Elsevier

Journal of Veterinary Behavior

Volume 7, Issue 1, January–February 2012, Pages 21-26
Journal of Veterinary Behavior

Research
Effects of prescription diet on dealing with stressful situations and performance of anxiety-related behaviors in privately owned anxious dogs

https://doi.org/10.1016/j.jveb.2011.05.025Get rights and content

Abstract

The objectives of this study were to evaluate the effects of a diet (CALM CANINE) supplemented with alpha-casozepine and L-tryptophan on the stress response of anxious dogs with a focus on anxiety-related behavioral parameters and physiological parameters. Forty-four privately owned dogs were first fed with the control diet, followed by the study diet, each for an 8-week period, with a transitional period of 1 week between the diets. After 7 weeks on a particular diet, owners reported their dogs' behavior by filling out a questionnaire. Using the Canine Behavioral Assessment and Research Questionnaire, the effect of the study diet was found to be significant for 4 anxiety-related behavioral parameters, possibly mirroring a placebo effect. After 7 weeks on each diet, the urine cortisol-to-creatinine ratio (UCCR) was measured to assess the stress response to a visit to a veterinary practice for toenail clipping. UCCR was measured to complement the interpretation of behavioral data with regard to the stress susceptibility of the dogs. A positive correlation was found between baseline UCCR, as measured in the home situations, and poststressor UCCR. The stressor-induced increase was significantly lower in the dogs when they were fed the study diet than earlier when they were fed the control diet. The supplementation of casozepine or the proportion of protein in a given diet could have been a determining factor. The study diet seems to improve the ability of an individual to cope with stress and may reduce anxiety-related behavior in anxious dogs.

Introduction

It is becoming apparent that food or feed constituents can affect behavior. Prominent examples include tyrosine (Banderet and Lieberman, 1989), phenylalanine (ten Hoedt et al., 2011), tryptophan (Leathwood, 1987), omega-3 fatty acids (Zanarini and Frankenburg, 2003), and low-protein diet (Dodman et al., 1996), of which the latter has been reported to reduce aggression in dominant dogs. It has also been demonstrated that a high-tyrosine diet may be beneficial during severe stress (Lehnert et al., 1984).

When dogs are exposed to excessive chronic stress, heart rates (Galosy et al., 1979) and the secretion of hormones such as epinephrine (Kook et al., 2007) and cortisol (Beerda et al., 1996) increase. In addition to physiological changes, behavior symptoms, occur such as foot licking, fright reactions, destructive behavior, barking, and fear-related aggression. These abnormalities can become a significant problem for dog owners and their families. It is generally agreed that anxiety-related conditions are one of the major groups of behavioral disorders in dogs (Beata et al., 2007). It is well known that behavioral problems are the primary reasons for owners who relinquish their dogs (Salman et al., 2000, Mondelli et al., 2004).

Neurotransmitters and hormones regulate behavior, presumably including those that are considered problematic, and changes in food composition influence the availability of their precursors (Gibson et al., 1982). Thus, food composition can contribute to the reduction of problem behavior. Psychoactive drugs have been used to treat behavioral disorders. However, because of their addiction potential and side effects, many dog owners are not prepared to give psychoactive drugs to their dogs. Dietary components have advantages over drugs in that they are relatively free of toxic effects and side effects as compared with psychoactive drugs. Although they are not risk-free, most dietary supplements available seem to be safe (Fugh-Berman and Cott, 1999). It is reported that the stress of living with fear or anxiety can have negative effects on health and lifespan in the domestic dogs (Dreschel, 2010). Therefore, nutritional management of stress and anxiety may be beneficial to both dogs and the dog owners.

Royal Canin's CALM CANINE (study diet) is a diet supplemented with alpha-casozepine (a tryptic bovine alpha s1-casein hydrolysate) and L-tryptophan. The specific formulation of the study diet includes alpha-casozepine, at the recommended dosages (for a dog under 15 kg: 20 mg⋅kg−1⋅day−1). Alpha-casozepine is a natural biological compound, originated in the alpha S1-casein portion of milk (Palestrini et al., 2010). The physiological activity of alpha-casozepine has several similarities with the effects of anxiolytic benzodiazepines. Alpha-casozepine is similar in spatial structure to gamma-aminobutyric acid (GABA) (Miclo et al., 2001); it has an affinity for benzodiazepine receptors in the brain and potentiates the activity of GABA (Beata et al., 2007). GABA is a neurotransmitter, widely known for its inhibitory effects on anxiety- and stress-related disorders (Sanacora and Saricicek, 2007). Beata et al. (2007) compared the effects of alpha-casozepine and the control anxiolytic molecule, selegiline hydrochloride, in dogs and found that the Emotional Disorders Evaluation on Dogs scale behavioral assessment score of dogs in the 2 groups was the same.

