Heat Stressin Dogsby Robert L. Downey

and illustrated by HOWL

HOWL gratefully thanks R.L. Downeyfor allowing us the liberty to use his 1981paper on heat stress in sled dogs. Thefollowing presentation edits the originalpaper and employs sections of the originaltext as captions with photos to illustratethe context. Some narrative informationnot found in the original text has beenadded. Capitals used for emphasis areadded.

Heat is one of the most severe en-vironmental stresses a dog can be sub-jected to. It may decrease appetite,growth, reproduction, and workingability.

Major changes in body fluids andtissues associated with over heating isknown as Hyperthermin. This conditionmay be influenced by the dog’s muscularexertion, physical condition, hair coat,and surrounding factors like relativehumidity and ventilation. The severityand duration of hyperthermia is influenc-ed by 3 separate but often interrelatedsyndromes.

HEATSTROKE

HEATSTROKE also known assunstroke, can be noted by the suddenonset of high fever and sudden collapse.It is the most lethal and most common ofthe three syndromes. It most frequentlyoccurs when environmental temperatureexceeds normal body temperature andresults from inadequate elimination ofheat from the body. Immediate coolingof the animal must occur to avoid possi-ble permanent brain damage if not death.

The optimum environmentaltemperature for the dog is between 60-70degrees F. In this range there is little or

WAG.. .GROWL.. .BARK.. .

If these dog’s have been worked TOO HARD for TOO LONG they maynot cot we// tonight or exercis? m well tomorrow due to HEA T STRESS.

There may be little outward evidence of clinical harm associated with heatstress, while major changes have occurred in bodyJ7uids and /issues. This overheating is called HYPERTHERMIA

no temperature stress on him. Extremecaution should be used when cooling offthe dog. When the body temperature ofthe dog falls to within 2-3 degrees F ofhis normal temperature, cooling off ef-forts should cease for fear of the bodytemperature continuing to fall below nor-mal. This equally serious problem is call-ed HYPOTHERMIA.

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It is very important for warm climatetrainers to INCREASE their CONDI-TIONING program SLOWLY duringwarmer weather periods in their area,especially in the absence of wind and/orwhen the humidity is high along with thetemperature.

Since physical FITNESS INCREASESHEAT TOLERANCE. Take your time to

Shepherd.7 like noted veteranBorder Collie trio/w, Lewis Pulfer,knows the dangers of working in thehigh humidity and severe heat ofsummer in places like Ohio,Virginia or Texas.

ACCLIMATIZE your dogs to warmweather. Acclimation to a hotter environ-ment INCREASES ABILITY to WORKin HIGHER TEMPERATURES. The ac-climation process takes 7 to 9 days to 3weeks. devending on the condition of theanimal.

Generally speaking, most heat pro-blems can be avoided with proper ventila-tion, shade, and plenty of clean, colddrinking water.

HEAT CRAMPS

Heat cramps, the rarest of the 3 heatcaused syndromes, is usually seen inworking dogs following severe exertion inhot weather. These are painful musclespasms.

HEAT EXHAUSTION

An interesting theory has evolved inregards to heat exhaustion in dogs. HeatExhaustion is complicated by the dog’spanting to dissipate heat. Severe andstrenuous exercise in dogs leads tometabolic acidosis from the accumulationof lactic and other acids in the body. This

allows the respiratory center in the brainto become overly sensitive to the slightdecrease in oxygen headed for the brain.Panting increases even more to increaseoxygen intake and dissipate heat. Increas-ed panting leads to excessive depletion ofcarbon dioxide hypocapnia. The body at-tempts to conserve carbon dioxide bydecreasing breathing thus limiting thedissipation of heat and oxygen availabili-ty. If the breathing does not decrease, theexcessive losses of carbon dioxide leadsto constriction of the small vessels carry-ing blood to the brain, which can causecollapsing. This under-ventilationdiminishes heat loss from the dog, allow-ing increased danger of heat exhaustion.This is commonly seen in dogs workingin temperatures in which they arc notacclimated.

