| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Department of Animal Science, Michigan State University, East Lansing, 48824
3 Correspondence:
2209 Anthony Hall (phone: 517-355-8398; fax: 517-432-0190; E-mail:
rozeboom{at}msu.edu).
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResults and DiscussionImplicationsLiterature Cited |
|---|
Key Words: Minerals • Nutrient Content • Pigs • Vitamins • Wheat Milling Residues
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResults and DiscussionImplicationsLiterature Cited |
|---|
The effect of supplement deletion on pork’s nutrient content or oxidative stability is not conclusive. Patience and Gillis (1996) removed dietary vitamin supplements from wheat-barley-canola meal–based diets during the 35 d prior to slaughter and found that the longissimus dorsi muscle (LDM) thiamin concentration was reduced by 20%. In contrast, preliminary work by our research group (unpublished) identified no change in LDM thiamin concentration following a 31-d preslaughter supplement withdrawal period, when corn-soybean meal–based diets were fed. Edmonds and Arentson (2001) reported that the vitamin E concentration of the LDM was 75% less with 6-wk preslaughter supplement withdrawal. Conversely, Choi et al. (2001) reported no difference in the LDM vitamin E concentrations with 4-wk supplement withdrawal. Both research groups concluded, however, that there was a decrease in pork oxidative stability.
The first objective of our research was to determine the effects of removing vitamin and trace mineral premixes as well as two-thirds of the inorganic P from diets during the 28 d prior to slaughter on growth performance, nutrient excretion, carcass characteristics, nutrient content, and oxidative stability of pork. Furthermore, the effect of dietary wheat middling inclusion from weaning to slaughter on the same parameters was evaluated because of differences noted in the diets and outcomes reported among studies previously cited.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResults and DiscussionImplicationsLiterature Cited |
|---|
Animals and Housing.
Sixty-four crossbred barrows ([Yorkshire x Landrace] x DRU; Kerns Farms Inc., Clearfield, IA), with an average initial weight of 8.5 ± 0.7 kg, were individually penned (1.51 (1.58 m) in a totally enclosed, environmentally controlled nursery-to-finish facility, with 23% solid-concrete and 77% slatted-concrete flooring. Pigs were randomly assigned to pens, which were constructed of vertical-rod fencing. Each pen contained a single nipple waterer and a stainless steel single-sided, single-hole feeder (30.5 cm wide x 38.1 deep x 101.6 high).
Experimental Design.
The experiment was a randomized complete block design. Barrows were blocked by weight and allotted to dietary treatments arranged in a 2 x 2 factorial, replicated twice over time with 32 pigs per replicate. The factors evaluated were the effects of supplement withdrawal (omitting vitamin and trace mineral premixes and two-thirds of the inorganic phosphorus) 28 d preslaughter in corn-soybean meal–based diets with or without added wheat middlings from weaning to slaughter. The first and second replications were conducted from February to June and from July to November, respectively.
Diets.
Over the course of the experiment, each barrow received seven different diets during seven different dietary phases (nursery 1, 2, and 3, grower 1 and 2, early finisher, and late finisher; Tables 1
, 2, and 3, respectively). The nursery 1 diet was provided at the time of weaning. Subsequent diet changes were made as animals attained a desired body weight of 10, 15, 25, 45, and 65 kg for nursery 2 and 3, grower 1 and 2, and early finisher, respectively. Weights were measured two times each week. The change to the late-finisher diet was made 28 d before slaughter.
|
|
|
The inclusion of wheat middlings was evaluated by feeding half of the pigs corn-soybean meal–based diets with added wheat middlings (CSBM+WM) at the inclusion rates of 5% in nursery diets 1 and 2, 15% in nursery diet 3, and 30% in grower and finishing diets, and by feeding the other half typical corn-soybean meal–based (CSBM) diets. Diets of both treatment groups were formulated to contain similar lysine, ME, Ca, and total P concentrations for each phase, and they had identical vitamin and trace mineral premixes additions. This was accomplished by varying the inclusion rates of other feedstuffs by following a least-cost formulation approach. The study was planned to compare the effect of the diet as a whole on selected response variables, and not the specific effect of wheat middlings alone.
