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ANIMAL NUTRITION |
* INRA, Research Unit on Herbivores, Nutrients and Metabolisms Group, Research Centre of Clermont-Ferrand/Theix, Saint Genès-Champanelle, France; and
and
INSERM Unit 551, CHU Pitié-Salpétrière, Paris, France
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionLiterature Cited |
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-tocopherol (x2.5; P < 0.05) leading to similar resistance against peroxidation. After depletion of this vitamin, the rates of peroxidation and production of conjugated dienes were greater (twofold; P < 0.05) with the ISO and ILO diets than with the others. In conclusion, infusion of sunflower or linseed oil into the duodenum altered the composition and distribution of plasma lipids and increased the plasma concentration of PUFA. The sensitivity of plasma PUFA to peroxidation depends on the plasma level of antioxidants, especially vitamin E, a nutrient important both for the health of animals and for the stability of the blood lipids until their tissue deposit.
Key Words: Antioxidant Capacity • Dietary Polyunsaturated Fatty Acids • Fattening Steers • Lipoperoxidation • Oil Seeds • Plasma Lipids
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Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionLiterature Cited |
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; Williams, 2000). Ruminant fat, which is relatively abundant in foods in Western countries, has a high ratio of atherogenic fatty acids as saturated fatty acids (SFA; such as myristic and palmitic acids) and trans MUFA to PUFA (Geay et al., 2001; Wood et al., 1999).
Several studies have been undertaken to increase the content in PUFA in meat lipids and in milk. Cattle have been fed rations supplemented with protected (from ruminal hydrogenation) or unprotected oilseeds or free oils rich in n-6 PUFA (sunflower, cotton, canola, safflower, soybean) or in n-3 PUFA (linseed, fish oils; Clinquart et al., 1995; Demeyer and Doreau, 1999; Wood et al., 1999); however, PUFA are preferential targets for free radical attacks initiating peroxidation. Within the context of such dietary strategies, level of peroxidation process was evaluated in ruminant products (meat and milk) for their effect on nutritional quality (Durand et al., 2004), but not in the blood compartment. Nonetheless, lipoperoxidation may be involved in the alteration of animal performance (growth, reproduction) and health (immunological disturbances), owing to metabolic disturbances (Aurousseau, 2002) as described in humans (Slater, 1984; Pré, 1991).
We hypothesised that the relative susceptibility of plasma lipids to peroxidation in fattening steers receiving PUFA-rich diets would be increased. This study was designed to evaluate the intensity of these peroxidation processes according to 1) the origin and the type of PUFA (n-6 PUFA from sunflower seed or n-3 PUFA from linseed); and 2) the degree of protection of PUFA administered against hydrogenation by ruminal bacteria. The latter effect was assessed by comparing feeding of oilseeds with duodenal infusions of free oils from these oilseeds.
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Materials and Methods |
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Sunflower Experiment.
A total of 18 crossbred Salers x Charolais steers (454 ± 20 d of age; 528 ± 36 kg BW) was used in a 70-d experimental period between January and May 2000. Six groups of three animals blocked by their initial BW and preexperimental ADG were assigned randomly to one of the three diets. These diets were 1) a control diet (CS, n = six) consisting of 54% of DM from meadow hay and 46% of DM from concentrate; 2) a sunflower seed diet (SS, n = six), consisting of crushed sunflower seeds added to the control diet to give a supplement of 40 g of oil/kg of dietary DM; or 3) an infused sunflower oil diet (ISO, n = six), consisting of the control diet plus sunflower oil continuously infused by a peristaltic pump into the proximal duodenum through a chronic cannula at a rate of 4% of diet DM during the 70-d experimental period. Animals in each group were managed in pair-feeding conditions to gain at a rate of 1.0 to 1.2 kg/d. The concentrate mix contained (per kilogram; DM basis) 575 g of corn, 240 g of soybean meal, 120 g of dehydrated alfalfa, 20 g of cane molasses, 25 g of urea, and 20 g of a vitamin and mineral mixture. The vitamin and mineral mixture named Boviphos was provided by Centre Aliment (Cantal, France).
Linseed Experiment.
