Transportation-induced nausea-like behavior in goats and the effects of anti-motion sickness medication
Abstract
This study investigated the nausea-like behavior induced by road transportation in goats, and the effects of an anti-motion sickness (MS) medication on this behavior. In the first experiment, 11 adult Shiba goats were road transported twice with either a saline (control) or a commercial anti-MS medication (Travelmin) injection at the first or second transportation. Almost all goats showed nausea-like behavior, which was defined as pointing their heads downward, closing their eyes, and staying relatively still. These goats did not respond when they were touched during blood collection. The anti-MS medication significantly reduced the total time spent in nausea-like behavior (P < 0.05) and tended to increase the frequency of escape attempts during blood collection (P < 0.1). In a second experiment, the effects of the anti-MS medication were examined in goats held under normal housing. The anti-MS medication increased the time spent feeding (P < 0.01) and reduced the time spent in rumination (P < 0.05) but did not change the frequency of lying down nor plasma cortisol concentrations. Our results indicate that the nausea-like behavior in transported goats might be induced, at least in part, by regulatory mechanisms similar to the MS.
1 INTRODUCTION
Road transportation can be severely stressful for domestic animals, such as cattle (Caffazo et al., 2012; Uetake et al., 2011), sheep (Broom et al., 1996), and goats (Aoyama et al., 2008). Relieving transportation stress is essential for animal welfare and for high quality and quantity animal production. However, the underlying physiological responses of transportation-related stress have not yet been fully clarified.
Previously, we investigated the physiological and behavioral effects of road transportation in goats and investigated the influence of sex and the effects of sexual hormones (Aoyama et al., 2003, 2005), the expression of c-Fos protein in the central nervous system (Maejima et al., 2005) and adrenal grand (Maejima et al., 2006), and the effects of prior experience of transportation (Sanuka et al., 2016). During these earlier investigations, we noted that some goats showed abnormal, sickness like behavior during transportation. The affected goats tended to lie down with their heads pointing downward, closed their eyes, and remained relatively still even when their faces or bodies were touched. Many previous reports have described the types of behavioral response to road or sea transportation in domestic ruminants, and some have indicated similar behavior as found in goats: Dunston-Clarke et al. (2020) and Willis et al. (2021) reported that some sheep could not stand up when transported by ship, and this unusual behavior was considered as an indicator of stress in these animals. To date, however, this aspect of goat behavior has not been investigated in detail. This study focused on these kinds of behaviors induced by road transportation in goats.
Unfamiliar motion can induce nausea and vomiting in humans (Graybiel & Knepton, 1976; Shupak & Gordon, 2006), and similar symptoms have been observed in dogs (Conder et al., 2008; Worth et al., 2016), shrew (Suncus murinus) (Uchino et al., 2001; Ueno et al., 1988), and pigs (Bradshaw et al., 1996, 1999). These symptoms are known as motion sickness (MS) (or travel sickness). In species that possess an emetic reflex, MS can be easily diagnosed by observing emesis as an indicator. Other animal species, such as rodents, rabbits, and horses, that do not possess an emetic reflex (Andrews & Horn, 2006; Horn et al., 2013), are less frequently used in studies on MS. However, although rodents do not possess an emetic reflex, they do exhibit “pica,” which is defined as the abnormal behavior that eat a non-nutritive substance. When rats and mice experienced the unfamiliar motion, they begun to consume kaolin (hydrated aluminum silicate) that is not food for them normally, and this behavior can be suppressed by the use of anti-MS treatments (Takeda et al., 2001). The ingestion of kaolin is considered an alternative indicator of MS in rats and mice. Thus, even animal species that do not possess an emetic reflex can exhibit motion-induced, abnormal behavior patterns. Santurtun and Phillips (2015) reviewed that the MS could be one of the significant factor in transportation stress in livestock, but MS in domestic ruminants is not clear yet because they also do not possess the emetic reflex (Horn et al., 2013).
We made the hypothesis that the sickness like behavior induced by transportation in goats is a result of the developing MS or other similar symptoms. In this study, the abnormal behaviors during and after road transportation were analyzed, and the effects of anti-MS medication on these behaviors were examined. We used the commercial anti-MS medicine “Travelmin” in this study. This medicine includes diphenhydramine (DH) hydrochloride, which is an antagonist for the histamine type 1 (H1) receptor. Previous reports indicated that DH and other H1 receptor antagonists relieved the emesis and other symptoms induced by MS in humans (Schmäl, 2013) and other animals (Ueno et al., 1988; Worth et al., 2016).
