Guidelines for Large Animal Euthanasia and Disposal

Guidelines for Large Animal Euthanasia & Disposal

(Provided by UW School of Veterinary Medicine)

 

Background:  Federal regulations and vendor policies exist prohibiting the use of barbiturates in euthanasia of equine and bovine species disposed of by rendering or landfill.

Species affected and disposal options: Pigs, foals and calves may be disposed of by incineration, rendering or digestion. Small ruminants are disposed of by digestion. Adult horses may be disposed of by rendering (necessitating euthanasia by something other than barbiturate overdose), or digestion. Digestion is an option when barbiturates are used (costs > $0.50/pound).

In bovines aged 30-60 months, at a minimum the brain and spinal tissue need to be digested. For bovines greater than 60 months of age, the entire carcass needs to be digested.

Alternative Chemical Euthanasia Protocols: Equine and Bovine Patients

 Note #1: These are suggested doses and agents – every patient is unique and doses of each agent may need to be adjusted according to clinical indication and the safety of personnel involved in the procedure. For example, very-compromised animals may need lower doses; on the other hand, extremely excited or stressed animals may need higher doses.

Note #2: The use of potassium chloride is UNACCEPTABLE in conscious animals. Refer to the AVMA Guidelines for the Euthanasia of Animals: 2013 Edition for further information (https://www.avma.org/KB/Policies/Documents/euthanasia.pdf).

  1. SEDATION
  • Equine: Xylazine (1.0-1.5 mg/kg IV)
  • Bovine: Xylazine (0.1-0.5 mg/kg IV)

Ensure adequate sedation (ear/head drooping, reduced muscle tone [tongue/tail/neck relaxation], reduced activity to stimuli). Then follow with:

  1. ANESTHETIC INDUCTION
  • Equine and Bovine: Ketamine (2.2-5.0 mg/kg IV) and Midazolam (0.1-0.2 mg/kg IV)

Ensure a surgical plane of anesthesia (loss of consciousness, reflexive muscle responses [lateral recumbency], and response to noxious stimuli). Then follow with:

  1. EUTHANASIA
  • Potassium chloride (75-150 mg/kg IV quickly)

Potassium Chloride (KCL) can be purchased for injection or made from salts widely available at pharmacies, grocery stores or feed mills. Check the label for ingredients as you MUST use chemical or food grade 100% KCL.  Because it is used to euthanize an animal, it does not need to be filtered or sterilized. The dosage needed for KCL euthanasia (under anesthesia) is 75-100 mg/kg, which will require substantial volumes of KCL.  KCL as a saturated solution can be made with 35.5g of KCL in 100 mls of water.  Super-saturated solutions can be made but are difficult to maintain in solution.  Precipitated salts will clog catheters and needles (especially in cooler weather) so we do not recommend using more than a saturated solution of KCL. Always have more KCL solution than needed to ensure proper and humane euthanasia under AVMA guidelines.

ALWAYS have extra potassium chloride syringes readily available if the above is inadequate.

ALWAYS be aware of the effects associated with injected potassium solutions such as muscle twitching, tremors, and gasping.

If adequate sedation or anesthesia is NOT achieved with the above doses, additional sedation with xylazine (equine: 1.0 mg/kg IV; bovine: 0.1 mg/kg IV) or anesthesia with ketamine (2 mg/kg IV) and midazolam (0.1 mg/kg IV) may be given. ALWAYS be prepared to administer higher initial doses if there is any question.

NEVER administer potassium chloride to an animal that is not in a surgical plane of anesthesia.

  • USE OF CAPTIVE BOLT

Following sedation, as previously described, bovine patients may be euthanized by penetrating captive bolt. Personnel performing captive bolt euthanasia should be familiar with the technique as described in the AVMA guidelines for the euthanasia of animals (https://www.avma.org/KB/Policies/Documents/euthanasia.pdf).

