- Email: [email protected]
The Pretransport Management of Stress in Performance Horses
Accepted Manuscript The pre-transport management of stress in performance horses Chance Butterfield, Bernie Grumpelt, Darrell Kimmel, Rob Patterson, Krisjan Jones, Shannon L. Scott, Ph.D., Al Schaefer, Ph.D. PII:
S0737-0806(18)30407-6
DOI:
10.1016/j.jevs.2018.07.006
Reference:
YJEVS 2562
To appear in:
Journal of Equine Veterinary Science
Received Date: 11 May 2018 Revised Date:
13 July 2018
Accepted Date: 14 July 2018
Please cite this article as: Butterfield C, Grumpelt B, Kimmel D, Patterson R, Jones K, Scott SL, Schaefer A, The pre-transport management of stress in performance horses, Journal of Equine Veterinary Science (2018), doi: 10.1016/j.jevs.2018.07.006. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
SHORT COMMUNICATION: The pre-transport management of stress in performance horses
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Wetaskiwin Co-op Country Junction Feeds, 4707-40 Ave., Wetaskiwin, Alberta, Canada T9A 2B8 DeStress Nutritional Technology, 4389-112 Ave SE, Calgary, Alberta, Canada T2C 0J7 c Cross the T Consulting, 32 Signature Cove, Sherwood Park, Alberta, Canada T8H 0W8
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Chance Butterfield a, Bernie Grumpelt a, Darrell Kimmel a, Rob Patterson b, Krisjan Jones b, Shannon L. Scott Ph.D. c and Al Schaefer Ph.D. b,1
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Corresponding author: Allan Schaefer, Ph.D., DeStress Nutritional Technology, 4389-112 Ave SE, Calgary, Alberta, Canada, T2C 0J7 E-mail address: [email protected]
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Key words Performance horses, transportation stress, nutritional therapy, infrared thermography
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Abstract The aim of this study was to ascertain whether DeStress® nutritional therapy administration to performance horses prior to transportation would reduce stress expression in these animals. Ten performance horses were used in the present study offered either control (rice hulls) or treated (DeStress crumbles) diets pre transport. A cross-over design whereby all animals were tested both under control and treatment conditions was used. Orbital eye temperatures determined non-invasively pre-transport and post-transport with infrared thermography were used to monitor the efficacy of this nutritional therapy. Baseline eye temperatures pre-transportation were 34.1 ± 1.1 °C for the control group and 34.3 ± 1.2 °C for the treatment group (P > 0.05). After the horses had been transported, the eye temperatures were 35.3 ± 0.32 °C for the control group and 34.7 ± 0.8 °C for the treatment group (P < 0.05). These results suggest that providing a nutritional supplement (DeStress®) to horses prior to transportation can reduce the physiological activation of the hypothalamus–pituitary–adrenal axis due to that stress.
Introduction
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Performance horses entered in rodeo events experience a great deal of stress associated with activities such as transportation, loading, unloading, training, mixing, and the competitions themselves[1]. Any of these events which are perceived as threatening or even as novel can act as a stressor, bringing about the animal’s fight-or-flight response. As Moberg [2] explains, a certain amount of ‘good stress’ resulting from non-threatening situations can be differentiated from ‘bad stress’ resulting from long-term perceived threats. Depending on its intensity and duration, over time ‘bad stress’ can negatively influence an animal’s metabolism, immune system, and welfare, which in turn can have a negative impact on its performance. For example, Padalino et al. [3] found that thoroughbred horses transported long distances (94 h with approximately 51 h in transit and 43 h for rest stops.) exhibited an acute-phase response characterised by impairment of the immune system and weight loss. Transport conditions of a few hours are more commonly experienced by horses and in these situations an increase in heart rate, cortisol levels and beta endorphin are also reported [4]. In a review of the topic of transport and handling stress in livestock, Schaefer et al. [5] noted that these stressors are documented to cause four primary insults; 1) catabolism of tissue, particularly skeletal muscle; 2) depletion of physiological ions, notably cations such as potassium and magnesium [6] depletion of glycogen and energy reserves and hypoglycemia; and 4) dehydration. As a result of these insults, animals may lose weight and body condition. As reported by Padalino et al 2018 [7] for horses in particular the first hour of the journey is the most stressful.
