Agricultural and Food Science in Finland 9 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 8 (1999): 9–18. © Agricultural and Food Science in Finland Manuscript received December 1998 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 8 (1999): 9–18. Effect of supplemental vitamin E on the performance of growing-finishing pigs fed stored versus freshly harvested barley and on the storage stability and eating quality of frozen pork Kaija Suomi Agricultural Research Centre of Finland, Animal Production Research, Pigs, Tervamäentie 179, FIN-05840 Hyvinkää, Finland, e-mail: kaija.suomi@mtt.fi Kirsi Partanen Agricultural Research Centre of Finland, Animal Production Research, Animal Nutrition, FIN-31600 Jokioinen, Finland Timo Alaviuhkola, Hilkka Siljander-Rasi Agricultural Research Centre of Finland, Animal Production Research, Pigs, Tervamäentie 179, FIN-05840 Hyvinkää, Finland Satu Sankari University of Helsinki, Faculty of Veterinary Medicine, Department of Clinical Veterinary Medicine, PO Box 57, FIN-00014 University of Helsinki, Finland A 2 × 4 factorial experiment was conducted with 80 growing-finishing pigs to evaluate effects of barley storage (stored barley harvested the previous year or freshly harvested barley) and supplemen- tal vitamin E (0, 40, 80 or 160 mg/kg as all-rac-α-tocopheryl acetate) on pig performance and the storage stability and eating quality of frozen pork. Pigs were fed isoenergetic barley-soybean meal diets and vitamin E was rationed on the top of feed, a 2-d dose at a time. Stored and freshly harvested barley contained 33.5 and 31.2 mg/kg of vitamin E in the beginning and 33.0 and 38.7 mg/kg at the end of the study, respectively. Supplemental vitamin E had a quadratic effect on pig growth (P < 0.05), the greatest weight gains being observed with 40 mg/kg of supplemental vitamin E in both barley diets. Vitamin E supplementation increased linearly serum (P < 0.001) and quadratically back fat α -tocopherol (P < 0.01). Plasma gluthathione peroxidase activity increased as pigs grew older (P < 0.001), and at slaughter it decreased linearly with supplemental vitamin E (P < 0.05). Dietary vitamin E supplementation did not affect the content of thiobarbituric acid reactive substances (TBARS) or the organoleptic quality of pork stored frozen (–18°C) for 16 weeks. The TBARS con- tent of pork increased with time (0 to 8 d) thawed meat was displayed under fluorescent light at 8°C (P < 0.001) which was detected as a poorer taste. In conclusion, supplemental dietary vitamin E above 40 mg/kg feed does not improve pig performance nor the storage stability or eating quality of frozen pork when freshly harvested or stored barley from good harvest conditions is fed to growing- finishing pigs. Key words: cereals, meat quality, oxidation, α-tocopherol mailto:kaija.suomi@mtt.fi 10 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Suomi, K. et al. Effect of vitamin E on pigs and frozen pork Introduction Traditionally, it is believed that freshly harvest- ed cereals have a low vitamin E content or that vitamin E is poorly available immediately after harvesting and drying. Dried, stored barley is however a good natural source of vitamin E. Vitamin E develops in barley during the milk ripeness stage, i.e. several weeks before harvest- ing, and the content is similar to that of fully matured barley (Kivimäe and Carpena 1973, Pohjanheimo et al. 1975). The vitamin E con- tent of cereal grains is influenced by several fac- tors, e.g. harvesting time, weather, drying, han- dling and storage time (Kivimäe and Carpena 1973). According to Hakkarainen et al. (1983b) the moisture content