The impact of supplement withdrawal was studied by providing barrows four different diets in the late-finishing phase or for the 28 d prior to slaughter (Table 3
). Vitamin and trace mineral premixes and two-thirds of the inorganic P were removed from the diets of half of the pigs in each of the CSBM and CSBM+WM treatment groups. Limestone additions were adjusted to maintain a Ca:available P ratio of 2.5:1. All four diets were formulated to contain identical lysine and ME concentrations.
Performance and Sample Collection.
Pig weights and feed disappearance were determined for each dietary phase and were used to calculate ADG, ADFI, and gain/feed. Random samples of feed were placed in whirl-pac bags and frozen at -20°C until analyzed for thiamin, riboflavin, niacin, vitamin E, Ca, Cu, Fe, Mn, P, and Zn content. Ten random samples of wheat middlings were collected over the course of the entire study for bulk density measurement and were stored at -20°C until analyzed for Ca, Cu, Fe, Mn, P, and Zn.
In order to estimate fecal nutrient excretion during the early- and late-finishing periods, the top portion of three freshly voided feces were obtained from each pig 48 h prior to placement on the late-finishing diet, and again 48 h prior to slaughter. Fecal samples were weighed, freeze-dried, ground in a stainless steel blender, and frozen at -20°C until mineral analyses were performed.
After the 28-d late-finishing or supplement withdrawal period, all pigs were slaughtered at the Michigan State University Meat Laboratory according to standard operating procedures. Average (±SD) live weight, days on feed, and age at slaughter were 106.6 ± 7.0 kg, 115.8 ± 4.8, and 143.4 ± 4.7 d, respectively. Barrows were switched from the early-finisher diet to their designated late-finisher diet 28 d in advance of a predetermined slaughter date. Opportunities to slaughter at the laboratory were limited because of its use for other research and teaching purposes. Consequently, live weight at slaughter, days to slaughter, and hot carcass weight were not studied as treatment-dependent variables. Alternatively, they were evaluated statistically as covariates in certain models as explained below. Dressing percentages were calculated using hot carcass weights, which excluded heads.
Following a 24-h chill at 1°C, longissimus muscle area and backfat depth were recorded at the 10th rib. Two 2.5-cm-thick loin chops were taken at the 10th rib and anteriorly, vacuum-sealed in plastic bags, and frozen at -80°C until analyzed. Tissue from one chop was analyzed for thiamin by fluorometric method, and for riboflavin and niacin by microbial method (AOAC, 1995). These analyses were done commercially by Covance Laboratories (Madison, WI). The vitamin E content of the second chop was determined as DL-
-tocopherol by the method of Liu et al. (1996; assay conducted by Roche Vitamins Inc., Kansas City, MO). The remaining tissue from the second chop was analyzed for Cu/Zn superoxide dismutase activity (Cu/ZnSOD), glutathione peroxidase activity (GPX1), and mineral concentrations.
Mineral Analyses.
Feed, LDM, and fecal samples obtained in replication 1 were prepared for mineral analyses using nitric-perchloric acid wet digestion (Hill et al., 1983c). Feed, LDM, and fecal samples obtained in replication 2 were prepared for mineral analyses using microwave digestion (model HP-500Plus, CEM, Matthews, NC). For feed and fecal microwave digestion, 10 mL of nitric acid (70% trace-metal grade; Fisher Scientific, Pittsburgh, PA) was added to either a 0.5-g feed sample or a 0.4-g fecal sample in a pressurized Telfon-lined digestion vessel. For LDM digestion, approximately 0.5 g of LDM samples was sliced from within the area of the frozen tissue and 5 mL of nitric acid and 2 mL of double-distilled water were added. Samples were allowed to digest for 1 h at room temperature. Vessels were then placed in the microwave digestor and power was intermittently applied for 25 min to gradually increase vessel pressure to 210 psi while maximal vessel temperature was 210°C. Vessels were maintained at 210 psi for 10 min, allowed to cool for 10 min, and were vented. Two mL of hydrogen peroxide (30%; J. T. Baker, Phillipsburg, NJ) was added to the digested feed and fecal samples, and 1 mL was added to the digested LDM. Digested samples were transferred to volumetric flasks and brought to a uniform volume.