2 MATERIALS AND METHODS
All experimental procedures and care of animals were carried out according to “The Guide for Care and Use of Laboratory Animals at Utsunomiya University.” The experiments were approved by the Committee of Animal Experiments at Utsunomiya University (A08-0008, A10-0018, A16-0003, and A21-0011).
All experiments were performed at the research farm of the Faculty of Agriculture, Utsunomiya University (Moka-city, Tochigi prefecture, Japan). The experiments were conducted during April–July or October–December in 2008–2022 at temperatures ranging between 10°C and 25°C.
2.1 Experiment 1: Nausea-like behavior induced by road transportation and the effects of anti-MS medication
2.1.1 Animals
Eleven adult Shiba goats, consisting of six male (25–35 kg, 3–7 years old) and five females (20–25 kg, 3–5 years) were used. The animals were housed in individual pens (3.0 × 2.0 m) and adjacent paddock (3.0 × 5.0 m) and fed ad libitum with timothy hay and provided with ad libitum water; fresh hay and water were provided at 10:00 h every day.
2.1.2 Transportation and drug administration
Transportation was conducted as described in our previous study (Aoyama et al., 2008). In brief, two goats, housed in neighboring pens, were driven around for 1 h (09:00–10:00 h) in a truck (V-DD51T, Suzuki, Tokyo, Japan) with an open carrier. While on the truck, they were kept in individual cages (60 × 120 cm for each goat). The floor of the truck was covered with a rubber mat. A circular course (length 6.4 km) was established at the research farm, and the truck made 4 rounds of this course. The average or maximum speed was 26 and 60 km/h, respectively. There were 12 corners on the course. At the completion of each round, the truck was stopped for 2 or 3 min, and blood samples were collected. After the fourth round, the goats were re-housed in their own pens and fed as usual. The goats used in this study had previously experienced transportation in the same manner on at least one occasion.
At 08:45 h (15 min before transportation began), each animal was injected intramuscularly with either saline or the commercially available anti-MS medicine Travelmin (Eisai Co., Ltd., Tokyo, Japan); the drug was administered at 20 μL/kg body weight, and the equivalent volume of saline was used as the control. The dose of Travelmin was based on the recommended dose for adult humans. It is recommended to have Travelmin orally 30 min prior to the travel in humans. Because the effects of drugs thought to be earlier when it is administrated intramuscularly than orally, Travelmin administration to goats was conducted 15 min prior to the transportation start. Each milliliter of Travelmin contains 30-mg DH hydrochloride and 26-mg diprophylline. As we describe later, Travelmin was administrated at 8:45, and the data sampling was finished at 11:00. A previous report indicated that the initial half-life and terminal elimination half-life of DH in the blood were about 5–8 and 35–60 min, respectively, when DH was given intravenously in ewes (Yoo et al., 1990). In this study, although goats administrated DH intramuscularly instead of intravenously, the blood level of DH during the experiments could be maintained, and the effects of DH were kept. We considered the effects of diprophylline in Travelmin could be negligible because its content was so small compared with the previous report examined the effects of diprophylline in some species of animals (The European Agency for the Evaluation of Medicinal Products, 1998) that it might not induce some physiological changes in this work. Five animals received Travelmin first; the other six goats received saline first. One of the two goats that were subjected together to transportation received Travelmin; the other received saline.
2.1.3 Observation of behavior
Each goat was videotaped between 08:45 and 11:00 h, and the tape subsequently analyzed; the behavior of the transported goats was classified with regard to “posture” (standing or lying), “direction of head” (downward or not), and “foaming at the mouth.” The time interval (“latency”) between the initiation of transport and lying down, the total duration of the lying down period, and the frequency of lying down/standing up were analyzed. When goats were approached for blood collection, their attempts to escape were recorded. These escape attempts were classified as “standing up from the lying down posture,” “changing body direction,” and “shaking the head free” when horns or necks were touched. Foaming at the mouth was also observed at the blood collection.
