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J. Anim. Sci. 2004. 82:2410-2420
© 2004 American Society of Animal Science

ANIMAL PRODUCTION

Effect of supplemental tryptophan, vitamin E, and a herbal product on responses by pigs to vibration1

E. Peeters2, B. Driessen, R. Steegmans, D. Henot and R. Geers

Laboratory for Quality Care in Animal Production, Zootechnical Centre, Katholieke Universiteit Leuven, B-3360 Lovenjoel, Belgium


   Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 Literature Cited
 
Economic losses related to increased stress during the transport of pigs are well documented. The effects of supplementing of tryptophan (Trp), vitamin E, or a herbal product via feed or drinking water were investigated in terms of effects on stress response in pigs during transport simulation. The study consisted of three analogous experiments. For the testing in each experiment, the pigs (23.5 ± 3.2 kg) were allocated to one of two treatments, with and without supplementation of a product. The applied doses were Trp (5 g/L drinking water for 3 d), vitamin E (additional amount of 300 mg/kg feed for 21 d, as-fed basis), and Sedafit (2.5 g/L drinking water for 2 d). Sedafit is a commercial herbal product containing Valeriana officinalis L. and Passiflora incarnata L. as active components. In each experiment of the study, at least 47 pigs were involved, which were treated in groups of 3. The day before transport simulation, a Holter device was attached to the pigs to produce an electrocardiogram during the night (rest values), as well as during vibration in the transport simulator (1.2 Hz, 1 m/s2), where the behavior of the pigs (standing-sitting-lying) was also observed. Samples of saliva (taken before, during, and after [3x] vibration) and blood (taken before and after vibration) were analyzed for cortisol and intermediate metabolites (glucose, lactate, creatine kinase, and nonesterified fatty acids), respectively. Pigs supplemented with Trp tended to spend more time lying down during the second hour of vibration (P < 0.05). Vitamin E decreased the peak heart rate (P < 0.05), ventricular ectopic beats (P < 0.01), and ST elevation (P < 0.10). The supplementation of Sedafit resulted in smaller increases of the investigated heart variables (minimum heart rate, P < 0.05; ventricular ectopic beats, P < 0.05; ST elevation, P < 0.01) during and after stress evocation compared with the control group. None of the tested products influenced the intermediate metabolites; one possible explanation for this finding may be that peak values were reached before the time of bleeding. In conclusion, Trp had a positive behavioral effect in this experiment, and vitamin E and Sedafit mediated an increase in some heart variables, suggesting sedative and antianxiety effects.

Key Words: Heart Rate • Herbs • Pig • Stress • Tryptophan • Vitamin E


   Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 Literature Cited
 
Economic profit is a principal factor in transport and slaughter processes, but all parties involved are also striving for humane food production techniques. The transport of pigs can cause stress, thereby raising the issue of animal welfare. Economic losses, including mortality, carcass damage, and reduction of meat quality (Tarrant, 1989Go) must also be taken into account. The use of pharmacological sedatives before transport of animals to avoid stress and mortality is forbidden in the European Community to avoid risky food residues. There is a need for alternatives, such as supplementation of legal feed additives or herbal substances with a positive functional effect on the stress response. The calming of animals before and during transport, thereby improving both their welfare and their meat quality without introducing a residue risk for food safety, is a more ethically acceptable method. In pigs, as in other species (Fernstrom and Wurtman, 1972Go), increasing the intake of tryptophan (Trp), in competition with large neutral amino acids, elicits a higher brain serotonin concentration (Henry et al., 1992Go). This neurotransmitter influences temperature regulation, arousal, pain sensitivity, feeding, sexual behavior, and aggression (Leathwood, 1987Go). The supplementation of another feed component, vitamin E, is frequently investigated in relation to meat quality (Buckley et al., 1995Go; Cheah et al., 1995Go; Dirinck et al., 1996Go). Vitamin E is generally recognized to prevent lipid oxidation, although its effect on stress response has not yet been examined. Valeriana officinalis L. and Passiflora incarnata L., components of a commercial herbal product (Sedafit), have tranquilizing and sedative properties owing to their influences on neuromediators, such as µ-aminobutyric acid (GABA; Riedel et al., 1982Go; Medina et al., 1990Go). The objective of this study was to examine the effect of tryptophan, vitamin E, and Sedafit on responses of pigs during a transport simulation.


   Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 Literature Cited
 
Animals and Housing

Crossbred (Piétrain x Hypor) pigs, heterozygous for the halothane gene, were kept at the Zootechnical Center of Katholieke Universiteit Leuven in standardized housing conditions. Three (Trp) or 2 d (vitamin E and Sedafit) before being subjected to vibration, three animals from the same pen with an average body weight of 23.5 ± 3.2 kg were selected at random and moved to a smaller group pen. This weight was chosen to allow easy handling of the animals. It is assumed that pigs of this BW have physiological stress responses comparable to those of market pigs (Dantzer and Mormède, 1983Go). To avoid damage to the attached heart rate device, they were housed individually 1 d before vibration (after anesthesia, detailed later), although with auditory contact with other pigs.

The animals were vibrated in groups of three to avoid the effect of social isolation, which was taken into account in the statistical analysis and were alternately treated as a control group or as a group with product supplementation. Each group contained at least one representative from each sex (barrow or sow).

Supplementation

The animals were given free access to drinking water (via a nipple) and feed. All pigs received a commercial feed (17.5% CP and 11.7 MJ/kg DE, as-fed), with 100 mg of vitamin E/kg and 250 mg of Trp/kg, as-fed. Three products were tested in separate, analogous experiments: Trp, vitamin E, and Sedafit. The experiments consisted of two treatments: 1) extra supplementation of the product in drinking water or feed and 2) control treatment without supplementation (i.e., commercial feed and drinking water without supplements). The doses and the duration of the supplementation are presented in Table 1Go. The vitamin E (D,L-{alpha}-tocopheryl acetate; Rovimix E-50 SD; DSM Nutrition, Deinze, Belgium) was added to the feed using a feed mixer for 30 min. The L-Trp (98%; Ajinomoto Eurolysine, Orffa, Londerzeel, Belgium) and the Sedafit (Photosynthèse; Saint-Bonnet de Rochefort, France) were dissolved in water. Lack of blood and saliva samples resulted in missing data for one of the animals in the vitamin E and Sedafit experiments.


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  		Table 1. Dose and duration of supplementation of tryptophan, vitamin E, and Sedafit, and number of tested animals without (control) and with product supplementation
 
Preparation of the Animals

The experimental animals were treated in accordance with the Belgian law on the protection of animal well-being (Belgisch Staatsblad [Belgian Law Gazette], 1986Go). The pigs were weighed and then anesthetized by an intramuscular injection of xylazine (3 mg/kg BW, XYL-M; V.M.D., Arendonk, Belgium) and the combination of tiletamine and zolazepam (5.5 mg/kg BW, Zoletil; Virbac Laboratories, Carros, France). During anesthesia, a Holter device (model No. 43400B, Philips Medical System [formerly Hewlett Packard], Andover, MA) was attached to the pigs to produce an electrocardiogram over a 24-h period. Five adhesive leads (Unilect; Maersk Medical, Stonehouse, Gloucestershire, U.K.) were placed at the fourth intercostal space at the border of the sternum right and left and at the fifth intercostal space on the left and right anterior axillary line, with the reference electrode on the fifth rib at the right side of the sternum (Geers et al., 1990Go). The Holter device was fixed on the back of the pig using a protective bandage (Tricodur Softgrip; BSN medical, Brierfield, U.K.) around chest and abdomen. Peak, minimum and mean heart rate, the number of ventricular ectopic beats (VEB), and the ST elevation (STE) from the isoelectric line on the two lead positions (Channels A and B) were registered, and the averages per hour were calculated. These measurements are considered representative of the animal’s emotional response to a new environment (Broom and Johnson, 1993Go). To decrease the effect of isolation stress, the recording for the rest or reference period took place under sleeping conditions (2200 until 0600), and the average was calculated for this interval.

