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Effect of High Levels of Dietary Iron, Iron Injection, and Dietary Vitamin E on the Oxidative Stability of Turkey Meat During Storage1
PROCESSING AND PRODUCTS Effect of High Levels of Dietary Iron, Iron Injection, and Dietary Vitamin E on the Oxidative Stability of Turkey Meat During Storage1 I. BARTOV and J. KANNER Departments of Poultry Science and Food Science, Agricultural Research Organization, The Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel The TBARS values of the meat up to about 30 d of storage were significantly lower due to the supplementation of the diet with vitamin E at a level of 28 mg/kg in one out of three experiments and at a level of 150 mg/kg in two out of two experiments. The protective effect of the higher level of vitamin E remained evident after about 108 d of storage. No interaction was observed between Fe and vitamin E treatments in their effect on TBARS values. Blood hemoglobin concentrations were significantly increased by the supplementation of the diet with the high levels of Fe, in one experiment only. This variable was consistently and significantly increased from about 10 to 23 wk of age. The results show that high levels of dietary Fe do not adversely affect the oxidative stability of thigh meat of turkey; however, stability might be reduced by injected Fe. Dietary vitamin E, at a level of 150 mg/kg, consistently increased this stability.
{Key words: turkey, iron, dietary vitamin E, meat oxidative stability, storage duration) 1996 Poultry Science 75:1039-1046
INTRODUCTION Turkey meat is prone to oxidative rancidity during frozen storage (Wilson et al., 1976). This sensitivity is particularly pronounced in the dark meat (Webb et al, 1973; Wilson et al, 1976). Dietary vitamin E has been reported to reduce or prevent the process of lipid oxidation occurring in turkey meat during storage, as indicated by the thiobarbituric acid test (Webb et al, 1973; Marusich et al, 1975; Bartov et al, 1983). Iron mainly in its free ionic form (Kanner et al, 1988; Ahn et al, 1993), or as heme proteins (Johns et al, 1989) plays an important role in the process of lipid oxidation
Received for publication September 18, 1995. Accepted for publication April 12, 1996. Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel, Number 1718-E, 1995 series.
in meat. Nevertheless, the effect of dietary Fe level on the stability of meat from farm animals has hardly been investigated. Kanner et al. (1990) reported that removal of the Fe supplement (25 mg/kg) from the diet fed to turkeys 3 to 7 wk prior to slaughter improved the oxidative stability of their meat. Iron overload, either applied directly to liver slices or by injection of Fe-dextran, was reported to increase oxidation damage in chicks (Andersen et al, 1993). The extent of this damage was less in birds fed a vitamin Esupplemented diet than in those fed an unsupplemented diet. Toxic damage, mortality, and reduction in hepatic vitamin E stores in mice due to Fe overload, either by the diet or by injection, were partly ameliorated by vitamin E (Omara and Blakley, 1993). In the present study, the combined effect of excess Fe (supplemented through the diet or by injection) and dietary vitamin E level on the oxidative stability of turkey meat was determined.
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ABSTRACT A study was carried out to evaluate the combined effect of excess Fe, supplied either in the diets (Experiments 1, 2, and 3) or by injection (Experiment 4), and various levels of dietary vitamin E on the oxidative stability of the thigh muscle of turkeys stored at -18 C for various periods. Iron was added to a commercial diet that already contained 20 mg/kg supplemental Fe, at concentrations of 0, 100, 250, and 500 mg/kg as ferrous sulfate or injected as Fe-dextran to the left drumstick muscle (total amount of 1.2 g per turkey). Vitamin E was added to the experimental diets not already supplemented with this vitamin, at levels of 0, 28, and 150 mg/kg. Thiobarbituric acid reactive substances (TBARS) values of the meat gradually increased as its storage duration increased from about 15 to 120 d. Increasing dietary Fe supplementation from 0 to 500 mg/kg tended to decrease TBARS values in one experiment only; otherwise, this variable was not affected by dietary Fe level. Injection of Fe significantly (P < 0.05) increased TBARS values, only in meat from the injected side.
BARTOV AND KANNER
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MATERIALS AND METHODS Birds and Diets
Experiment 1 The combined effects of the supplementation of the basal diets with four levels of Fe (0,100,250, and 500 mg/ kg) and two levels of vitamin E (0 and 28 mg/kg) on meat oxidative stability were evaluated. The four Fe treatments started with 7-d-old birds, two groups per treatment, and the two vitamin E treatments at 70 d of age. In order to prevent possible damage to the young birds, the feeding of the highest level of Fe started only at 4 wk of age. Up to that age the birds allotted to this treatment were fed on the diet containing 250 mg Fe/kg. The birds were slaughtered at 162 d of age. The thiobarbituric acid reactive substances (TBARS) values of the meat were determined after 25 and 120 d of storage.
Experiment 2 The combined effects of the supplementation the basal diet with three levels of Fe (0, 250, and 500 mg/kg) and two levels of vitamin E (0 and 28 mg/kg) on meat oxidative stability were evaluated in order to confirm the results of Experiment 1 (see below). The three Fe treatments started with 7-d-old birds, two groups per treatment, and the two vitamin E treatments at 59 d of age. The treatment with the highest level of Fe started at 28 d of age (as described above). The birds were slaughtered at 158 d of age. The TBARS values of the meat were determined after 37 and 45 d of storage.
Experiment 3 Management Individual body weights were recorded bi-weekly and feed consumption data were obtained at the same times, on a group basis. Blood was taken from the brachial vein with a heparinized syringe at 70,91,84, and 84 d of age in Experiments 1, 2, 3, and 4, respectively, and at the termination of the experiments, for the determination of hemoglobin content. At 22 to 23 wk of age, five birds from each treatment of Experiments 1, 2, and 3, whose body weights were within ± 7.5% of the treatment average and four birds from each treatment of Experiment 4 (see below) were slaughtered. The meat of the thigh (the muscles around the femur) was removed, chilled on ice, and kept as is in polyethylene bags under natural
2
Fluka Chemie AG CH-9470, Buchs, Switzerland. ROVIMIX E-50 SD; Hoffmann-La Roche CH-4002, Basel, Switzerland. *Fe-dextran; The Butler Co., Columbus, OH 43228. 3
The combined effects of the supplementation of the basal diets with two levels of Fe (0 and 500 mg/kg), and three levels of vitamin E (0, 28, and 150 mg/kg) on meat oxidative stability were evaluated. The two Fe treatments started with 28-d-old birds, three groups per treatment, and the three vitamin E treatments at 56 d of age. The birds were slaughtered at 154 d of age. The TBARS values of the meat were determined after 28 and 101 d of storage.