of stored grain is one of the critical factors affecting the vitamin E con- tent of grain. Eight isomers of vitamin E occur in nature, and α -tocopherol has the greatest vitamin E ac- tivity (Ullrey 1981). Generally, it is also the iso- mer which is analysed in feeds as well as being used for dietary supplementation (Ullrey 1981). According to Työppönen et al. (1988) α-toco- pherol isomer accounts for over 90% of vitamin E in pig tissue. The vitamin E in freshly harvest- ed barley is absorbed at a similar efficiency as that in stored barley or that as all-rac-α-tocoph- eryl acetate. Supplemental vitamin E resulted in similar tissue vitamin E concentrations in pigs, irrespective of the storage time of barley, and 40 mg/kg was enough to maintain serum vita- min E concentration at 0.3 mg α-tocopherol/g lipid (Työppönen et al. 1988). When barley from poor harvest year is fed to pigs, greater vitamin E supplementation may become necessary, be- cause the natural vitamin E content is lower than that in a crop harvested in good conditions (Hakkarainen et al. 1983a). In addition, both stress and dietary fat supplementation increase the vitamin E requirement of pigs (Ullrey 1981). Meat quality declines during the long term freezer storage of pork primarily due to fat oxi- dation (Pearson et al. 1977). This is because car- bonyl compounds that are formed in fat oxida- tion have strong off-flavours (Pearson et al. 1977). Dietary vitamin E supplementation has been shown to prevent the oxidation of unsatu- rated fatty acids and the formation of oxidation products in pork (Monahan et al. 1992b). The content of oxidation products in meat is meas- ured as thiobarbituric acid reactive substances (TBARS) (Astrup 1973). Abundant vitamin E supplementation (100 to 200 mg/kg) as all-rac- α-tocopheryl acetate has decreased TBARS con- tent and thus oxidation risk in pork during freeze- storage (Monahan et al. 1992a). The aim of this study was to investigate whether growing-finishing pigs require addition- al vitamin E supplementation, i.e. above 40 mg/ kg feed, when they are fed freshly harvested or stored barley and to evaluate the effect of die- tary vitamin E supplementation on the storage stability and eating quality of frozen pork. Material and methods Animals, diets and measurements Eighty pigs (16 Yorkshire, 25 Landrace and 39 crossbred) of initial body weight 26.6 ± 0.65 kg were used in a 2 × 4 factorial growth experiment (5 gilts and 5 barrows per treatment) in two ran- domised blocks, with each block consisting of 40 pigs (the distribution of races was 7 + 13 + 20 or 9 + 12 + 19 per block, respectively). The factors were barley storage (stored or freshly harvested) and dietary vitamin E supplementa- tion (0, 40, 80 or 160 mg/kg in the form of all- rac-α -tocopheryl acetate). Prior to this study, pigs received barley-oats-fish meal-soybean meal diet with 25 mg/kg of supplemental vita- min E. Experimental diets consisted of stored or freshly harvested barley and soybean meal as the protein source (Table 1). Both barleys were of variety ‘Pohto’. Stored barley was produced in 1993 and freshly harvested barley in 1994, both on the same field under good harvesting condi- tions. Pigs were fed twice a day according to a 11 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 8 (1999): 9–18. restricted age-based feeding scale (1.2 to 2.8 feed units/d) for 15 weeks. Vitamin E was given to pigs every second day on the top of feed, a 2-d dose at a time. Chemical analyses and organoleptic grading Feed ingredients were analysed for proximate composition according to standard procedures (AOAC 1990). Barleys were