Most of the work done in acclimationto heat has been done in humans. In un-fit humans it took some almost 3 weeksclimatize, while some very fit humanstook only 4 days! Remember, heat ac-climatization and physical conditioningboth lead to LARGE INCREASES ofPERFORMANCE in HEAT, resultinglargely from changes in the cardiovascularsystem.

Mushers Bill Brisbois, Ginger Dunlap, HOWL Editor, and Harris Dunlop watch Lewis PulJer at his/arm near Quincy,Ohio. Acclimatized and physically fit dogs, like (I trail competing Border Collie, con work better in the dangerous 20neof body temperatures above 106 degrees F.

The most effective method o/cooling o Ii/e-threatening over heated dog was thought to be toplunge him into ice water.More recently the recommended method oJcooling ofJ the animal is the use of tepid (moderately cool) water. BorderCollie people have been doing this, perhaps unknowingly, by using tubs located outdoors in the shade. A good sourceOJ /i/e saving, gradual temperature reducing, tepid water.

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These dogs have just finished ofast 20 mile heat of the NorthAmerican where they ran thefastestfor the day. They ore in good spiritsand assisting their COOLINGDOWN by GRABBING SNOWand RUBBING their bodies, on im-portant cooling technique asmassaging con stimulate heatdissipation and help move stagnantair.

THE HARD DRIVING LEADER HAS THE MOST STRESSFUL JOB:Which leader shows the affects of training the most? You should be able totell that the leader on the right is still gasping for air. Close IO hyperventila-tion. she is illustrating the fatigue and near circulatory collapse followingstrenuous exertion. The mole leader to her right, is still showing signs of rapidbreathing (IS seen through observing the heaving of the rib cage; now shallow,rapid inhalation persists. Mental stress can increase brain temperature. Whenyou deal with your leaders, remember many fail due the emotional drain. Whenthe dog becomes nervous, the nerves constrict the surface blood vessels thusreducing heat loss and thereby raising core temperature. This con affect leadability, (1s soon after the brain temperature rises and impairs mentalfunctioning.

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Learning the PantOne of the ways to “read” your dog’s stress threshold is to study the attitude of

the hard working dog, particularly the body and breathing.

ALL DOGS ARE NOT CREATED EQUAL: Which Dog shows morefatigue of this pair? The differences ore especially noted ot the onset of condi-tioning. Some dogs are less excitable or their systems are better at dealing withheat due to their calmer personality, or beginning fitness, coat density, in-dividual musculature, or personnel exertion and drive. Do not make the mistakeof evaluating all dogs by the some measures.

THIS PANT INDICA TES SAFE HEAT DISSIPA TION: The standing dognot only shows you did not go beyond the safe limits of his physical fitness!but affords the dog better air circulation and cooling opportunity then thedog lying down after exercise. It is better to walk an almost exhausted dogif he is not prostrate, or almost so, due to over exertion.

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Mmt PANTING animals ore we// structuredfor MAX-IMUM efficiency of E VA PORA TION by two methods.Firsl, the NOSE has complex infolding of bones of whichtheir TOTAL SURFACE AREA IS GREATER than theTOTAL BODY SURFACE arm of rhe ENTIRE DOG.

TRANSPOR TA TfON IN POORL Y VENTILA TED DOG BOXES can heextremely dangerous. These Canadian constructed dog boxes, by J. Verbeek,show how effective unrestricted door openings allow maximum air passage;bars are excellent as fhey restrict little air flow.

Cages should not have (TOSS ventilation during the Winter oc rhe CROSSDRAf..TS CAN CA USE RESPIRA TORY PROBLEMS. Still ample Ope,,i,lgand boxes about 23” b.v 23” and 30” or more deep, provide adequateventilation.

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Strenuous interval training in humansin a cool environment is more effectivefor heat acclimimatization than trainingby continuous, moderate work.

The nasal interior and the nasal glandis an organ unique to dogs and other pan-ting mammals. The gland secrets fluid on-to the mucosa, providing a constant supply of water for ‘evaporation. The mouthis also an evaporative region which ob-tains moisture from the salivary glandsfor cooling. This evaporation is minimiz-ed with increased relative humidity orpoor ventilation. Of major importance isthe continual air change immediately sur-rounding the body of the dog. Stagnantair near the body is quickly elevated tobody temperature thus rendering uselessthe most important means of heatelimination in the body.