Experiment 4 The combined effects of the supplementation of the basal diets with two levels of vitamin E (0 and 150 mg/kg) and the injection of iron hydrogenated dextran4 on meat stability were evaluated. Twenty 7-d-old birds were fed the basal diets up to 56 d of age. They then were divided, as mentioned above, into two groups and were fed the two diets differing in vitamin E content. At 84 d of age, two birds (the lightest ones) from each of the vitamin E treatments were removed. The remaining birds were
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Day-old males of a large strain of Broad Breasted White turkeys (British United Turkeys, T6) were raised in electrically heated battery brooders placed in a temperature-controlled room at 25 ± 2 C up to 28 d of age, and then in individual cages with wire floors in a temperature-controlled (22 ± 2 C) building. Twenty-four hours of light were provided in both rooms. The basal diets, composed mainly from sorghum grains, yellow corn, soybean meal, and acidulated soybean oil soapstock, were formulated for the age periods 0 to 4,4 to 8,8 to 12,12 to 16, 16 to 20, and 20 to 24 wk, according to National Research Council (1984) recommendations. The mineral and vitamin mixes provided 20 mg Fe, 28 mg vitamin E, and 125 mg ethoxyquin/kg diet. After a preparatory period of 7 d, two-thirds of the birds (those closest to the average weight) were wing-banded and divided according to body weight into groups of 10 birds each. Mean group weights and within-group individual weight distributions were the same for all groups. Two of three such groups were assigned to the dietary Fe treatments, which started at 7 or 28 d of age (see below). Iron was supplemented to the basal diet as ferrous sulfate.2 The treatments with vitamin E were started at about 8 wk of age when the birds within each of the Fe treatments were divided into two or three subgroups, as mentioned above, and allotted to the vitamin E treatments. Thus, in each experiment, the combined treatment of dietary Fe and vitamin E was given to one group of 10 birds each. Vitamin E supplied as DL-a-tocopheryl acetate3 was added to the experimental diets whose vitamin mix did not contain vitamin E and ethoxyquin, but supplied 125 mg butylated hydroxytoluene/kg diet. The experimental diets were consumed ad libitum in mash form.
atmosphere at -18 C for various periods for the determination of its oxidative stability. Before these determinations the frozen meat was transferred to room temperature for 2 h and then to 3 C for 18 h. After sampling it was stored again at -18 C.
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IRON, VITAMIN E, AND MEAT STABILITY TABLE 1. Effect of various dietary iron supplementations (Fe-Sup) on the concentrations of blood hemoglobin of turkeys at different ages, Experiments 1 to 41 Experiment no.
Blood hemoglobin
Fe-sup
SEM
(mg/kg)2 0 100 250 500 SEM Age average
SEM Age average 0 500
SEM Age average 0 12003 SEM Age average
162 d 13.8c 14.5^ 15.6» 14.8»b 0.30 14.3*
0.25
158 d 13.8 14.2 13.8 0.41 13.9A
0.19
84 d
154 d 12.2 11.8 0.26 12.0A 112 d
10.4 10.8 0.35 10.6B
11.7 12.4 0.31 12.0A
0.15
0.23
a_c
Values in the same column of each experiment with no common superscript differ significantly (P < 0.05). ' Values in each experiment with no common superscript differ significantly (P < 0.001). x Means of 10 and 8 turkeys in Experiments 1 to 3 and Experiment 4, respectively. 2 The basal diets contained 20 mg Fe/kg supplemented by the mineral mix. 3 This amount of Fe was injected as Fe-dextran, at 85, 90, 100, and 105 d of age. AB
again reallocated within each of the vitamin E treatments to create four groups of four birds each. The Fe-dextran (100 mg Fe/mL) was injected into the left drumstick (1,2, 2.5, 3, and 3.5 mL per bird, at 85, 90, 95,100, and 105 d of age, respectively) to one group of birds on each of the vitamin E treatments. The other groups of birds were injected at the same time with the same amounts of saline. The birds were slaughtered 7 d after the last injection, at 112 d of age. The TBARS values of the meat from the right and the left thighs were determined during storage that lasted up to 108 d.
Chemical Determination The oxidative stability of the meat was evaluated by the thiobarbituric acid test before and after incubation, as described by Machlin et al. (1959) except that cold water was used during homogenization (Desai and Scott, 1966). The developing color of the TBARS, measured by a spectrophotometer,5 was related to a standard curve of malonaldehyde bis-bisulfite sodium salt prepared according to Saslaw and Waravdekar (1957) and expressed as milligrams per kilogram of tissue. The TBARS values determined before the incubation (initial levels) represent
sSequoia-Turner Corp., Mountain View, CA 94043.
the oxidative stability of the meat during frozen storage, whereas the values observed after this step represent its oxidative stability during an accelerated oxidation test. Blood hemoglobin concentration was determined according to Sigma Chemical Co. (1984).
Statistical Analysis The individual bird was used as the experimental unit. Factorial ANOVA was carried out, for each experiment separately, according to Snedecor and Cochran (1967). The main factors tested were the levels of dietary Fe and vitamin E (Experiments 1, 2, and 3), Fe-dextran injection, and dietary vitamin E level (Experiment 4). Data of the meat from the right and left thighs obtained in the last experiment were separately analyzed. Difference among treatment and factor means were determined by Duncan's multiple range test (1955), at a significance of level 5%.
RESULTS Experiment 1 The treatments did not affect body weight throughout the experiment, the average value at 162 d of age was 16.89 kg. Blood hemoglobin, in the present and the other experiments, was not affected by dietary vitamin E levels, therefore only the effect of Fe is detailed (Table 1). At 70
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0 250 500
70 d 8.9" ND ND 10.1» 0.25 9.5B 91 d 10.6 10.9 11.1 0.26 10.9B 84 d 10.6 11.0 0.19 10.8B
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BARTOV AND KANNER TABLE 2. Effect of various levels of dietary iron supplementation (Fe-sup) and vitamin E (Vit. E) on the thiobarbituric acid reactive substances (TBARS) of thigh meat during storage, Experiment l 1 Storage duration 3 25 d
Dietary variables 2 Fe-sup
0 28 0 28 0 28 0 28
Initial level
After incubation 4
2.97" 1.83* 2.16* 1.67* 2.16* 0.83b 1.32* 0.57b 0.58
28.6" 30.4' 26.9* 26.8* 23.7* 18.1b 17.7b 17.3b 3.37
2.40 1.91 1.49 0.94 0.10
29.5" 26.9* 20.9bc 17.5' 0.01
6.58 5.43 5.73 6.06 NS
32.1 32.0 31.2 29.6 NS
2.15 1.22
24.2 23.1 NS
5.85 6.05 NS
30.6 31.9 NS
0.05
Initial level
• (TBARS values^ 6.38 6.78 4.86 6.00 6.24 5.22 5.92 6.20 0.866
After incubation 31.6 32.7 28.1 36.0 32.6 29.9 30.2 29.0 2.32
'"Values with no common superscript differ significantly (P < 0.05). M e a n s of 5, 10, and 20 turkeys per treatment, Fe level, and Vit. E level, respectively. 2 The basal diet contained 20 mg Fe/kg supplemented by the mineral mix, but not Vit. E supplement. 3At -18 C. 4 In water bath at 37 C for 1 h under constant shaking. 5 Expressed as milligrams sodium salt of malonaldehyde-bis-bisulfite per kilogram meat.
and 162 d of age, birds fed the unsupplemented diet had significantly lower concentrations of hemoglobin than those fed the diets supplemented with 250 or 500 mg Fe/ kg. Intermediate concentrations were observed in birds fed the diet supplemented with 100 mg Fe/kg. Hemoglobin concentrations increased significantly (P < 0.001) with age. The effects of the treatments on meat oxidative stability are summarized in Table 2. Supplementation of the diets with Fe decreased, at times significantly, the TBARS values (initial and after incubation) determined after 25 d of storage. This effect of Fe was proportional to the level of its supplementation, and a significant effect was observed in meat of birds fed the diets supplemented with either 250 or 500 mg Fe/kg (TBARS values after incubation, on a factorial basis); however, after an additional 95 d this protective effect of Fe disappeared. Vitamin E supplementation significantly reduced initial TBARS values (on a factorial basis) after 25, but not 120 d of storage. At both periods it had no effect on TBARS values observed after incubation. Initial TBARS values markedly increased during the additional 95 d of storage.
