dietary fat source, and diminishes with a longer time on feed [104]. Apple et al. [6, 7] reported that the fatty acid profile of pork LM and subcutaneous fat was altered substantially within the first 17.4 kg of BW gain, with IV of pork fat increasing almost 12 points during the first feeding phase in pigs fed 5% soybean oil (Table 3). In addition, Anderson and co-workers [2] found that the half-life of linolenic acid (C18:3n-3) in pork subcutaneous fat was almost 300 d; thus, the economic savings associated with increased efficiency during the grower phases, when high levels of fat are traditionally fed, may also cause damage to the fat quality of pigs at slaughter. Moreover, it is doubtful that removing all fat from the late-finishing diet or replacing an unsaturated fat source with tallow or a hydrogenated fat source will have dramatic effects on pork fat quality [9].


Table 3. Interactive effect of dietary fat source and slaughter weight on the iodine value (IV) of the pork fat and muscle [6, 7].

Slaughter weight (kg)
28.1 45.5 68.1 90.9 113.6
No fat 72.5def 72.1def 67.9ghi 67.0ij 67.3hij
Tallow 72.8de 70.5efg 68.5ghij 65.2j 65.3j
Poultry fat 73.2de 77.6c 74.1d 72.4def 69.8fgh
Soybean oil 73.5d 85.2a 83.9ab 85.7a 82.6b
Longissimus muscle
No fat 65.8b 63.0de 58.9g 59.3g 58.7g
Tallow 65.6bc 63.3cde 62.2er 60.7fg 59.3g
Poultry fat 65.2bcd 67.2b 63.6cde 61.8ef 60.4g
Soybean oil 65.9b 69.9a 66.7b 66.1b 65.1bcd


By-Products of Biofuel Production. In an attempt to reduce reliance upon fossil fuels considerable efforts have been made to generate biofuels from renewable resources. Ethanol production from corn, as well as sorghum and wheat, has increased substantially over the past 10 yr, leading to substantial supplies of dried distillers’ grains with solubles (DDGS) which can be incorporated in swine diets. The crude fat content of DDGS ranges between 10 and 15%, and the fat from DDGS has a high proportion of unsaturated fatty acids; thus, it is not surprising that feeding pigs high levels of DDGS increases the PUFA content and IV of pork subcutaneous fat [96, 106]. Moreover, the degree of polyunsaturation of fat in fresh pork bellies increases linearly with the amount of DDGS included in swine diets [96, 97], which leads to soft, pliable, undesirable fresh pork bellies [95, 97, 99]. Moreover, Weimer et al. [99] reported greater fat-lean separation with increased dietary DDGS, and Xu et al. [106] noted linear reductions in bacon fattiness and tenderness with increased dietary inclusion rates of DDGS, even though DDGS did not affect the crispiness, flavor, or overall acceptability of cooked bacon [99, 106].


New or recycled animal fats or vegetable oils can easily be converted into biodiesel, and, like DDGS, the major by-product of biodiesel production, glycerol, has received a great deal of interest as an energy source in swine diets. Mourot et al. [70] and Della Casa et al. [27] found that including 5 to 10% crude glycerol in swine diets increased the proportion of oleic acid (C18:1cis9) and all MUFA in pork backfat, whereas Mourot et al. [70] and Lammers et al. [56] observed reductions in C18:2n-6 in subcutaneous fat and muscle. Moreover, the reduction in fat polyunsaturation associated with feeding glycerol has been shown to produce firmer pork bellies [84].



Conjugated Linoleic Acid. Supplementing swine diets with CLA routinely increases the proportions of SFA, especially palmitic (C16:0) and stearic acid (C18:0), in both pork fat [34, 88] and muscle [64, 88]. There are conflicting results on the impact of CLA on the MUFA and PUFA composition of pork fat and muscle [63, 88]; however, the increases in SFA lead to reductions in IV [58] and firmer pork fat [34] and fresh bellies [58].


Dietary Modifications on Lipid and Color Stability


It would be expected that any dietary modification that increases the PUFA content of pork would also increase the susceptibility of pork to lipid oxidation. Thus, a great deal of research has focused on either the feeding of antioxidants, especially vitamin E, as well as stimulating endogenous antioxidative enzymes via mineral supplementation.


Vitamin E. Vitamin E (α-tocopherol) is an antioxidant that protects cell membrane integrity and retards lipid oxidation, especially during refrigerated storage and/or retail display. So, it is not surprising that incorporating supranutritional levels of vitamin E in diets of growing-finishing swine may be the most widely tested nutritional modification to improve pork quality.


Research has repeatedly shown that feeding pigs an additional 100 to 200 mg/kg of dl-α-tocopherol acetate effectively delays the onset of lipid oxidation in fresh whole-muscle pork cuts [20] and ground pork [79], as well as precooked [46] and cured pork products [25]. Vitamin E supplementation of cattle finishing diets not only slows the rate of discoloration but actually improves the color stability of fresh beef, but the vast majority of research has yet to prove any benefits of elevating the levels of vitamin E in swine diets with either dl-α-tocopherol acetate [46, 79] or the natural-occurring stereoisomer, d-α-tocopheryl acetate [20], on fresh pork color or color stability during refrigerated storage.


Vitamin C. Vitamin C has antioxidant properties, and pigs typically produce adequate amounts of this water-soluble vitamin from D-glucose in the liver; yet, feeding ascorbic acid within 4 h of slaughter produced darker, redder pork [78]. However, neither short-term [75] nor long-term vitamin C supplementation [41] affected pork color or WHC. Furthermore, there is no evidence to suggested that supplementing swine diets with vitamin C improves the oxidative stability of LM lipids during storage or retail display [41], and, in fact, Ohene-Adjei and others [75] reported that feeding pigs diets formulated with elevated levels of vitamin C actually increased TBARS values of LM chops during refrigerated storage.


