Nelson Road Veterinary Clinic

08/18/2026

Hay Testing, Drought and Hay Fires
Hay Stack and Barn Fires and Preventing Them

Drought is a cycle that will occur every decade or so in our area. We cannot always plan for or predict a drought. Hopefully we can learn from mistakes we have made during the last drought cycle(s).
Feed is a major cost for livestock when one has to supply the forage. Pasture is the least cost method of maintaining and feeding animals if the vegetation is adequate and nutritious. Our cow feeding handout has some information about by-products and alternative feeds, winter feeding on pasture, etc. When hay prices are high some horse owners tend to purchase the Sudan hays, such as oat hay. Sudan poisoning can occur in horses even though this same hay can be fed safely to cattle. Ask for our horse Sudan poisoning handout if you area feeding an oat type hay to horses. We also do not recommend feeding oat hay to male goats, male sheep or male camelids, due to urolithiasis problems.
Protein may need to be supplemented. We do not recommend over 1/3 of the diet as NPN to be fed to ruminants; these are usually tubs of molasses containing urea. NPN should not be fed to horses and camelids. If you have experienced a grass tetany (low magnesium), a milk fever (low calcium) or a low phosphorous problem in your herd please ask for our comparison information for these protein tubs. Even though alfalfa hay or pellets may be more expensive, this legume hay usually is a good, safe source of natural protein for livestock and horses. Never feed moldy hay to animals. Feeding an ionophore (i.e. 200 mg monensin) in two pounds of a 30% crude protein supplement can be considered for cattle on a prairie hay pasture. In a drought, hay testing becomes very important to help balance a ration; reducing the herd to 75% of the carrying capacity of the land should also be considered. If forage is limited, then 6 hours of access to hay can be a minimum level to keep up the cows maintenance level and reduce overgrazing on your pasture. Our winter feeding tips handout discusses the amount of hay lost when you feed on the ground versus in feeders or etc. We have other low cost feeding mixtures if you have the ability for a TMR ration and over 50+ head of cattle to feed through the winter. For most farms we instead recommend the NPN winter range tubs, if they calculate to be cost effective over your own grown or purchased hay crop.
When there are periods of drought we see nutritional problems not normally seen when food is plentiful. Cyanide poisoning can occur when cattle are allowed to graze corn that is drought stressed. If you cannot harvest corn properly let it dry in the field, and be aware of the mature cow who knows how to eat the ears (only) off the corn stocks as she goes through the field; grain overload can then occur. Rotational type fencing helps the cattle to graze only a small, new part of the field each day or so in the late fall or winter. Ensilaging stressed corn can also cause a cyanide poisoning. Nitrate poisoning can also occur in corn during the same type of stressful conditions, and grazing access being limited to the stress corn is crucial. Nitrate poisoning also can be seen with broadleaf w**ds undergoing stress, drought and/or w**d spraying with 2-4 D. If the hay has not been sprayed for insects blister beetle poisoning can occur, especially with stressed hay. Many poisonous w**ds, such as the white hoary alyssum, can thrive in a hay field undergoing stress and drought.
When silage corn is harvested in a drought period it may not ferment properly if the silage was cut with a low moisture content. Listeriosis, aflatoxin, vomit-toxin and other problems can be a result due to improper fermentation and/or feeding practices with silage from stressed plants. Aflatoxin is produced by a mold growing on the corn, especially if stressed. Ensilaging may kill the fungus but it will not kill the toxin. Vomitoxin and other similar toxins can easily develop in feeds grown and processed in a drought. If there is not enough grain to properly ferment the propionic, lactic and acetic acids then butyric acid can develop. Using buffered propionic acid additives should be considered if diluting such marginal silage to feed out with other forages. If one grazes the stressed corn the nitrate and cyanide poisoning problems can occur as mentioned above; and especially the cyanide problem if there has been a recent frost or first freeze. Mowed Sudan (corn, oat hay, etc) which has been left alone for a few days will allow some of the cyanide to escape; yet as to be mentioned below this sitting can worsen a nitrate problem. We recommend testing drought affected Sudan forages possibly before harvesting and/or definitely before feeding to livestock; we have a list of the laboratories which will do forage testing. If the forage has a high nitrate content in the field the silage chopper can be adjusted higher, as the lower part of the stock contains a lot of nitrate. Ensilaging can remove up to 1/3 of these nitrates. Nitrogen oxide is released and can cause silage poisoning in humans which can occur if one enters a silo within 3-4 weeks of filling; turning on the silo fan 15+ minutes before entering helps reduce this problem. Allowing this green chop hay to sit and heat up may cause a higher nitrite level to develop from the nitrates in the hay. Nitrite is 10x more toxic than nitrate. Feeding green chop silage fresh can be the most hazardous method if allowed to sit, yet feeding as fresh chop within a few hours this may be adequate if the nitrate levels are not high and the feed is mixed with other forages or feeds. The nitrogen oxide gasses from high nitrate silage can kill cattle (and humans) within 12-60 hours after harvesting. (As noted above green chop silage after a frost can create a cyanide problem). If the corn is left to dry in the field, and cattle are allowed to graze down the corn, to prevent acidosis and grain overload/bloat you should SLOWLY strip graze the corn as mentioned above for cyanide problems, and feed hay before turning out the cattle into the new small strip. If you think you have a high nitrate forage, we recommend you test the field before harvesting. When cutting stressed, high nitrate corn for silage, remember that the lower part of the stock can have the highest concentrate of toxic compounds; something to remember if you are thinking of turning cattle immediately out onto the corn stover after harvest. This concentration especially occurs during a drought, and also if there is a wet period in the fall before the corn is harvested.
Minerals need to be supplemented in a drought. We strongly recommend the brown mineral salt blocks for all livestock. In a drought phosphorus is also one of the limiting factors, and simple mixing dicalcium phosphate with the trace mineral salt (50/50 mixture) should resolve this problem.
Water should be located every 1/2 mile if possible. When a cow has to walk more than 1 mile to water, a lot of energy is wasted. When placing the salt blocks, one should have the blocks 1/4 mile away from the water source and/or protein tubs. Placing them together will cause the cattle to stay in one spot and create problems by destroying the vegetation. Move these salt and protein supplemental tubs periodically.
Vitamin A is a concern, especially if the forage or supplemental hay is not green in color. It is especially important to give a vitamin A injection to newborn livestock born during a drought.
When there is a shortage of forage and hay available feeding smaller amounts more frequently in a hay feeder will be more efficient, compared to feeding on the ground where 1/4+ of the hay is lost. If one is able to feed a TMR the use of monensin will increase feed efficiency and allow up to 8% less feed/forage needed.
Strongly consider early weaning of calves if the pasture is short on forage. This will allow the mother cows to regain their weights for pregnancy, heifers to grow and the pasture to not be overgrazed.