Transport Simulation

After a group of three pigs was transferred (a procedure lasting 3 min) by trolley from their pen to an air-conditioned (average temperature = 20.9°C, SD = 1.2°C) vibration room, they were manually lifted into the vibration crate (a procedure taking 2 min). This crate was designed and assembled by the Silsoe Research Institute (United Kingdom) with dimensions of 0.77 m x 1.22 m x 0.64 m (width x length x height). The simulation started at 1000. The pigs were subjected to vibrations in the vertical axis at a frequency of 1.2 Hz and root mean square (RMS) acceleration of 1 m/s2 for 2 h (Randall et al., 1995Go). In the middle of this period, the simulation was interrupted for 10 min to take saliva samples. During vibration, the dry air temperature was registered (Hobo H8 Logger; Onset Computer Corp., Bourne, MA). Subsequently, the animals were moved to their individual pens, where they could rest for another 2 h (1215 until 1415). The first and second hour of vibration will be indicated hereis as v1 and v2, respectively, and the first and second hour of the recovery period as r1 and r2, respectively.

Behavioral Measurements

During transport simulation (1000 until 1200), the experimental animals were observed by a camera (KP-143; Hitachi, Brussels, Belgium) connected to a monitor. Their behavior (i.e., the time in seconds that each animal spent standing/sitting or lying down) was noted for evaluating their level of restlessness as a measure of stress during transport (Lambooij, 1988Go).

Saliva Sampling

Saliva samples were collected with cotton swabs at five points in time: before the onset of simulation (0915, reference sample), during simulation (1100), after simulation (1200), and at two points during the recovery time (1315 and 1415). After the cotton swabs were spun (Laborefuge 400R; Heraeus Instruments, Brussels, Belgium) in salivettes for 10 min at 4,000 x g, the saliva was frozen and stored at –20°C. Cortisol in the saliva was analyzed by using a commercial RIA (ImmuChem cortisol assay; ICN Biomedicals, Asse, Belgium). The detection limit was 0.15 µg/dL and the cross-reactivity was maximum 37% with prednisolone. The intra- and interassay coefficients of variation were 7.0 and 7.9% for low (4.4 and 4.8 µg/dL), 5.8 and 6.5% for medium (22.3 and 23.1 µg/dL), and 5.1 and 6.0% for high (35.1 and 36.6 µg/dL) concentrations of cortisol.

Blood Sampling

Blood was collected into 4-mL tubes containing 9.00 mg of sodium fluoride and 9.00 mg of potassium oxalate (Venoject; Terumo, Haasrode, Belgium) by venipuncture of the jugular vein and were immediately stored on ice. The order of blood collection for each pig also was noted. This handling occurred on the day before (reference sample) and on the day of the transport simulation, both days at 1215. The same point in time was chosen to exclude the influence of circadian variations. Furthermore, the samples were centrifuged for 15 min at 3,500 x g and the plasma was frozen and stored at –20°C.

Enzymatic colorimetric methods were used to analyze these samples to determine the concentrations of glucose (GOD/POD Trinder’s method; Instrumentation Laboratory, Zaventem, Belgium), lactate (NAD/LD; Sigma-Aldrich, Bornem, Belgium), creatine kinase (CK-NAC; Instrumentation Laboratory), and NEFA (NEFA C; Wako Chemicals GmbH, Neuss, Germany).

Statistical Analyses

The data (heart rate parameters, intermediate metabolites and cortisol) were calculated for each animal as the relative increase or decrease with regard to its own reference values or samples; (Xi – Xref)/Xref, with Xi = the value of the investigated parameter at a defined time i and Xref = the reference value for that parameter. For the behavioral observation data, the total time each pig spent lying during a given hour was calculated as a percentage of that hour. The pigs were the experimental units. If necessary, a transformation to a normal distribution was performed (VEB, STE of Channel A and B, cortisol, glucose, lactate, creatine kinase, and NEFA). The data were analyzed using a mixed model (Littell et al., 1996Go) with sex and treatment as the main effects and weight as the covariable. Group was used as random factor, thereby taking into account the relationship between the measurements from the same group. The following model was used:


with

µ = mean
{alpha}i = sex (i = male, female)
ßj = treatment (j = 1 . . . 6)
{chi}k = weight
{varepsilon}ijkl = error

Nonsignificant interactions were eliminated. Each pair of least squares means within a given experiment of the study was compared with a t-test. The means of transformed data were retransformed, and the standard errors were calculated using the delta method (Serfling, 1980Go).


