ASK THE NUTRITIONIST

Ask the Nutritionist DR. ROBERT JACOBS, PH.D., EQUINE INNOVATION MANAGER, PURINA ANIMAL NUTRITION SPECIAL ADVERTISING SECTION ?Ask the Nutritionist is a monthly column featuring questions answered by PhD equine nutritionists and sponsored by Purina Animal Nutrition. Have a nutrition question you want to see featured? Email Marie Rosenthal. For clinics looking for specific nutrition advice, submit your question here.

What signs should I look for in clients’ horses related to ionophore toxicity? What do feed manufacturers do to protect against feed contamination?

Feed contamination is a critical risk of feed manufacturing for which all reputable feed manufacturers should account. Proper “feed hygiene” is crucial to minimize the health risks to horses due to physical, chemical or biological contamination. Horse feed contaminated with ionophores is especially problematic, and feed manufacturers should remain diligent with safety protocols to prevent cross-contamination.

Ionophores are a class of antibiotics that may be added to poultry and cattle diets as growth-promoting agents and as potent coccidiostats. These compounds function to alter the membrane potential of certain tissues, and in horses, can result in a multitude of aberrant clinical symptoms. Often, the first clinical symptom observed in horses afflicted with ionophore toxicities is sudden death. However, other clinical signs may develop, including unexplained colic, ataxia, diarrhea and excessive urination. Ionophores affect various body tissues, including cardiac muscle, skeletal muscle and the nervous system; therefore, symptoms are typically non-specific. Bloodwork on horses with suspected ionophore toxicity may show elevated muscle enzymes. Horses may have individual tolerances to ionophore toxicities. Still, it is widely accepted that any presence of ionophores in equine feeds is considered toxic and levels as low as 1.4 mg per kg of body weight can be lethal. Treatments for ionophore toxicity are largely palliative and supportive, and survivors are known to have long-term health effects.

WHAT TO DO

If ionophore contamination is suspected, the horse owner and veterinarian should take these steps: 1. Gather all suspect feed and securely quarantine it from other feed products. 2. Cease feeding suspect feed to other horses. 3. Take a sample of the feed for future analysis and store it in a temperature-controlled environment. 4. Gather relevant information about the feed, including: a. Name of product b. Place of purchase

c. Date of purchase d. Manufacturer’s date code (typically printed on the packaging or the tape sewn on the end of the feed bag ) See graphic left. 5. Contact the feed manufacturer to file a report and submit a feed sample for analysis. Various commercial laboratories can analyze feeds for ionophore contamination.

Ionophore contamination is typically the result of a mistake or improper feed hygiene protocols. The Purina® FeedGuard® Nutrition System is an example of a feed hygiene protocol and is one of the industry’s most innovative quality-assurance programs. As part of this program, it is required that all equine feeds are manufactured within a 100-percent, ionophore-free manufacturing system. But opportunities for contamination still exist outside the feed manufacturing plant. Care should be taken to prevent bulk horse feed from being transported or stored in locations that have previously held feed containing ionophores.

If you or your clients have questions about feed hygiene, contact the feed manufacturer and inquire about their protocols and how they ensure the safety of their horse feeds.

Contact a Purina Ph.D. nutritionist for consultations through Purina Customer Service, 800-227-8941 or visit EquineVetNutrition.com to submit your question.

LOOKING FOR NUTRITION RESOURCES?

Find helpful nutritional management information for common equine conditions and request feed coupons for your clients on the new EquineVetNutrition.com page.

Have a question you want to see featured? Please send them to modernequinevet@gmail.com.

ABOUT THE AUTHOR Dr. Robert Jacobs, Ph.D., is the Equine Innovation Manager at Purina Animal Nutrition. He is responsible for conducting research to understand how nutrition impacts various areas of equine physiology.

Break the Back Pain Cycle, Then Hit the Gym By Paul Basillio

Most of the work in the management of equine back pain comes down to the diagnosis. After a thorough history, physical exam and imaging, it’s important to not let all of that important diagnostic work go waste with an incomplete or improper treatment plan, according to Erin Contino, MS, DVM, DACVSMR.

