J Sci Food Agric 1991,57, 19-29

Influence of Supranutritional Vitamin E Supplementation in the Feed on Swine Growth Performance and Deposition

in Different Tissues

Ali Asghar,” J Ian Gray,” Elwyn R Miller,b Pao-Kwen K u , ~ Alden M Booren”

Departments of “Food Science and Human Nutrition, and bAnimal Science, Michigan State University, East Lansing, Michigan 48824, USA

and

D Joseph Buckley

Department of Food Technology, University College, Cork, Ireland

(Received 23 July 1990; revised version received 27 March 1991; accepted 23 April 1991)

ABSTRACT

The efects of supranutritional vitamin E supplementation in the diet on the growth performance of pigs, the deposition of a-tocopherol in diferent tissues and the activity of certain blood enzymes were investigated. Pigs receiving diets supplemented with 100 and 200 IU vitamin E kg-‘ feed exhibited signiJcant improvement in daily body gain and feed conversion eficiency in the early growth phase ( P < 0.05). With advance in age, the growth curves of pigs fed the higher levels of vitamin E tended to become parallel to that of the control group (10 IU vitamin E kg-’ feed), suggesting that the advantage gained in body weight in the early growth period actually persisted in subsequent phases.

The concentrations of a-tocopherol in blood plasma and difereitt tissues (heart, kidney, lung and liver) significantly increased ( P < 0.05) with increasing levels of dietary vitamin E. However, the activity of lactate dehydrogenase, creatine kinase and aspartate aminotransferase in blood plasma was not influenced by the levels of vitamin E supplementation.

Key words: Vitamin E supplementation, swine growth, tissue deposition, u-tocopherol.

19

J Sci Food Agric 0022-5142/91/$03.50 0 SCI, 1991. Printed in Great Britain

20 A A s y l w , J I Gray. E R Miller. P - K Ku, A M Booren, D J Buckley

INTRODUCTION

A function of vitamin E in biological systems is to protect the unsaturated fatty acids from oxidation by free radicals (Tappel 1962). However, various opinions exist regarding the mechanism(s) involved. Tappel ( 1962) coupled the role of ascorbate, glutathione and NADPH in the action of vitamin E for quenching free radicals. Diplock and Lucy (1973) assigned a specific location for vitamin E in the biological membrane, and its antioxidant function in uiuo was thought to protect the reduced form of protein-bound selenium from oxidation. McCay et a1 (1971) proposed that a-tocopherol protects the polyunsaturated fatty acids at the 2-position of the phospholipids in the membranes from the peroxidative side reaction of TPNH oxidase (NADPH oxidase). There is now ample experimental evidence indicating the protective role of a-tocopherol against peroxidative reactions in cellular (Ingold et a1 1987) and subcellular membranes (Asghar et a1 1988).

Vitamin E deficiency has also been associated with different disorders such as muscular dystrophy (Serafin et a1 1987), atherosclerosis (Ursini and Bindoli 1987), haemolysis (Tanaka and Mino 1986), endocrine disturbances (Umeda et a1 1986) and decreased immunity (Reffett et a1 1988). Certain ‘vitamin E-dependent disorders’ have also been recognised (Ogunmekan and Hwang 1988). These are believed to be the result of an inherited etiology caused by mutant genes of large effect, and require supranutritional doses (mega-supplementation) for correction (Bieri et a1 1983). Even though there are some divergent reports on the side effects of excessive intake of vitamin E (Roberts 1981), the bulk of the evidence indicates no adverse symptoms for daily intakes up to 600 mg vitamin E by humans (Horwitt 1986). In fact, mega-doses of vitamin E can counteract the harmful effects produced by the ingestion of massive amounts of vitamin A (Jenkins and Mitchell 1975).

The present study is based on the hypothesis that undesirable lipid peroxidation that possibly occurs in the subcellular membranes and other tissue components during normal growth and development of meat animals can be minimised by supplementation of vitamin E in the diet at supranutritional levels which are approximately 5 to 10 times the minimal requirement of pigs. This may contribute to exploiting the full growth potential of the animal and yielding meat with better keeping quality. The first phase of the study is reported herein and focuses on the growth performance, carcass characteristics and deposition of a-tocopherol in certain tissues. The effects of vitamin E supplementation on meat quality and the rate of lipid peroxidation in the subcellular membranes isolated from pork are reported in a subsequent paper (Asfhar et a1 1991).