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These negative effects of stress are the result of activation of the sympathetic nervous system and the hypothalamus–pituitary–adrenal axis (HPAA). Release of epinephrine and norepinephrine into the bloodstream from the adrenal medulla as a result of sympathetic stimulation ramps up the animal’s metabolism to provide the energy and extra blood flow needed by the heart and skeletal muscles to respond to the stressor. The neuroendocrine component mediated by the HPAA can result in the release of cortisol, which has broad, long-lasting effects on the body. These increases in catecholamine and cortisol concentrations, in addition to a plethora of related biochemical events and blood flow responses, can produce changes in heat production and heat loss from the animal [8]. Given the impact that stress can have on performance horses, it is essential to quantify its impact on individual animals. One potential indicator of stress is the expected change in heat production due to stress mentioned above. Since 40 to 60% of heat production in mammals is dissipated in the infrared energy
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wavelength [ 9], infrared thermography (IRT) has been used as a non-invasive tool to measure heat radiated from the body surface of domestic animals whose welfare may be compromised by stress [ 10]. The eye and surrounding orbital tissue has been especially useful in this regard [ 10]. The ultimate goal of this research was not only to non-invasively detect stress in performance horses, but to intervene in some way to counter it and to alleviate its negative impact on the animal’s metabolism, immune system, and welfare. As discussed in the review by Schaefer et al. [ 5], nutritional therapy can be used to attenuate these metabolic outcomes. Amino acid therapy, particularly therapy with branch chain amino acids and serotonergic precursors, can be effective in reducing the catabolic effect of stress. Nutritional augmentation with physiological ions can assist in reducing the electrolyte imbalance due to stress [6] and in providing the animals with water. Offering such nutrition can concurrently assist in maintaining appropriate osmolality in blood, intracellular and extracellular fluid pools [ 6, 11]. The nutrition company DeStress Nutritional Technology has taken these concepts and formulated a supplemental feed product designed to reduce stress in transported and handled horses. This pre-transport nutritional therapy (DeStress Nutrition Technology, Calgary AB) comprises an energy source to meet heightened metabolic needs, electrolytes to restore depleted physiological ions, selected amino acids to counteract protein catabolism and a means to promote hydration. To date, however, such a nutritional therapy is novel and has had limited use with horses. The aim of this study was to administer DeStress® nutritional therapy to performance horses prior to transportation and to monitor its efficacy for reducing transportation stress in these animals. Orbital eye temperatures determined non-invasively pre-transport and post-transport with infrared thermography was used to monitor the efficacy of this nutritional therapy. Material and methods 2.1 Animal care In order to determine the impact of a nutritional supplement on the response of performance horses to a transportation event, a transportation study was conducted on two separate study periods (April 15 and 21, 2015 and April 5 and 12, 2018) using performance horses at the Butterfield Ranch located near Ponoka, Alberta, Canada. These animals were trained to participate in the rodeo events of steer wrestling and barrel racing. The ten animals participating in the study included both mares and geldings between the ages of 5-22 years. The horses were kept in separate pens and maintained on a basic ad libitum timothy hay diet with an additional 2.27 kg of oats per day. All horses had access to water ad libitum. All animals were cared for and transported in accordance with the Canadian Council on Animal Care Codes of Practice for Horses.
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2.2 Treatments and sampling Twenty-four hours prior to the transportation, 1 kg of the nutritional supplement (a crumble from DeStress Nutritional Technology, Calgary, AB, Canada) was mixed into each treatment animal’s oats. The proximate analysis for the supplement is shown in Table 1. Each of the control animals received 1 kg of soy hulls mixed into their oats. On the day of transportation, duplicate infrared thermographic (IRT) images of all animals’ medial posterior palpebral border of the lower eyelid and the lacrimal caruncle were captured at 08h00 using a FLIR T450sc camera (FLIR Co., Boston, MA, USA); the left eye of all horses was scanned from a distance of 1 m at approximately 90° angle. The Environmental temperature and relative humidity were recorded on treatment days with a Kestrel model 3000 digital weather meter (Boothwyn, PA, USA) to calibrate the camera results. The horses were then loaded onto a conventional horse trailer (Featherlite® twenty-foot stock trailer, Red Deer Alberta). The transportation commenced at 08h30 and terminated at 10h00. Horses were unloaded and duplicate post-transportation IRT scan samples were obtained.
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2.3 Analysis of infrared thermography images Image analysis software (FLIR ResearchIR, Boston, MA, USA) was used to process the images and to determine the maximum temperature within an oval area traced around the eye, including the eyeball and approximately 1 cm surrounding the outside of the eyelids (Figure 1) Specifically the area of the medial posterior palpebral border of the lower eyelid and the lacrimal caruncle was used. The maximum eye temperature was used for the statistical analyses. The delta T value refers to the change in temperature between pre-loading and post hauling times.
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Each horse served as either a control subject or a treatment subject on one of the two transportation days. If a horse served as a control subject on the first day, it served as a control subject on the second day, and vice-versa. Both control and treated animals were represented on each of the two transportation days. On the second day of transportation, Horse 2 was intended to be a treatment subject. However, it did not consume the DeStress® product, so its data for that day were removed from the statistical analysis.
2.4 Statistical Analyses The statistical analysis of data was performed using a repeated measures ANOVA in Med Calc® software (Statistics for Biomedical Research. Version 9. Broekstraat Mariakerke, Belgium) since all horses were tested both under control and treatment nutritional regimes. A significant difference was declared when P ≤ 0.05. There were no significant interaction effects within groups.