Calcium, copper (replication 1), iron, manganese, and zinc analyses (Hill et al., 1983c) were conducted by flame atomic absorption spectrophotometry (Unicam 989, Thermo Elemental Corp., Franklin, MA), and P concentrations were determined (Gomori, 1942) using a DU 7400 spectrophotometer (Beckman, Palo Alto, CA). In replication 2, LDM Cu was determined by graphite furnace atomic absorption spectroscopy (GF90 Plus, Thermo Elemental Corp.). Feed, LDM, and fecal mineral concentrations were reported on an as-fed, fresh, and DM basis, respectively.
Instrument accuracy for all mineral analyses was established using bovine liver standard (1577b; Natl. Inst. Stand. Technol., Gaithersburg, MD). All glassware used in the mineral analyses was washed in 30% nitric acid and rinsed with double-deionized water.
Superoxide Dismutase and Glutathione Peroxidase Activities.
Longissimus dorsi muscle Cu/ZnSOD (EC 1.15.1.1) activity was determined with the method of Hill et al. (1999). Longissimus dorsi muscle samples (approximately 1 g each) were sliced from within the area of the frozen tissue and homogenized in a 10x volume of ice-cold 0.5 M potassium phosphate and 0.24 M sucrose buffer (pH 7.2) with an Ultra Turrax T25 homogenizer (Tekmar-Dohrmann Corp., Cincinnati, OH). The subsequent procedures were the same as those for red blood cell hemolysates, as described by Hill et al. (1999). One unit of Cu/ZnSOD activity was defined as the amount of SOD necessary to inhibit the autoxidation of pyrogallol by 50%. Muscle GPX1 (EC 1.11.1.9) activity was determined by the method of Sunde and Hoekstra (1980). One GPX1 unit was defined as 1 µmol NADPH oxidized/min, using the molar extinction coefficient of 6.22 x 103 for NADPH and the stoichiometry of reaction of 2 moles GPX1 formed per mole NADPH oxidized. Protein concentrations of the supernatant were determined by the method of Lowry et al. (1951), and units of Cu/ZnSOD and GPX1 activity were expressed per gram of protein.
Statistical Analysis.
All data were analyzed by least squares ANOVA using the PROC MIXED procedures of SAS (SAS Inst., Inc., Cary, NC) for a randomized complete block design. Pig served as the experimental unit. The model included the fixed effects of the factorial treatments, their interaction, replication, and block by initial weight. Litter within replication was specified as a random effect. Hot carcass weight was used as a covariate for analyses of backfat thickness and longissimus muscle area. Age at slaughter (d) and days on feed were included as covariates in separate preliminary analyses of longissimus tissue mineral content, longissimus tissue vitamin content, and carcass measurements. However, because they did not explain a significant (P < 0.50) portion of the variability in any dependent variable, they were excluded in all final analyses. All means presented are least square means. Differences were considered significant at the level of P < 0.05. To evaluate interactions, least square means were compared using the Student’s t-test for probability.
|
Results and Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResults and DiscussionImplicationsLiterature Cited |
|---|
Growth Performance and Carcass Characteristics.