Selenium. Selenium (Se) is a component of the endogenous antioxidant enzyme glutathione peroxidase, and research has shown that serum glutathione peroxidase activity is increased by supplementing swine diets with either sodium selenite or a selenium-yeast compound [62]. Yet, the increased glutathione activity associated with supplemental Se does not equate into changes in fresh color and WHC [62] or lipid stability during storage of fresh pork [49].


Manganese. Manganese (Mn) and Mg are both divalent, transition metal cations that may be interchangeable in several biological functions; however, Mn is a required for the activation of superoxide dismutase, which is involved in the breakdown of superoxide free radicals; so, it was not surprising that TBARS values of fresh LM chops were reduced by dietary Mn supplementation [11], and the LM from pigs fed diets supplemented with 350 mg/kg of Mn were less discolored after 2 and 4 d [11] and 5, 6, and 7 d [83] of simulated retail display than the LM from non-supplemented pigs. Additional benefits of supplementing swine diets with Mn include increased LM pH and visual color scores, and reduced L* values of fresh pork LM [10, 11].


Vitamin-Trace Mineral Removal. There is growing sentiment among swine nutritionists that most growerfinisher diets are formulated to equal or, in most cases, exceed the NRC [74] requirements for vitamins and/or minerals. It is thought that reducing vitamins and minerals, especially during the last month of the finishing period, will reduce not only production costs but also excretion of phosphorus and other mineral elements into the environment [66]. Moreover, there is little evidence to suggest that removing all vitamins and trace minerals during the late-finishing phase will affect fresh pork color, marbling, or firmness, as well as Warner-Bratzler shear force (WBSF) values [23]. The lone disadvantage of vitamin and trace mineral removal may be that TBARS values were elevated during refrigerated storage by vitamin/trace mineral removal [23], whereas fortifying finishing diets with 150, 200, and 250% of the NRC [74] vitamin and trace minerals during the last few weeks before slaughter substantially reduced TBARS values during as much as 3 weeks of refrigerated storage [23, 48].


Dietary Modifications on Cooked Pork Palatability


Even though fresh pork color is the single most important factor in the purchasing decision of a consumer, their perception of cooked pork palatability will impact whether or not they purchase pork again. Therefore, it is vitally important that palatability is either not affected or improved by any dietary modification.


Crude Protein/Lysine. Shear force values of cooked LM chops increased almost 23% as CP content increased from 10 to 22% in the finishing diet [42]. Furthermore, Goodband et al. [43, 44] reported linear increases in WBSF values in cooked LM and SM chops as dietary lysine levels were elevated from 0.6 to 1.4% (Figure 2), whereas Apple et al. [4] observed a linear increase in WBSF values as the lysine-to-energy ratio of the late-finishing diet increased from 1.7 (0.56 to 0.59% lysine) to 3.1 g/Mcal (1.02 to 1.08% lysine). Goodband et al. [44] also noted decreased sensory panel myofibrillar and overall tenderness scores with increasing dietary lysine levels; yet, for the most part, elevating dietary lysine levels in swine diets does not affect juiciness or flavor intensity of cooked pork [43].


Figure 2. The effect of dietary lysine level on Warner-Bratzler shear force (kg) values [43, 44]. In both experiments, there was a linear (P < 0.05) increase in shear force values with increasing dietary lysine levels.

Figure 2. The effect of dietary lysine level on Warner-Bratzler shear force (kg) values [43, 44]. In both experiments, there was a linear (P < 0.05) increase in shear force values with increasing dietary lysine levels.

Energy Content and Sources. Reducing the energy density in diets of growing-finishing swine does not affect the palatability of pork [60]; however, LM chops from pigs fed ad libitum received greater tenderness scores and had lower WBSF values than pork from pigs fed at 75% [21] or 80% [19] ad libitum, even though neither total and soluble muscle collagen contents [59] nor myofibrillar fragmentation index (an indicator of postmortem proteolysis; [21]) were affected by dietary intake. Furthermore, a number of studies have shown that pork from pigs with ad libitum access to grower-finisher diets was rated higher for pork flavor [19, 21], flavor-liking, juiciness, and overall acceptability [21, 36] by trained sensory panelists.


The cereal grain source included in swine diets can create palatability differences. For example, cooked chops from wheat-fed pigs received higher flavor scores than chops from sorghum-fed pigs [65], whereas LM chops from pigs fed a 33%:67% or 67%:33% mixture of yellow and white corns received higher juiciness and flavor scores than chops from pigs fed yellow corn or white corn and barley, respectively [57]. Furthermore, McConnell et al. [65] reported that the LM from wheat-fed pigs had lower WBSF values and higher tenderness scores than the LM from sorghum-fed pigs, and Robertson et al. [80] noted that sensory panelists rated LM chops from barley-fed pigs more tender than chops from pigs fed corn or barley with triticale. Conversely, WBSF values [57, 87] and palatability scores [87] were similar among pigs fed yellow corn, white corn, wheat, barley, or triticale.


Feeding canola oil and/or fish oil has been shown to impart more abnormal odors and off-flavors, thereby reducing the overall acceptability of cooked pork [68]. However, there is no effect of animal fat sources on WBSF values [8, 12, 37, 68] or sensory panelists’ evaluations of tenderness, juiciness, or flavor intensity [37, 68]. Neither WBSF values nor palatability ratings of cooked LM chops have been affected by feeding pigs DDGS- [97, 99, 106] or glycerol-formulated diets [27, 56]. In addition, it doesn’t appear that supplementing swine diets with CLA affects WBSF values [33] or palatability scores [33, 34, 58, 100] of cooked pork LM chops or bacon.