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3 Results and Discussion The temperatures and relative humidity were within the thermal neutral zone for the horses on all trial days. The thermal environmental data for sampling days was as follows: T1 (April 15, 2015) T=6.5 ⁰C, RH 41.9% for pre-loading vs 10.9⁰ C and 22.8% for unloading post-transport. T2 (April 21, 2015) T= 5.2 ⁰C, RH= 61.6% for pre-loading vs 15.9 C and 33.5 % for unloading. T3 (April 5, 2018) T= -12.0 ⁰C and RH 66.0% for pre-loading vs -10.0 ⁰C and 60.0% for post-transport. T4 (April 12, 2018), T=-1.0 ⁰C and RH = 84.1% pre-loading vs 2.0 ⁰C and 62.0% RH unloading post-transport. The baseline eye temperatures pre-transportation were 34.09 ± 1.08 °C for the control group and 34.31 ± 1.24 °C for the treatment group. There was no significant difference between these pre-transportation temperatures (P > 0.05). These values are similar to eye temperatures measured by IRT in horses prior to undertaking the physical exertion of a show jumping competition [12, 13], or prior to being exposed to the physical stress of severe noseband tightening [ 14]or the psychological stress of a fear test [ 15]. The thermal values listed in Table 2 represent the combined stress of both loading and transport. After the horses had been transported in the current study, the eye temperatures were 35.29 ± 0. 0.32 °C for the control group and 34.65 ± 0.77 °C for the treatment group, which represented a significantly higher eye temperature in the control group compared with the treatment group (P < 0.05). The ability of the DeStress® treatment to attenuate the increase in eye temperature observed in horses that did not receive this nutritional supplement suggests that it is helping the horses to counter the effects of transportation stress. The composition of the DeStress product includes elevated levels of the amino acid tryptophan. This amino acid is a known neuro transmitter precursor of serotonin. Using nutritional approaches to manage serotonergic levels has been reported to be an effective means of managing stress and cortisol levels in several animal models [16]. The observed parallel between cortisol levels and infrared thermal values in horses has also been reported (17). In support of this observation in a different animal model, beef cattle fed a similar nutritional supplement immediately prior to transportation to an abattoir for slaughter demonstrated a reduction in percentage live weight loss as well as greater hot carcass yield as a proportion of pre-treatment farm weight compared with control animals [ 5]. Moreover, the prevalence of a stress induced condition in these cattle, dark – firm-dry beef, was reduced in treated animals.
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The positive values for delta T for both control and treatment groups indicate that eye temperature rose as a result of transportation stress. Although the delta T values were numerically higher for the control group compared with the treatment group (1.2 ± 0.94 °C vs. 0.34 ± 1.04 °C, respectively), this difference was not significant at the P > 0.05 level. The magnitude of delta T is similar to that seen for show jumping horses just after a show jumping competition [ 12, 13], or following exposure to the physical stress of severe noseband tightening [14] or the psychological stress of a fear test [14]. A similar increase in maximum IRT eye temperature was also observed in horses injected intramuscularly with ACTH [17], and this increase was significantly correlated with a concomitant increase in salivary cortisol. This latter study suggested that activation of the HPA axis increased the metabolic rate of the horses in the study.
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4 Conclusions These results suggest that IRT can detect differences in stress due to transportation in performance horses. Furthermore, they suggest that providing a nutritional supplement (DeStress®) to horses prior to transportation can reduce the physiological activation of the HPAA due to that stress. Properly applied, the use of nutritional therapy could prove a useful tool in managing stress in performance horses and other valuable animals such as breeding stock.
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Acknowledgements The authors wish to acknowledge the contribution of Country Junction Feeds of Wetaskiwin, Alberta, Canada, for the preparation and provision of the DeStress® Nutrition product. The invaluable collaboration of the Butterfield family by granting access to and use of their highly valuable performance horses is also greatly appreciated.
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Table 1. Ingredient proximate analysis for the DeStress nutritional therapy used in the present study (as-fed basis) Crude protein (min) 16.5% Crude fat (min) 4.5% Crude fiber (max) 20.0% Calcium (actual) 0.7% Phosphorus (actual) 0.5% Sodium (actual) 0.35% -1 Vitamin A (min) 10,000 IU kg -1 Vitamin D3 (min) 1000 IU kg -1 Vitamin E (min) 400 IU kg -1 Selenium 0.3 mg kg
T2 T1 T2 T1 T2 T4 T4 T3 T3 T3
H1 H2 H3 H4 H5 H6 H7 H8 H9 H10
Control PreTransport ⁰C 33.6 34.3 33.3 34.4 35.3 34.4 32.6 35.4 32.4 35.2 34.1 1.1 0.74
Control PostTransport ⁰C 35 35.5 34.7 35.7 35.3 35.5 35.2 35.7 35.1 35.2
Delta T ** ⁰C 1.4 1.2 1.4 1.3 0 1.1 2.0 0.3 2.7 0
35.3 0.3 0.029
Transportation Day
Horse
T1 T2 T1 T2 T1 T3 T3 T4 T4 T4
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Mean SD P *** 152 153
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Table 2. Pre-transportation and post-transportation eye temperatures and the difference between the two (delta T) in °C for performance horses fed soybean hulls (Control) or DeStress crumbles (treatment) prior to transportation.