analysed for sele- nium according to Kumpulainen and Saarela (1992). Vitamin E isomers were determined in barleys at the beginning and the end of the study by high performance liquid chromatography (Pi- ironen et al. 1984). The total vitamin E content, i.e. as α-tocopherol equivalents, was calculated from different isomers according to McLaughin and Welhrauch (1979). Blood samples were taken from vena jugu- laris of three randomly selected gilts and two barrows per treatment before the experiment started, 30 d later and at slaughter (104 d). Plas- ma and serum was separated by centrifugation (3000 rpm for 10 minutes) and serum was ana- lysed for α-tocopherol (Biesalski et al. 1986) and plasma for gluthathione peroxidase (GSH-Px) activity (Günzler et al. 1974). Samples were also taken from the back fat of the same animals at slaughter and analysed for α-tocopherol content by high performance liquid chromatography us- ing fluorescence detection (Biesalski et al. 1986). Six 1.5-cm thick samples were cut from the long- issimus muscle of two gilts and three barrows per vitamin E level (same animals as before). Meat samples were vacuum packed and stored frozen (–18°C) for 16 weeks, after which they were thawed at 4°C for 18 h, removed from the vacuum package, and kept under fluorescent light (Philips DLD 58 W/86 5 ) at 8°C for 0, 3 or 8 d. Meat samples were fried and graded for or- ganoleptic quality (taste, tenderness and juici- ness) by a five member panel using a seven point scale (7 was the best and 1 the poorest score ) as described by Siljander-Rasi et al. (1996) and analysed for TBARS using the procedure of Pikul et al. (1989) incorporating the modifica- tions of Yoshida et al. (1990) and Halliwell and Chirico (1993). In this analysis, thiobarbituric acid (TBA) reacts with fat oxidation products, such as malonaldehyde. A minced 10-g meat sample, 1 ml of 0.3% butylhydroxytoluene-eth- anol solution (w/v) and 40 ml of cold (4°C) 10% trichloroacetic acid (TCA) solution (w/v) were mixed (Ultra turrax T25, Janke & Kunkel) in a 50 ml bottle for 2 min (13 000 rpm). The sus- pension was rinsed from the mixer with 2 ml of TCA-solution and from the bottle with 5 ml of distilled water to a centrifuge tube and centri- fuged (3000 rpm) for 5 min. The supernatant was filtered through Whatman no 1 paper and dilut- ed to 50 ml with 10% TCA-solution. Then 5 ml Table 1. Formulation and chemical composition of experi- mental diets. SB-diet FHB-diet Ingredient composition, g/kg Stored barley (SB) 779 – Freshly harvested barley (FHB) – 779 Soybean meal 185 185 Mineral-vitamin mix.1 35 35 L-lysine-HCl 1 1 Calculated chemical composition Dry matter, g/kg 868 873 Net energy, FU/kg2 0.91 0.91 Crude protein, g/FU 169 180 Crude fat, g/FU 21.4 23.2 Lysine, g/FU 9.1 9.6 Ileal digestible lysine, g/FU 7.5 7.8 Calcium, g/FU 9.7 9.7 Phosphorus, g/FU 7.8 7.8 Selenium, mg/FU 0.3 0.3 Vitamin E, mg/FU 30.7 28.6 (= α-tocopherol equivalents) 1 Provided per kg diet: 7.9 g Ca, 3.5 g P, 0.4 g Mg, 3.6 g NaCl, 105 mg Fe, 95 mg Zn, 46 mg Mn, 31 mg Cu, 1.2 mg Co, 0.2 mg I, 0.1 mg Se, 5000 IU vitamin A, 800 IU vita- min D 3 , 2 mg thiamine, 7 mg riboflavine, 4 mg pyridoxine, 40 mg nicotinic acid, 15 mg pantothenic acid, 4 mg folic acid, 140 µg biotin, 20 µg vitamin B 12 . 2 FU = feed unit. 1 FU = 9.3 MJ net energy, calculated according to Tuori et al. (1995) based on published digest- ibility coefficients. 