For testing forages and hay nearby is Dairy Authority, 8215 We 20th Street, Greeley, Colo 80634, 970-351-8102

We have a handout on forage harvesting, moisture meters on the baler and using a microwave to test hay that you have purchase for moisture content. These and more handouts are on our website. Moisture should not be over 16-18% in a large bale or 18-22% in a small bale or you have a potential for a hay fire. The first cutting usually has a higher moisture level. With 1+ month of the inability to cut hay this year, and with a shortage of hay, many hay producers will have to cut as early as possible once the weather cooperates.
We recommend placing a few heat temperature monitors into the haystack, or approximately one sensor per 100' of a linear stack. These should be placed a couple feet inside the edge of the stack. If you take a core sample to test your hay for moisture and nutrient content, consider using a 20-36" long compost thermometer at minimum to place into the core hole of this large bale until the moisture contents of this bale is back. Our website has the hay labs for forage quality testing.
If there is a core temperature of 150 degrees in a hay stack you have a potential for a hay fire; at 175 degrees a fire probably will occur. Moving hay when it is over 175 degrees may create the potential to start a spontaneous hay fire. Hay should be watered if you are attempting to move it out of the hay barn. Always remove the equipment and other valuable items first from the barn. To pump nitrogen or carbon dioxide gases into the hay stack to reduce the oxygen content and potential for fire is not usually very successful unless the hay is in an air proof type of barn or silo. It is best to call the local fire department if you have a reading over 175 degrees Fahrenheit before you do anything. If the hay was baled with a curing agent such as ethoxyquin or butylated hydroxytoluene (BHT) these compounds can form a deadly cyanide gas if there is a hay fire and you need to mention this to the fireman when you call them about the potential for a hay fire at your place.
To prevent fires in an animal barn do not store hay inside at all with animals if you have large enough facilities and especially if it is not properly cured and/or baled within a month. Place a fire/smoke alarm near the hay inside where animals are housed if their hay is within 50” or inside the same barn. There are some fire/smoke alarms available that will also alert your cell phone.
Botulism in horses does occur in our area. It is usually seen with the large bales and some of the Clostridium bacteria producing this toxin grows in these large bales when the condition is right. These bacteria are normally found and replicate in our soils. Smaller bales do not usually have this issue. This may be a good year to vaccinate your horse for botulism and we can leave out such a vaccine after hours for currently active clients to pick up.