The study diet also provides an increased ratio of tryptophan to large neutral amino acids (trp/LNAA of 0.048) as compared with other commercial diets. Amino acids are used as precursors for the synthesis of neurotransmitters, and L-tryptophan is the precursor of serotonin (Fernstrom, 1983). It has long been known that tryptophan administration increases brain 5-hydroxytryptamine (serotonin) synthesis in both rats (Ashcroft et al., 1965) and human beings (Eccleston et al., 1970). Tryptophan-induced serotonergic activity in the brain has been implicated in the regulation of many behavioral processes such as mood, aggression, and susceptibility to stress (Leathwood, 1987, van Hierden et al., 2004; Koopmans et al., 2005). De Napoli et al. (2000) reported the behavior-moderating effects of a diet with an increased ratio of L-tryptophan/LNAA in dogs.

Increases in cortisol concentrations have been shown to occur after various stressors (Vincent and Michell, 1992, Beerda et al., 1998, Beerda et al., 1999). Physical and emotional stresses result in elevated salivary and urinary cortisol excretion in dogs (Dreschel and Granger, 2005, Horváth et al., 2007, Bergamasco et al., 2010). It has been shown that monitoring of urine cortisol is a useful noninvasive method for investigating stress levels in dogs (Beerda et al., 1996). Cortisol is sequestered into the bladder over several hours, as a result of which, titers in urine can be used to measure background levels of stress over the preceding period (Hiby et al., 2006). A quantitative measurement of urine cortisol excretion can be determined by the urine cortisol-to-creatinine ratio (UCCR). A stressful situation, such as a new housing situation or visit to a veterinarian, may cause a mild increase in this ratio (van Vonderen et al., 1998, Beerda et al., 1998). In this study, visit to a veterinary practice for toenail clipping was chosen as the stressor to induce and assess stress responses in the dogs. By comparing UCCR-measured poststressor (at home 2 hours after veterinary visit) and prestressor (in the home environment), the efficacy of study diet on the dogs' physiological signs of stress can be evaluated.

The study diet is expected to reduce a dog's susceptibility to stress. The objectives of this study were to evaluate the effects of the study diet on the stress response of dogs in a stressful situation such as a visit to a veterinary practice for toenail clipping, and its effect on the behavior of dogs, focusing on anxiety-related behaviors.

Section snippets

Justification of the trials

All experimental procedures were approved by the Animal Experiment Committee of Azabu University (authorization number: 090727). The feeding trials were conducted as single-blind crossover trial. Informed consent was obtained from the owners of the dogs.

Eligibility criteria

The dogs were recruited at veterinary clinics in Tokyo, Kanagawa, and Hiroshima, and also from colleagues of researchers. Candidate participants completed a questionnaire containing questions related to their dog's behavior as derived from the

Study population data

Twenty-eight dogs completed the study (Table 2). Sixteen dogs did not complete the study for various reasons; 3 dogs did not start dietary treatment, 5 withdrew for health reasons not associated with the diets, 4 withdrew for reasons not associated with the diets (moving, hospitalization of the dog owner, and personal reasons), and 4 were lost to follow-up during the study.

Behavior

The scores for the behavioral parameters in the home situation derived from the questionnaire entries are shown in Table 3.

Discussion

A previous study has shown that a diet supplemented with tryptophan does not change anxiety-related behavior in privately owned dogs (Bosch et al., 2007). However, in the present single-blind crossover trial, the ingestion of the study diet reduced specific owner-reported anxiety-related behaviors: stranger-directed fear, nonsocial fear, and touch sensitivity. Unlike a previous study performed by Bosch et al. (2007), only highly anxious dogs were included in the present study population. This

Conclusions

In conclusion, the results of the present study provide some support for the efficacy of the study diet in aiding anxious dogs to deal with stressful situations. Furthermore, the ingestion of the study diet appears to be effective in reducing anxiety-related behavior, although a placebo effect cannot be excluded. In addition to tryptophan content, supplementation with casozepine and the proportion of protein in the study diet may have been determining factors. Veterinarians may consider dietary

Acknowledgments

The authors thank all the dog owners who participated in this study. This study was financially supported by Royal Canin, and partially supported by The Promotion and Mutual Aid Corporation for Private Schools of Japan, Grant-in-Aid for Matching Fund Subsidy for Private Universities.

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