Experiment 2 Neither of the treatments nor the factors affected body weight at 158 d of age, the average value was 15.59 kg.
Blood hemoglobin concentrations were also unaffected at 91 and 158 d of age by the level of Fe supplementation, but the concentrations observed in the older birds were significantly (P < 0.001) higher than those of the younger ones (Table 1). The TBARS values, after the two periods of storage, were not significantly affected by either of the treatments or any of the factors evaluated, in contrast with the results of Experiment 1 (data not detailed for the sake of brevity). As in the previous experiment, initial TBARS values were markedly increased during the additional storage (1.42 and 2.45 after 37 and 45 d of storage, respectively).
Experiment 3 The various dietary treatments did not affect body weight at 154 d of age (average value 15.85 kg), as well as blood hemoglobin concentrations at 84 and 154 d of age (Table 1). Blood hemoglobin levels increased slightly, but significantly (P < 0.001), with age. Supplementation of the diets with 500 mg Fe/kg had no effect on meat oxidative stability (Table 3). Vitamin E supplementation at a level of 150 mg/kg significantly reduced the level of oxidation of the meat after 28 d of storage (initial and postincubation TBARS) (Table 3). This effect was still evident, although by then not significant, after 101 d of storage. There was no
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(mg/kg) 0 0 100 100 250 250 500 500 SEM Factorial effects Fe-sup 0 100 250 500 P< Vit. E 0 28 P<
Vit. E
120 d
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IRON, VITAMIN E, AND MEAT STABILITY TABLE 3. Combined effect of two levels of dietary iron supplementation (Fe-sup) and three levels of vitamin E (Vit E) on the thiobarbituric acid reactive substances (TBARS) of thigh meat during storage, Experiment 31 Storage duration 3 101 d
28 d Dietary variables 2 Vit. E
0 0 0 500 500 500 SEM Factorial effects Fe-sup 0 500 P<
0 28 150 0 28 150
Vit. E 0 28 150 P<
Initial level
After incubation 4
Initial level
2.28» 1.171> 1.31ab 1.88ab 1.68»b 1.13b 0.38
18.4 17.1 12.5 17.7 15.4 13.2 2.38
6.63» 4.92>b 4.72* 5.18 ab 4.71* b 2.77b 1.06
1.59 1.56 NS
16.0 15.4 NS
5.42 4.22 NS
2.08' 1.42ab 1.22b
18.1* 16.2"b 12.8b 0.05
5.90 4.81 3.74
0.05
NS
ab
' Values with no common superscript differ significantly (P < 0.05). Means of 5, 10, and 15 turkeys per treatment, Vit. E level, and Fe-sup, respectively. 2 The basal diet contained 20 mg Fe/kg supplemented by the mineral mix, but not Vit. E supplement. 3At -18 C. 4 In water bath at 37 C for 1 h under constant shaking. 5 Expressed as milligrams sodium salt of malonaldehyde-bis-bisulfite per kilogram meat. 1
significant difference in TBARS values of meat from turkeys fed diets supplemented with either 28 or 150 mg vitamin E/kg; however, the factorial effect of vitamin E supplementation at a level of 28 m g / k g was not significant.
Experiment 4 The various treatments did not affect body weight at 112 d of age (average value 10.52 kg) or blood hemoglobin concentrations (Table 1). Blood hemoglobin concentrations were significantly (P < 0.001) increased with age. Vitamin E supplementation consistently improved the oxidative stability of the meat of the right and the left thighs evaluated without or with incubation u p to 108 d of storage and, on a factorial basis, in most cases the improvement was significant (Tables 4 and 5). The injection of Fe-dextran into the left drumstick significantly decreased initial TBARS values in meat from the right thigh of birds fed the diet without vitamin E supplementation, as determined after 15 d of storage. This unexplained effect was not observed in birds fed the vitamin Esupplemented diet. That effect in turn resulted in a significant interaction between vitamin E and Fe injection (Table 4). However, the factorial effect of the latter on TBARS values was consistently not significant. On the other hand, Fe injection significantly increased initial and
postincubation TBARS values of the meat from the left thigh of birds fed the diets containing each level of vitamin E, determined after 23 and 36 d of storage (Table 5). This effect of Fe disappeared after 107 d of storage, by which time initial TBARS values were markedly increased in all the treatments, as in the previous experiments.
DISCUSSION Data obtained in Experiment 4, in which Fe injected to the left drumstick decreased the oxidative stability of thigh meat of the same side (Table 5) clearly demonstrate that Fe does play an important role in inducing lipid oxidation in meat, in agreement with Ahn et al. (1993), who added Fe directly to meat homogenate. However, the data also show that this effect of Fe was limited only to the thigh of the injected side and was not observed in the other thigh (Table 4). Moreover, relatively high levels of dietary Fe consistently did not reduce meat oxidative stability (Tables 2 and 3, and Experiment 2). The lack of effects of Fe injection into the left drumstick or of a high dietary Fe level, on the oxidative stability of the thigh meat (the right one in the case of Fe injection) was probably due to the fact that these treatments did not increase muscle Fe content despite their effect of increasing liver Fe concentration by about 23% (Kanner et al, 1995). In other words, it
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Fe-sup
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BARTOV A N D K A N N E R TABLE 4. Effect of dietary vitamin E (Vit E) level and Fe-dextran injections on the thiobarbituric acid reactive substances (TBARS) of meat from the right thigh (the uninjected side) during storage, Experiment 4 1 Storage duration 3 30 d
15 d Treatment 2 Dietary Vit. E
Initial level
After incubation 4
Initial level
After incubation
Initial level
(TBARS values) 5 No Yes No Yes
1.08" 0.41b 0.06b 0.16b 0.159
18.0" 18.9» 6.0b 11.7* 2.81
2.20" 2.17" 0.14b 0.37b 0.389
20.3* 22.8" 5.0= 12.4b= 2.62
5.21» 4.56<»b 2.58b 2.88* 0.758
0.74 0.11 0.01
18.4 8.8 0.01
2.18 0.26 0.001
21.6 8.7 0.001
4.88 2.73
0.57 0.28
12.0 15.3
1.17 1.27
12.6 17.6
3.89 3.72
NS
NS
NS
NS
NS
0.05
NS NS 0.05 NS NS Values with no common superscript differ significantly (P < 0.05). 1 Means of 4, 8, and 8 turkeys per treatment, Vit. E level, and Fe-dextran injection, respectively. 2 The basal diet contained 20 mg Fe/kg supplemented by the mineral mix, but not Vit. E supplement. Vitamin E treatments were given from 56 to 112 of age and Fe-dextran injections (to the left drumstick) from 84 to 105 d of age. 3 At -18 C. 4 In water bath at 37 C for 1 h under constant shaking. 5 Expressed as milligrams sodium salt of malonaldehyde-bis-bisulfite per kilogram meat. a_c
TABLE 5. Effect of dietary vitamin E (Vit E) level and Fe-dextran injections on the thiobarbituric acid reactive substances (TBARS) of meat from the left thigh (the injected side) during storage, Experiment 4 1 Storage duration 3
Dietary Vit. E
Fe-dextran
Initial level
After incubation 4
(mg/kg) 0 0 150 150 SEM Factorial effects Vit. E 0 150 P< Fe-dextran No Yes P< a b
No Yes No Yes
107 d
36 d
23 d Treatment 2