The 2 pillars of that treatment plan are breaking the pain cycle and increasing or restoring strength, function, and stability, according to Dr. Contino, assistant professor in equine sports medicine at the Colorado State University College of Veterinary Medicine and Biomedical Science’s Equine Orthopaedic Research Center.

Shutterstock/Rolf Dannenberg Anti-inflammatories “For me, the cornerstone of breaking the pain cycle is corticosteroids,” she said in a virtual presentation at the 66th Annual AAEP Convention. “They’re potent, they’re effective, they’re great anti-inflammatories, and I find them to be one of the most effective ways to get ahead of the game in treating back pain.”

The diagnosis will dictate where steroids should be injected. For impinging or overriding spinous processes, the drug could be injected between the affected processes, although in some cases the interspinous ligament might not be injectable.

“You can’t typically inject into a healthy ligament, so sometimes you have to go just a bit abaxially with your needle placement,” Dr. Contino explained. “You’re diluting the corticosteroid out in enough volume that it will diffuse to the entire area.”

A combination of corticosteroid injections and the muscle relaxant methocarbamol is another common treatment in Dr. Contino’s practice. She gives it twice daily for 2 weeks, then tapers once daily for another 2 weeks. Keep in mind the dose allowed under US Equestrian Federation (USEF) rules, because often doses used to treat back are higher than what is permitted by USEF.

For thoracolumbar articular facet joint osteoarthritis, she typically uses triamcinolone diluted with saline instead of hyaluronic acid with or without amikacin.

Nonsteroidal anti-inflammatories (NSAIDs) are a staple treatment for back pain in humans, but Dr. Contino hasn’t found that to be the case in horses.

“I typically only use a nonsteroidal if I’m combining

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IMPORTANT SAFETY INFORMATION: Avoid skin contact. Always wear protective gloves when administering REGU-MATE®. This product is contraindicated for use in mares with a previous or current history of uterine inflammation. Pregnant women, or women who suspect they are pregnant, should not handle this product. For complete safety information, please read product label.

1Data on file. Merck Animal Health.

REGU-MATE® (altrenogest) Solution 0.22% Intervet/Merck Animal Health

ORAL PROGESTIN FOR USE IN ANIMALS ONLY SOLUTION 0.22% (2.2 mg/mL) For suppression of estrus in mares. Suppression of estrus allows for a predictable occurrence of estrus following drug withdrawal in mares with ovarian follicles 20 mm or greater. Suppression of estrus will facilitate: • Attainment of regular cyclicity during the transition from winter anestrus to the physiological breeding season. • Management of prolonged estrus conditions. • Scheduled breeding during the physiological breeding season. WARNING: DO NOT USE IN HORSES INTENDED FOR HUMAN CONSUMPTION.

Keep this and all medication out of the reach of children. CAUTION

Federal law restricts this drug to use by or on the order of a licensed veterinarian.

DESCRIPTION

Regu-Mate® (altrenogest) Solution 0.22% contains the active synthetic progestin, altrenogest. The chemical name is 17α-allyl-17βhydroxyestra-4,9,11-trien-3-one. The CAS Registry Number is 850-52-2. The chemical structure is:

Each mL of Regu-Mate® (altrenogest) Solution 0.22% contains 2.2 mg of altrenogest in an oil solution.