A total of 24 crossbred Salers x Charolais steers (412 ± 33 d of age; 536 ± 33 kg BW) was used in a 70-d experimental period between February and April 2001 (n = 12) or between January and May 2002 (n = 12). Eight groups of three animals, blocked by initial BW and preexperimental ADG, were given either 1) a control diet (CL, n = eight) consisting of 45% of DM from meadow hay and 55% of DM from a concentrate described previously; 2) a linseed diet (LS, n = eight), consisting of extruded linseed added to the control diet to give a supplement of 40 g oil/kg of dietary DM; or 3) an infused linseed oil diet (ILO, n = eight), consisting of the control diet supplemented with 4% (DM) linseed oil continuously infused into the proximal duodenum through a chronic cannula. Animals in each group were pair-fed to gain at a rate of 1.0 to 1.2 kg/d over the experimental period.
Surgery
Only the steers that received oil infusion treatment into the duodenum were equipped with a chronic cannula. General anesthesia was induced with oxygen-isoflurane (10%) using a mask and maintained with oxygen-isoflurane (4 to 5%) using an endotracheal tube connected to a closed-circuit anesthesia apparatus. The steers were placed in left lateral recumbency, and an incision 20 to 25 cm long was made under the last rib. The incision was continued through muscle to enter the peritoneum. A 25-mm-diameter cannula in silicon was placed in the duodenum approximately 10 to 15 cm distal to the pylorus and exteriorized through the skin approximately 10 cm above the incision.
Animal Management.
During the preexperimental period (1 mo), all animals received a basal diet consisting of 50% meadow hay and 50% concentrate mixture on a DM basis. In both experiments, diets were formulated weekly to meet protein and energy requirements as well as feed intake capacity of growing animals, using the INRAtion micro computer program (Micol et al., 1989). During the first week of the experiment, animals from groups SS, LS, ISO, and ILO were adapted to added lipid by receiving only 2% of DM as fat. Steers in the ISO and ILO groups received the nonlipid part of seeds provided as sunflower seed (271 g/d) and linseed cake (455 g/d), respectively. The amount of sunflower seed (238 g/d) and linseed (303 g/ d) lipid infused into the duodenum to reach 4% of DM took into account the amount of lipid provided by cake (9 and 67 g/d in sunflower seed and linseed cake, respectively). Moreover, the amount of wheat bran added to Diets CL and ILO (296 g/d) corresponded to that of the commercially extruded linseed fed in Diet LS. The DM and fatty acid composition of nutrients supplied (diets plus infusion) with the six treatments is reported in Tables 1 and 2, respectively.
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Plasma Lipids and Apolipoproteins
Plasma concentrations of free cholesterol, cholesteryl esters, triglycerides, phospholipids, and NEFA were determined enzymatically as previously described by Leplaix-Charlat et al. (1996). Concentrations of apolipo-proteins A–I and B in plasma were estimated by the technique of Mancini et al. (1965) adapted for the bovine by Auboiron et al. (1994).
Plasma Lipid Peroxidation
Kinetics of Conjugated Diene Generation.
Susceptibility of plasma PUFA to peroxidation was determined by monitoring the kinetics of generation of conjugated dienes after induction of the peroxidation process by copper (Schnitzer et al., 1995) subsequently adapted for bovine samples (Scislowski et al., 2000) using data reported by Ziouzenkova et al. (1996). Thus, after a 50-fold dilution of a citrated-plasma sample in degassed 0.01 M PBS (pH 7.4), the oxidation reaction was induced at 37°C by adding 200 µM of a freshly prepared aqueous copper chloride solution. Absorbance of conjugated dienes was continuously recorded at 245 nm using a Uvikon 923 double-beam spectrophotometer (Kontron Analysis Division). The kinetics of conjugated diene generation can be divided into three phases from which three response variables were calculated as described by Esterbauer et al. (1989): 1) length of the lag phase (Lp) corresponding to the resistance time of PUFA against oxidation; 2) maximum rate of peroxidation (Rmax) during the propagation chain reaction; and 3) maximum amount of conjugated dienes (CDmax) accumulated after the propagation phase.
Plasma Antioxidant Capacity.