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1.2 0.9 0.077
Treatment PreTransport ⁰C 34.6
Treatment Post – Transport ⁰C 34.7
Delta T ⁰C
34.5 33.8 32.1 35.2 35.8 32.7 34.6 35.5
33.8 34.7 33.2 35.7 35.3 35 35.1 34.4
-0.7 0.9 1.1 0.5 -0.5 2.3 0.5 -1.1
34.3 1.2
34.7 0.8
0.34 1.0
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*T1 = April 15, T2 = April 21. 2015. T3 = April 5, T4 = April 12. 2018 **Delta T = Post-transport eye temperature – pre-transport eye temperature. ***P-value from ANOVA repeated measures test comparing means of control animals with means of animals treated with DeStress
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Figure 1: Example of infrared thermography images and maximum eye temperature values in Horse 3 on two study days a) H3 Control pre-transport; Maximum eye temperature 33.3 °C
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b) H3 Control post-transport; Maximum eye temperature 34.7 °C
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c) H3 Treatment pre-transport; Maximum eye temperature 34.5 °C
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d) H3 Treatment post-transport; Maximum eye temperature 33.8 °C
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References [1] Collyer PB and Harris BC. Comparison of exercise and stress parameters in barrel racing horses in the home and competitive environment. 2016; 15:93-94.
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[2] Moberg GP. In: The biology of animal stress: Basic principles and implications for animal welfare, Wallingford, UK: CABI Publishing; 2000, p. 1-21.
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[3] Padalino B, Raidal SL, Carter N, Celi P, Muscatello G, Jeffcott L, et al. Immunological, clinical, haematological and oxidative responses to long distance transportation in horses. Research in Veterinary Science 2017; 115:78-87.
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[4] Tateo A, Padalino B, Boccaccio M, Maggiolino A and Centoducati P. 2012. Transport stress in horses: Effects of two different distances. J. of Vet Behavior. 7: 33-42.
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[5] Schaefer AL, Dubeski PL, Aalhus JL, Tong AKW. Role of nutrition in reducing antemortem stress and meat quality aberrations. Journal of Animal Science 2001; 79:E91.
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[6] Schaefer AL, Stanley RW, Tong AKW, Jones SDM. Effect of transport and handling stress on vascular ions in cattle: Response to electrolyte therapy. 1994; Proceedings of the Society of Nutrition Physiology (Germany).
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[7] Padalino B., Raidal SL, Knight P, Celi P, Jeffcott L and Muscatello G. 2018. Behaviour during transportation predicts stress response and lower airway contamination in horses. Plos One. March. 1-20.
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[8] Schaefer AL, Matthews LR, Cook NJ, Webster J, Scott SL. Novel non-invasive measures of animal welfare. 2002: Proceedings International Society for Animal Ethology (ISAE). Hamilton, New Zealand. 22.
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[9] Kleiber M. The Fire of Life: An Introduction to Animal Energetics. Huntington, N.Y.: R. E. Krieger Publishing Company, 1975.
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[10] Stewart M, Webster JR, Schaefer AL, Cook NJ, Scott SL. Infrared thermography as a non-invasive tool to study animal welfare. Animal Welfare 2005; 14:319-25.
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[11] Gortel K, Young BA, Kawamoto SC, Schaefer AL. Effects of transport stress and electrolyte supplementation on body fluids and weights of bulls. Canadian Journal of Animal Science 1992; 72:547-53.
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[12] Valera M, Bartolomé E, Sánchez MJ, Molina A, Cook N, Schaefer A. Changes in eye temperature and stress assessment in horses during show jumping competitions. Journal of Equine Veterinary Science 2012; 32:827-30.
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[13] Bartolomé E, Sánchez MJ, Molina A, Schaefer AL, Cervantes I, Valera M. Using eye temperature and heart rate for stress assessment in young horses competing in jumping competitions and its possible influence on sport performance. Animal 2013; 7:2044-53.
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[14] Fenner K, Yoon S, White P, Starling M, McGreevy P. The effect of noseband tightening on horses’ behavior, eye temperature, and cardiac responses. PLOS ONE 2016; 11:e0154179.
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[15] Dai F, Cogi NH, Heinzl EUL, Dalla Costa E, Canali E, Minero M. Validation of a fear test in sport horses using infrared thermography. Journal of Veterinary Behavior: Clinical Applications and Research 2015; 10:128-36.
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[16] Roberts S A, Thibault L, Murray A C and Schaefer A L. The effect of dietary protein source on biochemical indicies of stress in stress - susceptible pigs. Canadian Journal of Animal Science 1996; 76: 401-408.