ACTIONS

Regu-Mate® (altrenogest) Solution 0.22% produces a progestational effect in mares. INDICATIONS Regu-Mate® (altrenogest) Solution 0.22% is indicated to suppress estrus in mares. Suppression of estrus allows for a predictable occurrence of estrus following drug withdrawal. This facilitates the attainment of regular cyclicity during the transition from winter anestrus to the physiological breeding season. Suppression of estrus will also facilitate management of prolonged estrus conditions. Suppression of estrus may be used to facilitate scheduled breeding during the physiological breeding season. CONTRAINDICATIONS Regu-Mate® (altrenogest) Solution 0.22% is contraindicated for use in mares having a previous or current history of uterine inflammation (i.e., acute, subacute, or chronic endometritis). Natural or synthetic gestagen therapy may exacerbate existing low-grade or “smoldering” uterine inflammation into a fulminating uterine infection in some instances. PRECAUTIONS Various synthetic progestins, including altrenogest, when administered to rats during the embryogenic stage of pregnancy at doses manyfold greater than the recommended equine dose caused fetal anomalies, specifically masculinization of the female genitalia. DOSAGE AND ADMINISTRATION While wearing protective gloves, remove shipping cap and seal; replace with enclosed plastic dispensing cap. Remove cover from bottle dispensing tip and connect luer lock syringe (without needle). Draw out appropriate volume of ReguMate® solution. (Note: Do not remove syringe while bottle is inverted as spillage may result.) Detach syringe and administer solution orally at the rate of 1 mL per 110 pounds body weight (0.044 mg/kg) once daily for 15 consecutive days. Administer solution directly on the base of the mare’s tongue or on the mare’s usual grain ration. Replace cover on bottle dispensing tip to prevent leakage. Excessive use of a syringe may cause the syringe to stick; therefore, replace syringe as necessary.

DOSAGE CHART

Approximate Weight in Pounds Dose in mL

770

880

990

1100

1210

1320 7

8

9

10

11

12

WHICH MARES WILL RESPOND TO REGU-MATE® (altrenogest) SOLUTION 0.22%: Extensive clinical trials have demonstrated that estrus will be suppressed in approximately 95% of the mares within three days; however, the post-treatment response depended on the level of ovarian activity when treatment was initiated. Estrus in mares exhibiting regular estrus cycles during the breeding season will be suppressed during treatment; these mares return to estrus four to five days following treatment and continue to cycle normally. Mares in winter anestrus with small follicles continued in anestrus and failed to exhibit normal estrus following withdrawal. Response in mares in the transition phase between winter anestrus and the summer breeding season depended on the degree of follicular activity. Mares with inactive ovaries and small follicles failed to respond with normal cycles post-treatment, whereas a higher proportion of mares with ovarian follicles 20 mm or greater in diameter exhibited normal estrus cycles post-treatment. Regu-Mate® (altrenogest) Solution 0.22% was very effective for suppressing the prolonged estrus behavior frequently observed in mares during the transition period (February, March and April). In addition, a high proportion of these mares responded with regular estrus cycles posttreatment

SPECIFIC USES FOR REGU-MATE® (altrenogest) SOLUTION 0.22%: SUPPRESSION OF ESTRUS TO

1. Facilitate attainment of regular cycles during the transition period from winter anestrus to the physiological breeding season.

To facilitate attainment of regular cycles during the transition phase, mares should be examined to determine the degree of ovarian activity. Estrus in mares with inactive ovaries (no follicles greater than 20 mm in diameter) will be suppressed but these mares may not begin regular cycles following treatment. However, mares with active ovaries (follicles greater than 20 mm in diameter) frequently respond with regular post-treatment estrus cycles. 2. Facilitate management of the mare exhibiting prolonged estrus during the transition period. Estrus will be suppressed in mares exhibiting prolonged behavioral estrus either early or late during the transition period. Again, the posttreatment response depends on the level of ovarian activity. The mares with greater ovarian activity initiate regular cycles and conceive sooner than the inactive mares. Regu-Mate® (altrenogest) Solution 0.22% may be administered early in the transition period to suppress estrus in mares with inactive ovaries to aid in the management of these mares or to mares later in the transition period with active ovaries to prepare and schedule the mare for breeding. 3. Permit scheduled breeding of mares during the physiological breeding season. To permit scheduled breeding, mares which are regularly cycling or which have active ovarian function should be given Regu-Mate® (altrenogest) Solution 0.22% daily for 15 consecutive days beginning 20 days before the date of the planned estrus. Ovulation will occur 5 to 7 days following the onset of estrus as expected for non-treated mares. Breeding should follow usual procedures for mares in estrus. Mares may be regulated and scheduled either individually or in groups.