 

Excerpts from AVMA Guidelines for the Euthanasia of Animals (2013):

POTASSIUM CHLORIDE AND MAGNESIUM SALTS, p. 31: ‘Personnel performing this technique must be trained and knowledgeable in anesthetic techniques, and be competent in assessing the level of unconsciousness that is required for administration of potassium chloride and magnesium salt solutions IV. Administration of potassium chloride or magnesium salt solutions IV requires animals to be in a surgical plane of anesthesia characterized by loss of consciousness, loss of reflex muscle response, and loss of response to noxious stimuli.’

RUMINANTS, p. 54: ‘While not acceptable as a sole method of euthanasia, rapid IV injection of potassium chloride may assist in ensuring death after cattle have been rendered unconscious by penetrating captive bolt, gunshot, or administration of general anesthetics (a-2 adrenergic agents such as xylazine alone are insufficient; see comments under Unacceptable methods).’

EQUINE, p. 64: ‘Although unacceptable when used in unanesthetized equids, the use of a saturated solution of potassium chloride injected IV or intracardially in an equid in a deep surgical plane of general anesthesia is an acceptable method to invoke cardiac arrest and death.’

 

 

 

Calf Maintenance in Cold Weather

Low Temperatures and Negative Energy Balance in Calves

D.C. Sockett DVM, PhD, Wisconsin Veterinary Diagnostic Laboratory
T.J. Earleywine PhD, Director of Nutrition Land O’ Lakes Animal Milk Products

Cold weather has arrived in the upper Midwest. Calf raisers know that cold temperatures increase the calf’s maintenance requirements for energy, but many do not know that the maintenance requirements also increase for protein and fat-soluble vitamins if the calf is ill from conditions like scours and pneumonia. Optimizing nutrition of sick calves can make the difference between a dead and a healthy calf.

It is important for livestock producers and veterinarians to understand that when the ambient temperature drops to 15 °F, feeding 3 quarts of milk (12.5% total solids) or a 22% protein, 20% fat milk replacer powder (12.5% total solids) twice a day will provide an 88 lb. calf with enough nutrition for less than 0.75 lbs/day of growth.  However, if the calf is stressed further (draft, wet or dirty hair coat, develops scours, pneumonia etc.), there is insufficient energy and protein in the diet to meet the needs of the calf, and she will begin losing weight. Since calves are born with roughly 3-4% of body weight as fat, they will die if the negative energy balance continues for more than 3-5 days. Calf scours is a common problem on US dairy operations: therefore, winter feeding programs should be formulated to take into account the increased protein, fat-soluble vitamins and energy demands caused by calf scours. Also, calves should be provided with a jacket and kept in a dry, draft-free environment that is bedded with straw deep enough to cover their legs. Calves should be offered a highly palatable calf starter that is high in protein (18-22%) and energy beginning at 2-3 days of age and have access to free-choice (low sodium/not softened) warm water within 30 minutes of being fed milk or milk replacer.

Winter Feeding Program

Since ruminants do not metabolize fat as efficiently as non-ruminants, just providing more fat in the diet is the least satisfactory way of providing additional nutrition to the calf. The diet must be consistent (less than 1% daily variation in percent total solids) and have enough energy and protein so the calf can have efficient, lean growth, adequate immune function and healing of damaged tissue caused by events like scours or pneumonia. The dairy producer can pick one of the following 3 options:

  • Continue to feed the calves 3 quarts of milk or milk replacer twice a day but increase the total solids content from 12.5 to 15%. To avoid problems, producers need to work closely with their dairy calf nutritionist if they choose this option.
  • Continue feeding the calves twice a day but increase the volume of milk or milk replacer per feeding from 3 to 4 quarts.
  • Feed the calves 3 quarts of milk or milk replacer 3 times a day instead of twice a day. There should be at least a 13-14 hour interval between the first and third feeding. This is the best option because calves do better when they are fed three times a day instead of twice a day.