EXPERIMENTAL

Feeding trial

Sixty pigs (barrows and gilts) averaging 29 kg in weight were assigned from litters to six pens with restricted randomisation, balancing for initial weight and sex. Pens containing barrows and gilts together were then randomly assigned to receive

Injuence of vitumin E supplementation on swine 21

TABLE 1 Composition of pig grower diets used in the feeding trial

Ingredients Vitamin E supplementation (IU k g - ' feed)

I0 100 200

Ground shelled corn Soya bean meal Soya bean oil Mono-dicalcium phosphate Calcium carbonate Sodium chloride Vitamin-trace mineral mix" Selenium 90 premixb Vitamin E (BASF (SOYO) Aureomycin 50

1418 450

60 30 22 6

10 3 0.04 1

1418 450

60 30 22

6 10 3 0.40 1

1418 450

60 30 22

6 10 3 0.80 1

2000.04 2000.40 2000.80

"Supplied the following per kg of diet: vitamin A, 3300 IU; vitamin D, 660 IU; menadione sodium bisulphite, 2 mg; riboflavin, 3 mg; niacin, 18 mg; D-pantothenic acid, 13 mg; choline, 110 mg; vitamin B,,, 20 pg; zinc, 75 mg; manganese, 10mg; iodine, 1 mg; copper, 10 mg; iron, 60 mg.bSupplied 0.3 mg Se per kg of diet.

grower diets with a basic level of 10 IU vitamin E kg-' feed (group 1) or supplemented with vitamin E to provide diets containing 100 (group 2) and 200 IU vitamin E kg-' feed (group 3). Vitamin E was added as all-rac DL-a-tocopheryl acetate (BASF Corp, Parsippany, NJ). Thus, there were two pens of pigs fed each of the three diets in a 2 x 3 factorial design as shown in Table 1. Pigs were housed in an environmentally controlled, complete-confinement, slotted-floor, modern swine facility. Feed was available at all times as a meal in self-feeders. There was one three-hole feeder available in each pen at all times and water was available ad libitum from one nipple waterer in each pen. Pen size was such that pen space was 0.56 m2 per pig.

Pigs were weighed individually every 2 weeks and pen feed consumption was also determined every 2 weeks. Blood was drawn at 4-week intervals from four pigs from each pen from the anterior vena cava in heparinized disposable syringes for determination of plasma enzyme activities and u-tocopherol content.

All pigs were slaughtered at the Michigan State University Meat Laboratory according to standard commercial practices at the termination of the feeding trial. The dressed carcasses were weighed (hot weight) and immediately transferred to a chiller. Tissue samples (heart, liver, lungs, kidneys) were collected and frozen. The carcasses were again weighed (cold weight) 24 h post-mortem. The loin portions from each carcass were removed, vacuum packed, and frozen at - 20°C for subsequent study (Asghar et a1 1991).

22 A Asyhar. J I G r q . E R Miller, P-K Ku. A M Booren, D J Buck1e.v

Chemical and biological assays

Blood collected in the heparinised disposable syringes from randomly selected pigs (four pigs per pen, ie eight pigs per group) was centrifuged at 1900xg for 15 min to collect the plasma. The a-tocopherol was isolated from the plasma according to the method of Bieri et a1 (1979) directly without saponification, and quantitated by a reverse phase high performance liquid chromatographic (HPLC) procedure (Shearer 1986) with certain modifications. For instance, quantitation of a-tocopherol was achieved with an HPLC system (Waters Associates, Milford, MA) equipped with a 4.6 x 150 mm ultrasphere-ODS column (Beckman Instruments Inc, Fullerton, CA), using 100% HPLC-grade methanol as the eluant at a flow rate of 1 ml min-'. cr-Tocopheryl acetate was used as an internal standard with ultraviolet detection at 280 nm.

The activities of lactate dehydrogenase (EC 1.1 . I .27), creatine kinase (EC 2.7.3.2) and aspartate aminotransferase (EC 2.6.1.1 ) in plasma were assayed following the Sigma technical procedure (Sigma Bulletin 1988) as indicators of membrane damage in biological systems (Reddy et a1 1987).