Supplement withdrawal did not affect growth performance as measured by ADG, ADFI, and gain/feed (Table 4), or carcass traits as measured by backfat depth, loin eye area (LEA), and dressing percentage (Table 5). These data agree with previous studies (Kim et al., 1997; Mavromichalis et al., 1999; McGlone, 2000) in which withdrawing vitamin and/or mineral supplementation for 17 to 45 d prior to slaughter did not affect growth or carcass traits.
|
|
Previous research (Patience et al., 1977) reported that a maximum of 20% wheat middlings can be included in growing diets before decreasing growth performance, while others found that inclusion rates of 30% (Young, 1980; Erickson et al., 1985) did not decrease growth. Cromwell et al. (1992) reported that when wheat middlings with a light bulk density are used, growth performance of growing-finishing pigs decreased linearly as the amount of wheat middlings increased. However, wheat middlings with a heavy bulk density could constitute 20 to 40% of the diet without substantially affecting performance. The bulk density of the wheat middlings used in our study was 387.4 g/L, much heavier than the average wheat middling bulk density of 320 g/L, as reported by Cromwell et al. (2000). Thus, we do not fully understand why a decrease in ADG was observed during the growing phase, as the estimated energy and lysine concentrations in the control and wheat middling diets were formulated to be the same. Possibly, ADG was related to the slight numerical decreases in ADFI and efficiency of gain observed in the same phase.
Fecal Mineral Concentration.
Supplement withdrawal reduced (P < 0.01) fecal Ca, Fe, Cu, Mn, and Zn concentrations by 35 to 74%, and fecal P concentration by 10% (Table 6). Fecal P concentrations were similar when supplemented CSBM and CSBM+WM diets were fed, but decreased only when supplement was removed from the CSBM diet—not when supplement was removed from the CSBM+WM diet. Michal and Froseth (1999) and O’Quinn et al. (1997) observed 40 and 12% decreases in P excretion, respectively, when deleting inorganic P from barley-pea and sorghum-soybean meal–based finishing diets, respectively. These decreases are noteworthy when considering that the market pig consumes approximately one-third of its total lifetime feed intake during the final 4 wk prior to slaughter, thus producing approximately one-third of its total fecal excretion.
|
). Interactions between the main effects of supplement withdrawal and wheat middling inclusion were observed, including that described above for P. Additionally, there was more (P < 0.01) Ca in the feces of pigs fed the supplemented CSBM diet than in the feces of pigs fed the supplemented CSBM+WM diet, but the inverse was true when the supplement was removed from both diets. Less (P < 0.01) Cu was excreted with the supplemented CSBM+WM diet than with the supplemented CSBM diet, but no difference was observed between the two diets when supplement was not fed.
In the present study, differences in fecal P, Mn, and Zn concentrations among the four treatment groups were reflective of differences in daily mineral intakes (data not presented; calculated using analyzed dietary mineral concentration [Table 3] and ADFI [Table 4]). However, this was not true for fecal Ca, Cu, or Fe concentration. The National Research Council’s Subcommittee on Swine Nutrition has stated that fecal mineral concentration is a function of available mineral intake relative to the animal’s requirement for growth and maintenance (NRC, 1998). For several of the minerals measured in the present study, information about the pig’s dietary requirement and about availability in nontraditional feedstuffs is limited, making further explanation of the effects of supplement withdrawal and wheat middling inclusion on fecal mineral concentrations limited as well.
Vitamin Content of Pork.
Both supplement withdrawal and wheat middling inclusion altered the B vitamin content of the LDM (Table 7). Supplement withdrawal decreased (P < 0.01) the LDM riboflavin and niacin concentrations, but not thiamin. Feeding wheat middlings increased (P < 0.04) LDM thiamin, riboflavin, and niacin concentrations.
|
The impact of supplement withdrawal on muscle vitamin content of broilers has been studied. Patel et al. (1997) reported that removing supplemental riboflavin from diets for 7 and 14 d prior to slaughter decreased pectoralis major bioavailable riboflavin by 22 and 43%, respectively. Deyhim et al. (1996) found that a 21-d vitamin withdrawal period decreased broiler pectoralis major total thiamin and niacin concentrations by 45 and 31%, respectively. Standard practice is to slaughter broilers at 7 to 8 wk of age. Comparatively, a 2- or 3-wk preslaughter withdrawal period for broilers would be a much greater portion of their lifetime than a 4-wk withdrawal period would be for pigs that are slaughtered at 23 to 25 wk of age.