Update on MDR Salmonella serotype Heidelberg

Update on MDR Salmonella serotype Heidelberg Case Count

The WVDL and our state and federal collaborators would like to remind veterinarians and producers to use caution when working with animals with confirmed or suspected multidrug resistant (MDR) Salmonella enterica subspecies enterica serotype Heidelberg. To date, there are 54 confirmed human infections in 15 states (n=18 in Wisconsin; Figure 1), in which 35% (n=17) of infected people have been hospitalized and 15% (n=8) had invasive disease.  Moreover, 33% (n=18) of ill persons were under the age of 5 years.  There continues to be human infections with MDR Salmonella ser. Heidelberg (Figure 2) where 63% (n=34) reported having contact with cattle including ill dairy beef calves. The Center for Disease Control and Prevention (CDC) has updated their website (https://www.cdc.gov/salmonella/heidelberg-11-16/index.html) and provide several documents related to advice and information for livestock handlers, veterinarians and healthcare providers.

Figure 1: People Infected with the Outbreak Strains of Salmonella Heidelberg, by State of Residence, as of October 30, 2017 (n=54)

 

Figure 2: People Infected with the Outbreak Strains of salmonella Heidelberg, by Date of Illness Onset

 

The WVDL continues to isolate MDR Salmonella ser. Heidelberg from bovine tissues and feces.  We would like to stress the importance of cleaning and disinfection when this MDR Salmonella has been identified on a premise.  Preliminary evidence suggests that even after 1-2 years post identification of a MDR Salmonella ser. Heidelberg on a premise, we are able to culture Salmonella ser. Heidelberg from one or more locations on that premise.  Below are the number of MDR Salmonella ser. Heidelberg cases that the WVDL has identified from 2009 to 2017 (U.S. and Wisconsin maps). As expected Wisconsin has the most number of isolates at 61 with Missouri at 33 (Figure 3).  Additionally, Barron County (n=10) has the most isolates followed by Marinette and Shawano Counties (n=6 each) and Grant County (n=5) (Figure 4). The data here is a gross under estimation of the true burden of disease. The WVDL provides information about cleaning and disinfection protocols, bovine environmental sampling instructions, Salmonella molecular and culture testing options and work flow and a Salmonella ser. Heidelberg interview questionnaire on our website in the Diagnostic Aids tab.

https://www.wvdl.wisc.edu/index.php/diagnostic-aids/

 

Figure 3: Map of Salmonella ser. Heidelberg isolates by State from 2009-2017.

 

Figure 4: Map of Salmonella ser. Heidelberg isolates by Wisconsin County from 2009-2017

 

The WVDL continues to work closely with state and federal agents to make producers, veterinarians, physicians and other interested parties aware of this MDR zoonotic disease.  WVDL staff have recently given presentations at:

1) The American Association of Veterinary Laboratory Diagnosticians (AAVLD) Annual Conference on October 15 in San Diego, Calif. (Megin Nickels of the CDC also talked on this topic.)

2) The Inform 2017 Conference on November 8 in Garden Grove, Calif.  Additionally, a USDA veterinarian talked about preliminary data from a case control study the WVDL is participating in.

3) The One Health Symposium on November 10 in Madison, Wis.

4) The Conference of Research Workers in Animal Diseases (CRWAD) in Chicago, Ill. on December 5.

 

 

Increased Awareness for Multi-drug Resistant Salmonella Heidelberg Infections

Notice of Increased Awareness for Multi-drug Resistant Salmonella enterica subspecies enterica serotype Heidelberg

High zoonotic potential for farm workers, especially children

Recently, the Wisconsin Veterinary Diagnostic Laboratory (WVDL), the Wisconsin Division of Public Health (DPH), the Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP), the Wisconsin State Laboratory of Hygiene (WSLH) and the Centers for Disease Control and Prevention (CDC) have been tracking a multi-drug resistant (MDR) strain of Salmonella enterica subspecies enterica serotype Heidelberg (Group B).  The reason for this close collaboration is the strong connection between human infections and recent bull calf purchases.  The purpose of this communication is to educate the veterinary community of the risk these MDR Salmonella Heidelberg pose to both cattle and people, provide testing options for diagnosis, and disinfection recommendations.