Statistical treatment of data

The repeated measure (time) design was analysed using the General Linear Model procedure of the Statistical Analysis System (SAS 1987), The weight gain data of individual animals from both pens for each group were used for statistical analysis. However, feed intake and feed efficiency were derived from the means of each pen. Sex response was not considered in this study. For other parameters (eg carcass characteristics, a-tocopherol concentrations in plasma and tissues), analysis of variance based on a factorial design was performed. Means were separated by a priori contrasts (10 vs 100+200; 10 vs 100, and 100 vs 200) using Bonferonni t-statistics (Gill 1986).

RESULTS AND DISCUSSION

Effect of dietary vitamin E supplementation on swine performance

Data in Table 2 show that pigs receiving the higher levels of vitamin E (100 and 200 IU kg-' feed) had improved growth rates (4 and 6%, respectively) compared with the control group of pigs. The daily weight gained for each group indicated that the advantage in body weight acquired during the first 4 weeks of feeding actually persisted in the subsequent growth phases. Another noticeable feature was the higher rate of daily weight gain in group 2 compared with group 3 during the first 4 weeks, which was followed by a decline. This suggests that, during the early growth phase, 200 IU vitamin E kg- feed may be more than the optimal amount needed at those body weights. Bieri et ul (1983) reported that a large intake of vitamin E reduces the intestinal absorption of vitamin A which is an important growth-promoting vitamin. Thus, supplementation of swine feed with vitamin E at levels approximately 10 times greater than the minimal requirement might partially obscure the favourable response of high dietary supplementation in the early growth phase.

Injuence of uitamin E supplementation on swine 23

TABLE 2 Average daily gain, feed intake and feed efficiency of pigs fed three

levels of dietary vitamin E

Vitamin E supplementation SE P

I0 100 200

(IU kg-lfeed) value

Average daily gain (kg day-' per pig)" Week 0-2 0.55 0.72 068 0.03 Week 0-4 062 0.75 0.70 0.03 Week 0-6 0.66 0.73 0-72 003 Week 0-8 0.69 0.74 076 0.02 Week 0-10 0.69 0.72 0.74 0.02 Week 0-12 0.70 0.7 1 075 002 Week 0-14 0.72 0.74 0.77 0.02

Week 0-2 1.40 1.57 1.40 0.08 Week W 1.64 1 *86 1.69 0.03 Week 0-6 1.75 1 -90 1.83 0.03 Week 0-8 1.90 1.97 1.99 0.05 Week 0-10 1.97 2.01 2.08 0.05 Week 0-12 2.05 2.08 2.16 0.05 Week 0-14 2.13 2.25 2.30 0.05

Week C 2 2.66 2-21 2.28 0.04 Week 0-4 2.7 1 2.49 2.55 0.0 1 Week 0-6 2.70 2.62 2.64 0.04 Week 0-8 2.78 2.67 2.72 004 Week 0-10 2.9 1 2.8 1 2.88 0.0 Week C12 2.98 2.9 t 2.94 0.02 Week 0-14 3.00 3.03 3.05 0.04

Average dailyjeed intake (kg day-' per pig)d

Feed eficiencyf

0.15b 0.01' NS NS NS NS NS

NS 002' NS NS NS NS NS

0.059 0.02 NS NS NS NS NS

a Trt ( P < 0.1 1); Time*Trt ( P < 0.01). b10 vs 100+200 (P<001); 10 vs 100 (P<O.Ol).

10 vs 100+200 (P<001); 10 vs 100 (P<O.OI) .

10 vs 100 (P<0.05); 100 vs 200 (P<O.lO). Trt ( P < 0 2 1 ; Time * Trt ( P < 0.10).

f Trt ( P < 0.32); Time*Trt ( P < 0.01). g 10 vs 100 (P<0*05); 10 vs 100+200 (P<0-05).

Data on feed conversion efficiency of each group are presented in Table 2 and indicate that both groups receiving the higher vitamin E supplements had significantly superior (P < 0.05) feed conversion efficiency than the control group during the early growth period. The difference between the groups tended to decrease with advance in the age of the pigs, and after 13 weeks the feed conversion efficiency was almost identical in all groups.