Total plasma antioxidant capacity was determined by the method based on the absorbance of the ABTS°+ radical cation (2,2'-azinobis-(3-ethylbenzothiazoline-6-sulphonic acid)) described by Miller et al. (1993) and adapted to the bovine in our laboratory. Briefly, production of ABTS°+ was initiated by addition of 75.15 µM hydrogen peroxide in a 1-mL quartz cuvette containing 12 µL of plasma, 75 µM ABTS, and 1.22 µM metmyoglobin diluted in degassed-PBS. Absorbance at 732 nm was measured immediately (At0) and 3 min after the addition of hydrogen peroxide (At3) at 37°C using a Uvikon 923 double-beam spectrophotometer. Absorbance of a blank (i.e., containing distillated water in place of plasma) was measured at 732 nm to calculate the inhibition percentage of the reaction as follows:
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Finally, inhibition percents were expressed as trolox equivalent antioxidant capacity (TEAC) at trolox concentrations ranging from 0 to 2.5 mM (inhibition percent proportional to trolox concentration).
Plasma -Tocopherol.
Concentration of -tocopherol was determined using the HPLC method described by Hatam and Kayden (1979) and adapted to bovine plasma. Extraction of -tocopherol from plasma (500 µL) was realized in 350 µL of ethanol and 1 mL of hexane under agitation during 10 min. To calculate the yield of extraction, tocopherol acetate (150 µL of a 60 µg/mL ethanol solution) was added to the plasma sample as an internal standard. Both -tocopherol and the internal standard contained in the hexane phase were extracted by centrifugation (10 min at 1,200 x g). A second extraction with 1 mL of hexane was subsequently conducted. The hexane phase was evaporated under a stream of N2 and redissolved in 150 µL of methanol/dichloromethane (65:35; vol/vol). Conditions of separation for -tocopherol in the HPLC system (Kontron Analysis Division) were as follows: an aliquot of 60 µL was injected on the HPLC column (nucleosil 5µ C18, 250 x 4.6 mm; Interchim, Montluçon, France), the mobile phase being methanol delivered at a flow rate of 2 mL/min by the HPLC pump system (model 325, Kontron Analysis Division). The column effluent was monitored by UV spectrophotometry at 292 nm using a HPLC detector (model 430, Kontron Analysis Division). Chromatographic signals were analyzed using the Kroma System 2000 software (Kontron Analysis Division). Retention times of -tocopherol and tocopherol acetate were 6.1 and 7.9 min, respectively. The concentration of -tocopherol in the samples was determined (by measuring the respective peak areas corresponding to the respective -tocopherol concentrations) from a series of -tocopherol standards ranging from 3 to 25 µg/mL and from 20 to 150 µg/mL for plasma poor and rich in vitamin E, respectively.
Fatty Acid Gas-Liquid Chromatography Analysis
Total lipids in plasma samples were extracted according to the method of Folch et al. (1957) and saponified overnight in an ethanolic potassium hydroxide solution (100 g/L). The fatty acids present in these samples were methylated at room temperature by the BF3/Na methanolate method (Sébédio et al., 1999) and subsequently analyzed by GLC using a DI 200 chromatograph (Perichrom, Saulxles-Chartreux, France) equipped with a CP-Sil 88 glass capillary column (length = 100 m; i.d. = 0.25 mm). Conditions for GLC analysis have been described previously (Scislowski et al., 2004). The oven temperature was held constant for 30 s at 70°C, increased from 70 to 175°C at 20°C/min, held at 175°C for 25 min, increased again from 175 to 215°C at 10°C/min, and finally held at 215°C for 41 min. The carrier gas was hydrogen (1.1 mL/min) in conditions of split injection (1/50). Injector and detector temperatures were 235 and 250°C, respectively. Fatty acids were identified by comparing their retention times with those of fatty acid standards (Supelco Park, Bellefonte, PA). Chromatographic signals were analyzed using the Wininlab II Chromatography data systems software (Perichrom).
From the fatty acid composition of plasma total lipids, the index of peroxidizability (IP), which estimates the concentration of bisallylic hydrogen atoms present in unsaturated fatty acids was calculated as follows from the equation reported by Nagyova et al. (2001):
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Statistical Analyses
In all of these experiments, data from the FA composition of plasma total lipids with the three diets C, S, and O were analyzed as a randomized complete block design with the six or eight blocks being sets of matched steers, by ANOVA using the GLM procedure of SAS (SAS Inst., Inc., Cary, NC). When a treatment response was detected (P < 0.05), the respective means of the three groups were compared using the Student’s t-test of SAS.