Previous swine research suggests a relationship between the thiamin concentrations of the diet and skeletal muscle. Miller et al. (1943) fed diets containing 2.9, 7.6, and 12.7 mg/kg of thiamin for 100 d prior to slaughter. Increasing thiamin intake from 2.9 to 7.6 mg/kg and from 7.6 to 12.7 mg/kg increased loin thiamin concentrations by 110% (0.95 ± 0.21 to 2.00 ± 0.44 mg/100g) and 15% (2.00 ± 0.44 to 2.31 ± 0.51 mg/100g), respectively. Pence et al. (1945) supplemented finishing diets with 50 mg/d of thiamin for 8, 15, 22, 35, or 155 d prior to slaughter. Loin thiamin concentrations increased with longer periods of supplementation up to 35 d prior to slaughter. In our study, 30% wheat middling inclusion increased the thiamin content of the diet by 1.8 to 2.5 mg/kg, as wheat middlings contain more thiamin than corn (9.0 vs 3.0 mg/kg, respectively; NRC, 1998). This may explain why wheat middling inclusion significantly influenced LDM thiamin concentrations, whereas supplement withdrawal did not. The lack of difference in LDM thiamin concentration with supplement withdrawal in the present study is not surprising given the small difference in dietary thiamin concentration. The fully supplemented preslaughter diets included a vitamin premix that provided only 1 mg of thiamin per kilogram of feed.
Like thiamin, dietary niacin is strongly correlated to pork niacin concentrations. Christensen et al. (1943) increased the niacin content of pork from 4.66 to 7.35 mg/100 g by feeding 100 mg/d of supplemental niacin to growing and finishing pigs. In our study, supplement withdrawal decreased dietary niacin intake by 27 mg/d, and LDM niacin from 7.25 to 5.32 mg/100 g. Pigs that received 30% wheat middlings throughout the grow-finish period received approximately 150 mg/d more dietary niacin, increasing LDM niacin concentration from 4.94 to 7.64 mg/100 g. Although NRC (1998) states that the niacin in wheat is totally unavailable, these data indicate that a large portion of the niacin in wheat middlings is bioavailable to the pig.
Dietary riboflavin concentrations influence muscle riboflavin content, but to a lesser extent than other B vitamins. Ittner and Hughes (1941) found that increasing dietary riboflavin supplementation from 0 to 6 mg/d increased loin riboflavin concentrations from 0.14 to 0.25 mg/100 g. However, when doubling supplementation to 12 mg/d, loin riboflavin remained at 0.26 mg/100 g. Miller and coworkers (1943) observed no difference in loin riboflavin concentrations when diets containing 3.68 to 5.44 mg/kg were fed, confirming that the LDM approaches its saturated storage capacity at 0.23 mg/100 g. In our study, LDM riboflavin concentrations increased as the dietary concentration increased from 1.3 to 3.6 mg/kg. Muscle concentrations did not approach the 0.23 mg/100 g concentration in loin muscle, as observed by Miller et al. (1943), when a comparable dietary riboflavin concentration of 3.68 mg/kg was fed.
The vitamin content of pork depends not only on the vitamin concentrations in the feed consumed by the animal, but also on the bioavailability of each vitamin. For example, available thiamin in the feed may be influenced by feed processing and storage factors such as pH, temperature, oxidation, radiation, moisture, sulfites, and antithiamin factors (Tanphaichitr, 2001). As described earlier, certain precautions with premix storage, feed storage, and feeder management were taken in the present study to prevent the loss of all vitamins. The same control measures may not be equally employed in commercial pork production settings, and consequently, the vitamin concentrations in pork may possibly be less even if similar diet formulations are used. Furthermore, any comparison of pork vitamin contents as determined in different settings, experimental or commercial, should take into consideration pig genotype, protein status, and health status, as well as differing muscle tissue collection and analytical procedures. The bioavailability of vitamins has been considered here; however, similar thoughts may also be appropriate in understanding the relationship between pig diet and mineral content of pork.
Mineral Content of Pork.