   Results
Top
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 Literature Cited
 
The supplementation of Trp, vitamin E, or Sedafit might already have influenced the reference values of the investigated variables, so analyses were carried out to discover possible differences between control and supplemented groups. No significant differences were revealed for heart rate variables, cortisol, or intermediate metabolites. Thus, attention was focused on relative decreases or increases during transport simulations. The actual values of the investigated variables per treatment are represented in Table 2Go.


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  		Table 2. Mean (n = 24) and standard deviation (in parentheses) per treatment for variables investigated for the experiments with tryptophan (Exp. 1), vitamin E (Exp. 2), and Sedafit (Exp. 3)
 
The three experiments of the study were executed at different times and with pigs from different herds. For this reason, control groups for the different experiments were not mixed, but were considered separately.

Figure 1Go shows the relative minimum heart rate of the control groups and of the group used for experiments with supplementation of Trp, vitamin E, or Sedafit. The Sedafit lowered the relative minimum heart rate compared with the control group during vibration (P < 0.05).



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  		Figure 1. Relative minimum heart rate (mean ± SEM) during first and second hour of vibration (v1, v2) and first and second hour of recovery period (r1, r2) of the control groups and of the groups supplemented with tryptophan, vitamin E, and Sedafit, respectively. Within an experiment, means between a control and a supplemented group with *P < 0.05 or {dagger}P < 0.10 differ.

 
None of the products were able to influence the relative mean heart rate, as can be seen in Figure 2Go.



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  		Figure 2. Relative mean heart rate (mean ± SEM) during first and second hour of vibration (v1, v2) and first and second hour of recovery period (r1, r2) of the control groups and of the groups supplemented with tryptophan, vitamin E, and Sedafit, respectively.

 
Due to supplementation of vitamin E, the peak heart rate (Figure 3Go) at the start of vibration remained nearly the same as during the night for the treated group, whereas the control group showed an increase, although this increase was significant only in the female pigs (P < 0.05). The peak heart rate of female pigs supplemented with Trp increased by almost 15 ± 4% at the start of vibration (v1), as compared with the 4 ± 4% increase for the female control pigs (P < 0.10). As for Sedafit, no significant differences were found during the following hours. Peak heart rate gives an indication of a fear reaction on the part of the animals when a situation changes. In this experiment, the peak occurs at two points: when the vibration started and when the pigs are moved from the vibration crate to their housing pens.



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  		Figure 3. Relative peak heart rate (mean ± SEM per sex) during first and second hour of vibration (v1, v2) and first and second hour of recovery period (r1, r2) of the control groups and of the groups supplemented with tryptophan, vitamin E, and Sedafit, respectively. Within an experiment means between a control and a supplemented group of the same sex with *P < 0.05 or {dagger}P < 0.10 differ.

 
The STE of Channel A was not influenced by supplementation of either of Trp, vitamin E, or Sedafit (Figure 4Go). For the deviation of Channel B, a different result was observed (Figure 5Go): the test with Sedafit indicated that during the first hour of vibration the STE of control animals increased 48%, as compared with the 12% STE increase of the treated group (P < 0.01). Vitamin E produced a decreasing trend in the STE of Channel B with reference to the night values (P < 0.10). One hour later (v2), the STE of the Sedafit-supplemented male pigs remained approximately the same as during the night, whereas the male control pigs showed an increase of 45 ± 5% (P < 0.001). The female vitamin E-supplemented animals showed an increase of relative STE, in contrast with the decrease in the female control animals (P < 0.01). In the recovery period (r1), the three investigated products influenced this variable; vitamin E and Sedafit lowered the STE, whereas supplementation of Trp increased this deviation.



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  		Figure 4. Relative ST-elevation of Channel A (mean ± SEM) during first and second hour of vibration (v1, v2) and first and second hour of recovery period (r1, r2) of the control groups and of the groups supplemented with tryptophan, vitamin E, and Sedafit, respectively.