ADDITIONAL INFORMATION

A 3-year well controlled reproductive safety study was conducted in 27 pregnant mares, and compared with 24 untreated control mares. Treated mares received 2 mL Regu-Mate® (altrenogest) Solution 0.22% /110 lb body weight (2 x dosage recommended for estrus suppression) from day 20 to day 325 of gestation. This study provided the following data: 1. In filly offspring (all ages) of treated mares, clitoral size was increased. 2. Filly offspring from treated mares had shorter interval from Feb. 1 to first ovulation than fillies from their untreated mare counterparts. 3. There were no significant differences in reproductive performance between treated and untreated animals (mares & their respective offspring) measuring the following parameters: • interval from Feb. 1 to first ovulation, in mares only • mean interovulatory interval from first to second cycle and second to third cycle, mares only. • follicle size, mares only. • at 50 days gestation, pregnancy rate in treated mares was 81.8% (9/11) and untreated mares was 100% (4/4). • after 3 cycles, 11/12 treated mares were pregnant (91.7%) and 4/4 untreated mares were pregnant (100%). • colt offspring of treated and control mares reached puberty at approximately the same age (82 & 84 weeks respectively.) • stallion offspring from treated and control mares showed no differences in seminal volume, spermatozoal concentration, spermatozoal motility, and total sperm per ejaculate. • stallion offspring from treated and control mares showed no difference in sexual behavior. • testicular characteristics (scrotal width, testis weight, parenchymal weight, epididymal weight and height, testicular height, width & length) were the same between stallion offspring of treated and control mares. REFERENCES Shoemaker, C.F., E.L. Squires, and R.K. Shideler, 1989. Safety of Altrenogest in Pregnant Mares and on Health and Development of Offspring. Eq. Vet. Sci. (9); No. 2: 69-72. Squires, E.L., R.K. Shideler, and A.O. McKinnon. 1989. Reproductive Performance of Offspring from Mares Administered Altrenogest During Gestation. Eq. Vet. Sci. (9); No. 2: 73-76.

WARNING For oral use in horses only. Keep this and all other medications out of the reach of children. Do not use in horses intended for human consumption. HUMAN WARNINGS: Skin contact must be avoided as Regu-Mate® (altrenogest) Solution 0.22% is readily absorbed through unbroken skin. Protective gloves must be worn by all persons handling this product. Pregnant women or women who suspect they are pregnant should not handle Regu-Mate® (altrenogest) Solution 0.22%. Women of child bearing age should exercise extreme caution when handling this product. Accidental absorption could lead to a disruption of the menstrual cycle or prolongation of pregnancy. Direct contact with the skin should therefore be avoided. Accidental spillage on the skin should be washed off immediately with soap and water. INFORMATION FOR HANDLERS: WARNING: Regu-Mate® (altrenogest) Solution 0.22% is readily absorbed by the skin. Skin contact must be avoided; protective gloves must be worn when handling this product. Effects of Overexposure

There has been no human use of this specific product. The information contained in this section is extrapolated from data available on other products of the same pharmacological class that have been used in humans. Effects anticipated are due to the progestational activity of altrenogest.Acute effects after a single exposure are possible; however, continued daily exposure has the potential for more untoward effects such as disruption of the menstrual cycle, uterine or abdominal cramping, increased or decreased uterine bleeding, prolongation of pregnancy and headaches. The oil base may also cause complications if swallowed.In addition, the list of people who should not handle this product (see below) is based upon the known effects of progestins used in humans on a chronic basis.

PEOPLE WHO SHOULD NOT HANDLE THIS PRODUCT

1. Women who are or suspect they are pregnant. 2. Anyone with thrombophlebitis or thromboembolic disorders or with a history of these events. 3. Anyone with cerebral-vascular or coronary-artery disease. 4. Women with known or suspected carcinoma of the breast. 5. People with known or suspected estrogen-dependent neoplasia. 6. Women with undiagnosed vaginal bleeding. 7. People with benign or malignant tumors which developed during the use of oral contraceptives or other estrogencontaining products. 8. Anyone with liver dysfunction or disease.