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[17] Cook NJ, Schaefer AL, Warren L, Burwash L, Anderson M, Baron V. Adrenocortical and metabolic responses to ACTH injection in horses: An assessment by salivary cortisol and infrared thermography of the eye. 2001; 81:621.
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HIGHLIGHTS SHORT COMMUNICATION: The pre-transport management of stress in performance horses
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DeStress® nutritional therapy was administered to rodeo horses prior to transportation Orbital eye temperatures determined with infrared were used to monitor the efficacy After transportation the eye temperatures were higher for the control group (P < 0.05). Providing DeStress® to horses prior to transportation reduced the thermal response to stress
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Ethics Statement The authors would note that all animals used in the study were treated humanely and subjected only to normal industry standard practices for the transport of animals as defined in the Canadian Codes of Practice. The research tools used, infrared thermography are fully non invasive.
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Dr. Al Schaefer Principle Investigator
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May 11, 2018
S0737-0806(18)30407-6
DOI:
10.1016/j.jevs.2018.07.006
Reference:
YJEVS 2562
To appear in:
Journal of Equine Veterinary Science
Received Date: 11 May 2018 Revised Date:
13 July 2018
Accepted Date: 14 July 2018
Please cite this article as: Butterfield C, Grumpelt B, Kimmel D, Patterson R, Jones K, Scott SL, Schaefer A, The pre-transport management of stress in performance horses, Journal of Equine Veterinary Science (2018), doi: 10.1016/j.jevs.2018.07.006. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
SHORT COMMUNICATION: The pre-transport management of stress in performance horses
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Wetaskiwin Co-op Country Junction Feeds, 4707-40 Ave., Wetaskiwin, Alberta, Canada T9A 2B8 DeStress Nutritional Technology, 4389-112 Ave SE, Calgary, Alberta, Canada T2C 0J7 c Cross the T Consulting, 32 Signature Cove, Sherwood Park, Alberta, Canada T8H 0W8
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Chance Butterfield a, Bernie Grumpelt a, Darrell Kimmel a, Rob Patterson b, Krisjan Jones b, Shannon L. Scott Ph.D. c and Al Schaefer Ph.D. b,1
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Corresponding author: Allan Schaefer, Ph.D., DeStress Nutritional Technology, 4389-112 Ave SE, Calgary, Alberta, Canada, T2C 0J7 E-mail address: [email protected]
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Key words Performance horses, transportation stress, nutritional therapy, infrared thermography
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Abstract The aim of this study was to ascertain whether DeStress® nutritional therapy administration to performance horses prior to transportation would reduce stress expression in these animals. Ten performance horses were used in the present study offered either control (rice hulls) or treated (DeStress crumbles) diets pre transport. A cross-over design whereby all animals were tested both under control and treatment conditions was used. Orbital eye temperatures determined non-invasively pre-transport and post-transport with infrared thermography were used to monitor the efficacy of this nutritional therapy. Baseline eye temperatures pre-transportation were 34.1 ± 1.1 °C for the control group and 34.3 ± 1.2 °C for the treatment group (P > 0.05). After the horses had been transported, the eye temperatures were 35.3 ± 0.32 °C for the control group and 34.7 ± 0.8 °C for the treatment group (P < 0.05). These results suggest that providing a nutritional supplement (DeStress®) to horses prior to transportation can reduce the physiological activation of the hypothalamus–pituitary–adrenal axis due to that stress.
Introduction
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Performance horses entered in rodeo events experience a great deal of stress associated with activities such as transportation, loading, unloading, training, mixing, and the competitions themselves[1]. Any of these events which are perceived as threatening or even as novel can act as a stressor, bringing about the animal’s fight-or-flight response. As Moberg [2] explains, a certain amount of ‘good stress’ resulting from non-threatening situations can be differentiated from ‘bad stress’ resulting from long-term perceived threats. Depending on its intensity and duration, over time ‘bad stress’ can negatively influence an animal’s metabolism, immune system, and welfare, which in turn can have a negative impact on its performance. For example, Padalino et al. [3] found that thoroughbred horses transported long distances (94 h with approximately 51 h in transit and 43 h for rest stops.) exhibited an acute-phase response characterised by impairment of the immune system and weight loss. Transport conditions of a few hours are more commonly experienced by horses and in these situations an increase in heart rate, cortisol levels and beta endorphin are also reported [4]. In a review of the topic of transport and handling stress in livestock, Schaefer et al. [5] noted that these stressors are documented to cause four primary insults; 1) catabolism of tissue, particularly skeletal muscle; 2) depletion of physiological ions, notably cations such as potassium and magnesium [6] depletion of glycogen and energy reserves and hypoglycemia; and 4) dehydration. As a result of these insults, animals may lose weight and body condition. As reported by Padalino et al 2018 [7] for horses in particular the first hour of the journey is the most stressful.