Currently, there are twelve confirmed human infections from seven Wisconsin counties in 2016. The median age for Wisconsin residents with Salmonella Heidelberg infections is 7 years old, and four individuals were hospitalized.  Upon interview, greater than 90% of the infected individuals reported purchasing Holstein bull calves from livestock dealers or sales barns. Many of these calves died shortly after becoming ill.  During 2015 and 2016, the WVDL has isolated several MDR Salmonella Heidelberg isolates from calves located in mostly Wisconsin, but isolation has also occurred from calves located outside of Wisconsin during 2015 and 2016.  Pulsed-field gel electrophoresis (PFGE) and whole genome sequencing of 2016 isolates indicates that the human and bovine Salmonella Heidelberg isolates are very closely related, and may share a common source.  This strain of Salmonella Heidelberg is highly pathogenic and multi-drug resistant; only one antimicrobial drug is an effective treatment option for human cases and no effective options exist for cattle.  Individuals working with sick pre-weaned calves, particularly bull calves that have been recently purchased, are recommended to adhere to strict biosafety protocols and wash hands, change clothing, and clean affected areas and items frequently.  Children and immunocompromised individuals should limit their access to calves with diarrhea.  Additionally, any human diarrheal illnesses should be seen by a physician and reported to DPH if salmonellosis is confirmed.

Veterinarians suspecting salmonellosis, particularly infection caused by Salmonella Heidelberg, should submit fecal samples for Salmonella culture and/or PCR to the WVDL.  Results for confirmation of Salmonella are within 24-72 hours with serotyping taking an additional 24-72 hours.  Fecal samples should be collected in a leak-proof vial rather than glove, Whirl pack, or bag as these are more likely to leak.  Culture-positive Salmonella isolates will be serotyped and Salmonella Heidelberg isolates will be subject to antimicrobial susceptibility testing to confirm MDR status. WVDL staff veterinarians will contact submitting veterinarians upon isolation of this MDR Salmonella Heidelberg to discuss herd health, provide cleaning and disinfection recommendations and supply the veterinarians with an interview questionnaire to be filled out.

Cleaning and disinfection is absolutely necessary after confirmation of Salmonella as the cause of calf diarrhea or adult enteric disease.  This is particularly important for this particular MDR Salmonella strain, given the human and bovine health implications and lack of antimicrobials available.  Reinfection on the affected premise is highly likely and has been detected with this outbreak; therefore, it is highly recommended to perform environmental testing for Salmonella.  The WVDL has kits specific to this type of testing and cleaning and disinfection protocols that producers can use.

The WVDL, DATCP and DPH would like to increase surveillance for MDR Salmonella Heidelberg and encourages veterinarians to submit diagnostic samples when possible.  Veterinarians, please encourage producers to submit samples from suspect animals, particularly pre-weaned dairy calves that were recently purchased and die suddenly and unexpectedly.  Other state veterinary diagnostic laboratories have been notified of this outbreak and are prepared to culture diagnostic samples for Salmonella.  Salmonella Group B or Heidelberg isolates will be submitted to NVSL for PFGE and whole genome sequencing.  Cooperation between Wisconsin veterinarians, producers, and the human and animal health officials should reduce the incidence rates of salmonellosis in both humans and animals.

For more information please contact the following authorities:

Wisconsin Veterinary Diagnostic Laboratory at 608-262-5432 and Salmonella@wvdl.wisc.edu or info@wvdl.wisc.edu. The WVDL will respond to requests within 24-48 hours during the work week.

Wisconsin Division of Public Health at 608-267-7143 and DHSDPHEnterics@dhs.wisconsin.gov

Department of Agriculture, Trade, and Consumer Protection at 608-224-5012

 

State-of-the-art MALDI-TOF Technology at WVDL Identifies Emerging Bacterial Pathogens

State-of-the-art MALDI-TOF Technology at WVDL Identifies Emerging Bacterial Pathogens

Maldi-tof

WVDL Microbiologist Maureen Peterson

The Microbiology Section at WVDL has been using a MALDI-TOF machine to rapidly and accurately identify bacterial pathogens for several months now, starting in the spring of 2014. MALDI-TOF is a matrix-assisted laser desorption ionization/mass spectrometry machine that identifies bacteria based on their unique signature.   Along with the usual pathogens the MALDI-TOF unit has been identifying several emerging bacterial mastitis pathogens, such as Lactococcus garvieae, which is aiding bovine veterinarians to improve milk quality and profitability on Wisconsin Dairies.