 


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  		Figure 5. Relative ST-elevation of Channel B (mean ± SEM per sex) during first and second hour of vibration (v1, v2) and first and second hour of recovery period (r1, r2) of the control groups and of the groups supplemented with tryptophan, vitamin E, and Sedafit, respectively. Within an experiment means between a control and a supplemented of the same sex group with ***P < 0.001, **P < 0.01, *P < 0.05, or {dagger}P < 0.10 differ.

 
The v1 differences in the relative number of VEB were observed between the controls and the groups treated with vitamin E (P < 0.01) or Sedafit (P < 0.05), as shown in Figure 6Go. The number of VEB reflects the anomalous beats not generated in the pacemaker of the heart but elsewhere in the myocardium, and VEB is considered a measure of stress (Ellestad, 1987Go).



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  		Figure 6. Relative ventricular ectopic beats (mean ± SEM) during first and second hour of vibration (v1, v2) and first and second hour of recovery period (r1, r2) of the control groups and of the groups supplemented with tryptophan, vitamin E, and Sedafit, respectively. Within an experiment means between a control group and a supplemented group with *P < 0.05 or **P < 0.01 differ.

 
The effects of the supplementation of Trp, vitamin E, or Sedafit on the behavior are presented in Figure 7Go. Even though the products had an effect on the heart rate variables several times during the first hour of vibration, this was not reflected in the behavior of the pigs, because no differences between the controls and the treated groups were observed. In the second period of vibration, a favorable effect of Trp was noted (P < 0.05); pigs supplemented with Trp spent more time lying down (97.8 ± 0.8%) than unsupplemented animals (93.9 ± 0.8%).



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  		Figure 7. Percentage of the time spent lying (mean ± SEM) during first and second hour of vibration (v1, v2) of the control groups and of the groups supplemented with tryptophan, vitamin E, and Sedafit, respectively. Within an experiment means between a control and a supplemented group with *P < 0.05 differ.

 
As for the intermediate metabolites (glucose, lactate, creatine kinase, and NEFA), there were no significant differences between control and treated groups in any of the experiments (Figure 8Go).



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  		Figure 8. Relative concentration of glucose, lactate, creatine kinase (CK), and NEFA (mean ± SEM) after vibration of the control groups and of the groups supplemented with tryptophan, vitamin E, and Sedafit, respectively.

 
Figure 9Go shows that vitamin E influenced the relative concentration of cortisol in interactive manner with sex. During the first hour of vibration, vitamin E lowered the cortisol concentration in male pigs, with respect to the concentration before vibration (P < 0.01), and the same trend was observed during the second hour of vibration. Neither vitamin E nor the other products influenced the relative cortisol concentration at other moments (r1, r2).



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  		Figure 9. Relative cortisol concentration (mean ± SEM per sex) during first and second hour of vibration (v1, v2) and first and second hour of recovery period (r1, r2) of the control groups and of the groups supplemented with tryptophan, vitamin E, and Sedafit, respectively. Within an experiment means between a control group and a supplemented (of the same sex) group with **P < 0.01 or {dagger}P < 0.10 differ.

 

   Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
Literature Cited
 
Supplemental vitamin E and Sedafit in feed or drinking water affected stress response, especially heart variables, whereas supplemental Trp resulted in less-active pigs during the second hour of vibration.