After the end of the transportation, the goats were rehoused in their own pens, and feeding behavior was observed for 1 h. If a goat interrupted feeding for more than 1 min, this was scored as a feeding interruption. The occurrence of feeding interruption during water consumption or blood collection was not included as abnormal behavior.
2.1.4 Blood collection and cortisol assay
One to 2 days before data collection, a catheter was fitted to the jugular vein of each animal for blood sampling. Blood samples were collected at 08:45 (just before saline or drug administration); 09:15, 09:30, 09:45, and 10:00 (the completion of each round of transportation); and 10:30 and 11:00 h (30 and 60 min after return to the pen). Blood samples were immediately transferred to polypropylene tubes containing sodium heparin and were stored in an ice bath. Within 30 min of collection, plasma samples were separated by centrifugation (1400 g, 4°C, 10 min) and stored at −30°C.
Plasma cortisol concentrations were assayed as described previously (Aoyama et al., 2009). In brief, cortisol was extracted from the plasma with diethyl ether, and concentrations were measured by radioimmunoassay using the anti-cortisol antibody FKA-404 (CosmoBio Co., Ltd., Tokyo, Japan) and [3H]-labeled hydrocortisone (NET-396, Perkin Elmer Inc., Waltham, MA). After incubation at 4°C for 36–48 h, free cortisol was removed by a dextran-coated charcoal solution containing dextran (Dextran T-70, Pharmacia Corporation, Peapack, NJ) and charcoal (Norit sx-3, Wako Co., Ltd., Osaka, Japan). Finally, the radioactivity of each sample was measured with a scintillation counter (LSC-6100, Aloka Co., Ltd., Tokyo, Japan). The intra- or inter- assay CV was 6.7% and 12.1%, respectively.
2.2 Experiment 2: Effects of treatment with an anti-MS medicine
In the second experiment (Exp 2), the effects of Travelmin on the behavior and plasma cortisol concentrations were examined in goats housed under normal conditions.
2.2.1 Animals
Eight adult Shiba goats, consisting of four male (25–35 kg, 3–7 years old) and four females (20–25 kg, 3–6 years), were used. The housing conditions were identical to those described for the first experiment (Exp. 1).
2.2.2 Drug administration
At 08:45 h, each animal was injected either with Travelmin or the same volume of saline. All goats received both Travelmin and saline, with at least 6-day separation between the two treatments. Two males and two females received Travelmin first; the others received saline first.
2.2.3 Observation of behavior and cortisol assay
As in Exp. 1, each goat was videotaped between 08:45 and 11:00 h, and the tape subsequently analyzed. The same criteria were used to assess behavior as in Exp. 1. As fresh hay was provided to each goat at 10:00 h, the behavior analyses were performed between 9:00 and 10:00 h and 10:00 and 11:00 h separately.
Blood samples were collected as the same manner as Exp. 1: at 08:45 (just before saline or drug administration), 09:15, 09:30, 09:45, 10:00, 10:30, and 11:00 h. The concentrations of cortisol in the plasma were analyzed.
2.3 Data analysis
In order to compare the behavioral parameters obtained from the same goat in saline and Travelmin treatment, Wilcoxon's matched-pairs signed-rank tests were used. Because each pair having the same value was excluded from the analysis with Wilcoxon's matched-pairs signed-rank tests, the numbers of each pair used for analysis were presented in the results as the available number.
Prior to the statistical analysis, the plasma cortisol concentrations were converted to common logarithmic values to fit normal distribution. The two-way (time × treatment) repeated measured analysis of variance (ANOVA) was conducted by using programming language “R.” The differences in time or treatment were evaluated as the effect of transportation or anti-MS medication, respectively. The Mauchly's test was conducted to test the sphericity, and when it was significant, Greenhouse–Geisser correction was conducted. When the significant difference was found in time or treatment, the Tukey's test was performed for the post-hoc comparison.
The significance level was considered as P < 0.05, and when the P value was less than 0.1, the result was mentioned.