Sources of Thermometers to Prevent Hay Fires:
We recommend that you check Ace Hardware, Budget Home Center and the Flower Bin locally first for the compost thermometers. For some other examples:

Hay thermometers-manual , The 20” size is adequate and found locally. There are also 36” compost thermometers available.
Hay and soil type thermometers-electric (battery) - all traceable (minimum/maximum recall).
Usually have to find on line at www.LSS.com, etc.
With/alarms:
-58 to 158 F @ LSS ( -91825)
Extech portable pocket thermometer w/alarm @ www.mscdirect.com
With heat sensor and remote alarm, wireless:
Oregon Scientific, 100 or a 33' range, low battery indicator
Winland EA 800 - 11-26 V, 8 sensors, 1000' @ Absolute Automation
Watch Dog by Wireless Corporation for greenhouses, 1300' @ Absolute Automation
Dakota Alert, Wireless Alert WPR 3000 = 3000' @ AA battery (for dogs in cars, pager receiver)
Dakota Alert, Wireless Transmitter, WR 3000 open/closed circuit, to use w/Sensaphone,
600 @ Absolute Automation
Sensaphone - FDG 2800, $1075 @ absoluteautomation.com
With sensor and remote alarm, not wireless:
Cooking thermometers, wireless:
Acu-rite oven thermometer, 100' range, AA batteries
Grill Alert, 300' range, AA/AAA batteries
Oregon Scientific, AW 131, 330' range
Others = Outset (120' range), Maverick (100 & 150' range), Nu-Temp (75' range)
Redi Check (120' range)
Taylor makes a 32-392F (0-200C) thermometer w/alarm ( #32-392) for less than
$15 found in many hardware stores (2011)
Taylor makes a Remote cooking thermometer with an alarm, #1479, 200' range
Taylor #532 Connoisseur, 200', AA/AAA batteries
Cooking thermometers with a cable, not wireless:
Polder , Pyrex cooking thermometer
Cooking thermometers with audible alarms (not remote) = President's Choice Infrared
Also LSS.com/lab supplies, www.gemplers.com, www.vwrlabshop.com
** Many infrared thermometers may only have < 24" range **, and infrared only reads the outside of the hay bale and not inside; we do not recommend these on average.

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07/21/2026

Curated by Smartbrief. Dogs see the world differently than humans do, with dichromatic vision that allows them to distinguish blue and yellow but not red and green, according to the VCA Animal Hospitals. Dogs are good at detecting movement and seeing in low light, but their vision is not as s...