Results in Table 3 indicate that the trend in the advantages in live weight gained by pigs in groups 2 and 3 were also reflected in their carcass weights (both hot and cold). The weights were greater by 2-4 to 4.8% relative to those of the control

24 A Asghar, J I Gray, E R Miller, P-K Ku, A M Booren, D J Bucklqv

TABLE 3 Effect of vitamin E supplementation on carcass characteristics of pigs

Vitamin E supplementation (IU kg-' feed)

10 100 200

Live weight (slaughter wt) (kg) 101.1 k8.7" 103.8 f 6.3" 106.3 f 7.3" Hot carcass weight (kg) 75.5 6.9" 77.3 f 4.7" 79.1 f 6.5"

Cold carcass weight (kg) 73.0 f 6.5" 74.8 f 4.5" 76.6 6.2" Shrinkage loss % 3.43" 3.23" 3.10"

Dressing percentage 74.7" 74.4" 74.4"

Cold carcass weight was determined 24 h after slaughter and storage at 1°C. Values in the table are the group meansf standard deviation. Values in a row having the same superscript are not significantly different (P >0.05).

pigs, although the differences were not statistically significant. However, the dressing percentage and evaporative losses in carcasses were identical for all groups after chilling at 1°C for 24 h.

Effect on enzyme activities

Changes in the activities of lactate dehydrogenase (LDH), creatine kinase (CK) and aspartate aminotransferase (AST) in the blood plasma of pigs from the three groups are summarized in Table 4. More variation in enzyme activities was observed in relation to the date of sampling rather than to the level of vitamin E in the diet. For example, AST activity continued to decline with age, but LDH activity did not follow any distinct pattern. During the initial phase of the feeding trial, CK activity tended to be higher and AST to be lower in the blood from pigs fed high levels of vitamin E compared with activities in the control pigs.

The activities of LDH, CK and AST have been used as indicators of cell damage as a result of vitamin E deficiency in calves (Reddy et a1 1987), sheep (Horton et a1 1978) and swine (Ruth and van Vleet 1974). The high activity of these enzymes in blood plasma was considered indicative of a high rate of cell destruction. From this viewpoint, the magnitude of the activities observed in the present study was lower than reported for sheep (Horton et a1 1978) and calves (Reddy et a1 1987). As vitamin E deficiency was not a factor in the present study, it is not surprising to find the activities of LDH, CK and AST within normal limits. It has also been reported that administration of excess vitamin E protects the membranes of mature red blood cells which are not equipped with de nouo lipid synthesis and alleviates oxidative stress (Elsas and McCormick 1986). Tolonen et a1 (1988) observed a decrease in the formation of thiobarbituric acid (TBA) reactive substances (TBARS) in blood serum of elderly patients. We did not determine TBARS development in the blood fractions of pigs, although a similar function of vitamin E can be expected in the blood of normal growing pigs.

Concentration of a-tocopherol in plasma and different organs

The a-tocopherol content in blood plasma is considered an index of the vitamin

Influence of vitamin E supplementation on swine 25

TABLE 4 Plasma enzyme activity in pigs fed different dietary levels of

vitamin E

Vitamin E supplementation SE P ( IU kg- ' f eed )

10 100 200 value

Creatine kinase (unitsfdl)" Day 0 24.9 22- 1 29.1 4.4 NS Day 29 24.2 56.9 77.3 10.1 NS Day 56 30.4 34.7 47.7 26.9 NS Day 80 27.4 24.8 28.4 4.5 NS Day 95 23.9 16.7 27.1 5.8 NS

Lactate dehydrogenase (units/dl)* Day 0 18.9 17.3 18.3 2.1 NS Day 29 25.6 24.3 21.4 1.8 NS Day 56 31.6 32.1 32.4 3.7 NS Day 80 19.1 21.2 23.1 1.6 NS Day 95 18.5 18.0 18.1 1.8 NS

Aspartate aminotransferase (unitsldw Day 0 2.20 2.07 2.36 0.28 NS Day 29 1-91 1.90 1.82 0 1 8 NS Day 56 1-95 1.61 1.75 0.17 NS Day 80 1-54 1.39 1.64 0 1 1 NS Day 95 1.17 1.21 1.11 0.16 NS

SE = Mean standard error. "Trt ( P < 0 1 1); Time * Trt ( P < 0.1 1) . bTrt (NS); Time*Trt (NS). 'Trt (NS); Time*Trt (NS).