Cage confinement with inadequate ven-tilation can be very dangerous. Dogs havedied from heatstroke in cages, where theair temperatures were 20 degrees FBELOW the dog’s normal bodytemperature, while dogs in outside runswith SHADE RARELY suffer fromheatstroke even when temperature reach105 degrees F. (See article on SHADEbeginning on page 13.)

Panting dogs at REST in a hot environ-ment inhale through the nose and exhalethrough the mouth. But EXERCISINGdogs inhale and exhale both through thenose and the mouth, thus increasingevaporation. Finally, blood flow to thetongue may be increased six-fold, allow-ing larger amounts of blood to be cooledto help prevent the potentially devastatingalterations of brain function.

Behavior also plays a major role inbrain temperature regulation. Theautonomic nervous system controls thedilation and constriction of blood vesselsnear the skin. This system is affected byemotion and activity. When an animalbecomes excited the nerves constrict theblood vessels in the skin, reducing heatloss and raising core temperature, soonafter the brain temperature rises. Thus ex-citability puts the animal that much closerto the threshold of brain damage fromheat. Thus calmness before any exerciseor stressful situation can possibly improveperformance.

Shade over GRASS is cooler thanshade over bare soil. Coat lengthand density are overplayed in theirability to fight hyperthermia. Clip-ping (I dog’s coat in the summerprobably makes the ownerfeel bet-ter than the dog, especially if thedog is kept outside where the longercoat may actually keep the dogcooler by insulating against thesun’s rays.

COAT LENGTH MAY RE OVERPLA YED in causing the dog discomfort in wormer climates. Polar breeds have(I very dense undercoat which helps insulate against the sun’s rays. This provides these dogs with goodprotection againstthe heat of summer os well (IS the bitter cold of winter. Reproduction is also greatly affected by the heat. Male spermcounts ore &creasedfrom direct heat on the testicles. Unacclimatedfemales resorb fetuses at rates (IS high (IS 30percent.Often, the young that ore born hove decreased body weights.

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Rf.7’RODUCTlON co,, lx pr~w/l~~ u[fr<‘tcd 0~ heat in both MALE SPERM COUNT and RESORBED FETUSES.If you have litter sizes of I to 3 pups. you might review your kennel and training environment.

OBESE (very fat) DOGS aremore prone to heat regulation pro-blems than lean dogs. Subcutaneousfat has about twice the insulativevalue of muscle, so heat dissipationis greatly reduced. For animalsabout the size of the dog, heavy ex-ercisepresents the most severe ther-mal stress that may be encountered.The brains cooling mechanism isgreatly affected by heavy exercise inextreme heat.

In RUNNING DOGS, the L-XC.KS.7 rote of HEATproduction is TEN-TIMES the heat gain that could oc-cur in the HOTTEST DESERT on Earth! It seems thatmaximum efficiency of brain cooling in dogs occurs dur-ing exercise. In dogs exposed to hot, dry air, the bloodsupplying the brain is cooled slightly lower than the coretemperature. But during heavy exercise in less severe, butstill warm temperatures, the brain cools almost 3 timesgreater than the core body temperature.

D o g s ore bu>icolly known /or their EXTREMETOLERANCE oJheat as well as the ability to work forlong periods in the heat. However once the tolerancethreshold is crossed over the dangers of severe heatdamage suddenly becomes of primary concern.

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About the Author:Robert Downey, along with wife Mary

Jo, are well known sprint racers. I” ad-dition, Rob Downey is known for his fre-quent presentations on the sled dog sym-posium circuit, where he presents onnutritional matters.

Downey has extensive practical ex-perience in this arena too. Rob publish-ed papers while associated with thecelebrated sled dog studies at the Univer-sity of Pennsylvania School of VeterinaryMedicine. While at New Bolton Center heworked with Dr. David S. Kronfeldmanaging the study models comprised ofboth Beagle and sled dogs.