0.53b 2.10» 0.30b 0.97* 0.46
14.1* 22.9" 5.9' 16.9* 2.76
1.31 0.63 NS
18.5 11.4
0.41 1.53 0.05
Initial level (TBARS values) 5 1.15b 4.34" 0.24b 1.66* 0.99
After incubation
Initial level
15.7b 28.4" 6.7b 17.3b
6.55* 9.77' 5.38* 4.07b 1.45
3.38
8.16 4.72
22.0 12.0
0.05
2.74 0.95 NS
0.05
0.05
10.0 19.9 0.01
0.69 3.00 0.05
11.2 22.8 0.01
5.96 6.92 NS
- Values with no common superscript differ significantly (P < 0.05). Means of 4, 8, and 8 turkeys per treatment, Vit. E level, and Fe-dextran injection, respectively. 2 The basal diet contained 20 mg Fe/kg supplemented by the mineral mix, but not Vit. E supplement. Vitamin E treatments were given from 56 to 112 of age and Fe-dextran injections (to the left drumstick) from 84 to 105 d of age. 3 At -18 C. 4 In water bath at 37 C for 1 h under constant shaking. Expressed as milligrmas sodium salt of malonaldehyde-bis-bisulfite per kilogram meat. 1
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(mg/kg) 0 0 150 150 SEM Factorial effects Vit. E 0 150 P< Fe-dextran No Yes P< Vit. E x Fe-dextran P<
Fe-dextran
108 d
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IRON, VITAMIN E, AND MEAT STABILITY
Although the calculated Fe content of our basal diets, which consisted of common feedstuffs and supplemented with 20 mg Fe/kg by the mineral mix, was above the Fe requirement of the turkeys, blood hemoglobin concentrations in Experiment 1 were significantly increased by the supplementation of the diet with 250 and 500 mg Fe/kg (Table 1). It is difficult to explain this phenomenon, but it indicates that under certain conditions, increased Fe supplementation to commercial diets is necessary for maximal hemoglobin production. Blood hemoglobin concentrations consistently and significantly increased with age, in agreement with Wolterink et al. (1947). This study was not intended to evaluate the effect of high levels of dietary ferrous sulfate on the performance of turkeys. However, the data demonstrate that this compound, at a dietary level of 2.39%, has no adverse effects. Pescatore and Harter-Dennis (1989) observed that ferrous sulfate at a dietary level of 3% significantly decreased weight gain in broiler chicks. The results show that the oxidative stability of the turkey meat is not adversely affected by high levels of dietary Fe. However, Fe injection may reduce the stability of the meat sampled close to the injection site.
ACKNOWLEDGMENTS This study was supported by a grant from the United States-Israel Binational Agricultural Research and De-
velopment Fund (BARD), Project No. IS-1644-89. The authors are indebted to M. Ben-Mosheh, for technical assistance.
REFERENCES Ahn, D. U., F. H. Wolfe, and J. S. Sim, 1993. The effect of free and bound iron on lipid peroxidation in turkey meat. Poultry Sci. 72:209-215. Andersen, H. J., H. Chen, L. J. Pellett, and A. L. Tappel, 1993. Ferrous-iron-induced oxidation in chicken liver slices as measured by hemichrome formation and thiobarbituric acid-reactive substances: Effects of dietary vitamin E and /3-carotene. Free Radical Biol. Med. 15:37-48. Bartov, I., D. Basker, and S. Angel, 1983. Effect of dietary vitamin E on the stability and sensory quality of turkey meat. Poultry Sci. 62:1224-1230. Desai, I. D., and M. L. Scott, 1966. Bioassays for orally administered and injected tocopherols: A relationship with tissue peroxidizabiiity and lysosomal enzymes. Pages 643-649 in: Proceeding of the 7th International Congress of Nutrition. Vol. 5. Hamburg, Germany. Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics 11:1-42. Johns, A. M., L. H. Birkinshaw, and D. A. Ledward, 1989. Catalysts of lipid oxidation in meat products. Meat Sci. 25: 209-220. Kanner, J., I. Bartov, M. O. Salan, and L. Doll, 1990. Effect of dietary iron level on in situ turkey muscle lipid peroxidation. J. Agric. Food Chem. 38:601-604. Kanner, J., B. Hazen, and L. Doll, 1988. Catalytic "free" iron ions in muscle foods. J. Agric. Food Chem. 36:412-415. Kanner, J., D. D. Miller, I. Bartov, and S. Harel, 1995. Effect of dietary iron on lipid peroxidation of muscle food. Final Report to the United States-Israel Binational Agricultural Research and Development Fund (BARD), Project No. IS1644-89. Machlin, L. J., R. S. Gordon, and K. H. Meisky, 1959. The effect of antioxidants on vitamin E deficiency symptoms and production of liver "peroxide" in the chicken. J. Nutr. 67: 333-343. Marusich, W. L., E. De Ritter, E. F. Ogrinz, J. Keating, M. Mitrovic, and R. H. Bunnell, 1975. Effect of supplemental vitamin E in control of rancidity in poultry meat. Poultry Sci. 54:831-844. National Research Council, 1984. Nutrient Requirements of Poultry. 8th rev. ed. National Academy Press, Washington, DC. Omara, F. O., and B. R. Blakely, 1993. Vitamin E is protective against iron toxicity and iron-induced hepatic vitamin E depletion in mice. J. Nutr. 123:1649-1655. Pescatore, A. J., and J. M. Harter-Dennis, 1989. Effects of ferrous sulfate consumption on the performance of broiler chicks. Poultry Sci. 68:1063-1067. Saslaw, L. D., and V. S. Waravdekar, 1957. Preparation of malonaldehyde bis-bisulfite sodium salt. J. Org. Chem. 22: 843-844. Sigma Chemical Co., 1984. Total hemoglobin: Quantitative colorimetric determination in whole blood at 530-550 nm. Procedure No. 525. Sigma Chemical Co., St. Louis, MO. Snedecor, G. D., and W. G. Cochran, 1967. Statistical Methods. 6th ed. Iowa State University Press, Ames, IA.
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seems that Fe overload in the turkey caused either by high levels of dietary Fe or by Fe injection and evaluated from liver Fe content, did not play an important role in the process of muscle lipid oxidation. The finding that increasing the dietary Fe level tended to increase meat oxidative stability (Experiment 1, Table 2) is worth noting. However, this observation was not confirmed in Experiments 2 and 3 (text and Table 3). Moreover, the data of the present study do not support our initial hypothesis, based on a previous study (Kanner et al., 1990), that a high level of dietary Fe may decrease meat oxidative stability. Meanwhile, we have no explanation for these disagreements; however, they probably emphasize the complexity of this subject. Dietary vitamin E supplementation at a level of 28 m g / k g diet significantly improved the oxidative stability of thigh meat after relatively short storage in only one out of three experiments (Tables 2 and 3 and text), whereas at a level of 150 m g / k g , it significantly improved this stability in the two experiments in which it was used (Tables 3, 4, and 5). However, it is worth noting that the difference between the effect of these two levels of dietary vitamin E on meat oxidative stability was not significant (Table 3). In other words, the great difference between these two levels of vitamin E was hardly evident in terms of TEARS values. Nevertheless, it is worth noting that in spite of the marked increase in TBARS values during storage, the beneficial effect of the high level of vitamin E in improving meat oxidative stability was evident, at times significantly, also after 101 to 108 d of storage (Tables 3, 4, and 5).