E status of the animal (Machlin 1984). The a-tocopherol contents of plasma from the pigs fed the three dietary levels of vitamin E are listed in Table 5 . Although there were wide variations in the plasma a-tocopherol levels within a group, as evident from the magnitude of the standard deviation, the mean value of all the groups before commencing the feeding trial was somewhat below the level (0-8 pg ml- ') required for preventing nutritional muscular dystrophy (NMD) in pigs (Nelson 1980). Despite this, no clinical signs of vitamin E deficiency in the pigs was observed.

With the commencement of feeding the supplemented diets, the a-tocopherol concentrations in the blood plasma increased significantly (P < 0.05) during the initial 4 weeks of feeding and were dependent on the levels of vitamin E in the diet. In the subsequent feeding periods, only a marginal increase in the plasma a-tocopherol levels of pigs from groups 2 and 3 was observed whereas those in group 1 remained below the minimal level. Roth and Kirchgessner (1975) also reported a low a-tocopherol level (0.5 pg ml- ') in the serum of hogs fed 7.4-8-6 mg vitamin E kg-' feed. Considerable disparity seems to exist on the minimum level of vitamin E needed to avoid the incidence of NMD, for instance, in bovines. Blaxter (1953) reported a range between 005 to 0.2 pg ml-' in the case of calves,

26 A Asghar, J I Gray, E R Miller, P-K Ku. A M Boorm, D J Buckley

TABLE 5 Concentration of a-tocopherol (pg ml-I) in blood plasma of pigs fed vitamin E

supplemented diets

Bleeding interval (days) Vitamin E supplementation (IU k g - feed)

10 100 200

0 30 60 90

120

0.71 f 0.32" 0.62 f 0.30" 0.77 f 0.32" 0.55 f 0.28" 2.00 f 0.62b 3.14+ 1.30' 0.43 k 0 18" 2.20 k 0.56b 3.20 k 0.55' 0.54 f 0.27" 2.50 f 0.60h 3.80 f 0.63' 0.5 1 k 0.28" 2.48 f 0.5Sh 4.07 + 0.74'

Values in the table are the group means f standard deviation. Mean values in a row having similar superscripts are not significantly different ( P > 0.05).

TABLE 6

organs of pigs fed vitamin E supplemented diets Concentrations of a-tocopherol (pg g- ' tissue) in various

Organs Vitamin E supplementation (ZU k g - ' feed)

10 100 200

Kidneys 0.56 f0.16" 3.38 0.36b 4.02 f 0.49b Lungs 0.69 f 0.1 2" 5.02 f 0.97b 6.14 f 0.49' Heart 1.62 f 0.55" 7.77f 1.01b 9.39 f 0.8 1' Liver 3.06 f 0.53" 9.16 f 0.93' 12.62 f 1.94'

Values in the table are the group means standard deviation. Mean values in a row having similar superscripts are not significantly different (P> 0.05).

and others have considered 2 pg ml-' to be indicative of vitamin E deficiency in beef cattle (Hoelscher 1978).

It is also apparent from Table 6 that a-tocopherol concentrations in different organs increased significantly (P ~ 0 . 0 5 ) with dietary supplementation. However, the response of different organs varied depending upon their metabolic activities, and cr-tocopherol concentrations increase in the order: kidneys < lungs < heart -= liver. Similar trends were reported by Monahan et a1 (1989) for pigs receiving 200 mg a-tocopheryl acetate per kg feed from the time of weaning to slaughter.

It should be noted in the present study that, although the vitamin E was supplemented in the form of cr-tocopheryl acetate in the diet, only free cr-tocopherol was identified in the blood plasma and different organs. This is in conformity with the findings of others (Gallo-Torres 1980) on rats, and substantiates the general belief that tocopheryl acetate is converted to tocopherol in the intestine before or during absorption (Ogihara et a1 1985). The bulk of the tocopheryl esters is hydrolysed by mucosal esterases in the intestinal brush-border (Gallo-Torres 1980)

Influence of vitamin E supplementation on swine 21

and the remainder may be handled intraluminally by duodenal esterases (Mathias et a1 1981).