Data for plasma apolipoproteins A–I and B, lipids, antioxidants (-tocopherol and TEAC), and conjugated dienes (Lp, Rmax, and CDmax), obtained at five kinetic points (0, 15, 30, 45, and 70 d of experiment), were used in repeated measures for each of the six and eight blocks of animals, respectively. The statistical method used was the ANOVA test applied for repeated measures according to the PROC GLM procedure of SAS, which takes in account the result of the test of the symmetry and of the sphericity calculated automatically by the PRINTE option in the REPEATED statement. Thus, the adjusted Huynh-Feld probabilities on the GLM printout were used to determine the significance levels of our data. When the main factors (treatment effect and time effect) were statistically significant (P < 0.05), treatment means were compared. When the treatment x time interaction was statistically significant (P < 0.05), the significance of the main factors was not taken into account, and treatment means were compared at each time point by the Student’s t-test of SAS.
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Results |
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), the response being, respectively, 1.2- to 1.8-fold greater (P < 0.05) than initial values at the end of the experimental period. In steers receiving sunflower seeds (Diet SS), plasma concentrations of phospholipids, free cholesterol, and cholesteryl esters all increased after 15 d of supplementation, reaching concentrations approximately 1.4-fold greater (P < 0.05) than initial values (Figures 1C, 2A and 2C). In steers receiving oil infusion (Diet ISO), similar increases were observed but were more pronounced (i.e., approximately 50% greater, P < 0.05, for plasma phospholipids and 70% for plasma cholesterol; Figures 1C, 2A, and 2C), and occurred as soon as the 15th day of experiment.
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). In contrast, the fatty acid profile was strongly affected by the infusion of sunflower oil. The PUFA:SFA ratio became 2.1-fold greater (P < 0.05) than control steers, due to both a lower content in SFA (–33%; P < 0.05) and a higher content in n-6 PUFA (1.6-fold; P < 0.05), the latter being mainly the result of an enrichment in linoleic acid (1.8-fold; P < 0.05). Moreover, the MUFA content decreased with the ISO treatment (–62%; P < 0.05), particularly oleic acid (–59%; P < 0.05), and the n-3 PUFA content also was considerably less (–73%; P < 0.05).
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), whereas in steers receiving sunflower oil infusion, the IP value increased (1.2-fold; P < 0.05).
Effect of Dietary n-6 PUFA on the Susceptibility of Plasma Lipids to Peroxidation.
With the SS diet, the length of the lag phase (Figure 3A), the maximum rate of oxidation (Figure 3C) and the maximum amount of conjugated dienes (Figure 3E) all remained both constant and comparable to those noted for control steers during the whole experimental period. Oil infusion (ISO treatment) did not lead to modification of Lp (Figure 3A), but it led to a marked increase in both Rmax (Figure 3C) and CDmax values (Figure 3E) by 15 d of treatment (1.7- and 2-fold; P < 0.05, respectively). This trend continued to the end of the experimental period, with terminal values, respectively, 2.5- and 2.6-fold greater (P < 0.05) than control steers.
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-tocopherol increased by a factor of 1.7 (P < 0.05) after 15 d and by 2.5 (P < 0.05) after 70 d of treatment (Figure 4A). The TEAC was not modified during all the experimental period (Figure 4C).
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) and in both phospholipids (Figure 1D) and cholesterol (free cholesterol, Figure 2B; cholesteryl esters, Figure 2 D; total cholesterol, data not shown) after 15 d (P < 0.05); increases persisted until the end of the experimental period. In animals receiving a linseed oil infusion (Diet ILO), similar but more pronounced effects were observed with plasma apolipoprotein A–I, phospholipids, and cholesterol reaching values 1.4-, 1.8-, and 1.8-fold greater (P < 0.05) than those noted in steers fed the linseed supplement.
Effect of Dietary n-3 PUFA on Plasma Fatty Acids at the End of the Experimental Period.
