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Stress: The Good, The Bad, The Measurable

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Stress: we can’t live with it; we can’t live without it. Defined as emotional strain or tension resulting from environmental challenges or demanding circumstances, stress is an integral part of being alive. No living being or environment is completely stress-free, no matter how sedate the existence.

Stress jump-starts the body to meet challenging situations. The adrenal glands pump out stress hormones that kick the brain and body into action to react appropriately to the challenge.

Stress can be positive or negative. Good stress is the excitement we feel before a performance situation, and for animals it means searching for food or surviving a dangerous situation, learning from it, and avoiding it. The body revs up for the event and recovers.

Bad stress is chronic sustained exposure to stress with no relief or recovery. An animal is considered stressed when abnormal behaviors or extreme physiological changes are necessary to adapt to the perceived dangerous or negative environmental changes. The stress system has run amok and negatively affects the immune system, heart, brain, and overall health of the individual.

We can’t verbally question animals about their stress but we can measure signs of their stress by assessing physiological and behavioral changes in relation to the negative environment. One method alone doesn’t accurately measure stress in every situation so a combination is preferable to give more reliable results. With that knowledge, we can modify our pets’ environment to be less stressful, increasing their overall health and wellbeing.

Physiological Changes

When we go to the doctor we may feel nervous and our vital signs may be slightly elevated. This is known as the “white coat” effect, and animals experience the same feeling at the veterinarian. Vital signs, or physiological parameters, used to measure stress include serum cortisol, blood pressure, temperature, and heart and respiratory rates.

When a pet perceives a threat, such as a trip to the vet, physiological changes occur in the body to help the animal fight stress. The brain releases a chemical, adrenocorticotrophic hormone (ACTH), which in turn fires up the adrenal glands (located on near the kidneys)  to release cortisol and adrenaline to amp up the body for fight or flight.

Cortisol prepares the body for necessary action and suppresses unnecessary functions needed for the response. High levels of cortisol raise blood glucose, or blood sugar. High blood glucose is a marker for diabetes.

Cortisol is commonly measured in blood samples but also in saliva, urine or feces. New studies are looking at measuring cortisol levels in hair as an indicator of chronic stress.

Blood pressure is defined as the strength of pressure necessary to push the blood through the blood vessels from the heart. Measuring blood pressure in pets is done in different ways; one common way is a Doppler unit, which uses ultrasonic waves to measure blood pressure on the tail or limb using a pediatric cuff. Most veterinarians recommend using the average of at least five readings to determine blood pressure.

Temperature is taken with a rectal thermometer, definitely stress-inducing. Cats are especially prone to stress-induced temperature spike. Normal temperature for cats and dogs is 99.5-102.5º F.

Stress causes the heart to beat faster and increases the respiratory rate. For cats, normal heart rate is 160 to 220 beats per minute. For small dogs weighing 30 pounds or less, 100 to 140 BPM is normal and 60 to 100 BPM is normal for dogs weighing more than 30 pounds. Normal breathing rate for dogs is 10 to 30 breaths per minute; for cats it is 20 to 30 breaths per minute.

For physiological parameters to be meaningful, you first need to know a baseline, or “unstressed” level. Stressed-induced physiological levels may give skewed test results that complicate the interpretation. Measuring physiological parameters may increase stress, so this is an ideal time to redirect the pet’s attention with toys or treats.

Behavioral Methods

Veterinarians use pet questionnaires (filled out by owners and the vet team), videos and other assessment tools to measure deviations of normal behavior and measure signs of stress in pets. One such questionnaire is the Monash Dog-Owner Relationship Scale (MDORS). Videos give a real-time look at behavior in the home as well as in the clinic setting, so the two can be compared. Using many behavioral assessments helps to reduce the risk of subjective or anthropomorphic projections and provide more scientific measures.

You may recognize some signs of stress in your pets but overlook more subtle or incongruous signs such as yawning, panting or displaced grooming. Some notable changes include hiding, vocalization, increased lip licking, avoidance of eye contact, change in ear position, and pupil dilatation. Ask your vet for a chart of common signs of stress or download the Spectrum of Fear, Anxiety and Stress for your dog or cat.

This article was reviewed/edited by board-certified veterinary behaviorist Dr. Kenneth Martin and/or veterinary technician specialist in behavior Debbie Martin, LVT.

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