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These negative effects of stress are the result of activation of the sympathetic nervous system and the hypothalamus–pituitary–adrenal axis (HPAA). Release of epinephrine and norepinephrine into the bloodstream from the adrenal medulla as a result of sympathetic stimulation ramps up the animal’s metabolism to provide the energy and extra blood flow needed by the heart and skeletal muscles to respond to the stressor. The neuroendocrine component mediated by the HPAA can result in the release of cortisol, which has broad, long-lasting effects on the body. These increases in catecholamine and cortisol concentrations, in addition to a plethora of related biochemical events and blood flow responses, can produce changes in heat production and heat loss from the animal [8]. Given the impact that stress can have on performance horses, it is essential to quantify its impact on individual animals. One potential indicator of stress is the expected change in heat production due to stress mentioned above. Since 40 to 60% of heat production in mammals is dissipated in the infrared energy
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wavelength [ 9], infrared thermography (IRT) has been used as a non-invasive tool to measure heat radiated from the body surface of domestic animals whose welfare may be compromised by stress [ 10]. The eye and surrounding orbital tissue has been especially useful in this regard [ 10]. The ultimate goal of this research was not only to non-invasively detect stress in performance horses, but to intervene in some way to counter it and to alleviate its negative impact on the animal’s metabolism, immune system, and welfare. As discussed in the review by Schaefer et al. [ 5], nutritional therapy can be used to attenuate these metabolic outcomes. Amino acid therapy, particularly therapy with branch chain amino acids and serotonergic precursors, can be effective in reducing the catabolic effect of stress. Nutritional augmentation with physiological ions can assist in reducing the electrolyte imbalance due to stress [6] and in providing the animals with water. Offering such nutrition can concurrently assist in maintaining appropriate osmolality in blood, intracellular and extracellular fluid pools [ 6, 11]. The nutrition company DeStress Nutritional Technology has taken these concepts and formulated a supplemental feed product designed to reduce stress in transported and handled horses. This pre-transport nutritional therapy (DeStress Nutrition Technology, Calgary AB) comprises an energy source to meet heightened metabolic needs, electrolytes to restore depleted physiological ions, selected amino acids to counteract protein catabolism and a means to promote hydration. To date, however, such a nutritional therapy is novel and has had limited use with horses. The aim of this study was to administer DeStress® nutritional therapy to performance horses prior to transportation and to monitor its efficacy for reducing transportation stress in these animals. Orbital eye temperatures determined non-invasively pre-transport and post-transport with infrared thermography was used to monitor the efficacy of this nutritional therapy. Material and methods 2.1 Animal care In order to determine the impact of a nutritional supplement on the response of performance horses to a transportation event, a transportation study was conducted on two separate study periods (April 15 and 21, 2015 and April 5 and 12, 2018) using performance horses at the Butterfield Ranch located near Ponoka, Alberta, Canada. These animals were trained to participate in the rodeo events of steer wrestling and barrel racing. The ten animals participating in the study included both mares and geldings between the ages of 5-22 years. The horses were kept in separate pens and maintained on a basic ad libitum timothy hay diet with an additional 2.27 kg of oats per day. All horses had access to water ad libitum. All animals were cared for and transported in accordance with the Canadian Council on Animal Care Codes of Practice for Horses.
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2.2 Treatments and sampling Twenty-four hours prior to the transportation, 1 kg of the nutritional supplement (a crumble from DeStress Nutritional Technology, Calgary, AB, Canada) was mixed into each treatment animal’s oats. The proximate analysis for the supplement is shown in Table 1. Each of the control animals received 1 kg of soy hulls mixed into their oats. On the day of transportation, duplicate infrared thermographic (IRT) images of all animals’ medial posterior palpebral border of the lower eyelid and the lacrimal caruncle were captured at 08h00 using a FLIR T450sc camera (FLIR Co., Boston, MA, USA); the left eye of all horses was scanned from a distance of 1 m at approximately 90° angle. The Environmental temperature and relative humidity were recorded on treatment days with a Kestrel model 3000 digital weather meter (Boothwyn, PA, USA) to calibrate the camera results. The horses were then loaded onto a conventional horse trailer (Featherlite® twenty-foot stock trailer, Red Deer Alberta). The transportation commenced at 08h30 and terminated at 10h00. Horses were unloaded and duplicate post-transportation IRT scan samples were obtained.
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2.3 Analysis of infrared thermography images Image analysis software (FLIR ResearchIR, Boston, MA, USA) was used to process the images and to determine the maximum temperature within an oval area traced around the eye, including the eyeball and approximately 1 cm surrounding the outside of the eyelids (Figure 1) Specifically the area of the medial posterior palpebral border of the lower eyelid and the lacrimal caruncle was used. The maximum eye temperature was used for the statistical analyses. The delta T value refers to the change in temperature between pre-loading and post hauling times.