Compared with values in the control group, Diet LS led to a higher content in n-3 PUFA (2.2-fold; P < 0.05), due to enrichment in linolenic acid (2.6-fold; P < 0.05; Table 4); however, PUFA:SFA ratio did not increase with the Diet LS because there was a concomitant decrease (–23%; P = 0.147) in the n-6 PUFA content. As observed in the Sunflower experiment, the protected form of diet (ILO) led to modifications more pronounced than those observed with the unprotected form (LS). Compared with the control animals, the content of linolenic acid increased (5.7-fold; P < 0.05), leading to a PUFA:SFA ratio 1.9-fold greater (P < 0.05) than control steers. The SFA content decreased significantly (–27%; P < 0.05) with the ILO treatment compared with the two other diets (CL and LS).
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) and increased (1.5-fold; P < 0.05) in steers receiving oil infusion.
Effect of Dietary n-3 PUFA on the Susceptibility of Plasma Lipids to Peroxidation.
Similarly to Diet SS, the LS diet did not modify plasma lipid peroxidation responses (Figure 3B, 3D, and 3F). In contrast, as early as d 15, Diet ILO led to values for the corresponding Lp that were approximately 1.8-fold lower (P < 0.005) than those noted with the CL diet. As in the Sunflower experiment, the linseed oil infusion led to a large increase in Rmax and CDmax values as early as d 15 to the end of experiment, with values approximately 2.4-fold greater (P < 0.05; Figure 3) than those observed in control steers.
Effect of Dietary n-3 PUFA on Plasma Antioxidants.
Linseed supplements as seed or oil duodenally infused had no significant effect on plasma -tocopherol concentration (Figure 4B) or on TEAC (Figure 4D) during the 70 d of the experimental period.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionLiterature Cited |
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) and with preruminant calves given milk enriched with soybean oil (Leplaix-Charlat et al., 1996). Hypercholesterolemia and hyperphospholipidemia were associated with higher levels of high-density lipoprotein (HDL) particles because they were associated with higher concentrations of apolipoprotein A–I, the major HDL apolipoprotein in the bovine (Bauchart, 1993). Moreover, the lack of effects of added oils on plasma triglycerides and on apolipoprotein B suggested that the metabolism of triglyceride-rich lipoproteins (i.e., very low-density and low-density lipoproteins particles; Bauchart, 1993) was not altered by dietary PUFA. Additionally, we demonstrated for the first time that the effects of dietary PUFA on lipemia depended on the amount of PUFA consumed by steers whatever its chemical composition because similar effects were noted with diets supplemented with either n-6 PUFA (sunflower oil) or n-3 PUFA (linseed oil).
The linseed treatment LS resulted in a substantial incorporation of 18:3n-3 into plasma lipids despite the high intensity of ruminal biohydrogenation of this fatty acid (80 to 100%; Doreau and Ferlay, 1994). In contrast, feeding sunflower seed did not lead to the incorporation of linoleic acid into plasma lipids, even though ruminal bacteria activity leads to less intensity of biohydrogenation of 18:2n-6 (60 to 95%; Doreau and Ferlay, 1994). Such discrepancies might be explained by differences in the amounts of fatty acid consumed or absorbed by the small intestine among animals given the experimental diets. Although the fatty acid amounts consumed in both experimental diets were similar, the linseed-rich diet (Diet LS) provided a supplement of 157 g of 18:3n-3/(animal·d), whereas the sunflower seed-rich diet (Diet SS) provided 154 g of 18:2n-6/(animalmiddot;d). Thus, differences in the effect of oilseeds on plasma fatty acids are likely to be due to differences in PUFA absorption efficiency, depending on their respective technological treatments. Indeed, crushing the sun-flower seeds may have decreased the efficiency of intestinal absorption of n-6 PUFA. In contrast, the extrusion treatment of linseeds, as used in our experiment, should increase availability of n-3 PUFA for absorption.