Contact the WVDL if you receive a culture result with a microbial species that is new to your practice for more information.

 

The following is a recent article from Veterinary Microbiology highlighting the MALDI-TOF’s ability to speciate hard to identify Corynebacterium spp

Vet Microbiol. 2014 Sep 17;173(1-2):147-51. doi: 10.1016/j.vetmic.2014.06.028. Epub 2014 Jul 7.

Identification of Corynebacterium spp. isolated from bovine intramammary infections by matrix-assisted laser desorption ionization-time of flight mass spectrometry.

Author information: Gonçalves JL1, Tomazi T1, Barreiro JR1, Braga PA2, Ferreira CR2, Araújo Junior JP3, Eberlin MN2, Santos MV4.

Abstract

Corynebacterium species (spp.) are among the most frequently isolated pathogens associated with subclinical mastitis in dairy cows. However, simple, fast, and reliable methods for the identification of species of the genus Corynebacterium are not currently available. This study aimed to evaluate the usefulness of matrix-assisted laser desorption ionization/mass spectrometry (MALDI-TOF MS) for identifying Corynebacterium spp. isolated from the mammary glands of dairy cows. Corynebacterium spp. were isolated from milk samples via microbiological culture (n=180) and were analyzed by MALDI-TOF MS and 16S rRNA gene sequencing. Using MALDI-TOF MS methodology, 161 Corynebacterium spp. isolates (89.4%) were correctly identified at the species level, whereas 12 isolates (6.7%) were identified at the genus level. Most isolates that were identified at the species level with 16 S rRNA gene sequencing were identified as Corynebacterium bovis (n=156; 86.7%) were also identified as C. bovis with MALDI-TOF MS. Five Corynebacterium spp. isolates (2.8%) were not correctly identified at the species level with MALDI-TOF MS and 2 isolates (1.1%) were considered unidentified because despite having MALDI-TOF MS scores >2, only the genus level was correctly identified. Therefore, MALDI-TOF MS could serve as an alternative method for species-level diagnoses of bovine intramammary infections caused by Corynebacterium spp.

Copyright © 2014 Elsevier B.V. All rights reserved.

 

Dr. Donald Sockett Findings From Bovine Respiratory Disease (BRD) Study

 Dr. Donald Sockett Presents Poster on BRD

 

On Friday, Sept. 20, Dr.  Donald Sockett gave a poster presentation on bovine respiratory disease (BRD) at the American Association of Bovine Practitioners (AABP) Annual Conference in Milwaukee.  The most interesting findings of this study follow.  The link to view Sockett’s poster is included below.

Dr. Donald Sockett Veterinary Microbiologist DVM, Univ. of Guelph, 1981 PhD, Univ. of Wisconsin, 1991 Diplomate, A.C.V.I.M.

Dr. Donald Sockett
Veterinary Microbiologist
DVM, Univ. of Guelph, 1981
PhD, Univ. of Wisconsin, 1991
Diplomate, A.C.V.I.M.

  • Mycoplasma bovis and bovine respiratory corona virus were found in a high number of calves (≥ 50%) with BRD.
  • Treated calves with BRD consumed less dry feed (calf starter) and had poorer feed-to-gain ratios than calves that did not have BRD.
  • There was no difference in milk replacer consumption between calves with BRD (even if treated) and calves that did not have BRD, thus indicating that a reduction in liquid feed ( milk or milk replacer) intake is not a reliable metric to use for early detection of BRD.
  • Even if treated, calves with BRD weighed less at weaning time than calves that did not have BRD.
  • Pre-weaned calves that had a bout of BRD severe enough to require treatment with antimicrobial drugs should be fed milk or milk replacer for a longer period of time than calves that have not had BRD. The longer feeding time will give the BRD affected calves the time they need to catch up (growth) with the calves that did not have BRD.