Accidental Exposure

Altrenogest is readily absorbed from contact with the skin. In addition, this oil based product can penetrate porous gloves. Altrenogest should not penetrate intact rubber or impervious gloves; however, if there is leakage (i.e., pinhole, spillage, etc.), the contaminated area covered by such occlusive materials may have increased absorption. The following measures are recommended in case of accidental exposure. Skin Exposure: Wash immediately with soap and water. Eye Exposure: Immediately flush with plenty of water for 15 minutes. Get medical attention. If Swallowed: Do not induce vomiting. Regu-Mate® (altrenogest) Solution 0.22% contains an oil. Call a physician. Vomiting should be supervised by a physician because of possible pulmonary damage via aspiration of the oil base. If possible, bring the container and labeling to the physician.

Store at or below 25°C (77°F). HOW SUPPLIED

Regu-Mate® (altrenogest) Solution 0.22% (2.2 mg/mL). Each mL contains 2.2 mg altrenogest in an oil solution. Available in 1000mL plastic bottles.

Shockwave therapy can be useful for thoracolumbar pain.

it with gabapentin if I suspect neuropathic pain,” she said. “I also sometimes use systemic corticosteroids—typically prednisolone—as a last resort in horses that are unresponsive to other treatments, if I have a suspicion that they have dorsal root ganglionitis or wind-up pain.”

Bisphosphonates Tiludronate is a potential treatment for horses with thoracolumbar osteoarthritis. A study in 2007 found that tiludronate showed significant improvement in dorsoventral flexibility vs. controls at 60 days, but not at 120 days.

“There are certain times for when it’s indicated,” Dr. Contino said, “and that’s when you have osseous pathology. I measure kidney values prior to giving it, and I never give it with NSAIDs because of the extra load it places on the kidneys. You can cause kidney failure, and there have also been reports of colic, although in my experience it’s more common with tiludronate compared with clodronate.”

Extracorporeal shockwave therapy Dr. Contino uses shockwave therapy on a lot of horses with thoracolumbar pain.

“The only reason to not use it is because of the cost,” she said. “It is expensive, but it’s highly effective.”

She shared a recent paper that involved 12 riding horses with thoracolumbar pain. Results showed that after 2 or 3 treatments, the mechanical nociceptive threshold increased in all horses, indicating the horses were less painful. The increase continued out to 56 days.

“Clinically, some horses benefit from a single treatment, but if you do it in a series of 3 or 4, you will likely see more of an effect,” she said. “It’s a great way to break the pain cycle, especially in horses where you can’t use corticosteroids.”

While shockwave therapy is not permitted under FEI rules, it can be used on the back if it’s more than 12 hours prior to competition under USEF rules.

Building Strength After breaking the pain cycle, it’s time for the horse to get to the gym.

Dr. Contino discussed a study that evaluated 4 types of stretches (cervical extension, cervical flexion, and right and left lateral bending) on the multifidus muscle. The stretches were performed 5 days per week, and after 3 months the horses had increased cross-sectional area at all 6 levels the authors reviewed. There was also improved symmetry between the right and left sides.

Another study showed that the addition of gymnastic exercises—including pelvic tilts, backing the horse in hand, doing small circles, and raised pole walking—to dynamic mobilization exercises resulted in a greater increase in the cross-sectional area of the multifidus muscle when compared with dynamic mobilization alone.

“We also use elastic resistance bands with a lot of our rehab horses and horses with back pain,” Dr. Contino added.

A recent study showed that after 4 weeks, horses had decreased rotation and mediolateral movement in the thoracolumbar spine. For the first week, the horses were typically just being familiarized with the bands, but after that the horses used the bands in increasing amounts of time for fewer days each week.

“This evidence suggests we’re increasing their dynamic stability,” she said.

Whole-body vibration, which involves the horse standing on a vibrating vertical platform, also has some evidence showing improved symmetry of the multifidus muscle. The frequency, amplitude, acceleration and direction that the platform vibrates in can vary from brand to brand, but placing a horse on a vibration plate for 30 minutes 5 times a week has shown some positive results.

“In my clinical experience, I don’t find this to be nearly as good as the core exercises,” she added. MeVEcae

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