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ASK THE NUTRITIONIST
Ask the Nutritionist KELLY VINEYARD, MS, PHD, SENIOR EQUINE NUTRITIONIST, 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 nutritional advice, visit purinamills.com/ask-an-expert.
Where can I find good, science-based information to refer to when I have questions related to equine nutrition?
Many helpful equine nutrition resources are available for equine veterinarians, including textbooks, scientific publications, reputable websites and personal consultation with an experienced and credentialled equine nutritionist. The challenge can be ensuring the information is from a reputable source. Though not a comprehensive list, some top, science-based equine nutrition resources for equine veterinarians are highlighted below.
TEXTBOOKS
• The National Academy of Sciences National Research Council’s text “Nutrient Requirements of Horses, 6th Edition”, also referred to as the “NRC,” is a key Purina Animal Nutrition’s Ph.D. equine nutritionists experienced in clinical
equine nutrition text. Last published in 2007, it contains scientific research cally offer complimentary consultations. Consultation with an experienced equine
in equine nutrition until that time. This text focuses on the studies that led to current established nutrient requirements for horses, and it is a “musthave” reference for equine nutrition scientists. • The textbook “Equine Applied and Clinical Nutrition” published in 2013 contains in-depth equine nutrition information from experts in the field on topics ranging from basic nutrition principles to life stage feeding to applied and clinical nutrition principles. It is an excellent reference for practitioners looking to deepen their understanding of equine nutrition and for guidance on the practical application of these nutrition principles.
SCIENTIFIC PUBLICATIONS
• The Journal of Equine Veterinary Science (JEVS) is the official publication of the Equine Science Society (ESS), and often contains original scientific research in equine nutrition. • The Journal of Animal Science is the official journal of the American Society of Animal Science, and journal articles cover a wide range of topics in all animal species, including equine nutrition. clients at the new www.EquineVetNutrition.com page.
• Other scientific journals that often contain original equine nutrition research are the Journal of Animal Nutrition, Equine Veterinary Journal and the Journal of Animal Physiology and Animal Nutrition.
WEBSITES
ous topics. University websites are a good place to search for technical bulletins and articles related to equine nutrition. • The online NRC calculator available at https://nrc88.nas.edu/nrh/ is a handy tool when looking for equine nutrient requirements. The disclaimer popup is a good reminder that proper use requires some background knowledge of nutrition to effectively apply the calculator’s information. • The website EquineVetNutrition.com is a new resource specifically designed to support equine veterinary practitioners. All content has been created by
equine nutrition. Practical information, such as nutritional management of common equine conditions, how to interpret a hay analysis, enteral feeding guidelines, and more, can be found at this site.
EXPERT CONSULTATION
A personal consultation with a trained equine nutritionist is often the most efficient path to developing supportive nutrition recommendations on specific cases. Finding someone with experience and credentials is critical. To find a DVM that is a Board-Certified Veterinary Nutritionist, consult the American College of Veterinary Nutrition’s website directory. Universities with equine extension programs often have a Ph.D. nutritionist available to answer questions as well. Independent equine nutrition consultants can be found online (confirm credentials, ask for references), and reputable feed manufacturers with Ph.D. nutritionists on staff typinutritionist will allow for all variables to be considered and will result in a timely and customized recommendation specific to your needs.
Contact a Purina Ph.D. nutritionist for consultations through Purina Customer Service, 800-227-8941.
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ABOUT THE AUTHOR Kelly Vineyard, Ph.D., is a senior equine nutritionist with Purina Animal Nutrition. She is a frequent publisher and lecturer on equine nutrition topics, with expertise in omega-3 fatty acids, immune function and performance horse nutrition.
Shutterstock/Marie Charouzova Placentitis, which can affect up to 5% of broodmares in the United States, is a leading cause of reproductive loss.
Most cases are caused by bacteria ascending through the cervix where they enter the choriallantois and colonize the cervical star region, releasing pro-inflammatory cytokines and prostaglandins and causing placental separation and delivery of a stillborn or weak foal.
“This carries a huge economic burden in the form of loss of foal crop annually and sales at the yearling sale every year,” said Jennifer L. Sones, DVM, PhD, DACT, an assistant professor of theriogenology at Louisiana State University, School of Veterinary Medicine.