Compensatory Gain. Compensatory growth is the accelerated growth rate that occurs in pigs having ad libitum access to feed after a period of severely restricted feed intake. The increase in protein degradation during the period of restricted intake does not appear to decrease during the realimentation period, which led Kristensen and co-workers [55] to hypothesize that high antemortem proteolytic activity would lead to a more rapid postmortem muscle tenderization. Interestingly, both Kristensen et al. [55] and Therkildsen et al. [93] found that the activities of both μ- and m-calpain, but not calpastatin, were increased in the LM from pigs afforded ad libitum access to feed following a period of restricted feed intake, and Therkildsen et al. [93] noted that the longer the period of ad libitum feed intake prior to slaughter the greater the μ-calpain activity. Total collagen content does not appear to be affected by compensatory growth, but there is evidence that the proportion of soluble collagen in the LM is actually increased by feed restriction followed by ad libitum feed intake [54, 55, 93]. However, WBSF values and sensory panel tenderness scores were only improved in pork from pigs with confirmed compensatory growth [55]; in other words, in studies where the length or severity of the feed restriction was insufficient to cause a significant reduction in growth rate, the period of ad libitum intake had little to no effect on cooked pork palatability, especially tenderness [50, 54].


Vitamin D3 . Because of the well-established association between calcium and meat tenderness, it is generally accepted that increasing muscle calcium concentrations will increase postmortem calpain degradation of the cytoskeletal proteins and improve cooked meat tenderness. Vitamin D is involved in intercellular calcium mobilization and regulation, and feeding supranutritional levels of vitamin D3 to feedlot cattle was shown to elevate blood and muscle calcium levels and, more importantly, improve cooked beef tenderness [89]. Even though plasma and muscle calcium concentrations were increased over 125% by supplementing swine finishing diets with vitamin D3 [101], neither pork WBSF values [90, 101, 103], sensory panel tenderness ratings [90, 103], nor any other palatability attribute [90, 103] have been altered by supplemental vitamin D3. Interestingly, there is evidence that suggests that supplementing swine diets with supranutritional levels of vitamin D3 can cause improvements in fresh pork quality, including increased initial and ultimate muscle pH values, subjective color scores, and LM a* values, along with reductions in L* values and drip loss percentages [90, 103].




Pork quality is affected by a number of factors, but this review focused on the effects of modifying swine diets on traditional measures of pork lean quality (i.e., pH, color, firmness, and marbling/IMF content), as well as fat quality, shelf-life, and cooked pork palatability. Several “tried-and-true” dietary modifications were discussed, including feed withdrawal, restricted feed intake, CP/lysine nutrition, and the advantages of vitamin E supplementation on pork quality; however, this review also look into emerging concepts of altering swine nutrition to increase muscle pH and enhance pork color and WHC (glycogen-reducing diets), increase marbling (CLA supplementation), and improve tenderness (compensatory gain). It should be noted, however, that there is no proverbial “silver bullet” that can overcome inferior genetics and poor rearing environments , preslaughter handling, and/or inadequate harvest systems, and the added production costs associated with many of these nutritional strategies need to be weighed against the possibility of added value before implementation by swine producers.