Stress can be quantified by monitoring the electrocardiogram, which provides information on heart rate variability, arrhythmicities, and deviations from the isoelectric line (Ellestad, 1987Go). The relative changes of investigated variables were approximately equal for the control group and the group supplemented with Trp, with the exception of the STE of Channel B, the behavior and the peak heart rate of female pigs. As for the STE during the first hour of the recovery period, treatment with Trp resulted in a higher STE in comparison with the control group. In addition, the relative peak heart rate of supplemented female pigs was higher than that of the controls. The sedative effect of Trp only came to expression in the fact that the supplemented animals spent more time lying during v2. Other experiments with domestic animals reported the influences of Trp on anxiety and fear. Newberry and Blair (1993)Go noted a shorter duration of tonic immobility in broiler chicken supplemented with Trp (0.4%). According to Jones (1987)Go, a longer duration of tonic immobility indicates greater fearfulness. In another experiment (Shea et al., 1990Go) with broiler breeder males, an increased level of Trp decreased aggression (pecking and threatening behavior). Although Meunier-Salaun et al. (1991)Go found large variations in brain amino acids and 5-hydroxyindole concentrations, the changes in behavioral and cortisol response after an experiment with Trp-supplemented young pigs were relatively minor. The mean heart rate in horses was lowered by Trp (Bagshaw et al., 1994Go). It is noteworthy that the number of tested animals in the Bagshaw experiment was rather small. In our study, no influences of Trp on mean heart rate were found. One possible explanation for the lack of differences is that the arousal of animals was too low. Young (1991)Go mentioned that the effect of Trp may be more pronounced at higher levels of arousal, resulting in a higher rate of firing of serotonin neurons. Considering that the pigs were lying down almost half the time in the first hour of vibration, the stress evoked in this experiment may be not sufficient enough. Moreover, a short period of treatment (3 d) was applied, although in most experiments a longer application time, on the order of weeks, has been used. The reason for this is the anticipated application cost of the on-farm application of Trp. However, Adeola and Ball (1992)Go observed a decrease in the severity of pale, soft, and exudative (PSE) pork after a supplementation of 5g Trp/d for 5 d in pigs stressed before slaughter at 92 kg BW.

An application period of about 3 wk seems to be necessary to transport vitamin E from liver to fat and muscles (Flachowsky, 2000Go). In this experiment, an additional amount of 300 mg of vitamin E per kilogram of feed supplied over a period of 3 wk seemed to influence several heart variables. After vitamin E supplementation, the peak heart rate of v1 was equal to the night values. This difference was more pronounced in female pigs because this control group showed a higher peak heart rate at night. Assuming that the peak heart rate represents the initial fear level of the animals (Perremans et al., 1998Go), vitamin E may be able to reduce the anxiety of pigs in a novel situation. Additionally, less VEB were produced in the treated group. However, attention must be paid to the great amount of variation in the VEB data (Table 2Go). The more VEB, the greater the deficiency of blood supply to the heart when it is overloaded, a condition leading to arrhythmicities (Ellestad, 1987Go). Generally, the use of vitamin E also reduced the STE of Channel B in this experiment.

The positive role and the mechanism of vitamin E in preventing cardiovascular diseases have been discussed by many authors (e.g., Lonn and Yusuf, 1997Go; Neuzil et al., 2001Go; Clarke and Armitage, 2002Go). However, the biochemical effect of vitamin E on the heart rate of healthy animals has not yet been investigated as far as we know. One explanation for this positive role is the ability of vitamin E to prevent mitochondrial phospholipase A2 activity (Cheah et al., 1995Go). Douglas et al. (1986)Go observed the same inhibition in rat platelets. This enzyme specifically releases the arachidonic acid from phospholipids. The release of arachidonic acid by phospholipase A2 is believed to be the rate-limiting step for the biosynthesis of eicosanoids (Zubay, 1998Go). These eicosanoids (e.g., prostaglandins, thromboxanes) are involved in numerous biological systems, including the cardiovascular system.

None of the treatments (Trp, vitamin E, or Sedafit) influenced the relative values of glucose, lactate, creatine kinase, or NEFA compared with the control groups. One possible explanation is that the peak values were reached before the time of bleeding, which took place 2 h after the onset of the vibration. Further research relating to the time of bleeding is required.

The leakage of creatine kinase into the plasma is related to the injury of the membranes of the muscular tissue. Several authors (Asghar et al., 1991Go; Lauridsen et al., 1999Go) did not observe any change in the plasma creatine kinase concentration due to supplemental vitamin E. Asghar et al. (1991)Go found that the lactate dehydrogenase was not influenced by the levels of vitamin E supplementation.

The barrows of the control group had a substantial increase of cortisol in saliva during vibration treatment. This increase was responsible for the difference found between the treated and the control male pigs. The reason for this sex-dependent effect is not understood.