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Each horse served as either a control subject or a treatment subject on one of the two transportation days. If a horse served as a control subject on the first day, it served as a control subject on the second day, and vice-versa. Both control and treated animals were represented on each of the two transportation days. On the second day of transportation, Horse 2 was intended to be a treatment subject. However, it did not consume the DeStress® product, so its data for that day were removed from the statistical analysis.
2.4 Statistical Analyses The statistical analysis of data was performed using a repeated measures ANOVA in Med Calc® software (Statistics for Biomedical Research. Version 9. Broekstraat Mariakerke, Belgium) since all horses were tested both under control and treatment nutritional regimes. A significant difference was declared when P ≤ 0.05. There were no significant interaction effects within groups.
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3 Results and Discussion The temperatures and relative humidity were within the thermal neutral zone for the horses on all trial days. The thermal environmental data for sampling days was as follows: T1 (April 15, 2015) T=6.5 ⁰C, RH 41.9% for pre-loading vs 10.9⁰ C and 22.8% for unloading post-transport. T2 (April 21, 2015) T= 5.2 ⁰C, RH= 61.6% for pre-loading vs 15.9 C and 33.5 % for unloading. T3 (April 5, 2018) T= -12.0 ⁰C and RH 66.0% for pre-loading vs -10.0 ⁰C and 60.0% for post-transport. T4 (April 12, 2018), T=-1.0 ⁰C and RH = 84.1% pre-loading vs 2.0 ⁰C and 62.0% RH unloading post-transport. The baseline eye temperatures pre-transportation were 34.09 ± 1.08 °C for the control group and 34.31 ± 1.24 °C for the treatment group. There was no significant difference between these pre-transportation temperatures (P > 0.05). These values are similar to eye temperatures measured by IRT in horses prior to undertaking the physical exertion of a show jumping competition [12, 13], or prior to being exposed to the physical stress of severe noseband tightening [ 14]or the psychological stress of a fear test [ 15]. The thermal values listed in Table 2 represent the combined stress of both loading and transport. After the horses had been transported in the current study, the eye temperatures were 35.29 ± 0. 0.32 °C for the control group and 34.65 ± 0.77 °C for the treatment group, which represented a significantly higher eye temperature in the control group compared with the treatment group (P < 0.05). The ability of the DeStress® treatment to attenuate the increase in eye temperature observed in horses that did not receive this nutritional supplement suggests that it is helping the horses to counter the effects of transportation stress. The composition of the DeStress product includes elevated levels of the amino acid tryptophan. This amino acid is a known neuro transmitter precursor of serotonin. Using nutritional approaches to manage serotonergic levels has been reported to be an effective means of managing stress and cortisol levels in several animal models [16]. The observed parallel between cortisol levels and infrared thermal values in horses has also been reported (17). In support of this observation in a different animal model, beef cattle fed a similar nutritional supplement immediately prior to transportation to an abattoir for slaughter demonstrated a reduction in percentage live weight loss as well as greater hot carcass yield as a proportion of pre-treatment farm weight compared with control animals [ 5]. Moreover, the prevalence of a stress induced condition in these cattle, dark – firm-dry beef, was reduced in treated animals.
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The positive values for delta T for both control and treatment groups indicate that eye temperature rose as a result of transportation stress. Although the delta T values were numerically higher for the control group compared with the treatment group (1.2 ± 0.94 °C vs. 0.34 ± 1.04 °C, respectively), this difference was not significant at the P > 0.05 level. The magnitude of delta T is similar to that seen for show jumping horses just after a show jumping competition [ 12, 13], or following exposure to the physical stress of severe noseband tightening [14] or the psychological stress of a fear test [14]. A similar increase in maximum IRT eye temperature was also observed in horses injected intramuscularly with ACTH [17], and this increase was significantly correlated with a concomitant increase in salivary cortisol. This latter study suggested that activation of the HPA axis increased the metabolic rate of the horses in the study.
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4 Conclusions These results suggest that IRT can detect differences in stress due to transportation in performance horses. Furthermore, they suggest that providing a nutritional supplement (DeStress®) to horses prior to transportation can reduce the physiological activation of the HPAA due to that stress. Properly applied, the use of nutritional therapy could prove a useful tool in managing stress in performance horses and other valuable animals such as breeding stock.
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Acknowledgements The authors wish to acknowledge the contribution of Country Junction Feeds of Wetaskiwin, Alberta, Canada, for the preparation and provision of the DeStress® Nutrition product. The invaluable collaboration of the Butterfield family by granting access to and use of their highly valuable performance horses is also greatly appreciated.