  1.  Adeola O, Ball RO. Hypothalamic neurotransmitter concentrations and meat quality in stressed pigs offered excess dietary tryptophan and tyrosine. J Anim Sci 1992; 70:1888-1894.
  2.  Anderson DB, Kauffman, RG, Benevenga NJ. Estimate of fatty acid turnover in porcine adipose tissue. Lipids 1972; 7:488-489.
  3.  Apple JK. Effects of nutritional modifications on the water-holding capacity of fresh pork: a review. J Anim Breed Genet 2007; 124 Suppl 1:43-58.
  4.  Apple JK, Maxwell CV, , Brown DC, Friesen KG, Musser RE, Johnson ZB, et al. Effects of dietary lysine and energy density on performance and carcass characteristics of finishing pigs fed ractopamine. J Anim Sci 2004; 82:3277-3287.
  5.  Apple JK, Maxwell CV, deRodas B, Watson HB, Johnson ZB. Effect of magnesium mica on performance and carcass quality of growing-finishing swine. J Anim Sci 2000; 78: 2135-2143.
  6.  Apple JK, Maxwell CV, Galloway DL, Hamilton CR. Interactive effects of dietary fat source and slaughter weight in growingfinishing swine: II. Fatty acid composition of subcutaneous fat. J Anim Sci 2009; 87:1423-1440.
  7.  Apple JK, Maxwell CV, Galloway DL, Hutchison S, Hamilton CR. Interactive effects of dietary fat source and slaughter weight in growing-finishing swine: I. Growth performance and longissimus muscle fatty acid composition. J Anim Sci 2009; 87:1407-1422.
  8.  Apple JK, Maxwell CV, Kutz BR, Rakes LK, Sawyer JT, Johnson ZB, et al. Interactive effect of ractopamine and dietary fat source on pork quality characteristics of fresh pork chops during simulated retail display. J Anim Sci 2008; 86:2711-2722.
  9.  Apple JK, Maxwell CV, Sawyer JT, Kutz BR, Rakes LK, Davis ME, et al. Interactive effect of ractopamine and dietary fat source on quality characteristics of fresh pork bellies. J Anim Sci 2007; 85:2682-2690.
  10.  Apple JK., Roberts WJ, Maxwell CV, Rakes LK, Friesen KG, Fakler TM. Influence of dietary inclusion level of manganese on pork quality during retail display. Meat Sci 2007; 75:640-647.
  11.  Apple JK, Roberts WJ, Maxwell CV, Boger CB, Friesen KG, Rakes LK, et al. Influence of dietary manganese source and supplementation level on pork quality during retail display. J Muscle Foods 2005; 16:207-222.
  12.  Apple JK, Sawyer JT, Maxwell CV, Woodworth JC, Yancey JWS, Musser RE. Effect of L-carnitine supplementation on the performance and pork quality traits of growing-finishing swine fed three levels of corn oil. J Anim Sci 2008; 86 E-Suppl 2:37.
  13.  Averette Gatlin L, See MT, Hansen JA, Odle J. Hydrogenated dietary fat improves pork quality of pigs from two lean genotypes. J Anim Sci 2003; 81:1989-1997.
  14.  Averette Gatlin L, See MT, Larick DK, Lin X, Odle J. Conjugated linoleic acid in combination with supplementation dietary fat alters pork quality. J Nutr 2002; 132:3105-3112.
  15.  Bee G, Biolley C, Guex G, Herzog W, Lonergan SM, Huff-Lonergan E. Effects of available dietary carbohydrate and preslaughter treatment on glycolytic potential, protein degradation, and quality traits of pig muscles. J Anim Sci 2006; 84:191-203.
  16.  Berg EP, Allee GL. Creatine monohydrate supplemented in swine finishing diets and fresh pork quality: I. A controlled laboratory experiment. J Anim Sci 2001; 79:3075-3080.
  17.  Berg EP, Maddock KR, Linville ML. Creatine monohydrate supplemented in swine finishing diets and fresh pork quality: III. Evaluating the cumulative effect of creatine monohydrate and alpha-lipoic acid. J Anim Sci 2003; 81:2469-2474.
  18.  Bidner BS, Ellis M, Witte DP, Carr SN, McKeith FK. Influence of dietary lysine level, pre-slaughter fasting, and rendement napole genotype on fresh pork quality. Meat Sci 2004; 68:53-60.
  19.  Blanchard PJ, Ellis M, Warkup CC, Hardy B, Chadwick JP, Deans GA. The influence of rate of lean and fat tissue development on pork eating quality. Anim Sci 1999; 68:477-485.
  20.  Boler DD, Gabriel SR, Yan H, Balsbaugh R, Mahan DC, Brewer MS, et al. Effect of different dietary levels of natural-source vitamin E in grow-finish pigs on pork quality and shelf life. Meat Sci 2009; 83:723-730.
  21.  Cameron ND, Penman JC, Fisken AC, Nute GR, Perry AM, Wood JD. Genotype with nutrition interactions for carcass composition and meat quality in pig genotypes selected for components of efficient lean growth rate. Anim Sci 1999; 69:69-80.
  22.  Castell AG, Cliplef RL, Poste-Flynn LM, Butler G. Performance, carcass and pork characteristics of castrates and gilts self-fed diets differing in protein content and lysine:energy ratio. Can J Anim Sci 1994; 74:519-528.
  23.  Choi SC, Chae BJ, Han IK. Impacts of dietary vitamins and trace minerals on growth and pork quality in finishing pigs. AsianAust J Anim Sci 2001; 14:1444-1449.
  24.  Cisneros F, Ellis M, Baker DH, Easter RA, McKeith FK. The influence of short-term feeding of amino acid-deficient deits and high dietary leucine levels on the intramuscular fat content of pig muscle. Anim Sci 1996; 63;517-522.
  25.  Coronado SA, Trout GR, Dunshea FR, Shah NP. Effect of dietary vitamin E, fishmeal and wood and liquid smoke on the oxidative stability of bacon during 16 weeks’ frozen storage. Meat Sci 2002; 62:51-60.
  26.  Daza A, Rey A I, Menoyo D, Bautista J M, Olivares A, López-Bote CJ. Effect of level of feed restriction during growth and/or fattening on fatty acid composition and lipogenic enzyme activity in heavy pigs. Anim Feed Sci Technol 2007; 138:61-74.
  27.  Della Casa G, Bochicchio D, Faeti V, Marchetto G, Poletti E, Rossi A, et al. Use of pure glycerol in fattening heavy pigs. Meat Sci 2009; 81:238-244.
  28.  DeVol DL, McKeith FK, Bechtel PJ, Novakofski J, Shanks RD, Carr TR. Variation in composition and palatability traints and relationships between muscle characteristics and palatability in a random sample of pork carcasses. J Anim Sci 1988; 66:385-395.