12 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Suomi, K. et al. Effect of vitamin E on pigs and frozen pork of this solution and 5 ml of 0.02 M TBA-solu- tion were incubated in a 90°C water bath for 30 min. After being cooled down (10 min under run- ning tap water) and filtered through 0.2 mm fil- ter, absorbance was measured with a spectropho- tometer at 532 nm against a blank containing 5 ml of 10% TBA-solution and 5 ml of TBA-solu- tion prepared in a similar manner to samples. Statistical analysis Experimental data was analysed using the MIXED procedure of SAS (Littell et al. 1996) and covariance parameters were estimated us- ing residual maximum likelihood method. Per- formance and carcass data were analysed using the following mixed model (Snedecor & Cohran 1989): Y ijklm = µ + Bl i + B j + E k + (B × E) jk + S l + (B × S) jl + (E × S) kl + (B × E × S) ijkl + e ijklm , where Bl is the random effect of block, and B, E and S are fixed effects of barley, level of vitamin E supplementation and sex, respective- ly. The model for the statistical analysis of se- rum α-tocopherol content and enzyme activities, TBARS content and organoleptic quality of meat (mean score) was: Y ijklm = µ + B i + E j + (B × E) ij + e ijk + T l + (T × B) il + (T × E) jl + (T × B × E) ijl + e ijklm , where B, E and T are the fixed effects of bar- ley, level of vitamin E supplementation and time, respectively. The effect of the level of the vita- min E supplementation was tested with orthog- onal polynomials (linear, quadratic and cubic ef- fect). Results Both stored and freshly harvested barley had a similar vitamin E content at the beginning of study (33.5 and 31.2 mg/kg, respectively, Table 2). Vitamin E content of stored barley changed only little (0.5 mg/kg) during the course of the study (nearly four months) whereas that of fresh- ly harvested barley increased by 7.5 mg/kg. The α-tocopherol content of barley changed in the same manner as the total vitamin E content. Ba- sal stored and freshly harvested barley diets con- tained 27.7 and 25.9 mg/kg of vitamin E in the beginning, and 27.3 and 31.7 mg/kg at the end of the study, respectively. Both basal diets con- tained 0.3 mg/kg of selenium. Most pigs ate their diet willingly and were healthy. Two pigs fed stored barley diet without supplemental vitamin E, and one pig fed stored barley diet with 160 mg/kg of vitamin E had a lower feed intake during the middle and end of the study, respectively. One pig fed stored bar- ley diet was found at slaughter to have pleurisy. Incremental dietary vitamin E level had a curvi- linear effect on weight gain (P < 0.05) and tend- ed to influence feed conversion ratio (P = 0.06, Table 3). The best performance was observed with 40 mg/kg of supplemental vitamin E. The storage of barley did not affect pig performance (P > 0.05). Pigs ate slightly more dry matter for stored barley diets than those based on freshly harvested barley due to a higher dry matter con- tent of the former. There were no differences in energy intake. Carcass quality did not differ be- tween treatments. Dietary vitamin E supplemen- tation had a cubic effect on back fat thickness (P < 0.05). Gilts grew faster and had less back fat and more lean in the carcass than barrows (P < 0.05). Before this trial, pigs had received a diet which contained only 25 mg/kg of supplemental vitamin E, reflected by low serum α-tocopherol content (1.1–1.6 mg/l) at the beginning of the study. Supplemental vitamin E increased linear- ly (P < 0.001) serum α-tocopherol concentration in samples taken 30 d after the beginning of the study and at slaughter (Fig. 1). The back fat α- tocopherol content increased linearly (P < 0.001) with incremental increases in dietary vitamin E supplementation. Although there were no differ- ences between stored and freshly harvested bar- ley diets in serum α-tocopherol