 

Poster for Presentation

TB comes in small packages too

Dr. Cindy Bell Diagnostic Pathologist DVM, University of Wisconsin-Madison 2008 Diplomate ACVP

Dr. Cindy Bell
Diagnostic Pathologist
DVM, University of Wisconsin-Madison 2008
Diplomate ACVP

 

TB comes in small packages too

By C. Bell, DVM, DACVP

Strange as it is, one species that the pathologists at WVDL autopsy fairly frequently is the Budgerigar….you know, Budgies….“parakeets”…..those fairly inexpensive but attractive small versions of parrots.  Like parrots, they belong to the family of birds called psittacines.  Many older budgerigars we see have cancer, frequently of the reproductive tract.  In fact, ovarian carcinoma occurs in aged females of many species of birds.  I and others happen to think that it is an underexplored animal model for human ovarian cancer.   But I digress….the most memorable budgerigar autopsy that I have performed was not a cancer case.  While performing this particular autopsy, which is a “gross” post-mortem examination, I saw no tumor, no evidence of disease, not a single clue as to why the bird was sick and died.

This happens to pathologists a lot, but we don’t despair.  “That is why God created a microscope,” says an old pathologist friend, meaning that we perform histopathology, a “microscopic” post-mortem examination.  As I was looking at the glass microscope slides of this little bird’s tissues, I saw something that was not readily recognizable as a particular organ.  There were large cells, and these cells were stuffed full of something….something very small and very hard to see.  I had a hunch.  I ordered a special acid fast slide to be made, which made the little rod bacteria within the cells stand out like hot flamingo-pink confetti.  The cells were stuffed with these “acid fast bacilli” bacteria and the tissue was the sorry remains of this bird’s adrenal gland.

Although not strictly accurate, “acid fast bacilli” is synonymous with bacteria of the genus Mycobacterium.  The most famous is Mycobacterium tuberculosis, the case of Tuberculosis in humans.  There are many other species, some more important than others.  Mycobacterium bovis is the cause of Bovine Tuberculosis, a disease for which we monitor and hope not to see in Wisconsin.  Mycobacterium paratuberculosis causes Johnes Disease in ruminants.  There are other Mycobacterium species and subgroups.  Each tends to have a predilection for a certain group of animal ( birds, rodents, aquatic animals, etc.) yet has the potential to infect a broad range of species, including humans.   Immune-suppressed or immune-compromised humans are most at risk.  As a percentage of our modern population, this group of people is large and continues to grow each year.  Included are people with AIDS, transplant recipients, chemotherapy patients, and people treated for a broad array of immune system disorders.  A final key fact about Mycobacterium is that infections are very difficult to detect and may be impossible to cure.

So, there was my budgie with a Mycobacterium infection, an infection that is not particularly rare in birds, reptiles, aquatic animals, and even some mammals.  Nevertheless, I called the veterinarian who had submitted the bird to WVDL for diagnosis.  After contacting the bird’s owner, the submitting veterinarian and I were again on the phone discussing the implications of the bird having come from a household that included 1. Another bird and, 2. A human family member with a chronic disease condition.  Ultimately, the WVDL sent tissue to the National Veterinary Services Laboratory in Ames, IA.  There, they identified the species of Mycobacterium in the bird.  Fortunately, it was not Mycobacterium tuberculosis or another species known to typically infect humans.  However, the other bird in the household was likely to harbor the infection even if it never got sick, leaving the family with a tough decision regarding the future of the remaining pet bird.

 

 

Mysterious virus found in Wisconsin trout

State officials worry about impacts, but release infected fish

State natural resource officials are wondering how a mysterious virus found  its way to Wisconsin trout and what it will mean for the health of aquatic  life.

“It’s a big unknown,” said Susan Marcquenski, a fish health specialist for  the state Department of Natural Resources. “There’s very little information  about the effect of the virus on cool-water species.”