Diets rich in PUFA lead to higher susceptibility of plasma lipids to peroxidation compared with SFA- or MUFA-rich diets (Nielsen et al., 2000; Nagyova et al., 2001; Kratz et al., 2002). This relationship between dietary PUFA and plasma peroxidizability was not expected in steers fed the seed supplements because we did not observe any changes in the PUFA:SFA in plasma lipids. In contrast, effects on plasma PUFA were obtained, as expected, with oil infusion treatments, which led to higher PUFA:SFA and greater IP. The n-3 PUFA-rich diets led to an increase in plasma linolenic acid (18:3n-3), a more peroxidizable substrate (as indicated by the higher IP value) than linoleic acid (18:2n-6) provided by the n-6 PUFA-rich diet (Nielsen et al., 2000; Nagyova et al., 2001). The distribution of SFA, MUFA, and PUFA in plasma fatty acids was quite similar in steers given n-6 and n-3 PUFA-rich diets, but the distribution of PUFA between the n-6 and n-3 families was clearly different (n-6/n-3: 98/2 and 57/43 for n-6 and n-3 PUFA-rich diets, respectively). Consequently, from the theoretical calculation of the index of peroxidizability, one would expect greater plasma fatty acid oxidizability with n-3 PUFA treatment than with n-6 PUFA.
To confirm this hypothesis, we assayed lipid peroxidation response variables in an in vitro system using copper-induced oxidation. We monitored the production of conjugated dienes in whole plasma, thereby characterizing the early stage of the peroxidation chain reactions (Schnitzer et al., 1995). This approach is useful for screening because it depends not only on the fatty acid composition of plasma lipids but also on the balance between pro- and antioxidant factors in blood (Pré, 1991; Sutherland et al., 2002).
Duration of the lag phase observed in our experiments indicated that the resistance of plasma fatty acids to peroxidation in steers given oilseed-rich diets (unprotected PUFA) was not modified, as was expected from plasma fatty acid composition. In contrast, infusing linseed oil (2.8 g oil/kg BW0.75; PUFA:SFA = 4.6) led to less resistance of plasma fatty acids against peroxidation, noted as a 40% decrease in the duration of the lag phase. Differences noted between the effects on peroxidation of seed and oil supplementations can be considered to be due to PUFA protection and not to the activity of circulating seed antioxidants because the latter are equally provided by diets supplied to animals receiving an oil infusion. Moreover, linseed antioxidants are mainly composed of lignans (secoisolariciresinol diglycoside) of the phytoestrogen class that are hydrosoluble (Prasad, 1997) and lead to poor protection of linseed oil against lipoperoxidation. Indeed, in the linseed oil experiment, steer plasma seemed very sensitive to peroxidation.
Sensitivity to peroxidation was dependent on the origin and/or type of dietary PUFA, because with the sun-flower oil treatment (2.5 g oil/kg BW0.75; PUFA:SFA = 4.0), the duration of the lag phase was not significantly modified despite the greater IP value. This result is comparable to those obtained in healthy men given diets supplemented with safflower oil (2.9 g of oil/kg BW0.75; Sutherland et al., 2002) or sunflower oil (3.7 g oil/kg BW0.75; Kratz et al., 2002) where the lag phase was shortened by only 10 to 15%. This phenomenon can be explained by the specific antioxidant effect of -tocopherol contained in sunflower oil (625 mg/kg; Sauvant et al., 2004), of which the basal plasma concentration (2 µg/mL) increased rapidly in response to sun-flower seed and meal intake, as has been observed previously by Njeru et al. (1995) in beef heifers. -Tocopherol is considered the major lipophilic antioxidant in plasma through its scavenging action toward free-radical flux associated with a high level of copper salt (5 µM) added in our assay (Ziouzenkova et al., 1996; Thomas and Stocker, 2000).
The lack of effect of the higher plasma concentration of -tocopherol with n-6 PUFA supplementation (Diets SS and ISO) on the total antioxidant capacity of plasma (measured as TEAC) may first be due to counteraction by unidentified prooxidant components. In addition, in the Randox-TEAC assay, which makes use of hydrophilic radicals (ABTS radical cations; Miller et al., 1993), the contribution of vitamin E to the total antioxidant capacity probably is minor because water-soluble antioxidants form the first line of defense against oxidative damage (Yeum et al., 2003). This latter hypothesis is supported by the study of Cao and Prior (1998) in humans, which showed that the respective contributions of various plasma components to serum TEAC were 25% for albumin, 19% for uric acid, 3% for ascorbic acid, and only 2% for -tocopherol.