concentration, 13 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 8 (1999): 9–18. Table 2. Content of vitamin E isomers and selenium in stored and freshly harvested barley at the beginning and the end of the experiment. Stored barley Freshly harvested barley beginning end beginning1 end α-tocopherol, mg/kg 17 15 15 18 α-tocotrienol, mg/kg 52 57 51 66 β-tocopherol, mg/kg 1 1 1 1 γ-tocopherol, mg/kg 4 4 4 4 γ-tocotrienol, mg/kg 6 5 5 7 δ-tocopherol, mg/kg 5 5 4 7 Total vitamin E, mg/kg 33.5 33.0 31.2 38.7 (= α-tocopherol equivalent) Selenium, mg/kg 0.09 0.10 Dry matter, g/kg 858.3 865.1 1 6 weeks post-harvest. Table 3. Performance and carcass quality of pigs receiving different vitamin E supplements and diets based on stored (SB) or freshly harvested barley (FHB). Vitamin E-suppl., mg/kg Signif. of vitamin E1 Barley 0 40 802 1603 SEM Lin. Quadr. Cubic SB FHB4 SEM Signif.1 N 20 20 20 20 40 40 Final weight, kg 110.4 113.5 112.0 109.7 1.15 NS * NS 111.3 111.5 0.81 NS Weight gain, g/d 803 833 823 805 10.0 NS * NS 819 813 7.1 NS Feed consumption, kg DM/pig 206 207 207 207 0.6 NS NS NS 206 207 0.4 * FU/pig 215 216 215 216 0.6 NS NS NS 215 216 0.5 NS Feed conversion ratio, FU/kg 2.58 2.50 2.53 2.58 0.031 NS NS NS 2.54 2.56 0.022 NS Number of pigs 10 10 11 11 22 20 Carcass weight, kg 83.7 85.4 85.0 81.8 1.39 NS NS NS 83.7 84.2 0.94 NS Back fat thickness, mm 25 26 23 28 1.3 NS NS NS 27 24 0.9 NS Side fat thickness, mm 16 19 16 18 1.1 NS NS * 18 16 0.8 NS Firmness of fat (score 9–15) 13.5 14.0 12.7 14.2 0.36 NS * ** 13.6 13.6 0.27 NS Lean in carcass, % 57.1 56.5 57.7 56.5 0.55 NS NS NS 57.0 56.9 0.37 NS Colour of meat Minolta (Light) 52.9 54.8 53.7 52.1 1.53 NS NS NS 52.9 53.9 1.24 NS DM = dry matter, FU = feed unit. 1 Significance: NS = non-significant, * (P<0.05), ** (P<0.01). 2 SEM value for carcass traits is 0.962 times the value given in the table. 3 SEM value for carcass traits is 0.954 times the value given in the table. 4 SEM value for carcass traits is 1.045 times the value given in the table. 14 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Suomi, K. et al. Effect of vitamin E on pigs and frozen pork pigs fed FHB-diets tended to have a higher back fat α-tocopherol content (P = 0.06, Fig. 2). Plas- ma GSH-Px activity increased as pigs grew old- er (P < 0.001). Dietary vitamin E supplementa- tion decreased linearly (P < 0.05) GSH-Px ac- tivity in plasma samples collected at slaughter (Fig. 3). The TBARS content of pork stored frozen (–18°C for 16 wk) increased with time thawed meat samples were kept under fluorescent light (P < 0.001) indicating a reduction in stability of fat against oxidation (Fig. 4). This was also noticed as a poorer taste whereas no effect was observed in meat tenderness or juiciness (Table 4). Die- tary vitamin E supplementation did not affect the TBARS content or organoleptic quality of pork. Discussion The vitamin E content of stored barley decreased only a little during the experiment (0.5 mg/kg). Fig. 1. Effect of supplemental vitamin E on the develop- ment of serum α-tocopherol concentration (circle Day 0, square Day 30 and triangle at slaughter) in growing-finish- ing pigs fed stored (——) or freshly harvested (------) bar- ley (N = 5 pigs per treatment; Significance: vitamin effect P < 0.001, time effect P < 0.001, time × vitamin interaction P < 0.001). Fig. 3. Effect of supplemental vitamin E on the develop- ment of serum glutathione peroxidase activity (circle Day 0, square Day 30 and triangle at slaughter) in growing-fin- ishing pigs fed stored (——) or freshly harvested (------) barley (N = 5 pigs per treatment; Significance: time effect P < 0.001, time × vitamin interaction P < 0.05). Fig. 2. Effect of barley storage and supplemental vitamin E on back fat α-tocopherol concentration (N = 5 pigs per treat- ment; Significance of vitamin E level: linear P < 0.001, quadratic P < 0.001). According to Hakkarainen et al. (1983a) the vi- tamin E content of dried barley (13% moisture content) decreased 10 mg/kg dry matter during 11 month storage which is somewhat higher than in this study. The vitamin E content of freshly harvested barley increased during the experiment 15 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 8 (1999): 9–18. which started in October, one month after har- vesting, and ended in January. This increase in natural vitamin E content of freshly harvested barley during storage is an interesting phenom- enon and requires further study. In this study, supplemental vitamin E had a quadratic effect on pig weight gain and optimal performance was observed with vitamin E sup- plementation of 40 mg/kg feed. In the study of Ashgar et al. (1991), vitamin E supplementation of 100 and 200 mg/kg improved pig growth and feed to gain ratio in the growing period com- pared with 10 mg/kg of vitamin E, but not in the finishing period. In our study, the effect of vita- min E on pig performance was similar during both the growing and finishing periods. In gen- eral, vitamin E has had only minor effects on pig performance (Työppönen et al. 1988, Os- borne et al. 1994). Storage of barley did not af- fect pig performance, and supplemental vitamin E above 40 mg/kg did not result in improved performance, when pigs were fed freshly harvest- ed barley. This is in accordance with earlier re- sults of Työppönen et al. (1988). Observed dif- ferences in the thickness and firmness of back fat between different barleys may be due to dif- ferences in dietary protein and lysine content. Higher protein and lysine content in freshly har- vested barley diet resulted in less back fat. Thick- er back fat is generally firmer which was also observed in this study with barrows. In general, neither supplemental vitamin E nor the storage of barley has affected carcass composition (Os- borne et al. 1994, Työppönen et al. 1988). In the present study, dietary vitamin E sup- plementation increased serum α-tocopherol con- centration within a month after starting vitamin E supplementation. According to Jensen et al. (1990) dietary vitamin E supplementation in- Table 4. Effect of supplemental dietary vitamin E on the organoleptic quality of frozen pork kept under fluorescent light at 4°C for 0, 3 or 8 days. Vitamin E-suppl., mg/kg 0 40 80 160 SEM N 5 5 5 5 Flavour1,2 Day 0 4.6 4.8 4.6 4.4 0.17 Day 3 4.4 4.4 4.3 4.3 0.13 Day 8 4.2 4.1 4.2 4.1 0.14 Tenderness1 Day 0 4.8 4.8 4.3 4.3 0.26 Day 3 4.5 4.5 4.4 4.3 0.20 Day 8 4.7 4.3 4.6 4.6 0.20 Juiciness1 Day 0 4.5 4.8 4.6 4.5 0.11 Day 3 4.4 4.6 4.3 4.6 0.12 Day 8 4.7 4.4 4.3 4.4 0.12 1 Score 1 to 7 (1 is the lowest and 7 is the best score). 2 Effect of time was significant at P < 0.001. Fig. 4. Effect of supplemental vitamin E and time (0, 3 or 8 d) under fluorescent light on pork TBARS content (N = 5 pigs per vitamin E level; Significance: time effect P < 0.001). 