Divergent findings have been reported regarding the performance of meat animals in response to vitamin E supplementation. While some studies have indicated an improvement in growth rate and feed conversion efficiency in the case of cattle by vitamin E supplementation (Hutcheson and Cole 1985; Reddy et a1 1987), others have found no difference in the case of swine (Amer and Elliot 1973; Roth and Kirschgessner 1975). It is possible that the level of supplementation and animal age at which feeding of dietary vitamin E commences might be contributing to these discrepancies. Our results suggest that the positive effects of vitamin E supplementation are induced actually at an early age and carried through with advancement in age. Thus, vitamin E may be needed in supranutritional amounts during the rapid growth phase of the young animal for optimum physiological functions.

It is also apparent from the present study that the basal vitamin E requirement (10 IU kg-’ feed) as suggested in the literature (Scott 1978) may be regarded as ‘minimal’ for preventing the possible signs of deficiency or dystrophy. It may not be considered ‘optimal’ for exploiting the full potential growth rate and feed conversion of growing/finishing swine. A study of Bendich et a1 (1986) has also shown that while 15 IU vitamin E kg-’ diet prevented NMD in rats, more than 50 IU kg-’ feed were needed for optimum immune response. The advantages gained in feed conversion efficiency and growth rate may well justify the supplementation of vitamin E at a higher level in swine diet. In this study it was estimated, using current prices, that the cost of supplementing feed at the 200 IU vitamin E kg- ’ level during the 14-week feeding period was approximately 54 cents per pig.

ACKNOWLEDGEMENTS

This study was supported in part by the Michigan Agricultural Experiment Station and by grants from the National Live Stock and Meat Board and the National Pork Producers’ Council.

REFERENCES

Amer M A, Elliot J I 1973 Influence of supplemental dietary copper and vitamin E on the oxidative stability of porcine deposit fat. J Anim Sci 37 87-90.

Asghar A, Gray J I, Buckley D J, Pearson A M, Booren A M 1988 Perspectives in warmed-over flavor. Food Techno1 42 (6) 102-108.

Asghar A, Gray J I, Booren A M, Miller E R, Buckley D J 1991 Effects of supranutritional dietary vitamin E levels on subcellular deposition of a-tocopherol in the muscle and on pork quality. J Sci Food Agric 57 31-41.

Bendich A, Gabriel E, Machlin L J 1986 Dietary vitamin E requirement for optimum immune responses in the rat. J Nutr 116 675488.

Bieri J G, Tolliver T J, Catignani G L 1979 Simultaneous determination of alpha-tocopherol and retinol in plasma or red cells by high pressure liquid chromatography. Amer J Clin Nutr 32 2143-2149.

28 A Asghar, J I Gray, E R Miller. P-K Ku, A M Booren. D J Buckley

Bieri J G, Corash L, Hubbard V S 1983 Medical uses of vitamin E. New Engl J Med 308

Blaxter K L 1953 Muscular dystrophy. Vet Rec 65(47) 835-838. Diplock A T, Lucy J A 1973 The biochemical modes of action of vitamin E and selenium:

Elsas L J, McCormick D B 1986 Genetic defects in vitamin utilization. Vitam Horm 43

Gallo-Torres H E 1980 Absorption. In: Vitamin E: A Comprehensive Treatise, ed Machlin

Gill J L 1986 Repeated measurements: sensitive tests for experiments with few animals. J

Hoelscher M 1978. Vitamin E requirements for beef cattle. Feedstuffs 50 30-31. Horton G M, Jenkins W L, Rettenmaier R 1978 Haematological and blood chemistry

changes in ewes and lambs following supplementation with vitamin E and selenium. Br J Nutr 40 193-203.

1063- 1067

a hypothesis. FEBS Letters 29 205-210.

103- 144.

L J. Marcel Dekker, New York, pp 170-192.

Anim. Sci 63 943-954.

Horwitt M K 1986 The promotion of vitamin E. J Nutr 116 1371-1377. Hutcheson D P, Cole N A 1985 Vitamin E and selenium for yearling feedlot cattle. Fed

Proc 44 549 (Abstr 807). Ingold K U, Burton G W, Foster D 0, Hughes L, Lindsay D A, Webb A 1987 Biokinetics

of and discrimination between dietary RRR- and SRR-a-tocopherol in the male rat. Lipids 22 163-172.

Jenkins M Y, Mitchell G Y 1975 Influence of excess vitamin E on vitamin A toxicity in rats. J Nutr 105 1600-1606.