Supplement withdrawal did not affect the LDM Ca or trace mineral concentrations, but decreased (P < 0.05) LDM phosphorus. Wheat middling inclusion tended to decrease (P < 0.10) LDM concentration of Cu, but not concentrations of Ca, Fe, P, or Zn. All late-finishing diets contained Cu, Fe, Mn, and Zn in excess of the estimated requirements (NRC, 1998) for optimal growth, with the exception of Zn in the CSBM withdrawal diet, which was approximately 30% below NRC (1998) recommendations.
Similarly, Edmonds and Arentson (2001) reported that removing vitamin and trace mineral premixes from finishing diets either 6 or 12 wk prior to slaughter did not affect LDM Zn, Cu, or Fe concentrations. However, both 6 and 12 wk withdrawal reduced Cu concentrations in the ham. The trace mineral concentration of pork is relatively consistent regardless of dietary concentrations (Leonhardt and Wenk, 1997). Muscle Zn concentrations are maintained during times of low Zn intake (Hill et al., 1983b). Muscle Cu concentrations are not affected by dietary deficiencies (Hill et al., 1983a) or excesses (Zanardi et al., 1998; Lauridsen et al., 2000). An exception to the lack of variation in the mineral content of meat may be Fe. Injecting growing pigs with 1,600 mg of Fe i.m. from Fe-dextran during the nursery and growing phases increased ham Fe concentrations by 21% (Henry et al., 1961), and increasing dietary Fe from 62 to 209 mg/kg for 13 wk increased LDM Fe concentrations by 38% (Miller et al., 1994).
The reduced LDM phosphorus caused by supplement withdrawal in our study indicates that during periods of modest Ca and P deficiencies, the pig draws upon muscle P reserves to increase serum P and meet metabolic needs. Nicodemo et al. (1998) fed pigs diets containing high supplementation (0.86% Ca and 0.56% P), intermediate supplementation (0.6% Ca and 0.4% P), or low supplementation (0.39 % Ca and 0.25% P). After 56 d on trial, plasma Ca concentrations did not differ between dietary treatments, but low supplementation reduced (P < 0.001) plasma P concentrations. Other studies found that serum and plasma P concentration are reduced during periods of extreme (Howe and Beecher, 1983; Koch and Mahan, 1985), but not moderate (Carter et al., 1996), dietary P deficiencies. Thus, during periods of dietary P deficiency, the pig may rely upon secondary P reserves, such as those found in muscle, in order to sustain adequate circulating P concentrations.
Vitamin E Content and Pork Oxidative Stability.
Supplement withdrawal changed analyzed dietary -tocopherol from 12.9 to 2.2 IU/kg, but did not result in a decrease in LDM DL--tocopherol concentration (Table 7). O’Sullivan et al. (1997) and Choi et al. (2001) likewise observed no significant change in LDM vitamin E concentrations when omitting supplemental vitamin E from diets for 130 and 28 d prior to slaughter, respectively. Comparing the supplement withdrawal treatment to the control treatment used in both of these studies, analyzed dietary -tocopherol was only decreased from 19.6 to 16.4 mg/kg in the study of O’Sullivan et al. (1997), whereas estimated dietary vitamin E concentration decreased from 22 to 11 IU/kg in the work of Choi et al. (2001). In contrast, Dove and Ewan (1991) reported that deleting supplemental -tocopheryl acetate from pig diets (1.4 IU/kg analyzed dietary -tocopheryl acetate) for 13 wk prior to slaughter reduced LDM -tocopherol concentrations by 82% compared to feeding a diet containing 12.9 IU/kg analyzed -tocopheryl acetate for the same period. Likewise, Edmonds and Arentson (2001) reported that removing vitamin and trace minerals for 6 wk preslaughter decreased LDM vitamin E concentrations by 77%. Two diets with analyzed vitamin E contents of about 7 and 42 IU/kg were compared in that study. Although withdrawal times and premix vitamin E concentrations differed between our study and the Edmonds and Arentson report, the vitamin E analyses were performed by the same laboratory with the same methods.