3 RESULTS
3.1 Experiment 1
Unfortunately, during the transportation, the exact direction of the face of the goat was not always clear on the videotape; we therefore only included those occasions when the behavior during transportation was clear and scored the behavior as a proportion of the total observation period that we could judge exactly. The total period of observation ranged from 3120 to 3310 s (average ± SD was 3197 ± 63). If a behavior type was not observed during transportation, the latency of this behavior was regarded as 3600 s (60 min). Nine or 10 of 11 goats lay down in the truck during transportation saline or anti-MS treatment, respectively. There was no difference in the total time spent lying down between control and Travelmin-treated goats. The interval from initiation of transportation to first lying down in goats treated with Travelmin was significantly shorter than in the controls (P < 0.05) (Table 1). When goats lay down, usually they stood up again and repeated laying and standing several times (once–13 times) during transportation. The frequency of changing posture from standing to lying during transportation in goats treated with Travelmin was significantly greater than in the controls (P < 0.01) (Table 1).
| Treatment | Statistical analysis | |||
|---|---|---|---|---|
| Saline | Anti-MS | |||
During transportation (9:00–10:00) |
Latency to lying down (s) | 22.8 ± 6.4 (5.5–60.0) |
13.1 ± 5.1 (1.1–60.0) |
an = 10, R = 4, P < 0.05 |
Total time lying down (%) |
46.3 ± 10.6 (0.0–88.6) |
41.8 ± 9.7 (0.0–97.2) |
an = 10, R = 23, N.S. |
|
Frequency of lying and standing |
3.1 ± 0.8 (0.0–8.0) |
6.4 ± 1.2 (0.0–13.0) |
an = 10, R = 0, P < 0.01 |
|
| Total time showinga nausea-like behavior (%) | 41.3 ± 8.0 (0.0–89.1) |
30.7 ± 7.3 (0.0–87.7) |
an = 10, R = 6, P < 0.05 |
|
| Frequency of escape from blood collection | 1.8 ± 0.6 (0.0–4.0) |
2.7 ± 0.4 (0.0–4.0) |
an = 8, R = 5, P < 0.1 |
|
Frequency of foaming at the mouth |
1.1 ± 0.4 (0.0–4.0) |
0.8 ± 0.4 (0.0–4.0) |
an = 5, R = 4, N.D. |
|
After transportation (10:00–11:00) |
Latency to feeding interruption (min) | 48.8 ± 5.4 (15.0–60.0) |
55.2 ± 2.2 (36.0–60.0) |
an = 8, R = 12, N.S. |
Total time without feeding (min) |
2.7 ± 1.4 (0.0–14.0) |
1.9 ± 1.2 (0.0–13.0) |
an = 7, R = 11, N.S. |
|
Frequency of no feeding bouts |
1.3 ± 0.6 (0.0–6.0) |
1.2 ± 0.6 (0.0–7.0) |
an = 6, R = 10.5, N.S. |
|
- Note: Each value represents average ± SE (minimum–maximum) of 11 goats. Saline: the control goats received saline administration. Anti-MS: the goats received anti-motion sickness medication. Wilcoxon's matched-pair signed-rank tests were used for statistical analysis.
- Abbreviations: an, available number for analysis; N.D., analysis could not be performed because the available sample number was so small; N.S., not significant; R, calculated statistics.
- a See the text for the definition of “nausea-like behavior.”
Goats that lay down during transportation varied in their responses to environmental stimuli: some looked normal (Figure 1a), whereas others often pointed their head downward, closed their eyes, and were essentially still for several minutes (Figure 1b). Even when they remained standing, some goats pointed their heads downward and did not move (Figure 1c). We defined these behaviors (represented in Figure 1b,c) as “nausea-like behavior” and calculated the total time spent behaving in this manner as a proportion of the total observation period. The total time spent displaying nausea-like behavior in goats treated with Travelmin was significantly shorter than in control goats (P < 0.05) (Table 1).
Goats housed in normal conditions usually try to escape when approached for blood collection; however, during transportation, some goats showed depressed response when their horn or neck was touched for blood collection. Some goats that had lain down did not stand up when blood was collected (Figure 1d); even when animals remained standing, they did not change body direction nor move their heads when they were touched. The frequency of escape attempts during blood collection in goats treated with Travelmin did not differ significantly from those in the controls, but it was tended to be higher than those in controls (P < 0.1) (Table 1).
Five or four goats foamed at the mouth when they were given saline or anti-MS treatment, respectively (Figure 1e). There was no difference in the observed frequency of foaming among the saline and anti-MS treatment (Table 1).