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Webb, J. E., C. C. Brunson, and J. D. Yates, 1973. Effects of feeding fish meal and tocopherol on flavor of precooked, frozen turkey meat. Poultry Sci. 52:1029-1034. Wilson, B. R., A. M. Pearson, and F. B. Shorland, 1976. Effect of total lipids and phospholipids on warmed-over flavor in
red and white muscle from several species as measured by thiobarbituric acid analysis. J. Agric. Food Chem. 24:7-11. Wolterink, L. F., J. A. Davidson, and E. P. Reineke, 1947. Hemoglobin levels in the blood of Beltsville small white poults. Poultry Sci. 26:559. (Abstr.)
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{Key words: turkey, iron, dietary vitamin E, meat oxidative stability, storage duration) 1996 Poultry Science 75:1039-1046
INTRODUCTION Turkey meat is prone to oxidative rancidity during frozen storage (Wilson et al., 1976). This sensitivity is particularly pronounced in the dark meat (Webb et al, 1973; Wilson et al, 1976). Dietary vitamin E has been reported to reduce or prevent the process of lipid oxidation occurring in turkey meat during storage, as indicated by the thiobarbituric acid test (Webb et al, 1973; Marusich et al, 1975; Bartov et al, 1983). Iron mainly in its free ionic form (Kanner et al, 1988; Ahn et al, 1993), or as heme proteins (Johns et al, 1989) plays an important role in the process of lipid oxidation
Received for publication September 18, 1995. Accepted for publication April 12, 1996. Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel, Number 1718-E, 1995 series.
in meat. Nevertheless, the effect of dietary Fe level on the stability of meat from farm animals has hardly been investigated. Kanner et al. (1990) reported that removal of the Fe supplement (25 mg/kg) from the diet fed to turkeys 3 to 7 wk prior to slaughter improved the oxidative stability of their meat. Iron overload, either applied directly to liver slices or by injection of Fe-dextran, was reported to increase oxidation damage in chicks (Andersen et al, 1993). The extent of this damage was less in birds fed a vitamin Esupplemented diet than in those fed an unsupplemented diet. Toxic damage, mortality, and reduction in hepatic vitamin E stores in mice due to Fe overload, either by the diet or by injection, were partly ameliorated by vitamin E (Omara and Blakley, 1993). In the present study, the combined effect of excess Fe (supplemented through the diet or by injection) and dietary vitamin E level on the oxidative stability of turkey meat was determined.
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ABSTRACT A study was carried out to evaluate the combined effect of excess Fe, supplied either in the diets (Experiments 1, 2, and 3) or by injection (Experiment 4), and various levels of dietary vitamin E on the oxidative stability of the thigh muscle of turkeys stored at -18 C for various periods. Iron was added to a commercial diet that already contained 20 mg/kg supplemental Fe, at concentrations of 0, 100, 250, and 500 mg/kg as ferrous sulfate or injected as Fe-dextran to the left drumstick muscle (total amount of 1.2 g per turkey). Vitamin E was added to the experimental diets not already supplemented with this vitamin, at levels of 0, 28, and 150 mg/kg. Thiobarbituric acid reactive substances (TBARS) values of the meat gradually increased as its storage duration increased from about 15 to 120 d. Increasing dietary Fe supplementation from 0 to 500 mg/kg tended to decrease TBARS values in one experiment only; otherwise, this variable was not affected by dietary Fe level. Injection of Fe significantly (P < 0.05) increased TBARS values, only in meat from the injected side.
BARTOV AND KANNER
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MATERIALS AND METHODS Birds and Diets
Experiment 1 The combined effects of the supplementation of the basal diets with four levels of Fe (0,100,250, and 500 mg/ kg) and two levels of vitamin E (0 and 28 mg/kg) on meat oxidative stability were evaluated. The four Fe treatments started with 7-d-old birds, two groups per treatment, and the two vitamin E treatments at 70 d of age. In order to prevent possible damage to the young birds, the feeding of the highest level of Fe started only at 4 wk of age. Up to that age the birds allotted to this treatment were fed on the diet containing 250 mg Fe/kg. The birds were slaughtered at 162 d of age. The thiobarbituric acid reactive substances (TBARS) values of the meat were determined after 25 and 120 d of storage.
Experiment 2 The combined effects of the supplementation the basal diet with three levels of Fe (0, 250, and 500 mg/kg) and two levels of vitamin E (0 and 28 mg/kg) on meat oxidative stability were evaluated in order to confirm the results of Experiment 1 (see below). The three Fe treatments started with 7-d-old birds, two groups per treatment, and the two vitamin E treatments at 59 d of age. The treatment with the highest level of Fe started at 28 d of age (as described above). The birds were slaughtered at 158 d of age. The TBARS values of the meat were determined after 37 and 45 d of storage.
Experiment 3 Management Individual body weights were recorded bi-weekly and feed consumption data were obtained at the same times, on a group basis. Blood was taken from the brachial vein with a heparinized syringe at 70,91,84, and 84 d of age in Experiments 1, 2, 3, and 4, respectively, and at the termination of the experiments, for the determination of hemoglobin content. At 22 to 23 wk of age, five birds from each treatment of Experiments 1, 2, and 3, whose body weights were within ± 7.5% of the treatment average and four birds from each treatment of Experiment 4 (see below) were slaughtered. The meat of the thigh (the muscles around the femur) was removed, chilled on ice, and kept as is in polyethylene bags under natural
2
Fluka Chemie AG CH-9470, Buchs, Switzerland. ROVIMIX E-50 SD; Hoffmann-La Roche CH-4002, Basel, Switzerland. *Fe-dextran; The Butler Co., Columbus, OH 43228. 3
The combined effects of the supplementation of the basal diets with two levels of Fe (0 and 500 mg/kg), and three levels of vitamin E (0, 28, and 150 mg/kg) on meat oxidative stability were evaluated. The two Fe treatments started with 28-d-old birds, three groups per treatment, and the three vitamin E treatments at 56 d of age. The birds were slaughtered at 154 d of age. The TBARS values of the meat were determined after 28 and 101 d of storage.
Experiment 4 The combined effects of the supplementation of the basal diets with two levels of vitamin E (0 and 150 mg/kg) and the injection of iron hydrogenated dextran4 on meat stability were evaluated. Twenty 7-d-old birds were fed the basal diets up to 56 d of age. They then were divided, as mentioned above, into two groups and were fed the two diets differing in vitamin E content. At 84 d of age, two birds (the lightest ones) from each of the vitamin E treatments were removed. The remaining birds were
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Day-old males of a large strain of Broad Breasted White turkeys (British United Turkeys, T6) were raised in electrically heated battery brooders placed in a temperature-controlled room at 25 ± 2 C up to 28 d of age, and then in individual cages with wire floors in a temperature-controlled (22 ± 2 C) building. Twenty-four hours of light were provided in both rooms. The basal diets, composed mainly from sorghum grains, yellow corn, soybean meal, and acidulated soybean oil soapstock, were formulated for the age periods 0 to 4,4 to 8,8 to 12,12 to 16, 16 to 20, and 20 to 24 wk, according to National Research Council (1984) recommendations. The mineral and vitamin mixes provided 20 mg Fe, 28 mg vitamin E, and 125 mg ethoxyquin/kg diet. After a preparatory period of 7 d, two-thirds of the birds (those closest to the average weight) were wing-banded and divided according to body weight into groups of 10 birds each. Mean group weights and within-group individual weight distributions were the same for all groups. Two of three such groups were assigned to the dietary Fe treatments, which started at 7 or 28 d of age (see below). Iron was supplemented to the basal diet as ferrous sulfate.2 The treatments with vitamin E were started at about 8 wk of age when the birds within each of the Fe treatments were divided into two or three subgroups, as mentioned above, and allotted to the vitamin E treatments. Thus, in each experiment, the combined treatment of dietary Fe and vitamin E was given to one group of 10 birds each. Vitamin E supplied as DL-a-tocopheryl acetate3 was added to the experimental diets whose vitamin mix did not contain vitamin E and ethoxyquin, but supplied 125 mg butylated hydroxytoluene/kg diet. The experimental diets were consumed ad libitum in mash form.
atmosphere at -18 C for various periods for the determination of its oxidative stability. Before these determinations the frozen meat was transferred to room temperature for 2 h and then to 3 C for 18 h. After sampling it was stored again at -18 C.