It is difficult to compare the results of studies, which were designed to evaluate the effect of omitting supplemental vitamin E on muscle vitamin E concentration. Outcomes appear to differ depending on several factors, including the absolute difference in analyzed vitamin E concentration between the test and control treatments, and on the duration of the withdrawal period. Furthermore, we chose to mix our diets weekly and to remove any feed in the feeder within 72 h of being added. Dove and Ewan (1991) found that the rate of oxidation of natural tocopherols was increased in diets supplemented with Cu, Fe, Zn, and Mn. The use of similar practices is not reported by the researchers conducting other studies. Anderson et al. (1995) noted that vitamin E in the alcohol form lost stability during a 28-d study, whereas supplementation with the acetate form was stable. It is not clear what form of vitamin E was added in the studies of Edmonds and Arentson (2001) or Choi et al. (2001). Lastly, not only can diets and feeding practices differ, but slaughter and carcass fabrication procedures may also vary (e.g., chilling temperatures, product packaging, and storage times).
Wheat middling inclusion increased LDM vitamin E concentrations. However, laboratory analyses found that the diets containing wheat middlings had lower vitamin E concentrations than the diets without wheat middlings. Additional choice white grease was added to the CSBM+WM diets to balance for ME. We know of no data in the literature showing that choice white grease is an important source of vitamin E. Lard is rendered pork fat and the primary lipid in choice white grease, but it only has 1.2 mg/100 g of vitamin E (Slover et al., 1969). Alternatively, choice white grease may have influenced the bioavailability of the vitamin E in the wheat middling diet. Zanardi et al. (1998) reported that adding 6% dietary sunflower oil, which increased total dietary vitamin E by 27 mg/kg, had a greater influence on LDM vitamin E concentrations than did supplementing 200 mg/kg of -tocopheryl acetate.
Vitamin E acts as an antioxidant at the cellular level to prevent the peroxidation of polyunsaturated fatty acids. Supplementing 100 to 200 mg/kg of dietary -tocopherol for extended periods of time has been reported to decrease lipid oxidation, as measured by thiobarbituric acid-reactive substance (TBARS; Monahan et al., 1990a, b; Cannon et al., 1996; Jensen et al., 1997). Malondialdehyde is quantified as an indirect measure of lipid peroxidation in the TBARS assay developed by Ohkawa et al. (1979). To examine the oxidative stability of pork we chose a novel approach to measuring the enzymes Cu/ZnSOD and GPX1, which are essential in oxidation in the normal animal, and which are known to be induced during oxidative stress. Cytosolic GPX1 requires Se and Cu/ZnSOD needs Cu and Zn to function; hence, the activity of these two enzymes would indicate that the healthy animal has had adequate dietary vitamins and minerals. Our objective was to assess the oxidative stability of a consumable product, harvested using commercial procedures, including chilling the carcass for 24 h before fabrication and tissue sample collection. According to Zhang et al. (1986), GPX1 activity in swine plasma decreases only 17.8% with storage for 24 h at 4°C. The variation among stored samples was no different than the variation among samples analyzed after 0 h of storage. In the research reports cited below, fresh muscle tissues were analyzed. A comparison of treatment effects observed in the present study to those reported elsewhere is believed to be valid, as samples were processed and stored similarly across treatments in each study.
Dietary treatment did not affect the activity of the LDM antioxidative enzymes Cu/ZnSOD and GPX1 (Table 7). Likewise, Lauridsen et al. (1999) reported that vitamin E supplements did not influence the antioxidant status of porcine muscles. They found that pigs fed low concentrations of -tocopherol (9 mg/kg) did not suffer from oxidative stress and that GPX1 and Cu/ZnSOD activities were not altered. The results of our study also agree with previous research that has shown that removing supplemental Cu from the diets of growing pigs (Lauridsen et al., 1999) and rats (Paynter et al., 1979) does not affect Cu/ZnSOD activity in skeletal muscle. However, they disagree with previous research showing that 0.3 mg/kg of supplemental dietary Se is necessary to maintain muscle GPX1 activity in 4- to 9-wk-old weanling pigs (Lei et al., 1998). In our study, the analyzed concentrations of Cu in the withdrawal diets were 124 to 204% of the NRC (1998) estimated requirement, and the calculated Se concentrations of the withdrawal diets were 70 to 201% of the NRC estimated requirement.