After transportation and return to their pens at 10:00 h, all of the goats, even the goats that showed severe nausea-like behavior, started to feed immediately when presented with fresh hay; however, some goats later interrupted feeding for a few minutes. The goats that showed interrupted feeding after transportation usually stood normally or walked around, but two goats pointed their head downward (Figure 1f), although they started to feed again after a few minutes. Although the data are not presented, the interruption of feeding between 10:00 and 11:00 h was never seen in the goats that had not been subjected to road transport. There were no differences between control and Travelmin-treated goats in the latency between the end of transportation and the feeding interruption, the total time spent without feeding, or the frequencies of no feeding bouts (Table 1).
There were the significant differences in plasma cortisol concentration among sampling time (P < 0.01, F(6,60) = 47.6), but no significant differences in treatment (F(1, 10) = 0.0015) nor time-treatment interaction (F(6, 60) = 2.13). The results of Mauchly's test indicated that the sphericity of time could not be assured (P = 0.018). The Greenhouse–Geisser epsilon value of time was 0.55, and the final P value of sampling time was less than 0.01. The plasma cortisol concentrations during transportation were significantly higher than those before and 1 h after the transportation in both control and Travelmin-treated goats (Figure 2).
3.2 Experiment 2
The behavior of goats kept under normal housing conditions and treated with saline or Travelmin is summarized in Table 2. Between 9:00 and 10:00 h, only two goats injected with saline and one treated with Travelmin lay down; there were no differences in any parameters related to lying down behavior between the control and Travelmin-treated goats (Table 2). All goats ate leftover hay excepting one saline-treated male, and the total time spent feeding on this old hay in Travelmin-treated goats was significantly longer than in control goats (P < 0.01) (Table 2). The total time spent ruminating by Travelmin-treated goats was significantly shorter than in control goats (P < 0.05) (Table 2). Every time they were approached for blood collection, all goats in both treatment groups tried to escape.
| Treatment | Statistical analysis | |||
|---|---|---|---|---|
| Saline | Anti-MS | |||
| 9:00–10:00 | Latency to lying down (min) | 54.0 ± 5.7 (14.0–60.0) |
53.9 ± 6.1 (11.0–60.0) |
an = 2, R = 1, N.D. |
| Total time lying down (min) | 0.4 ± 0.3 (0.0–2.0) |
0.3 ± 0.3 (0.0–2.0) |
an = 1, R = 1, N.D. |
|
| Frequency of lying and standing | 0.2 ± 0.2 (0.0–1.0) |
0.2 ± 0.2 (0.0–2.0) |
an = 1, R = 1, N.D. |
|
| Total time feeding (min) | 20.5 ± 5.3 (0.0–40.0) |
34.1 ± 4.4 (16.0–50.0) |
an = 8, R = 0, P < 0.05 |
|
| Total time ruminating (min) | 22.3 ± 5.8 (0.0–50.0) |
4.9 ± 2.9 (0.0–25.0) |
an = 7, R = 1.5, P < 0.05 |
|
| Frequency of escape from blood collection | 4.0 ± 0.0 (4.0–4.0) |
4.0 ± 0.0 (4.0–4.0) |
an = 0, N.D. |
|
| 10:00–11:00 | Latency to feeding disruption (min) | 60.0 ± 0.0 (60.0–60.0) |
60.0 ± 0.0 (60.0–60.0) |
an = 0, N.D. |
| Total time not feeding (min) | 0.0 ± 0.0 (0.0–0.0) |
0.0 ± 0.0 (0.0–0.0) |
an = 0, N.D. |
|
| Frequency of no feeding bouts | 0.0 ± 0.0 (0.0–0.0) |
0.0 ± 0.0 (0.0–0.0) |
an = 0, N.D. |
|
- Note: Each value represents average ± SE (minimum–maximum) of eight goats. Fresh hay was provided at 10:00 h. Saline: the control goats received saline administration. Anti-MS: the goats received anti-motion sickness medication. Wilcoxon's matched-pair signed-rank tests were used for statistical analysis.
- Abbreviations: an, available number for analysis; N.D., analysis could not be performed because the available sample number was so small; R, calculated statistics.
After fresh hay was provided at 10:00 h, all goats in both treatment groups fed until 11:00 h and did not interrupt feeding.