07/03/2026

HEAT STOKE AND HEAT STRESS

Heat stress causes heat stroke. When the heat index reaches over 105 animals and people it can cause exhaustion, cramps, heat and sunstroke. If the air temperature is 85 degrees and the humidity is 80%, the heat index will be 99. Raising the air temperature 10 degrees F. will result in the heat index climbing to 113. A heat index over 130 is a very dangerous situation. In a closed car with an outside temperature of 72 degrees F, the temperature inside can rise 40 degrees F higher within an hour.
Pigs and dogs are very sensitive to heat because they do not sweat as much as other animals. Livestock in areas where heat stroke is possible should always have access to water and shelter from the sun. Dogs which have reduced nasal airway capacity, medically called brachycelphalic (i.e. bulldog type breeds), hypothyroid dogs, obese and older patients have more problems tolerating the heat. The brachycephalic airway obstructive syndrome is more common in the English bulldogs, pugs and Boston terriers; these dogs have stenotic nares, elongated soft palates, everted laryngeal saccules and/or everted tonsils. Should you ever take the temperature of an animal, and it is over 106 degrees then first start pouring water on this patient, before calling the veterinarian. Any patient with a temperature of 107 degrees should have alcohol sprayed or lightly poured over their body, if possible; this is the magic temperature that heat stroke is starting to occur, damage to tissues can possibly occur and medical treatment is needed. Alcohol evaporates much quicker and removes heat faster than water. Once you have run out of isopropyl alcohol, or even ethyl alcohol over 40 proof (i.e. vodka), then start using water. Cool down a hot animal until they are 103 degrees F re**al temperature, and then reduce the amount of water or alcohol rinses in order to not drop the body's temperature to below normal. If one cools down an animal too quickly and to a below normal temperature you may cause the patient to go into shock and thus we do not recommend ice water baths. Ice and ice packs are ok if you do not have any water available. After the initial wetting down/alcohol application use the air conditioner in the car on your wat to taking the patient into the veterinarian. We realize that water is usually quicker to find and start using than to wait until someone can run to the nearest store for rubbing alcohol. It should be noted that sheep and goats can normally have a temperature of 104 degrees during the day in summer, and birds can normally have a re**al temperature of 103-108 degrees. Birds and any other animals should be misted with a spray of water if they are showing signs of heat, such as spread out wings in a bird. Cattle that have been on fescue grass can easily develop heat stroke, due to a mold causing the body to not regulate its temperature very well. There are many other causes for a patient to have a high temperature, which can range from systemic infections to toxins to other poisonings affecting the body. We recommend blood tests with heat stroke patients for many reasons. Hypoglycemia, seizures, malignant hyperthermia, exercise induced collapse and other underlying problems can present as a recumbent patient with hyperthermia, especially in hot weather. A dog with malignant hyperthermia is rigid, while an exercise induced collapse in Labrador retrievers will have a flaccid muscle, and yet a similar Collie Collapse disorder has all 4 legs as stiffness. In livestock there are other medical conditions to consider such as anhidrosis in horses to fescue grass issues with cattle.
If any animal is in the hot weather, appears to have rigid muscles, an increased respiratory rate, salivation, an outstretched neck and/or weakness you should make an attempt to reduce the core temperature of the animal until veterinary care can arrive and/or you can transport. If under 104 degrees F. the animal should be placed in the shade and watered down. Giving too much water to drink at once can cause problems, especially in pigs. If the body temperature is greater than 105 degrees, a call to the veterinarian is indicated. Animals with a body temperature of 106 degrees Fahrenheit or greater should be examined as they can have a total body break down called disseminated intravascular coagulation occur later on. Disseminated Intravascular Coagulation (DIC) can then cause a brain problem; many strokes and shock can usually be prevented with an exam, tests and medicines before the collapse occurs. If the clotting factors are low and/or if the animal has had a serve hyperthermia there is an IV treatment with plasma which is indicated if available. With initial treatment some animals may even require a cold water e***a, while other species such as horses and pigs we do not give routinely give e***as to.
IV fluids and medicines are usually needed for animals that have a temperature over 106-107 and appear distressed; each species is treated differently. If in doubt with small animals we will recommend hospitalization, blood tests and IV fluids to prevent kidney problems and DIC from occurring. In many species from birds to pigs if there is dehydration then a hypernataremia (salt toxicity) can occur, along with a secondary acidosis and other problems. There are other causes for hyperthermia for which we have a handout for. Heat stroke and dehydration have similar signs as water toxicity which is seen mostly in humans and a low sodium level is seen on blood tests.