  29.  Dikeman ME. Effects of metabolic modifiers on carcass traits and meat quality. Meat Sci 2007; 77:121-135.
  30. D’Souza DN, Mullan BP. The effect of genotype, sex and management strategy on the eating quality of pork. Meat Sci 2002; 60:95-101.
  31.  D’Souza DN, Pethick DW, Dunshea FR, Pluske JR, Mullan BP. Nutritional manipulation increases intramuscular fat levels in the Longissimus muscle of female finisher pigs. Aust J Agric Res 2003; 54:745-749.
  32.  D’Souza DN, Warner RD, Leury BJ, Dunshea FR. The influence of dietary magnesium supplement type, and supplementation dose and duration, on pork quality and the incidence of PSE pork. Aust J Agric Res 2000; 51:185-189.
  33.  Dugan MER, Aalhus JL, Jeremiah LE, Kramer JKG, Schaefer AL. The effects of feeding conjugated linoleic acid on subsequent pork quality. Can J Anim Sci 1999; 79:45-51.
  34.  Dugan MER, Aalhus JL, Rolland DC, Jeremiah LE. Effects of feeding different levels of conjugated linoleic acid and total oil to pigs on subsequent pork quality and palatability. Can J Anim Sci 2003; 83:713-720.
  35.  Eggert JM, Grant AL, Schinckel AP. Factors affecting fat distribution in pork carcasses. Prof Anim Sci 2007; 23:42-53.
  36.  Ellis M, Webb AJ, Avery PJ, Brown I. The influence of terminal sire genotype, sex, slaughter weight, feeding regime and slaughter-house on growth performance and carcass and meat quality in pigs and on the organoleptic properties of fresh pork. Anim Sci 1996; 62:521-530.
  37.  Engel JJ, Smith JW, Unruh JA, Goodband RD, O’Quinn PR, Tokach MD, et al. Effects of choice white grease or poultry fat on growth performance, carcass leanness, and meat quality characteristics of growing-finishing pigs. J Anim Sci 2001; 79:1491-1501.
  38.  Essén-Gustavsson B, Karlsson A, Lundström K, Enfält A–C. Intramuscular fat and muscle fibre lipid contents in halothane-genefree pigs fed high or low protein diets and its relation to meat quality. Meat Sci 1994; 38:269-277.
  39.  Faucitano L, Saucier L, Correa JA, Méthot S, Giguère A, Foury A, et al. Effect of feed texture, meal frequency and pre-slaughter fasting on carcass and meat quality, and urinary cortisol in pigs. Meat Sci 2006; 74:697-703.
  40.  Friesen KG, Nelssen JL, Goodband RD, Tokach MD, Unruh JA, Kropf DH, et al. Influence of dietary lysine on growth and carcass composition of high-lean-growth gilts fed from 34 to 72 kilgrams. J Anim Sci 1994; 72:1761-1770.
  41.  Gebert S, Eichenberger B, Pfirter HP, Wenk C. Influence of different vitamin C levels on vitamin E and C content and oxidative stability in various tissues and stored m. longissimus dorsi of growing pigs. Meat Sci 2006; 73:362-367.
  42.  Goerl, KF, Eilert SJ, Mandigo RW, Chen HY, Miller PS. Pork characteristics as affected by two populations of swine and six crude protein levels. J Anim Sci 1995; 73:3621-3626.
  43.  Goodband RD, Nelssen JL, Hines RH, Kropf DH, Stoner GR, Thaler RC, et al. Interrelationships between porcine somatotropin and dietary lysine on growth performance and carcass characteristics of finishing swine. J Anim Sci 1993; 71:663-672.
  44.  Goodband RD, Nelssen JL, Hines RH, Kropf DH, Thaler RC, Schricker BR, et al. The effects of porcine somatotropin and dietary lysine on growth performance and carcass characteristics of finishing swine. J Anim Sci 1990 68:3261-3276.
  45.  Gorocica-Buenfil MA, Fluharty FL, Bohn T, Schwartz SJ, Loerch SC. Effect of low vitamin A diets with high-moisture or dry corn on marbling and adipose tissue fatty acid composition of beef steers. J Anim Sci 2007; 85:3355-3366.
  46.  Guo Q, Richert BT, Burgess JR, Webel DM, Orr DE, Blair M, et al. Effects of dietary vitamin E and fat supplementation on pork quality. J Anim Sci 2006; 84:3089-3099.
  47.  Guzik AC, Matthews JO, Kerr BJ, Bidner TD, Southern LL. Dietary tryptophan effects on plasma and salivary cortisol and meat quality in pigs. J Anim Sci 2006; 84:2251-2259.
  48.  Hamman LL, Gentry JG, Ramsey CB, McGlone JJ, Miller MF. The effect of vitamin-mineral nutritional modulation on pork quality of halothane carriers. J Muscle Foods 2001; 12:37-51.
  49.  Han Y–K, Thacker PA. Effect of L-carnitine, selenium-enriched yeast, jujube fruit and hwangto (red clay) supplementation on performance and carcass measurements of finishing pigs. Asian-Aust J Anim Sci 2006; 19:217-223.
  50.  Heyer A, Lebret B. Compensatory growth response in pigs: effects on growth performance, composition of weight gain at carcass and muscle levels, and meat quality. J Anim Sci 2007; 85:769-778.
  51.  James BW, Goodband RD, Unruh JA, Tokach MD, Nelssen JL, Dritz SS, et al. Effect of creatine monohydrate on finishing pig growth performance, carcass characteristics and meat quality. Anim Feed Sci Technol 2002; 96:135-145.
  52.  Johnston ME, Nelssen JL, Goodband RD, Kropf DH, Hines RH, Schricker BR. The effects of porcine somatotropin and dietary lysine on growth performance and carcass characteristics of finishing swine fed to 105 or 127 kiograms. J Anim Sci 1993; 71:2986- 2995.
  53.  Kerr BJ, McKeith FK, Easter RA. Effect on performance and carcass characteristics of nursery to finisher pigs fed reduced crude protein, amino acid-supplemented diets. J Anim Sci 1995; 73:433-440.
  54.  Kristensen L, Therkildsen M, Aaslyng MD, Oksbjerg N, Ertbjerg P. Compensatory growth improves meat tenderness in gilts but not in barrows. J Anim Sci 2004; 82:3617-3624.
  55.  Kristensen L, Therkildsen M, Riis B, Sørensen MT, Oksbjerg N, Purslow PP, et al. Dietary-inducted changes of muscle growth rate in pigs: effects on in vivo and postmortem muscle proteolysis and meat quality. J Anim Sci 2002; 80:2862-2871.
  56.  Lammers PJ, Kerr BJ, Weber TE, Bregendahl K, Lonergan SM, Prusa KJ, et al. 2008. Growth performance, carcass characteristics, meat quality, and tissue histology of growing pigs fed crude glycerin-supplemented diets. J Anim Sci 2008; 86:2962-2970.