At the conclusion of the research, Robturned his considerable energies to theformulation and marketing of a dogfood. This resulted in the formulation ofa line of very fine products and the for-mation of ANNAMAET PETFOODS,INC. This line of products have foundwide acclaim amongst kennel operators inmahy discriminating field and perfor-mance arenas of hunting as well as sled_ .

SARA OOWNEY, Rob and Mary Jo’s contribution 10 junior mushing.

dogs. An increasing mterest tram snow of Rob Downey’s diligent application and Sellersville, PA where they are engagedand breed kennel people has been occur- desire to meet the nutritional needs of in raising a” enthusiastic future mushingring of late. These products are, now canines. daughter, Sara, with ideas on caninerapidly becoming wide spread as a result Presently the Downey’s live in nutrition of her own.

SHADE

This narrrrul serrmg <,f ,ree.y IS o good p/we 10 locureyour kennel. The lemperorures are .\ign~/icanfly coolerunder trees.

A nice coolplacefor (I bitch 10 have herpups. A privaleplace with enough space so a fence is not needed for thefirsf few weeks. Remember, excitement, fear or worry conelevafe body femperoture. A large conlainer for water isonly good for /he adult bitch. Smaller containers oreneeded for pups who will first take water al aboul threeweeks.

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We all know shade can assist in mak-ing us more comfortable. Shade can alsomake the difference of life or death,especially to very young pups. Even adultdogs can have their lives threatened if thetemperatures are in the 90’s or above! Thedanger increases when the air is still; aircurrent can carry off heat and affect cool-ing. If you live where humidity is high.you run still another risk of heat relatedprostration.

If you have a choice, locate your ken-nel in trees, especially your whelpingareas.

If you have a hard time locating treesin your kennel area, you might find thevery fast growing Frysville HybridPoplars a significant advantage. The treescan be purchased from Miles W. Fry andSon Company, 300 Frysville Road,Ephrata, PA 17522. Send for a brochurewith current prices. Or call 717-354-4501.

The best planting time is spring. YouA beautiful spot for this young husky. Keep in mind, thof in time. any treewithin (I dog ore0 will probably be destroyed. Once (I tree is ringed (bark remov-ed 01.’ the way around) the tree will die.

Pups ore porricularly sensitive 10 environmental ex-tremes in temperature in thefirst 72 hours. They cannotregulate their body temperatures to adequately withstandhigh air temperatures. Shaded oreas will make IIdifference.

A Rood whe/p;nR and l;v;n,g “reu for (I birch ond herpups. Note the low dish for ea.~y access to woterforpups.The tree outside the pen insures protection from theshade.

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Dogs will seek the shade of (I vehicle, rock, building,or dog house, if no shade is provided. These yard dogs.illustrate this by locating under (I play house.

This poplar tree was planted 52 days before the photowas taken. It was receivedfrom the nursery and was owhip with no limbs. You could practically see it grow.

can purchase the trees as rooted stock for$1.50 each up to 49 trees. The price dropswith increasing numbers. 100 unrootedtrees costs only $30.00 this Spring. Ourexperience was with 4 foot rooted stockat $5.00 each. The Frysville nursery willreplace any stock that, does not live for

the first year. A good deal. They don’trequire any special handling. They havetwo basic varieties, one for coldtemperatures, the other for warmerclimates.

We have taken the low branches off.However the wind bends some trees near

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If you froin in the warmer months, you might be ableto locate your training and condifioning oreo in trees.Multiple coverage, or rows of trees o/low for extendedtraining periods. If the shaded area is large enough youmight be able to work dogs for on hour or more afterthe sun is too hot in open areas. Older larger trees holdthe cooler night temperatures longer.

Tefhering dogs in the trees while waiting to twin, conassist in keeping the dogs cool and refreshed beforeexercise.

the dogs. This waiving action has increas-ed with the branch size. Some of thesewere grabbed and yanked into the areas:Pups also mutilated one tree. You mightnote the trees should be given enoughspace. Most of these trees will be overtwenty feet high in less then three years.

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