A pulse rate over 65 indicates a problem if horses are undergoing possible heat stress. Rectally take the temperature of all animals if you feel they may be sick and/or hot. Because of the design of an animal’s ear, the ear thermometers are not as accurate (but better than nothing if you do not have any re**al or oral thermometer to use re**ally). Shock, intestinal shut down, muscle weakness and other signs indicate a possible heat stroke. Once the animal has been watered down then call the veterinarian, as there are drugs which may be indicated.
If the heat index is over 120 your horse should be cooled down if he appears hot. When watering a horse wipe the water off your horse if possible, as this is more effective than just spraying the horse. A small amount of water left against the skin can cause the cooler water to run off the patient before the water can cool him down; this minor loss of efficiency is probably only important in a down animal. Ensure you do not develop heat stroke by going out and preventatively treating your horse if he looks okay. A horse in the summer can easily require 5-6 gallons of water a day, and he needs at least this much more if he is undergoing only a few hours of endurance. Endurance horses should also be provided electrolytes when undergoing trials; the average horse with a brown mineral salt block available does not need daily electrolytes when on pasture or in the barn. In our area we recommend fans and/or the portable misting fans (swamp coolers) if possible, in hot barns on extremely hot days. Any horse that has anhidrosis, or inability to sweat, should be tested for a low thyroid condition.
Dehydration and heat stroke/heat stress go hand in hand. Compared to 70 degrees F livestock will required 2.5x the amount of water at 95 degrees F. Always ensure water is adequate and present twice a day in very hot weather. Stressed and high strung animals do not tolerate heat stress very easily. A good vaccination program, parasite and fly control programs helps to reduce the stress and animal loss during hot weather.
If an animal has been without water you need to SLOWLY rehydrate them, especially if it is a pig. For a pig you give a cup of water per 100 # every 30 minutes or so, as they are very, very sensitive to water deprivation and the concerns if rehydrated too quickly. For a 1000 # livestock this can be a gallon every 1/2 hour. Rehydrating an animal too quickly can cause seizures and death. Within 6 hours the animals should be rehydrated and more can be added at a time for pigs and after 10 gallons in adult livestock they can have water ad lib. We have a separate handout on this “salt toxicity” (lack of water) in pigs.
To help reduce heat stress one should provide shade or shelter if possible. Water sprinklers may help those livestock in confinement; especially with night sprinkling. If you feed less than 1/3 of the ration early in the morning, and 2/3+ near dark this can also help reduce activity during the heat of the day for livestock in confinement; feeding before night also helps reduce internal fermentation heat products within the herbivore's body during the daytime. Switching from a dark colored bedding to a lighter colored bedding or straw also helps somewhat. For non-milking adult livestock and horses feeding only once at night time is adequate. Always have adequate water available, especially if the animal is outside in hot weather. If you have a pig that has been without water for more than a couple hours, only provide a small amount of water (1 to 2 cups/100 # every 30+ minutes to 1 hour) to avoid salt toxicity and seizures. Fans do help to keep animal from overheating by evaporation of any sweat on the patient. A ceiling fan should blow down in the summer (up in the winter if in a closed room). We have more information on large fans, dairy barns, feedlots, etc.. For the range cattle heat shades need to be durable if on pasture (i.e. StrobelShades.com). A Quonset type hut can be used for summer and winter if adequate air flow in the summer, yet plastic and fabric will not hold up. Dairy barn-like awnings are also cost effective in some areas for shade and rain. There are no great products that are portable and will last for shade and to prevent heat stress. Our handout for cold livestock lists also the buldign and shades for heat.
If you are out for a walk and you yourself cannot hold your hand onto the asphalt or pavement for 5 seconds without it being too hot, then you probably should not be walking your dog at this time. Instead of boots consider instead waiting until it is cooler. Blowing a fan over a bowl of water towards a dog can help somewhat and if an evaporative cooler is used 5-15 degrees F the temperature can be reduced.
When one drives with their pet in a car, and the pet is not restrained, on a hot day it is tempting to have the windows down. Even if only the driver’s side is down we see many dogs that jump out of the open window anytime to go chase a squirrel they see, etc. It is true that if the car is sitting you especially want to crack the window, but as with driving not enough to allow an escape. When driving keep the windows up if the pet is not restrained.