Plasma cortisol concentrations in goats housed under normal conditions changed slightly throughout the experiment, and there were significant differences in plasma cortisol concentration among sampling time (P < 0.01, F(6,42) = 3.78), but no significant differences between control and Travelmin-treated goats (F(1,7) = 1.30) nor the interaction in the sampling time and treatment (F(6,42) = 0.36) (Figure 3). The results of Mauchly's test indicated that the sphericity of time could be assured (P = 0.12). The plasma cortisol concentrations at last sampling period (1 h after fresh hay given) were higher than those at third-fifth sampling (45–15 min before the fresh hay) in both control and Travelmin-treated goats.
4 DISCUSSION
In this study, some goats showed the abnormal behavior that we defined as the nausea-like behavior, and it was relieved by anti- MS medication. We suggest that some goats get MS or a similar response and, consequently, changed their behavior during road transportation.
In this study, we identified some goats that were subjected to a short period of road transportation lay down and pointed their head downward and did not stand up when blood was collected. The similar unusual behavior was also reported in sheep transported by ship (Dunston-Clarke et al., 2020; Willis et al., 2021).
We also identified some goats interrupted feeding once or several times when they were returned to their pens, and the fresh hay was given after the road transportation.
MS induces nausea and emesis (vomiting); thus, emesis had been used as an indicator of MS in humans (Graybiel & Knepton, 1976; Shupak & Gordon, 2006), dogs (Conder et al., 2008), and pigs (Bradshaw et al., 1996, 1999). However, ruminants do not possess an emetic reflex (Horn et al., 2013). While, emesis may be not the only indicator of MS; Kenward et al. (2015) reported that dogs show some nausea-induced behavioral changes other than emesis, such as “dropping the head,” “closing the eyes,” “decreased appetite,” or “hypersalivation.” Previously, we reported on behavioral responses of goats to the administration of cisplatin (cis-diamminedichloro-platinum II; CDDP), a drug used in cancer chemotherapy that induces severe nausea as a side effect (Aoyama et al., 2021). CDDP-treated goats showed specific behavioral responses, and we hypothesized that CDDP might induce similar physiological mechanisms in goats to those induced nausea in humans or other emetic animals. Some of the CDDP-induced behavioral responses in goats resembled the nausea-like behavior induced by road transportation in this study.
Foaming at the mouth is considered an indicator of MS in pigs (Bradshaw et al., 1999). Some goats foamed at the mouth during transportation in this study.
Because there are similarities between the nausea-induced behavioral responses described in previous studies and the transportation-induced nausea-like responses in this study, we examined the effects of an anti-MS treatment on the behavioral responses to transportation in goats. Administration of Travelmin, a commercial anti-MS treatment, altered some of the behaviors of the goats during road transportation. Although Travelmin did not affect the total time spent in the lying down posture, it shortened the latency to lying down, increased the frequency of lying down and standing up, reduced the total time spent showing nausea-like behavior, and tended to increase the frequency of attempts to escape from blood collection in transported goats. The nausea-like behavior and unresponsiveness to researchers' approach in transported goats resembled the responses of goats given CDDP (Aoyama et al., 2021). The ability of Travelmin to reduce the nausea-like behavior suggests that these behaviors might be induced, at least in part, via similar physiological mechanisms as MS. The main component of Travelmin is DH, which is an antagonist for the histamine type 1 (H1) receptor. Previous reports indicated that DH and other H1 receptor antagonists relieved the emesis induced by MS (Schmäl, 2013). The increase in the frequency of changes to body posture (lying down and standing up) by Travelmin might also be the result of the relief from transportation-induced unpleasant sensations. This behavioral change might be the result in an increase in responsiveness to environmental stimuli. Travelmin treatment shortened the latency to the first bout of lying down. Interpretation of this effect on lying down behavior is difficult because there were no significant effects on lying behavior in goats housed under normal conditions in Exp. 2. Previously, we investigated the effects of prior experience of transportation on behavioral changes during subsequent rounds of transportation; we showed that goats began to lie down earlier if they have prior experience of transportation (Sanuka et al., 2016). Our previous results indicate that transported goats lie down not only because of difficulty in remaining standing due to severe stress but voluntarily select the lying down posture to mitigate the unpredictable acceleration of the truck. In the present study, treatment with Travelmin might have increased the ability of the goats to respond to the environmental conditions and might have helped them to adopt the optimal posture; consequently, the goats might lie down earlier.