Read more: https://host.madison.com/news/local/mysterious-virus-found-in-wisconsin-trout/article_f84a4055-d482-5c86-8591-164586cee50f.html

 

Sodium Toxicity in Neonatal Dairy Calves

Dr. Donald Sockett Veterinary Microbiologist DVM, Univ. of Guelph, 1981 PhD, Univ. of Wisconsin, 1991 Diplomate, A.C.V.I.M.

Dr. Donald Sockett
Veterinary Microbiologist
DVM, Univ. of Guelph, 1981
PhD, Univ. of Wisconsin, 1991
Diplomate, A.C.V.I.M.

 

Sodium Toxicity in Neonatal Dairy Calves: 7.24.2013

Recently, the WVDL has confirmed sodium toxicity (salt poisoning) in 4 different dairy herds. All of the calves were less than 14 days of age and died within 6-24 hours after the onset of clinical signs. Neurological disease (abnormal gait, stiffness, muscle twitching, seizures and convulsions) was reported for some calves but for many calves the only observation made by the herd owner was lethargy and depression prior to death. Submitting veterinarians were suspicious of gram-negative septicemia particularly salmonellosis. Morbidity and mortality rates ranged from 25 – 100%. All four herds were feeding commercial milk replacer diets to their calves.

 Some of the calves had diarrhea caused by Cryptosporidium parvum, rotavirus or coronavirus but many calves did not. A few calves had pneumonia or dehydration. There were no consistent gross or histopathological lesions. Brains were often normal in appearance.

 Hypernatremia is defined as a serum or plasma sodium value of 155 mmol/L or higher. Calves are at risk of developing neurological disease when the serum or plasma values exceed 160 mmol/L.  A brain sodium level of 1,800 ppm or higher (wet matter basis) is considered confirmation of sodium toxicosis. Normal brain sodium values are less than 1,400 ppm. Serum, plasma, ocular fluid, CSF, and cerebral cortex are all appropriate samples to test for sodium toxicosis.

 

Published reports of salt poisoning in neonatal calves have led to the perception that it is caused by one or more of the following risk factors: Commercial oral electrolyte or milk replacer mixing errors, limited or no access to free choice drinking water or potable water with an excessively high concentration of sodium (≥ 500 ppm). Water that has passed through a water softener can have very high concentrations of sodium and should not be used to mix up commercial milk replacer or used as a source of potable water unless it has been tested and verified to have low levels of sodium (≤ 100 ppm).

 

While one or more of these risk factors were discovered in 2 of the 4 herds, they could not be confirmed in the other 2 herds despite intensive questioning by the herd veterinarians and testing of the milk replacer solution and potable drinking water.  The only risk factor that was identified in these two herds was heat stress causing mild dehydration and feeding a commercial milk replacer diet. Since neonatal calves do not drink much water during the first week of life, this coupled with mild to moderate dehydration may be sufficient to cause sodium toxicosis in some herds.

 

Sodium toxicosis should be considered for any dairy calf that dies within 4-24 hours of becoming ill that does not have complications of neonatal calf diarrhea (dehydration and metabolic acidosis) or gross lesions which can explain the cause of death such as abomasal tympany, perforating abomasal ulcers, omphalophlebitis, pneumonia, bacterial septicemia and meningoencephalitis. The likelihood of sodium toxicity increases if the calf has neurological disease as well.

 

It is very important that veterinarians submit the entire brain or cerebral cortex both fresh (≥ 50 grams) and formalin-fixed (≥ 1 x 2 cm slice) to the WVDL, along with serum or plasma for suspected cases of sodium toxicosis.

 

If sodium toxicosis is found, the WVDL recommends that a 1-2 ounce sample of milk replacer solution be submitted frozen to the Madison lab. It is a good idea to submit samples from two or more feedings particularly when more than one person is responsible for feeding the calves. Submitters should request analysis for percent total solids, sodium concentration and osmolality. In addition, a sample of potable water should be sent to a private laboratory for testing which includes sodium concentration of the water.