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IRON, VITAMIN E, AND MEAT STABILITY TABLE 1. Effect of various dietary iron supplementations (Fe-Sup) on the concentrations of blood hemoglobin of turkeys at different ages, Experiments 1 to 41 Experiment no.
Blood hemoglobin
Fe-sup
SEM
(mg/kg)2 0 100 250 500 SEM Age average
SEM Age average 0 500
SEM Age average 0 12003 SEM Age average
162 d 13.8c 14.5^ 15.6» 14.8»b 0.30 14.3*
0.25
158 d 13.8 14.2 13.8 0.41 13.9A
0.19
84 d
154 d 12.2 11.8 0.26 12.0A 112 d
10.4 10.8 0.35 10.6B
11.7 12.4 0.31 12.0A
0.15
0.23
a_c
Values in the same column of each experiment with no common superscript differ significantly (P < 0.05). ' Values in each experiment with no common superscript differ significantly (P < 0.001). x Means of 10 and 8 turkeys in Experiments 1 to 3 and Experiment 4, respectively. 2 The basal diets contained 20 mg Fe/kg supplemented by the mineral mix. 3 This amount of Fe was injected as Fe-dextran, at 85, 90, 100, and 105 d of age. AB
again reallocated within each of the vitamin E treatments to create four groups of four birds each. The Fe-dextran (100 mg Fe/mL) was injected into the left drumstick (1,2, 2.5, 3, and 3.5 mL per bird, at 85, 90, 95,100, and 105 d of age, respectively) to one group of birds on each of the vitamin E treatments. The other groups of birds were injected at the same time with the same amounts of saline. The birds were slaughtered 7 d after the last injection, at 112 d of age. The TBARS values of the meat from the right and the left thighs were determined during storage that lasted up to 108 d.
Chemical Determination The oxidative stability of the meat was evaluated by the thiobarbituric acid test before and after incubation, as described by Machlin et al. (1959) except that cold water was used during homogenization (Desai and Scott, 1966). The developing color of the TBARS, measured by a spectrophotometer,5 was related to a standard curve of malonaldehyde bis-bisulfite sodium salt prepared according to Saslaw and Waravdekar (1957) and expressed as milligrams per kilogram of tissue. The TBARS values determined before the incubation (initial levels) represent
sSequoia-Turner Corp., Mountain View, CA 94043.
the oxidative stability of the meat during frozen storage, whereas the values observed after this step represent its oxidative stability during an accelerated oxidation test. Blood hemoglobin concentration was determined according to Sigma Chemical Co. (1984).
Statistical Analysis The individual bird was used as the experimental unit. Factorial ANOVA was carried out, for each experiment separately, according to Snedecor and Cochran (1967). The main factors tested were the levels of dietary Fe and vitamin E (Experiments 1, 2, and 3), Fe-dextran injection, and dietary vitamin E level (Experiment 4). Data of the meat from the right and left thighs obtained in the last experiment were separately analyzed. Difference among treatment and factor means were determined by Duncan's multiple range test (1955), at a significance of level 5%.
RESULTS Experiment 1 The treatments did not affect body weight throughout the experiment, the average value at 162 d of age was 16.89 kg. Blood hemoglobin, in the present and the other experiments, was not affected by dietary vitamin E levels, therefore only the effect of Fe is detailed (Table 1). At 70
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0 250 500
70 d 8.9" ND ND 10.1» 0.25 9.5B 91 d 10.6 10.9 11.1 0.26 10.9B 84 d 10.6 11.0 0.19 10.8B
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BARTOV AND KANNER TABLE 2. Effect of various levels of dietary iron supplementation (Fe-sup) and vitamin E (Vit. E) on the thiobarbituric acid reactive substances (TBARS) of thigh meat during storage, Experiment l 1 Storage duration 3 25 d
Dietary variables 2 Fe-sup
0 28 0 28 0 28 0 28
Initial level
After incubation 4
2.97" 1.83* 2.16* 1.67* 2.16* 0.83b 1.32* 0.57b 0.58
28.6" 30.4' 26.9* 26.8* 23.7* 18.1b 17.7b 17.3b 3.37
2.40 1.91 1.49 0.94 0.10
29.5" 26.9* 20.9bc 17.5' 0.01
6.58 5.43 5.73 6.06 NS
32.1 32.0 31.2 29.6 NS
2.15 1.22
24.2 23.1 NS
5.85 6.05 NS
30.6 31.9 NS
0.05
Initial level
• (TBARS values^ 6.38 6.78 4.86 6.00 6.24 5.22 5.92 6.20 0.866
After incubation 31.6 32.7 28.1 36.0 32.6 29.9 30.2 29.0 2.32
'"Values with no common superscript differ significantly (P < 0.05). M e a n s of 5, 10, and 20 turkeys per treatment, Fe level, and Vit. E level, respectively. 2 The basal diet contained 20 mg Fe/kg supplemented by the mineral mix, but not Vit. E supplement. 3At -18 C. 4 In water bath at 37 C for 1 h under constant shaking. 5 Expressed as milligrams sodium salt of malonaldehyde-bis-bisulfite per kilogram meat.
and 162 d of age, birds fed the unsupplemented diet had significantly lower concentrations of hemoglobin than those fed the diets supplemented with 250 or 500 mg Fe/ kg. Intermediate concentrations were observed in birds fed the diet supplemented with 100 mg Fe/kg. Hemoglobin concentrations increased significantly (P < 0.001) with age. The effects of the treatments on meat oxidative stability are summarized in Table 2. Supplementation of the diets with Fe decreased, at times significantly, the TBARS values (initial and after incubation) determined after 25 d of storage. This effect of Fe was proportional to the level of its supplementation, and a significant effect was observed in meat of birds fed the diets supplemented with either 250 or 500 mg Fe/kg (TBARS values after incubation, on a factorial basis); however, after an additional 95 d this protective effect of Fe disappeared. Vitamin E supplementation significantly reduced initial TBARS values (on a factorial basis) after 25, but not 120 d of storage. At both periods it had no effect on TBARS values observed after incubation. Initial TBARS values markedly increased during the additional 95 d of storage.
Experiment 2 Neither of the treatments nor the factors affected body weight at 158 d of age, the average value was 15.59 kg.
Blood hemoglobin concentrations were also unaffected at 91 and 158 d of age by the level of Fe supplementation, but the concentrations observed in the older birds were significantly (P < 0.001) higher than those of the younger ones (Table 1). The TBARS values, after the two periods of storage, were not significantly affected by either of the treatments or any of the factors evaluated, in contrast with the results of Experiment 1 (data not detailed for the sake of brevity). As in the previous experiment, initial TBARS values were markedly increased during the additional storage (1.42 and 2.45 after 37 and 45 d of storage, respectively).