  57.  Lampe JF, Baas TJ, Mabry JW. Comparison of grain sources for swine diets and their effect on meat and fat quality traits. J Anim Sci 2006; 84:1022-1029.
  58.  Larsen ST, Wiegand BR, Parrish Jr FC, Swan JE, Sparks JC. Dietary conjugated linoleic acid changes belly and bacon quality from pigs fed varied lipid sources. J Anim Sci 2009; 87:285-295.
  59.  Lebret B, Juin H, Noblet J, Bonneau M. The effects of two methods of increasing age at slaughter on carcass and muscle traits and meat sensory quality in pigs. Anim Sci 2001; 72:87-94.
  60.  Lee CY, Lee HP, Jeong JH, Baik KH, Lee JH, Sohnt SH. Effects of restricted feeding, low-energy diet, and implantation of trenbolone acetate plus estradiol on growth, carcass traits, and circulating concentrations of insulin-like growth factor (IGF)-I and IGF-binding protein-3 in finishing barrows. J Anim Sci 2002; 80:84-93.
  61.  Lonergan SM, Stadler KJ, Huff-Lonergan E, Knight TJ, Goodwin RN, Prusa KJ, et al. Influence of lipid content on pork sensory quality within pH classification. J Anim Sci 2007; 85:1074–1079.
  62.  Mahan DC, Cline TR, Richert B. Effects of dietary levels of selenium-enriched yeast and sodium selenite sources fed to growingfinishing pigs on performance, tissue selenium, serum glutathione peroxidase activity, carcass characteristics, and loin quality. J Anim Sci 1999; 77:2172-2179.
  63.  Martin D, Muriel E, Antequera T, Andres AI, Ruiz J. Quantitative changes in the fatty acid profile of lipid fractions of fresh loin from pigs as affected by dietary conjugated linoleic acid and monounsaturated fatty acids during refrigerated storage. J Food Comp Anal 2009; 22:102-111.
  64.  Martin D, Muriel E, Gonzalez E, Viguera J, Ruiz J. Effect of dietary conjugated linoleic acid and monounsaturated fatty acids on productive, carcass and meat quality traits of pigs. Livest Sci 2008; 117:155-164.
  65.  McConnell JC, Skelley GC, Handlin DL, Johnston WE. Corn, wheat, milo and barley with soybean meal or roasted soybeans on feedlot performance, carcass traits and pork acceptability. J Anim Sci 1975; 41:1021-1030.
  66.  McGlone JJ. Deletion of supplemental minerals and vitamins during the late finishing period does not affect pig weight and feed intake. J Anim Sci 2000; 78:2797-2800.
  67.  Midgał W, Paściak P, Wojtysiak D, Barowicz T, Pieszk M, Pietras M. The effect of dietary CLA supplementation on meat and eating quality, and the histochemical profile of the M. longissimus dorsi from stress susceptible fatteners slaughtered at heavier weights. Meat Sci 2004; 66:863-870.
  68.  Miller MF, Shackelford SD, Hayden KD, Reagan JO. Determination of the alteration in fatty acid profiles, sensory characteristics and carcass traits of swine fed elevated levels of monounsaturated fats in the diet. J Anim Sci 1990; 68:1624-1631.
  69.  Morel PCH, McIntosh JC, Janz JAM. Alteration of the fatty acid profile of pork by dietary manipulation. Asian-Aust J Anim Sci 2006; 19:431-437.
  70.  Mourot J, Aumaitre A, Mounier A, Peiniau P, Francois AC. Nutritional and physiological effects of dietary glycerol in the growing pigs. Consequences on fatty tissues and post mortem muscular parameters. Livest Prod Sci 1994; 38:237-244.
  71.  Murray A, Robertson W, Nattress F, Fortin A. Effect of pre-slaughter overnight feed withdrawal on pig carcass and muscle quality. Can J Anim Sci 2001; 81:89-97.
  72.  Myer RO, Lamkey JW, Walker WR, Brendemuhl JH, Combs GE. Performance and carcass characteristics of swine when fed diets containing canola oil and copper to alter the unsaturated:saturated ratio of pork fat. J Anim Sci 1992; 70:1417-1423.
  73.  Nold RA, Romans JR, Costello WJ, Libal GW. Characterization of muscles from boars, barrows, and gilts slaughtered at 100 or 110 kilograms: differences in fat, moisture, color, water-holding capacity, and collagen. J Anim Sci 1999; 77:1746-1754.
  74.  NRC. Nutrient Requirements of Swine, 10th Edition. Washington, DC National Academy Press; 1998.
  75.  Ohene-Adjei S, Bertol T, Hyun Y, Ellis M, Brewe S, McKeith FK. The effect of dietary supplemental vitamin E and C on odors and color changes in irradiated pork. J Anim Sci 2001; 79 Suppl. 1:443.
  76.  Olivares A, Daza A, Rey AI, Lopez-Bote CJ. Interactions between genotype, dietary fat saturation and vitamin A concentration on intramuscular fat content and fatty acid composition in pigs. Meat Sci 2009; 82:6-12.
  77.  O’Quinn PR, Nelssen JL, Goodband RD, Unruh JA, Woodworth JC, Smith JS, et al. Effects of modified tall oil versus a commercial source of conjugated linoleic acid and increasing levels of modified tall oil on growth performance and carcass characteristics of growing-finishing pigs. J Anim Sci 2000; 78:2359-2368.
  78.  Peeters E, Driessen B,Geers R. Influence of supplemental magnesium, tryptophan, vitamin C, vitamin E, and herbs on stress response and pork quality. J Anim Sci 2006; 84:1827-1838.
  79.  Phillips AL, Faustman C, Lynch MP, Govoni KE, Hoagland TA, Zinn SA. Effect of dietary -tocopherol supplementation on color and lipid stability in pork. Meat Sci 2001; 58:389-393.
  80.  Robertson WM, Jaikaran S, Jeremiah LE, Salmon DF, Aherne FX, Landry SJ. Meat quality and palatability attributes of pork from pigs fed corn, hulless barley or triticale based diets. Adv Pork Prod 1999; 10:35.
  81.  Rosenvold K, Essén-Gustavsson B, Andersen HJ. Dietary manipulation of pro- and macroglycogen in porcine skeletal muscle. J Anim Sci 2003; 81:130-134.
  82.  Rosenvold K, Lærke HN, Jensen SK, Karlsson AH, Lundström K, Andersen HJ. Strategic finishing feeding as a tool in the control of pork quality. Meat Sci 2001; 59:397-406.
  83.  Sawyer JT, Tittor AW, Apple JK, Morgan JB, Maxwell CV, Rakes LK, et al. Effects of supplemental manganese on performance of growing-finishing pigs and pork quality during retail display. J Anim Sci 2007; 85:1046-1053.