www.NelsonRoadVet.com

Veterinarian Longmont, Colorado | Small and large animals | Dogs, cats, livestock, exotics | Preventative care, dentistry, surgery, acupuncture, ultrasound, in-house laboratory, pharmacy, farm calls, pet boarding.

06/15/2026

Rabbits and Tularemia in our area

This week a case of rabbit tularemia was diagnosed near Berthoud. This is a disease that is enzootic to our area, and it does appear every few years in various animals and people. Tularemia is a disease that can affect 250+ animal species, yet mostly rabbits, sheep and humans make up many of the cases diagnosed. It is caused by Francisella tularensis, a bacterium similar to Brucellosis. The only suggestion that tularemia is in the area is seeing rabbit die offs. To the west of us some of the prairie dog colonies we have noticed apparently have a reduction in numbers recently in more than just a few locations. Should prairie dogs be dying off we are also in an area of plague which every 6-10 years a colony will go through such a die off. Rabbit Hemorrhagic Disease (RHD) is yet another disease also in our area. If you are having rabbits dying in your yard then a call to the local health department is indicated. Visually we cannot tell the difference between a death from bubonic plaque, tularemia or in a rabbit RHD as all are acute deaths.
If you live near Berthoud the only practical thing to do is tick control as it is ticks that carry and transmit tularemia between animals (or to humans). If you have sheep and you find ticks on them their tick species can carry this disease from sheep to sheep, and up to 15% of the lambs may die. This tick concern in sheep is actually for every year as the western United States is endemic to tularemia.
Tuluremia is usually transmitted to humans by wood ticks, and less frequently by deer flies other insect bites (mosquitoes and rarely fleas), lice, animal bites, drinking contaminated water or inhaling contaminated dust. The virulent type A can have a 5% mortality in humans who do not receive treatment. The type B is less pathogenic, found in water or aquatic animals, and can survive months in a wet environment. Heat and most disinfectants easily kill this bacterium. When skinning a rabbit, hunters should routinely wear gloves. IF inside a rabbit one finds white specs of scar-like tissue inside the body, especially the liver and sometimes the spleen, lungs or the muscle tissue then properly discard this rabbit, and do not even feed it to the dogs. These white spots are pus nodules of Tularemia.
Signs of Tularemia include sores and ulcers near the insect bite. If infected meat is eaten then the lymph glands near the head and neck become infected. Should your dog or cat chew on an infected rabbit there can be an atypical mouth infection that develops. Vomiting and diarrhea are signs can also occur if the bacteria are ingested. Pneumonia can be the signs if tularemia is inhaled. Depending upon the route of infection, the patient develops a high fever and generalized sickness within 1-10 days.
For outdoor housed pet rabbits the application of the dog/cat Frontline flea/tick spot-on is lethal to rabbits. Revolution, Advantage II or Advocate labeled for cats/kittens can be used on rabbits if there is an outbreak and you have outdoor rabbits. Should your pet be exposed to dead rabbit and then you or they develop red spots this can be the early signs of Tularemia and a call to the veterinarian is indicated for your pet, especially if there is a high fever/temperature over 103 F that develops. The average pet rabbit in-doors in our area does not need flea control yet we do recommend the Rabbit Hemorrhagic Disease vaccine, and topical tick products if house or allowed outside
Since it is a gram-negative coccobacillus the routine antibiotics such as amoxicillin and penicillin will not treat this disease yet there are many antibiotics available to treat tularemia. There is no commercially available vaccine for tularemia. Tick control for the Dermacentor and/or Amblyomma species is essential for preventing sheep outbreaks. For your own concern if there are rabbits found dead for no apparent reason, used a shovel and bag to dispose of the body; and in a tularemia outbreak consider wearing a mask and long sleeve shirt when lawn mowing this area where the dead rabbit was found. For 99.9% of the time such lawn mowing procedures are not indicated to try to prevent this disease if there is not a local outbreak. For sheep in areas with an active Tularemia outbreak nearby we do advise the long acting permethrins even if you do not find ticks yet the disease is nearby. For sheep we carry a dilute formula to prevent an overdose and can leave outside for afterhours pick up for active clients.
If you find a colorful tick go to www.TickEncounter.org and if an Asian Longhorn tick or a Lone Start tick these are of great concern and please call us as these would be new ticks to the area. .