Experiment 3 The various dietary treatments did not affect body weight at 154 d of age (average value 15.85 kg), as well as blood hemoglobin concentrations at 84 and 154 d of age (Table 1). Blood hemoglobin levels increased slightly, but significantly (P < 0.001), with age. Supplementation of the diets with 500 mg Fe/kg had no effect on meat oxidative stability (Table 3). Vitamin E supplementation at a level of 150 mg/kg significantly reduced the level of oxidation of the meat after 28 d of storage (initial and postincubation TBARS) (Table 3). This effect was still evident, although by then not significant, after 101 d of storage. There was no
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(mg/kg) 0 0 100 100 250 250 500 500 SEM Factorial effects Fe-sup 0 100 250 500 P< Vit. E 0 28 P<
Vit. E
120 d
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IRON, VITAMIN E, AND MEAT STABILITY TABLE 3. Combined effect of two levels of dietary iron supplementation (Fe-sup) and three levels of vitamin E (Vit E) on the thiobarbituric acid reactive substances (TBARS) of thigh meat during storage, Experiment 31 Storage duration 3 101 d
28 d Dietary variables 2 Vit. E
0 0 0 500 500 500 SEM Factorial effects Fe-sup 0 500 P<
0 28 150 0 28 150
Vit. E 0 28 150 P<
Initial level
After incubation 4
Initial level
2.28» 1.171> 1.31ab 1.88ab 1.68»b 1.13b 0.38
18.4 17.1 12.5 17.7 15.4 13.2 2.38
6.63» 4.92>b 4.72* 5.18 ab 4.71* b 2.77b 1.06
1.59 1.56 NS
16.0 15.4 NS
5.42 4.22 NS
2.08' 1.42ab 1.22b
18.1* 16.2"b 12.8b 0.05
5.90 4.81 3.74
0.05
NS
ab
' Values with no common superscript differ significantly (P < 0.05). Means of 5, 10, and 15 turkeys per treatment, Vit. E level, and Fe-sup, respectively. 2 The basal diet contained 20 mg Fe/kg supplemented by the mineral mix, but not Vit. E supplement. 3At -18 C. 4 In water bath at 37 C for 1 h under constant shaking. 5 Expressed as milligrams sodium salt of malonaldehyde-bis-bisulfite per kilogram meat. 1
significant difference in TBARS values of meat from turkeys fed diets supplemented with either 28 or 150 mg vitamin E/kg; however, the factorial effect of vitamin E supplementation at a level of 28 m g / k g was not significant.
Experiment 4 The various treatments did not affect body weight at 112 d of age (average value 10.52 kg) or blood hemoglobin concentrations (Table 1). Blood hemoglobin concentrations were significantly (P < 0.001) increased with age. Vitamin E supplementation consistently improved the oxidative stability of the meat of the right and the left thighs evaluated without or with incubation u p to 108 d of storage and, on a factorial basis, in most cases the improvement was significant (Tables 4 and 5). The injection of Fe-dextran into the left drumstick significantly decreased initial TBARS values in meat from the right thigh of birds fed the diet without vitamin E supplementation, as determined after 15 d of storage. This unexplained effect was not observed in birds fed the vitamin Esupplemented diet. That effect in turn resulted in a significant interaction between vitamin E and Fe injection (Table 4). However, the factorial effect of the latter on TBARS values was consistently not significant. On the other hand, Fe injection significantly increased initial and
postincubation TBARS values of the meat from the left thigh of birds fed the diets containing each level of vitamin E, determined after 23 and 36 d of storage (Table 5). This effect of Fe disappeared after 107 d of storage, by which time initial TBARS values were markedly increased in all the treatments, as in the previous experiments.
DISCUSSION Data obtained in Experiment 4, in which Fe injected to the left drumstick decreased the oxidative stability of thigh meat of the same side (Table 5) clearly demonstrate that Fe does play an important role in inducing lipid oxidation in meat, in agreement with Ahn et al. (1993), who added Fe directly to meat homogenate. However, the data also show that this effect of Fe was limited only to the thigh of the injected side and was not observed in the other thigh (Table 4). Moreover, relatively high levels of dietary Fe consistently did not reduce meat oxidative stability (Tables 2 and 3, and Experiment 2). The lack of effects of Fe injection into the left drumstick or of a high dietary Fe level, on the oxidative stability of the thigh meat (the right one in the case of Fe injection) was probably due to the fact that these treatments did not increase muscle Fe content despite their effect of increasing liver Fe concentration by about 23% (Kanner et al, 1995). In other words, it
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Fe-sup
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BARTOV A N D K A N N E R TABLE 4. Effect of dietary vitamin E (Vit E) level and Fe-dextran injections on the thiobarbituric acid reactive substances (TBARS) of meat from the right thigh (the uninjected side) during storage, Experiment 4 1 Storage duration 3 30 d
15 d Treatment 2 Dietary Vit. E
Initial level
After incubation 4
Initial level
After incubation
Initial level
(TBARS values) 5 No Yes No Yes
1.08" 0.41b 0.06b 0.16b 0.159
18.0" 18.9» 6.0b 11.7* 2.81
2.20" 2.17" 0.14b 0.37b 0.389
20.3* 22.8" 5.0= 12.4b= 2.62
5.21» 4.56<»b 2.58b 2.88* 0.758
0.74 0.11 0.01
18.4 8.8 0.01
2.18 0.26 0.001
21.6 8.7 0.001
4.88 2.73
0.57 0.28
12.0 15.3
1.17 1.27
12.6 17.6
3.89 3.72
NS
NS
NS
NS
NS
0.05
NS NS 0.05 NS NS Values with no common superscript differ significantly (P < 0.05). 1 Means of 4, 8, and 8 turkeys per treatment, Vit. E level, and Fe-dextran injection, respectively. 2 The basal diet contained 20 mg Fe/kg supplemented by the mineral mix, but not Vit. E supplement. Vitamin E treatments were given from 56 to 112 of age and Fe-dextran injections (to the left drumstick) from 84 to 105 d of age. 3 At -18 C. 4 In water bath at 37 C for 1 h under constant shaking. 5 Expressed as milligrams sodium salt of malonaldehyde-bis-bisulfite per kilogram meat. a_c
TABLE 5. Effect of dietary vitamin E (Vit E) level and Fe-dextran injections on the thiobarbituric acid reactive substances (TBARS) of meat from the left thigh (the injected side) during storage, Experiment 4 1 Storage duration 3
Dietary Vit. E
Fe-dextran
Initial level
After incubation 4
(mg/kg) 0 0 150 150 SEM Factorial effects Vit. E 0 150 P< Fe-dextran No Yes P< a b
No Yes No Yes
107 d
36 d
23 d Treatment 2
0.53b 2.10» 0.30b 0.97* 0.46
14.1* 22.9" 5.9' 16.9* 2.76
1.31 0.63 NS
18.5 11.4
0.41 1.53 0.05
Initial level (TBARS values) 5 1.15b 4.34" 0.24b 1.66* 0.99
After incubation
Initial level
15.7b 28.4" 6.7b 17.3b
6.55* 9.77' 5.38* 4.07b 1.45
3.38
8.16 4.72
22.0 12.0
0.05
2.74 0.95 NS
0.05
0.05
10.0 19.9 0.01
0.69 3.00 0.05
11.2 22.8 0.01
5.96 6.92 NS
- Values with no common superscript differ significantly (P < 0.05). Means of 4, 8, and 8 turkeys per treatment, Vit. E level, and Fe-dextran injection, respectively. 2 The basal diet contained 20 mg Fe/kg supplemented by the mineral mix, but not Vit. E supplement. Vitamin E treatments were given from 56 to 112 of age and Fe-dextran injections (to the left drumstick) from 84 to 105 d of age. 3 At -18 C. 4 In water bath at 37 C for 1 h under constant shaking. Expressed as milligrmas sodium salt of malonaldehyde-bis-bisulfite per kilogram meat. 1
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(mg/kg) 0 0 150 150 SEM Factorial effects Vit. E 0 150 P< Fe-dextran No Yes P< Vit. E x Fe-dextran P<
Fe-dextran
108 d
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IRON, VITAMIN E, AND MEAT STABILITY
Although the calculated Fe content of our basal diets, which consisted of common feedstuffs and supplemented with 20 mg Fe/kg by the mineral mix, was above the Fe requirement of the turkeys, blood hemoglobin concentrations in Experiment 1 were significantly increased by the supplementation of the diet with 250 and 500 mg Fe/kg (Table 1). It is difficult to explain this phenomenon, but it indicates that under certain conditions, increased Fe supplementation to commercial diets is necessary for maximal hemoglobin production. Blood hemoglobin concentrations consistently and significantly increased with age, in agreement with Wolterink et al. (1947). This study was not intended to evaluate the effect of high levels of dietary ferrous sulfate on the performance of turkeys. However, the data demonstrate that this compound, at a dietary level of 2.39%, has no adverse effects. Pescatore and Harter-Dennis (1989) observed that ferrous sulfate at a dietary level of 3% significantly decreased weight gain in broiler chicks. The results show that the oxidative stability of the turkey meat is not adversely affected by high levels of dietary Fe. However, Fe injection may reduce the stability of the meat sampled close to the injection site.