16 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Suomi, K. et al. Effect of vitamin E on pigs and frozen pork creases serum α-tocopherol concentration with- in a week. They suggested that serum α-toco- pherol concentration reflects short term chang- es in vitamin E intake, whereas tissue vitamin E concentrations (e.g. fat) reflect longterm chang- es in vitamin E intake. In the current study, de- velopment of vitamin E in freshly harvested bar- ley during the course of the experiment tended to increase back fat α-tocopherol concentration. Serum α -tocopherol concentration of pigs giv- en no supplemental vitamin E remained low, less than 2 mg/l, during the entire study. According to Jensen et al. (1988a), 3 mg/l of α-tocopherol in serum is the minimun for normal functioning of immune cells. In their study, pigs that suf- fered from vitamin E and selenium deficiency had less than 1 mg/l of α-tocopherol in serum. In the present study, pigs given no supplemental vitamin E had no clinical signs of vitamin E de- ficiency, such as muscular dystrophy. Both ba- sal diets contained nearly 30 mg/kg of natural vitamin E that came from barley and soybean meal, in addition to added selenium. According to Ullrey (1981), 15 mg/kg of vitamin E and 0.135 mg/kg of selenium is enough to maintain normal tissue α-tocopherol concentrations. Plasma GSH-Px activity increased with pig maturity, which is in agreement with results of Jensen et al. (1988b). A linear response in plas- ma GSH-Px activity to the vitamin E supplemen- tation level was observed only in blood samples collected at slaughter. Vitamin E supplementa- tion has not been documented to have signifi- cant effect on GSH-Px activity. In this study, pigs were transported to the slaughter-house and the last blood samples were taken as the animals were bled. Transportation as a stressor may in- crease metabolic rate and hence the production of oxygen radicals. A decrease of cellular enzyme activity in plasma by vitamin E supplementation has been documented in stress-susceptible pigs (Duthie et al. 1989). Increases in the vitamin E level might protect cell membranes from dam- age during transportation, slaughter and prepa- ration of the blood samples, subsequently reflect- ed in plasma GSH-Px activity. Dietary vitamin E supplementation did not improve the storage stability (measured as TBARS) of pork stored frozen for 16 wk. High- er vitamin E supplementation (200 mg/kg) has improved the storage stability of frozen pork (Monahan et al. 1992a, Pfalzgraf et al. 1995). In those studies, diets contained 3% of added fat (maize oil, soybean oil or tallow). Differences between studies are probably not related to vita- min E supplementation but to differences be- tween added fats. Vegetable oils in particular, tend to increase the content of unsaturated fatty acids in tissues. Supplementary dietary vitamin E has increased vitamin E content in cell mem- branes and stabilised muscle tissue which con- tains substantial amounts of unsaturated fatty acids (Monahan et al. 1992b). Finnish pig breeds have only minor quantities of intramuscular fat, circa 1.9% (Kangasniemi and Honkavaara 1989), which may explain the lack of TBARS response to dietary vitamin E supplementation. Accord- ing to Toulová et al. (1977) intramuscular fat contains more unsaturated fatty acids than de- pot fat and is thus more sensitive to oxidation. In the present study, taste of pork was reduced the longer it was kept under fluorescent light as expected. Dietary vitamin E supplementation did not prevent off-flavours, nor did it increase meat tenderness or juiciness. However, numerical dif- ferences between treatments were seldom great- er than one point, and the number of samples was perhaps too small to draw firm conclusions. According to Astrup (1973) vitamin E supple- mentation improves meat quality by decreasing off-flavours of meat, and off-flavours are relat- ed to oxidation of fat. In conclusion, when growing-finishing pigs are fed freshly harvested or stored barley from good harvest conditions, 40 mg/kg of added vi- tamin E as all-rac-α -tocopheryl acetate is suffi- cient to maintain serum α-tocopherol concentra- tion above 3 mg/l, the level which is required for immune cell function. Increases in dietary vitamin E supplementation above 40 mg/kg did not improve pig performance, nor the storage stability or organoleptic quality of frozen pork. 17 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 8 (1999): 9–18. AOAC 1990. Official methods of analysis. 