NelsonRoadVet.com

How to stay safe from ticks when playing in the leaves

06/09/2026

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06/04/2026

6/4/2026

Screwworms

This week screwworms have been found in some goats and cattle in South Texas. Due to our control efforts they probably will not get up into our area. In the 1970s’ when we had screwworms in our area we did not have avermectin products and similar dewormer/insecticides nor many options for the systemic pour on products. Most of the organophosphate treatments used then have been replaced by safter and more effective products. Most cases of new diseases anywhere where there is a “jump” of a hundred miles or more are usually from animals transported into the area with animals returning home and/or recently purchased elsewhere. Until it gets into our area the routine biting insect control methods are adequate to keep down the population.
If concerned about screwworms we recommend the permethrin systemic pour ons for fly control until it is known that the screwworm is in the area. If within a couple of hundred miles then the injectable doramectin can be given before the livestock go out onto pasture, especially cattle. If/when there is an outbreak the FDA may authorize the use of ivermectin to be daily feed to cattle and susceptible livestock (yaks, sheep, goats). As of 2025 the approved FDA prevention/treatment of screwworms (Cochliomyia hominivorax) is the injectable Dectomax-CA1 which we will use if/when needed. This injectable will last up to 21 days but does require a chute to give the 11 ml/1000 # livestock SQ. It should be noted that to have an FDA approval the company needs to pay for a trial, and almost all products we do recommend and rely on FDA approval yet other products may be just as adequate in their use (i.e for fly control prevention pour on Dectomax is a good product). Newborn livestock, animals with diarrhea, wounds or recent surgical procedures are at risk for screwworms and maggots. Yet screwworms do not rely on wounds which makes it more difficult to control as the flies lay their eggs on another nearby animal. We see maggots in open wounds routinely in the summer, yet screwworms are found hidden under the skin in a swelling and only a small hole that looks infected. In our area grubs/bot flies can look very similar yet with Cochliomyia there are multiple larvae moving about. For fly control the pour on permethrins (last 2-4 weeks), moxidectin pour on (7 days) and doramectin pour (7 days) and maybe the ivermectin pour on for lice (up to 28 days for lice yet we feel 1 week is an ivermectin length of action for flies, etc). All of these are adequate until the screwworm cases are within 100 miles of the premises. It should be noted that the avermectin products were developed for internal and external/lice parasite treatments. Powders and sprays for fly control are not adequate (unless it is the 7.4-10% permethrin pour-on which lasts longer, and we do have quart bottles with sprayers for small producers and horses). Spot-ons for equine preventive use is adequate yet screwworms in horses and pets are rare compared to livestock/cattle. Dogs can be given an oral isoxazoline product that will kill screwworms 24 hours later.
As noted many of the distant outbreaks of screwworms are usually a result of animals traveling to an area with screwworms and then returning home. Livestock and all animals including pets are a concern for being affected and thus if you do travel and/or just returned and are concerned please contact the clinic. Apply these systemic products before traveling to an infected area and again before coming home if over 2-3 weeks the animals are in that area (i.e. Texas at this time). If you find larvae inside a hole and the flies look like blowflies then call us or at minimum before treating the wound collect some larvae in a zip lock bag and refrigerate until they are brought into the clinic.
IF screwworms are diagnosed in cattle there is the Dectomectin (Dextomaz-CA1) injecton, the pour on fulalaner (Exolt Cattle-CA1). In dogs and cats there is the chewable lotilaner (Credilio Quattro-CA1). There is also an F10 would spray that we have which is approved for screwworm treatment but not for treating cats or dogs.

Veterinarian Longmont, Colorado | Small and large animals | Dogs, cats, livestock, exotics | Preventative care, dentistry, surgery, acupuncture, ultrasound, in-house laboratory, pharmacy, farm calls, pet boarding.