The use of herbal products has been becoming more popular in recent years. Valeriana officinalis L. (Bormann, 1988Go; Houghton, 1999Go) and Passiflora incarnata L. (Soulimani, 1997Go; Akhondzadeh, 2001Go), the active components of Sedafit, have sedative and tranquilizing properties. Its action comes to expression, for example, in the reduction of the minimum heart rate and the STE of Channel B; the latter effect is due to a different propagation of the electric current related to the activation of the ventricle (Villé et al., 1993Go). For both variables, this effect was maintained until the recovery period. The interaction between treatment and sex in the second hour of vibration might possibly be explained by the fact that deviations from the isoelectric line may differ according to sex (Blomqvist and Mitchell, 1977Go). Additionally, the use of Sedafit resulted in a lower level of VEB. Cropley et al. (2002)Go discovered that the heart rate reaction to mental stress in a group of healthy volunteers declined after the administration of a dose of valerian under laboratory conditions. The effect of valerian seems to be mediated through the modulation of GABA neurotransmission and receptor function (Santos et al., 1994Go; Ortiz et al., 1999Go). These receptors mediate an inhibitory effect by increasing Cl– influx, which induces membrane hyperpolarization and neuronal inhibition (Bormann, 1988Go). Additionally, valerenic acid inhibits the enzyme system that causes the breakdown of GABA in the brain (Riedel et al., 1982Go). Passiflora also possesses sedative and anxiolytic properties in mice (Soulimani et al., 1997Go). However, no consensus exists regarding the bioactive compounds of Passiflora, such as the flavonoidic fraction (Medina et al., 1990Go; Wolfman et al., 1994Go; Zanoli et al., 2000Go) or the benzoflavone nucleus (Dhawan et al., 2001Go).

In general, Trp acted to calm the pigs by increasing the time they spent lying down, whereas vitamin E and Sedafit decreased the relative changes of some heart rate variables during and after vibration. Further research will be conducted to compare the effectiveness of the products in combination with one other, so that the adaptation capacity can be improved at a lower physiological cost, thereby increasing the welfare status of pigs during transport.


   Footnotes
 
1 The project was funded by IWT-Vlaanderen (Institute for the Promotion of Innovation by Science and Technology in Flanders). The authors thank the companies Orffa (Buggenhout, Belgium), DSM Nutritional Products (Deinze, Belgium), and Phytosynthèse (Saint-Bonnet-de-Rochefort, France) for supplying the tryptophan, vitamin E, and Sedafit, respectively. Thanks are also due to the staff of the Laboratory for Physiology and Immunology of Domestic Animals of the K.U. Leuven for the analyses of plasma and saliva samples. This study was funded by IWT-Vlaanderen (Institute for the Promotion of Innovation by Science and Technology in Flanders) and Katholieke Universiteit Leuven. Back

2 Correspondence: Bijzondere weg 12 (phone: +32-16-46 81 37; fax: +32-16-46 81 59; e-mail: ester.peeters{at}agr.kuleuven.ac.be).

Received for publication September 16, 2003. Accepted for publication April 16, 2004.


   Literature Cited
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 Literature Cited
 


Adeola, O., and R. O. Ball. 1992. Hypothalamic neurotransmitter concentrations and meat quality in stressed pigs offered excess dietary tryptophan and tyrosine. J. Anim. Sci. 70:1888–1894.[Abstract]

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Asghar, A., J. I. Gray, E. R. Miller, P. K. Ku, A. M. Booren, and D. J. Buckley. 1991. Influence of supranutritional vitamin E supplementation in the feed on swine growth performance and deposition in different tissues. J. Sci. Food Agric. 57:19–29.

Bagshaw, C. S., S. L. Ralston, and H. Fisher. 1994. Behavioral and physiological effect of orally administered tryptophan on horses subjected to acute isolation stress. Appl. Anim. Behav. Sci. 40:1–12.

Belgisch Staatsblad. 1986. Wet betreffende de bescherming en het welzijn van dieren (Law concerning the protection and welfare of animals). Belgisch Staatsblad 16382–16390.

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