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SELOSTUS Lihasikojen E-vitamiinin tarve ruokittaessa vastapuidulla ohralla ja rehuun lisätyn E-vitamiinin vaikutus lihan pakastussäilyvyyteen ja syöntilaatuun Kaija Suomi, Kirsi Partanen, Timo Alaviuhkola, Hilkka Siljander-Rasi ja Satu Sankari Maatalouden tutkimuskeskus ja Helsingin yliopisto Kasvatuskokeessa selvitettiin E-vitamiinilisäyksen (all-rac-α-tokoferyyliasetaattina) tarvetta ruokittaes- sa lihasikoja vastapuidulla, kuivatulla ohralla. Lisäksi selvitettiin, voidaanko tavanomaiseen rehuun lisätyllä runsaalla E-vitamiinimäärällä parantaa sianlihan pa- kastussäilyvyyttä ja syöntilaatua. Vastapuitu ja edel- liskesänä puitu ohra olivat samaa Pohto-lajiketta, joi- ta korjattaessa olosuhteet olivat hyvät. Koe aloitet- tiin kuukauden kuluttua ohran puinnista. Vastapuidun ohran E-vitamiinipitoisuus oli kokeen alussa 2,3 mg/ kg pienempi ja lopussa 5,7 mg/kg suurempi kuin va- rastoidun ohran. Koe oli 2 × 4 faktoriaalinen. Kum- mastakin ohrasta tehtyihin seoksiin lisättiin E-vita- miinia 0, 40, 80 ja 160 mg/kg. Yhteensä 80 sikaa, joi- den alkupaino oli keskimäärin 26,6 kg, jaettiin kah- deksaan ruokintaryhmään yksilöruokinnalle. Siat sai- vat rehua 1,2–2,8 ry/pv 15 viikon ajan. Jokaisen ryh- män viidestä siasta otettiin verinäytteet ennen kokeen alkua, 30 päivän kuluttua kokeen alkamisesta ja teu- rastuksen yhteydessä E-vitamiinin ja glutationiperok- sidaasientsyymin aktiivisuuden määritystä varten. Samojen sikojen ruhoista otettiin kyljysnäytteet sila- van E-vitamiinimääritystä varten ja jokaisen E-vita- miinitason 5 eläimestä kyljysnäytteet lihan pakastus- varastoinnin kestävyysmääritystä varten. Viimeksi mainitut näytteet olivat pakastettuina vakuumipakka- uksissa (–18°C) 16 viikon ajan. Sulatuksen jälkeen ne siirrettiin päivänvalolampun alle (+8°C). Näytteis- tä määritettiin tiobarbituurihappoon reagoivat yhdis- teet (TBARS) eli rasvan hapettumista kuvaava TBARS-luku päivänvaloon siirtopäivänä ja 3. ja 8. päivänä siirron jälkeen. Lisätty E-vitamiini paransi sikojen kasvua vain 40 mg/kg lisäystasolla. Eri ohrilla ruokittujen sikojen kasvu oli samanlainen. E-vitamiinilisäys lisäsi veren seerumin α-tokoferolipitoisuutta. Silavan α-tokofe- rolipitoisuus suureni myös rehuun lisätyn E-vitamii- nin myötä. Vastapuidulla ohralla ruokittaessa silavan α -tokoferolipitoisuus oli hieman suurempi kuin va- rastoidulla ohralla ruokittaessa, johtuen ilmeisesti vastapuidun ohran E-vitamiinipitoisuuden kohoami- sesta kokeen aikana. Sikojen plasman glutationiper- oksidaasiaktiivisuus kohosi iän myötä, mutta väheni E-vitamiinipitoisuuden lisääntyessä rehussa teuras- tuksen yhteydessä otetussa näytteessä. Ilmeisesti li- sääntynyt E-vitamiini yhdessä seleenin kanssa suo- jasi solukalvoja kuljetuksen ja teurastuksen aikana. Rehuun lisätyllä E-vitamiinilla ei ollut vaikutusta li- han pakastussäilyvyyteen, makuun, mureuteen eikä mehukkuuteen. Ruokittaessa sikoja vastapuidulla, hyvissä olosuhteissa korjatulla kuivatulla ohralla, riit- tää E-vitamiinilisäykseksi 40 mg/ry. Suuremmat li- säykset eivät parantaneet lihan pakastusvarastointi- kestävyyttä eivätkä syöntilaatua. Title Introduction Material and methods Results Discussion References SELOSTUS