|
Implications |
|---|
|
TopAbstractIntroductionMaterials and MethodsResults and DiscussionImplicationsLiterature Cited |
|---|
|
Footnotes |
|---|
2 Current address: Murphy-Brown, LLC, P.O. Box 856, Warsaw, NC 28398.
4 Joint appointment in the Departments of Animal Science and Food Science and Human Nutrition.
Received for publication February 26, 2002. Accepted for publication July 24, 2002.
|
Literature Cited |
|---|
|
TopAbstractIntroductionMaterials and MethodsResults and DiscussionImplicationsLiterature Cited |
|---|
-tocopherol deposition in porcine m. psoas major and m. longissimus dorsi and on drip loss, colour stability and oxidative stability of pork meat. Meat Sci. 45:491–500.
-tocopherol deposition and susceptibility to lipid oxidation of porcine membranal fractions of M. psoas major and M. longissimus dorsi. Meat Sci. 54:377–384.
-tocopherol supplementation on -tocopherol levels in porcine tissues and on susceptibility to lipid peroxidation. J. Food Sci. Nutr. 42F:203–212.
This article has been cited by other articles:
|
|
 |
|
  G. M. Hill, J. E. Link, M. J. Rincker, D. L. Kirkpatrick, M. L. Gibson, and K. Karges Utilization of distillers dried grains with solubles and phytase in sow lactation diets to meet the phosphorus requirement of the sow and reduce fecal phosphorus concentration J Anim Sci, January 1, 2008; 86(1): 112 - 118. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. T. Shaw, D. W. Rozeboom, G. M. Hill, M. W. Orth, D. S. Rosenstein, and J. E. Link Impact of supplement withdrawal and wheat middling inclusion on bone metabolism, bone strength, and the incidence of bone fractures occurring at slaughter in pigs J Anim Sci, May 1, 2006; 84(5): 1138 - 1146. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. L. Shelton, F. M. LeMieux, L. L. Southern, and T. D. Bidner Effect of microbial phytase addition with or without the trace mineral premix in nursery, growing, and finishing pig diets J Anim Sci, February 1, 2005; 83(2): 376 - 385. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. J. Rincker, G. M. Hill, J. E. Link, and J. E. Rowntree Effects of dietary iron supplementation on growth performance, hematological status, and whole-body mineral concentrations of nursery pigs J Anim Sci, November 1, 2004; 82(11): 3189 - 3197. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. W. Hastad, S. S. Dritz, M. D. Tokach, R. D. Goodband, J. L. Nelssen, J. M. DeRouchey, R. D. Boyd, and M. E. Johnston Phosphorus requirements of growing-finishing pigs reared in a commercial environment J Anim Sci, October 1, 2004; 82(10): 2945 - 2952. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. E. Rowntree, G. M. Hill, D. R. Hawkins, J. E. Link, M. J. Rincker, G. W. Bednar, and R. A. Kreft Jr. Effect of Se on selenoprotein activity and thyroid hormone metabolism in beef and dairy cows and calves J Anim Sci, October 1, 2004; 82(10): 2995 - 3005. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. L. Shelton, L. L. Southern, F. M. LeMieux, T. D. Bidner, and T. G. Page Effects of microbial phytase, low calcium and phosphorus, and removing the dietary trace mineral premix on carcass traits, pork quality, plasma metabolites, and tissue mineral content in growing-finishing pigs J Anim Sci, September 1, 2004; 82(9): 2630 - 2639. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. M. Martinez, G. M. Hill, J. E. Link, N. E. Raney, R. J. Tempelman, and C. W. Ernst Pharmacological Zinc and Phytase Supplementation Enhance Metallothionein mRNA Abundance and Protein Concentration in Newly Weaned Pigs J. Nutr., March 1, 2004; 134(3): 538 - 544. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