Management can be complex, and is expensive, she added. Both mares and any surviving foals often require intensive care. Some mares also experience repeated fertility issues the following year.
“There's still a lot, we don't know about equine placentitis,” she said at the AVMA Virtual Convention 2020.
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Ultrasonography is a useful tool—a transabdominal ultrasound can help determine fetal viability and a transrectal ultrasound will help measure the combined thickness of the uterus and placenta.
Bacterial causes include Streptococcus equi zooepidemicus, Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus and Nocardia species. If Candida or Aspergillus are found, they can be a secondary infection after a bacterial placentitis.
Clinical signs can be mild, moderate or severe, and some mares are asymptomatic. Their temperature, pulse and respiratory rates are often within normal limits. They might have premature utter development but that can be hard to appreciate.
If they have a vulvar discharge or premature lactation, you’ve caught a severe case. “We all know mares shouldn't be dripping milk until 24 to 48 hours before foaling. So if we see that at any time before 320 days, that can be alarming and it should be,” she said.
When placentitis is suspected, the mare will need a thorough reproductive examination, which includes
Biomarkers for Placentitis
From about day 110 until term, total estrogen assays help to confirm pregnancy and monitor fetal viability. “An interesting feature about equine pregnancy is that progestogens really go up, up, up, and then they precipitously drop 24 hours before foaling,” said Jennifer L. Sones, DVM, PhD, DACT, a theriogenologist at Louisiana State University, School of Veterinary Medicine. The entire fetal placental unit works together to produce progestational hormones, including 5-α dihydroprogesterone, a key progestogen for maintaining pregnancy. Circulating levels of 5-α DHP will eventually exceed that of progesterone. Once that happens, supplementation may not be necessary. The UC Davis Endocrinology laboratory can now distinguish 5-α DHP from progesterone, she said. Another key steroid hormone to consider when monitoring the pregnancy is estrone sulfate. Low estrogens and progestogens, especially5-α DHP may signal fetal distress. Other biomarkers to consider are: • Serum amyloid A, which is an acute-phase protein produced in response to infection or inflammatory event. Although it is not specific to placentitis, it can be combined with the reproductive exam and other tools to help make a diagnosis and to monitor the mare’s response to treatment. • Relaxin is produced by the placenta beginning on day 80 and is increased at delivery. Low levels of circulating relaxin could signal placental dysfunction. • Alpha fetoprotein has also been shown to increase in experimental model of placentitis, and may someday be a biomarker for the condition. a vaginal exam through a small speculum to inspect the cervix and to look for any cervical discharge.
Ultrasonography is a useful tool—a transabdominal ultrasound can help check for a fetal heart rate to determine its viability and a transrectal ultrasound will help measure the combined thickness of the uterus and placenta (CTUP). CTUP should be determined just cranial to the cervix between the middle uterine artery and allantoic space. Serial measurements should be taken because the CTUP is dynamic.
Dr. Sones offered a few suggestions to make it easier to determine CTUP: • always evaluate the same area and take several measurements; • watch for features that can increase the measurement, such as physiologic edema and the amnion, and • measure when the foal is calm.
“The foal sometimes can be very active,” she said, which can compress some of the structures together and change the measurement. “You want to do it when the foal is quiet. I often take this measurement first, and then do my reproductive exam, as I find that after I do the transabdominal ultrasound, the foal seems to be a lot more active.”
The CTUP depends on the stage of gestation, but a rule of thumb is that it should be less than or equal to the month of gestation (in millimeters) when the measurement is taken.
“Importantly, you want to assess if there's any placental separation. So that's going to occur in pretty severe cases of placentitis. When we see those bacteria colonize the cervical star region, and they create an inflammatory response, and they produce pus, then that mediates that placental separation. That means the placenta is not working efficiently for nutrient-oxygen exchange at those areas,” she said.
Treatment goals for ascending placentitis include inhibiting and eliminating bacterial growth within the choriallantois, maintaining uterine quiescence, minimizing uterine contractions, increasing cervical tone and increasing the blood supply to the uterus and placenta.