After consumption of available antioxidants (end of the lag phase), rapid oxidation occurred, characterized by the formation of conjugated dienes from oxidative degradation of PUFA (Pré, 1991). The Rmax value calculated from the slope for the propagation phase should be an accurate index of the efficacy and frequency of reactions between Cu-generated lipid radicals and surrounding plasma PUFA transported by lipoprotein particles (Esterbauer et al., 1989; Schnitzer et al., 1995). In steers, PUFA protected against ruminal biohydrogenation provided duodenally led to numerous peroxidation chain reactions (+90 to 140% at d 70 compared with d 1). The increase in Rmax value was similar with linseed or sunflower oil infusions, indicating that n-6 and n-3 PUFA had similar effects. This was explained by the similar shifts observed in plasma fatty acids between the SFA, MUFA, and PUFA classes in steers given either n-6 or n-3 PUFA-rich diets. The different proportions of n-3 and n-6 PUFA in plasma had no effect on the rate of peroxidation.
At the end of the propagation phase, the maximum amount of conjugated dienes (CDmax) depends on the amount of oxidizable fatty acids (Esterbauer et al., 1989; Sutherland et al., 2002). The higher value of CDmax determined in steers infused with oil compared to steers fed oilseeds was presumably the result of decreased ruminal biohydrogenation of PUFA. Compared with that observed in humans (Stalenhoef et al., 2000; Kratz et al., 2002; Sutherland et al., 2002), the greater production of conjugated dienes (eight- to 16-fold) noted in our steers given PUFA-rich diets probably resulted from the higher proportion of lipids in the experimental diets and/or from the long term effect of lipid supplementation. For rats fed a diet containing 5% of fish oil lipids for 16 wk (Miret et al., 2003), the increase (twofold) in CD production was similar to that observed in our steers given oil supplements (2.6-fold). As expected from the greater plasma IP value in steers receiving the linseed diet, the corresponding CDmax was greater than that noted in steers fed sunflower seeds. This difference might be related to the number of double bonds in plasma fatty acids because susceptibility to oxidation is proportional to their degree of unsaturation (Nielsen et al., 2000; Nagyova et al., 2001). Distinctions between the respective effects of n-3 and n-6 PUFA-rich diets have been revealed by measurement of conjugated diene generation. This method seems relevant to determine the intensity of peroxidation under our experimental conditions, particularly compared with the TBARS assay, which reflects malondialdehyde production from the peroxidation of fatty acids with at least three double bonds.
In conclusion, feeding PUFA to steers, via oilseed supplementation, did not alter plasma lipids and their fatty acids, and it had no manifest effect on the peroxidation process. In contrast, duodenal infusion of dietary PUFA induced large changes in plasma lipids and fatty acids, and it facilitated peroxidation in plasma. The n-3 PUFA-rich diets led to a higher susceptibility of plasma PUFA to peroxidation than n-6 PUFA-rich diets, probably as a result of presence of -tocopherol in the sun-flower-rich diet. The -tocopherol likely provided more protection of plasma PUFA against the initiation of peroxidation than lignans provided by a linseed supplement. Finally, n-3 PUFA-rich diets led to more oxidative degradations due to more numerous double bonds.
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Footnotes |
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2 Correspondence: 63122 Saint Genès-Champanelle (phone: 33 04 73 62 42 27; fax: 33 04 73 62 46 39; e-mail: durand{at}clermont.inra.fr).
Received for publication May 5, 2004. Accepted for publication June 8, 2005.
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Literature Cited |
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à l’ebgraissement. INRA Prod. Anim. 8:29–42.
iz, and M. T. Mitjavila. 2003. Effects of fish oil-and olive oil-rich diets on iron metabolism and oxidative stress in the rat. Br. J. Nutr. 89:11–18.[Medline]
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, n = 6; CL, •, n = 8), or the same basal diet supplemented with oilseeds (SS, 
, n = 6; LS, 
, n = 8), or with oils infused into the duodenum (ISO, 
, n = 6; ILO, 
, n = 8). Results are expressed as mean ± SE. Significant diet x time interactions were observed for plasma apo A–I concentration in sunflower (P < 0.001) and linseed (P < 0.001) experiments, and for plasma PL concentration in both sunflower and linseed (P < 0.001) experiments. * Indicates a difference between Diets SS and CS and between Diets LS and CL, P < 0.05; 
indicates a difference between Diets SS and ISO and between Diets LS and ILO, P < 0.05.