ACKNOWLEDGMENTS This study was supported by a grant from the United States-Israel Binational Agricultural Research and De-
velopment Fund (BARD), Project No. IS-1644-89. The authors are indebted to M. Ben-Mosheh, for technical assistance.
REFERENCES Ahn, D. U., F. H. Wolfe, and J. S. Sim, 1993. The effect of free and bound iron on lipid peroxidation in turkey meat. Poultry Sci. 72:209-215. Andersen, H. J., H. Chen, L. J. Pellett, and A. L. Tappel, 1993. Ferrous-iron-induced oxidation in chicken liver slices as measured by hemichrome formation and thiobarbituric acid-reactive substances: Effects of dietary vitamin E and /3-carotene. Free Radical Biol. Med. 15:37-48. Bartov, I., D. Basker, and S. Angel, 1983. Effect of dietary vitamin E on the stability and sensory quality of turkey meat. Poultry Sci. 62:1224-1230. Desai, I. D., and M. L. Scott, 1966. Bioassays for orally administered and injected tocopherols: A relationship with tissue peroxidizabiiity and lysosomal enzymes. Pages 643-649 in: Proceeding of the 7th International Congress of Nutrition. Vol. 5. Hamburg, Germany. Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics 11:1-42. Johns, A. M., L. H. Birkinshaw, and D. A. Ledward, 1989. Catalysts of lipid oxidation in meat products. Meat Sci. 25: 209-220. Kanner, J., I. Bartov, M. O. Salan, and L. Doll, 1990. Effect of dietary iron level on in situ turkey muscle lipid peroxidation. J. Agric. Food Chem. 38:601-604. Kanner, J., B. Hazen, and L. Doll, 1988. Catalytic "free" iron ions in muscle foods. J. Agric. Food Chem. 36:412-415. Kanner, J., D. D. Miller, I. Bartov, and S. Harel, 1995. Effect of dietary iron on lipid peroxidation of muscle food. Final Report to the United States-Israel Binational Agricultural Research and Development Fund (BARD), Project No. IS1644-89. Machlin, L. J., R. S. Gordon, and K. H. Meisky, 1959. The effect of antioxidants on vitamin E deficiency symptoms and production of liver "peroxide" in the chicken. J. Nutr. 67: 333-343. Marusich, W. L., E. De Ritter, E. F. Ogrinz, J. Keating, M. Mitrovic, and R. H. Bunnell, 1975. Effect of supplemental vitamin E in control of rancidity in poultry meat. Poultry Sci. 54:831-844. National Research Council, 1984. Nutrient Requirements of Poultry. 8th rev. ed. National Academy Press, Washington, DC. Omara, F. O., and B. R. Blakely, 1993. Vitamin E is protective against iron toxicity and iron-induced hepatic vitamin E depletion in mice. J. Nutr. 123:1649-1655. Pescatore, A. J., and J. M. Harter-Dennis, 1989. Effects of ferrous sulfate consumption on the performance of broiler chicks. Poultry Sci. 68:1063-1067. Saslaw, L. D., and V. S. Waravdekar, 1957. Preparation of malonaldehyde bis-bisulfite sodium salt. J. Org. Chem. 22: 843-844. Sigma Chemical Co., 1984. Total hemoglobin: Quantitative colorimetric determination in whole blood at 530-550 nm. Procedure No. 525. Sigma Chemical Co., St. Louis, MO. Snedecor, G. D., and W. G. Cochran, 1967. Statistical Methods. 6th ed. Iowa State University Press, Ames, IA.
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seems that Fe overload in the turkey caused either by high levels of dietary Fe or by Fe injection and evaluated from liver Fe content, did not play an important role in the process of muscle lipid oxidation. The finding that increasing the dietary Fe level tended to increase meat oxidative stability (Experiment 1, Table 2) is worth noting. However, this observation was not confirmed in Experiments 2 and 3 (text and Table 3). Moreover, the data of the present study do not support our initial hypothesis, based on a previous study (Kanner et al., 1990), that a high level of dietary Fe may decrease meat oxidative stability. Meanwhile, we have no explanation for these disagreements; however, they probably emphasize the complexity of this subject. Dietary vitamin E supplementation at a level of 28 m g / k g diet significantly improved the oxidative stability of thigh meat after relatively short storage in only one out of three experiments (Tables 2 and 3 and text), whereas at a level of 150 m g / k g , it significantly improved this stability in the two experiments in which it was used (Tables 3, 4, and 5). However, it is worth noting that the difference between the effect of these two levels of dietary vitamin E on meat oxidative stability was not significant (Table 3). In other words, the great difference between these two levels of vitamin E was hardly evident in terms of TEARS values. Nevertheless, it is worth noting that in spite of the marked increase in TBARS values during storage, the beneficial effect of the high level of vitamin E in improving meat oxidative stability was evident, at times significantly, also after 101 to 108 d of storage (Tables 3, 4, and 5).
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BARTOV AND KANNER
Webb, J. E., C. C. Brunson, and J. D. Yates, 1973. Effects of feeding fish meal and tocopherol on flavor of precooked, frozen turkey meat. Poultry Sci. 52:1029-1034. Wilson, B. R., A. M. Pearson, and F. B. Shorland, 1976. Effect of total lipids and phospholipids on warmed-over flavor in
red and white muscle from several species as measured by thiobarbituric acid analysis. J. Agric. Food Chem. 24:7-11. Wolterink, L. F., J. A. Davidson, and E. P. Reineke, 1947. Hemoglobin levels in the blood of Beltsville small white poults. Poultry Sci. 26:559. (Abstr.)
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