  84.  Schieck SJ, Johnston LJ, Shurson GC, Kerr BJ. Evaluation of crude glycerol, a biodiesel co-product, in growing pig diets to support growth and improved pork quality. J Anim Sci 2009; 87 E-Suppl 3:90.
  85.  Shackelford SD, Miller MF, Haydon KD, Lovegren NV, Lyson CE, Reagan JO. Acceptability of bacon as influenced by the feeding of elevated levels of monounsaturated fats to growing-finishing swine. J Food Sci 1990; 55:621-624.
  86.  Sterten H, Frøystein T, Oksbjerg N, Rehnberg AC, Ekker AS, Kjos NP. Effect of fasting prior to slaughter on technological and sensory properties of the loin muscle (M. longissimus dorsi) of pigs. Meat Sci 2009; 83:351-357.
  87.  Sullivan ZM, Honeyman MS, Gibson LR, Prusa KJ. Effect of triticale-based diets on pig performance and pork quality in deepbedded hoop barns. Meat Sci 2007; 76:428-437.
  88.  Sun D, Zhu X, Qiao S, Fan S, Li D. Effects of conjugated linoleic acid levels and feeding intervals on performance, carcass traits and fatty acid composition of finishing barrows. Arch Anim Nutr 2004; 58:277-286.
  89.  Swanek SS, Morgan JB, Owens FN, Gill DR, Strasia CA, Dolezal HG, et al. Vitamin D3 supplementation of beef steers increases longissimus tenderness. J Anim Sci 1999; 77:874-881.
  90.  Swigert KS, McKeith FK, Carr TC, Brewer MS, Culbertson M. Effects of dietary D3, vitamin E, and magnesium supplementation on pork quality. Meat Sci 2004; 67:81-86.
  91.  Teye GA, Sheard PR, Whittington FM, Nute GR, Stewart A, Wood JD. Influence of dietary oils and protein level on pork quality. 1. Effects on muscle fatty acid composition, carcass, meat and eating quality. Meat Sci 2006; 73:157-165.
  92.  Teye GA, Wood JD, Whittington FM, Stewart A, Sheard PR. Influence of dietary oils and protein level on pork quality. 2. Effects on properties of fat and processing characteristics of bacon and frankfurter-style sausages. Meat Sci 2006; 73:166-177.
  93.  Therkildsen M, Riis B, Karlsson A, Kristensen L, Ertbjerg P, Purslow PP, et al. Compensatory growth response in pigs, muscle protein turn-over and meat texture: effects of restriction/realimentation period. Anim Sci 2002; 75:367-377.
  94.  Tischendorf F, Schöne F, Kirchheim U, Jahreis G 2002. Influence of a conjugated linoleic acid mixture on growth, organ weights, carcass traits and meat quality in growing pigs. J Anim Physiol Anim Nutr 2002; 86:117-128.
  95.  Weimer, D., J. Stevens, A. Schinckel, M. Latour, and B. Richert. 2008. Effects of feeding increasing levels of distillers dried grains with solubles to grow-finish pigs on growth performance and carcass quality. J Anim Sci 2008; 86 E-Suppl 3:85.
  96.  White HM, Richert BT, Radcliffe JS, Schinckel AP, Burgess JR, Koser SL, et al. Feeding conjugated linoleic acid partially recovers carcass quality in pigs fed dried corn distillers grains with solubles. J Anim Sci 2009; 87:157-166.
  97.  Whitney MH, Shurson GC, Johnston LJ, Wulf DM, Shanks BC. Growth performance and carcass characteristics of grower-finisher pigs fed high-quality corn distillers dried grain with solubles originating from modern Midwestern ethanol plant. J Anim Sci 2006; 84:3356-3363.
  98.  Whittington FM, Prescott NJ, Wood JD, Enser M. The effect of dietary linoleic acid on the firmness of backfat in pigs of 85 kg live weight. J Sci Food Agric 1986; 37:753-761.
  99.  Widmer MR, McGinnis LM, Wulf DM, Stein HH. Effects of feeding distillers dried grains with solubles, high-protein distillers grains, and corn germ to growing-finishing pigs on pig performance, carcass quality, and the palatability of pork. J Anim Sci 2008; 86:1819-1831.
  100.  Wiegand BR, Parrish Jr FC, Swan JE, Larsen ST, Baas TJ. Conjugated linoleic acid improves feed efficiency, decreases subcutaneous fat, and improves certain aspects of meat quality in Stress-Genotype pigs. J Anim Sci 2001; 79:2187-2195.
  101.  Wiegand BR, Sparks JC, Beitz DC, Parrish Jr FC, Horst RL, Trenkle AH, et al. Short-term feeding of vitamin D3 improves color but does not change tenderness of pork-loin chops. J Anim Sci 2002; 80:2116-2121.
  102.  Wiegand BR, Sparks JC, Parrish Jr FC, Zimmerman DR. Duration of feeding conjugated linoleic acid influences growth performance, carcass traits, and meat quality of finishing barrows. J Anim Sci 2002; 80:637-643.
  103.  Wilborn BS, Kerth CR, Owsley WF, Jones WR, Frobish LT. Improving pork quality by feeding supranutritional concentrations of vitamin D3. J Anim Sci 2004; 82:218-224.
  104.  Wiseman J, Agunbiade JA. The influence of changes in dietary fat and oils on fatty acid profiles of carcass fat in finishing pigs. Livest Prod Sci 1998; 54:217-227.
  105.  Wood JD, Nute GR, Richardson RI, Whittington FM, Southwood O, Plastow G, et al. Effects of breed, diet and muscle on fat deposition and eating quality in pigs. Meat Sci 2004; 67:651-667.
  106.  Xu G, Baidoo SK, Johnston LJ, Cannon JE, Bibus D, Shurson GC. Shurson. Effects of adding increasing levels of corn dried distillers grains with solubles (DDGS) to corn-soybean meal diets on pork fat quality of growing-finishing pigs. J Anim Sci 2008; 86 E-Suppl 3:85.
  107.  Young JF, Bertram HC, Rosenvold K, Lindahl G, Oksbjerg N. Dietary creatine monohydrate affects quality attributes of Duroc but not Landrace pork. Meat Sci 2005; 70:717-725.
  108. Stevens JG, Schinckel AP, Latour MA, Kelly D, Legan B, Richert, BT. Evaluation of distillers dried grains with solubles withdrawal programs on grow-finish pig growth performance and carcass quality. J Anim Sci 2009; 87(E-Suppl. 3):82 White HM, Richert BT, Radcliffe JS, Schinckel AP, Burgess JR, Koser SL, et al. Feeding conjugated linoleic acid partially recovers carcass quality in pigs fed dried corn distillers grains with soluble. J. Anim Sci 2009; 87:157-166.