In Exp. 2, treatment with Travelmin increased the time spent in feeding on old hay within the hour before fresh hay was provided. Previous studies have shown that peripheral or central administration of H1 receptor antagonists can facilitate feeding behavior in rats and mice (Passani et al., 2011; White & Rumbold, 1988). In Exp. 2, administration of Travelmin might have increased appetite by blocking the H1 receptor before the presentation of fresh hay and, consequently, reduced the time spent in rumination. In Exp. 1, after the end of transportation, Travelmin treatment failed to affect feeding interruption. It is unclear why Travelmin treatment did not affect feeding behavior after transportation in spite of its effects on the behaviors during transportation and on the goats in Exp. 2. We conclude that even if there are similarities between MS in emetic animals and the behavioral responses to transportation of goats, there are still some inexplicable aspects of the nausea-like behavior of goats during road transportation, especially in the feeding behavior after transportation. For example, all of the goats started to feed immediately after road transportation finished; the first episode of feeding interruption was observed at 15 min or later. If the goats developed MS during transportation in the same manner as humans, they might not be expected to be able to start feeding immediately after transportation ended. In humans, MS is considered to be induced by mismatches between the unfamiliar real motion (or visual stimuli) and the anticipated model of motion formed under normal conditions (Zhang et al., 2016). Similar physiological responses might be induced in goats by road transportation, but other possible factors should not be disregarded. Ruminants have relatively large amounts of food in their digestive tract, especially in the rumen, compared with monogastric animals. Possibly, the rumen contents are moved irregularly by the motion of the truck, and the mechanical stimuli in the digestive tract might induce feelings of nausea and consequently might alter feeding behavior.
Plasma cortisol concentration is a reliable physiological index of stress; our previous studies indicated that transportation induces a significant increase in plasma cortisol concentrations in goats (Aoyama et al., 2008). Plasma cortisol concentrations increased significantly during transportation in both control and Travelmin-treated animals, and there were no differences between both treatments. The results from Exp. 2 confirmed that Travelmin treatment itself was not a stress factor in goats as there was no difference in cortisol concentrations between control and treated animals. If some transported goats felt nausea-like sensations, and even if Travelmin treatment relieved some of these, other stressors associated with transportation might also contribute to the altered behavior of the goats. Vibration, loud noise, and a rapidly changing environment could also be strong stressors. The increase in plasma cortisol concentrations was also seen in goats that showed little outward appearance of discomfort during transportation.
In this study, we revealed some aspects of the nausea-like behavior in the transported goats and effects anti-MS on it. Although further studies, such as the neuroscientific research, will be required to determine the mechanism of these behaviors, we will be able to mitigate the transportation stress in goats and other domestic ruminants by mitigating the nausea-like behavior.
4.1 Conclusions
During road transportation, goats displayed specific behavioral changes, consisting of a lowered head, closed eyes, and inactivity. These changes are similar to those induced by the administration of an emetic agent in dogs and goats. Treatment of the goats with an anti-MS ameliorated these behavioral responses to transportation. It is still unclear whether or not goats get MS; however, nausea-like sensations might be induced by road transportation. Undoubtedly, further investigation will reveal the underlying mechanisms of these behavioral responses to road transportation. Such knowledge will be beneficial for the welfare of farm ruminants during transportation.
ACKNOWLEDGMENTS
We are grateful to Prof. Y. Nagao and the staff members of the research farm of Utsunomiya University for their care of the animals. We are grateful to Dr. Yoshinori Fukazawa for his help in the statistical analysis. We thank Miss H. Kobayashi, Miss M. Suzuki, Mr. T. Haseyama, Mr. Deligeer, Miss Y. Takakusaki, and Miss H. Uehara for their technical help. This work was supported by Grant Aid for Scientific Research from Ministry of Education, Science, Culture, Sports and Technology of Japan (Nos. 20580291, 23580365, and 15K14875) and Research Grants for Meat and Meat Products from the Ito Foundation (2021 No. 155).
CONFLICT OF INTEREST STATEMENT
The authors declare there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.