Machlin L J 1984 Vitamin E. In: Handbook of Vitamins: Nutritional, Biochemical and Clinical Aspects, ed Machlin L J. Marcel Dekker, New York, pp 99-145.

Mathias P M, Harris J T, Peeters T J, Muller D P R 1981 Studies on the in viuo absorption of micellar solution of tocopherol and tocopheryl acetate in rat: demonstration and partial characterization of a mucosal esterase localized to the endoplasmic reticulum of the erythrocyte. J Lipid Res 22 829-837.

McCay P B, Poyer J L, Pfeifer P M, May H E, Gilliam J M 1971 A function for a-tocopherol: stabilization of the microsomal membrane from radical attack during TPNH-dependent oxidation. Lipids 6 297-306.

Monahan F J, Buckley D J, Gray J I , Morrissey P A, Hanrahan T J, Asghar A, Lynch P B 1989 The effect of dietary a-tocopherol supplementation on a-tocopherol levels in the pig and on oxidation in pork products. Proc 35th Int Congr Meat Sci Techno1

Nelson J S 1980 Pathology of vitamin E deficiency. In: Vitamin E: A Comprehensive Treatise, ed Machlin L J. Marcel Dekker, New York, pp 397428.

Ogihara T, Nishida Y, Miki M, Mino M 1985 Comparative changes in plasma and RBC a-tocopherol after administration of dl-a-tocopherol acetate and d-z-tocopherol. J Nutr Sci VitaminoI31 169-177.

Ogunmekan A 0, Hwang P A 1988 Vitamin E therapy-facts and fancies: a review. Inter CIin Nutr Rev 8 69-74.

Reddy P G, Morrill J L, Frey R A 1987 Vitamin E requirements of dairy calves. J. Dairji Sci. 70 123-129.

Reffett J K, Spears, J W, Brown T T 1988 Effect of dietary selenium and vitamin E on the primary and secondary immune response in lambs challenged with parainfluenza 3 virus. J Anim Sci 66 152Ck1528.

Roberts H J 1981 Perspective on vitamin E as therapy. J Amer Med Assoc 246 129-131. Roth F X, Kirchgessner M 1975 Vitamin E concentrations in blood and tissues of growing

pigs fed variable addition of dl-a-tocopheryl acetate [in German]. Int J Vitam Nutr Res 45(3) 333-341.

Ruth G R, van Vleet J F 1974 Experimentally induced selenium vitamin E deficiency in growing swine: selective destruction of type 1 skeletal muscle fibers. Amer J Vet Res 35

pp 1071-1076.

237-244.

Influence of vitamin E supplementation on swine 29

SAS 1987 SAS Series Package. SAS Institute Inc, Cary, NC. Scott M L 1978 Vitamin E. In: Handbook of Lipid Research, Vol 2, ed Deluca H F. Plenum

Press, New York, pp 133-152. Serafin W E, Dement S H, Brandon S, Hill E J, Park C R, Park J H 1987 Interactions of

vitamin E and penicillamine in the treatment of hereditary avian muscular dystrophy. Muscle Nerve lO(8) 685-697.

Shearer M J 1986 Vitamins. In: HPLC of Small Molecules, ed Lim C K. IRL Press, Oxford,

Sigma Bulletin 1988 Quantitative kinetic determination of CK (procedure # 47-UV), LADH (procedure #228-UV) and CT (procedure #58-UV) in serum or plasma. Sigma, St Louis, MO.

Tanaka H, Mino M 1986 Membrane-to-membrane transfer of tocopherol in red blood cells. J Nutr Sci Vituminol32 463-474.

Tappel A L 1962 Vitamin E as the biological lipid antioxidant. Vitamin Horm 20 493-510. Tolonen M, Sarna S, Halme M, Touminen S E J, Westermarck T, Nordberg V, Keinonen

M, Schrijver J 1988 Antioxidant supplementation decreases TBA reactants in serum of elderly. Biol Trace EIem Res 17 221-228.

Umeda F, Watanabe J, Ibayshi H 1986 Vitamin E and diabetes mellitus. Vitamin 60(12)

Ursini F, Bindoli A 1987 The role of selenium peroxidases in the protection against oxidative

pp 173-180.

561-566.

damage of membranes. Chem Phys Lipids 44 255-276.