Frequently Asked Questions


The fatty acid composition of a fat source obviously affects the fatty acid composition of pork fat, but does the fat source affect carcass composition?
Research has routinely shown that elevating the amount of fat in the diet may increase backfat depths, but there is little evidence to suggest that one dietary fat source will affect fat-free lean yields differently than another.


What affect to feeding antibiotics have on pork quality?
To date, there is little information on the impact of feeding antibiotics on pork quality attributes; however, there is antidotal evidence that healthy pigs tend to produce “quality” pork. Moreover, a number of the dietary supplements, especially vitamins and minerals, which have been shown to enhance pork quality, have also been shown to promote swine health. Therefore, it is plausible that some of the noted benefits of these supplements and/or feed ingredients on pork quality could be attributed to improvements in swine herd health.


Should you include an antioxidant in swine diets?
It is not uncommon to see diets formulated with very low levels of an antioxidant to combat the limited amount of lipid oxidation that may occur during feed storage. Even though diets are not typically stored for long durations, those with high polyunsaturated fat contents can oxidize rapidly, resulting in the feeding of diets with oxidized fats. And, recent research out of the University of Illinois has shown that feeding pigs diets containing oxidized fats can reduce fresh pork shelf-life; however, Fernández-Dueñas and others (2009) noted that including a blend of synthetic antioxidants not only counteracted the negative effects of oxidize dietary fat on pork shelf-life but improved some cooked pork palatability attributes. Fernández-Dueñas DM, Kutzler LW, Boler DD, Holmer SF, Zhao J, Harrell RJ, et al. Effects of oxidized corn oil and synthetic antioxidant blend on pork quality and shelf-life. J Anim Sci 20009; 87(E-Suppl. 3):366.


How can I combat the apparent negative effects of feeding high amounts of dried distillers’ grains with soluble?
A number of studies have shown that feeding as much as 30% dried distillers’ grains with solubles (DDGS) will not only impact fat quality but also reduce carcass yield, or dressing percent, up to 1%. It is apparent that removing DDGS from the late-finishing diet will recoup some, if not all, of the losses in carcass yield, but may have little to no impact on fat quality. Moreover, Stevens and co-workers (2009) at Purdue University noted that replacing DDGS with either beef tallow or choice white grease during the last 26 d before slaughter failed to reverse the effects of DDGS on pork quality. And, the results of White et al. (2009) indicated that supplementing 20 to 40% DDGS-diets with 0.6% conjugated linoleic acid (CLA) for only 10 days before slaughter improved pork belly firmness even though CLA had no appreciable effect on the fatty acid composition of the belly fat. It is plausible that longer durations of CLA-supplementation may alleviate some of the negative effects of DDGS on pork fat quality, but more research is needed before implementing this nutritional modification.