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Table 1. Ingredient proximate analysis for the DeStress nutritional therapy used in the present study (as-fed basis) Crude protein (min) 16.5% Crude fat (min) 4.5% Crude fiber (max) 20.0% Calcium (actual) 0.7% Phosphorus (actual) 0.5% Sodium (actual) 0.35% -1 Vitamin A (min) 10,000 IU kg -1 Vitamin D3 (min) 1000 IU kg -1 Vitamin E (min) 400 IU kg -1 Selenium 0.3 mg kg
T2 T1 T2 T1 T2 T4 T4 T3 T3 T3
H1 H2 H3 H4 H5 H6 H7 H8 H9 H10
Control PreTransport ⁰C 33.6 34.3 33.3 34.4 35.3 34.4 32.6 35.4 32.4 35.2 34.1 1.1 0.74
Control PostTransport ⁰C 35 35.5 34.7 35.7 35.3 35.5 35.2 35.7 35.1 35.2
Delta T ** ⁰C 1.4 1.2 1.4 1.3 0 1.1 2.0 0.3 2.7 0
35.3 0.3 0.029
Transportation Day
Horse
T1 T2 T1 T2 T1 T3 T3 T4 T4 T4
H1 H2 H3 H4 H5 H6 H7 H8 H9 H10
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Transportation Day *
Mean SD P *** 152 153
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Table 2. Pre-transportation and post-transportation eye temperatures and the difference between the two (delta T) in °C for performance horses fed soybean hulls (Control) or DeStress crumbles (treatment) prior to transportation.
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1.2 0.9 0.077
Treatment PreTransport ⁰C 34.6
Treatment Post – Transport ⁰C 34.7
Delta T ⁰C
34.5 33.8 32.1 35.2 35.8 32.7 34.6 35.5
33.8 34.7 33.2 35.7 35.3 35 35.1 34.4
-0.7 0.9 1.1 0.5 -0.5 2.3 0.5 -1.1
34.3 1.2
34.7 0.8
0.34 1.0
0.1
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*T1 = April 15, T2 = April 21. 2015. T3 = April 5, T4 = April 12. 2018 **Delta T = Post-transport eye temperature – pre-transport eye temperature. ***P-value from ANOVA repeated measures test comparing means of control animals with means of animals treated with DeStress
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Figure 1: Example of infrared thermography images and maximum eye temperature values in Horse 3 on two study days a) H3 Control pre-transport; Maximum eye temperature 33.3 °C
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b) H3 Control post-transport; Maximum eye temperature 34.7 °C
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c) H3 Treatment pre-transport; Maximum eye temperature 34.5 °C
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d) H3 Treatment post-transport; Maximum eye temperature 33.8 °C
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[2] Moberg GP. In: The biology of animal stress: Basic principles and implications for animal welfare, Wallingford, UK: CABI Publishing; 2000, p. 1-21.
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[5] Schaefer AL, Dubeski PL, Aalhus JL, Tong AKW. Role of nutrition in reducing antemortem stress and meat quality aberrations. Journal of Animal Science 2001; 79:E91.
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[7] Padalino B., Raidal SL, Knight P, Celi P, Jeffcott L and Muscatello G. 2018. Behaviour during transportation predicts stress response and lower airway contamination in horses. Plos One. March. 1-20.
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[9] Kleiber M. The Fire of Life: An Introduction to Animal Energetics. Huntington, N.Y.: R. E. Krieger Publishing Company, 1975.
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[12] Valera M, Bartolomé E, Sánchez MJ, Molina A, Cook N, Schaefer A. Changes in eye temperature and stress assessment in horses during show jumping competitions. Journal of Equine Veterinary Science 2012; 32:827-30.
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[13] Bartolomé E, Sánchez MJ, Molina A, Schaefer AL, Cervantes I, Valera M. Using eye temperature and heart rate for stress assessment in young horses competing in jumping competitions and its possible influence on sport performance. Animal 2013; 7:2044-53.
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[14] Fenner K, Yoon S, White P, Starling M, McGreevy P. The effect of noseband tightening on horses’ behavior, eye temperature, and cardiac responses. PLOS ONE 2016; 11:e0154179.
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[16] Roberts S A, Thibault L, Murray A C and Schaefer A L. The effect of dietary protein source on biochemical indicies of stress in stress - susceptible pigs. Canadian Journal of Animal Science 1996; 76: 401-408.
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[17] Cook NJ, Schaefer AL, Warren L, Burwash L, Anderson M, Baron V. Adrenocortical and metabolic responses to ACTH injection in horses: An assessment by salivary cortisol and infrared thermography of the eye. 2001; 81:621.
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HIGHLIGHTS SHORT COMMUNICATION: The pre-transport management of stress in performance horses
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DeStress® nutritional therapy was administered to rodeo horses prior to transportation Orbital eye temperatures determined with infrared were used to monitor the efficacy After transportation the eye temperatures were higher for the control group (P < 0.05). Providing DeStress® to horses prior to transportation reduced the thermal response to stress
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Ethics Statement The authors would note that all animals used in the study were treated humanely and subjected only to normal industry standard practices for the transport of animals as defined in the Canadian Codes of Practice. The research tools used, infrared thermography are fully non invasive.
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Dr. Al Schaefer Principle Investigator
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May 11, 2018