Ask Your Veterinarian Presented By Kentucky Performance Products: Why Are Broodmares So Prone To Colic?

Veterinarians at Rood and Riddle Equine Hospital answer your questions about sales and healthcare of Thoroughbred auction yearlings, weanlings, 2-year-olds and breeding stock.

Question: Why are broodmares so prone to colic, and what colic causes are most common for them?

Dr. Katy Dern, Rood and Riddle Equine Hospital: According to the Centers for Disease Control, 1.4 percent of human delivery hospitalizations in the United States in the year 2014 developed what are characterized as severe maternal morbidities. This means that, even in closely supervised and intensively managed births, 1.4 in every 100 women developed potentially life-threatening complications. Parturition (birth) has potential consequences for the mother, and broodmares are no exception to this biologic reality.

Dr. Kathryn Dern

When we discuss colic (abdominal pain) in the broodmare, the cause of the pain can be broadly divided into two categories: pain originating from the gastrointestinal tract and pain originating from the reproductive tract.

Colic signs attributable to the gastrointestinal tract are a common phenomenon in the broodmare, and can be further subdivided into those conditions seen prior to foaling and those seen in the post-parturient time period (after foaling). Prior to foaling, causes of colic include mild discomfort due to expanding uterine size and fetal movements, as well as displacements or abnormal motility of the large colon, cecum, or small intestine. Mares exhibiting colic secondary to fetal movements or impingement of the gravid uterus on the gastrointestinal tract will usually not have dramatic changes in their vital parameters (heart rate, respiratory rate, mucous membrane color), and will respond to analgesics (pain management). If the mare's colic signs do not respond to pain management or increase in severity, she may have a gastrointestinal issue which can be life threatening to her and/or the foal. In either case, veterinary evaluation is important to differentiate between mild and more severe forms of colic, and to ensure that more aggressive medical and surgical interventions can be instituted if necessary.

After foaling (and sometimes before foaling), gastrointestinal causes of colic can include large colon volvulus (twist) or displacement, cecal dysmotility or rupture, small intestinal incarceration, mesenteric tears leading to loss of intestinal viability, or rectal prolapse. Of these the most discussed and by far most common cause of colic is large colon volvulus. Broodmares are largely overrepresented in the large colon volvulus (LCV) caseload: one study evaluating the distribution of surgical LCV cases at a large referral hospital in California found that half of the admissions were broodmares that had foaled less than 60 days prior to admission.  This association between foaling and subsequent development of colonic displacement or LCV has been mirrored in multiple studies across various geographic areas and additional risk factors such as increased hours of stabling, increased feeding of concentrates, decreased dry matter intake, or a recent change in pasture have also been discovered.

Although our research has clearly shown that post-foaling broodmares are likely to develop large colon volvulus, we unfortunately have not yet determined exactly why they are prone to this disease. Common sense dictates that the presence of additional “room” in the abdomen post foaling must play a role, but this unfortunately does not account for the LCV cases we see in geldings, show horses, or preparturient [pregnant] mares.

Recent investigations into the role of intestinal microbiota in the development of colic suggest that significant changes in the fecal microbiota precede the development of colic. The changes in the bacterial population observed in the fecal samples of mares that developed colic are consistent with changes seen in both dysbiosis (imbalance in gastrointestinal bacteria) and inflammatory intestinal disease in other species, including humans. Further investigation into the role of intestinal microbiota in the development of large colon volvulus will hopefully allow us to not only fully characterize the disease process, but eventually identify at-risk mares and intervene prior to development of colonic displacement or volvulus.

Other gastrointestinal causes of post-foaling colic are usually more directly linked to the parturition itself. Cecal bruising or rupture can occur when the foal traumatizes the base of the cecum. These mares commonly present with abdominal discomfort within the first few days of foaling and then progress to signs of septic peritonitis (abdominal infection) if the wall of the cecum becomes devitalized to the point of rupture. Tears in the mesentery of the small colon or small intestine can subsequently trap segments of the small intestine, causing pain from the entrapment itself and, if prompt surgical intervention is not undertaken, these small intestinal segments can become devitalized, endangering the mare's life, necessitating resection (removal of the devitalized area). If the small colon mesentery is affected, the tear itself can often affect the blood supply to the small colon, causing a gradual necrosis (death) of a segment of the small colon requiring surgery.

Reproductive causes of colic are also common in the broodmare, and determining whether colic signs are gastrointestinal or reproductive in nature is one of the primary goals of the colic exam. In the pregnant mare, colic signs attributable to the reproductive tract can range from mild, medically manageable colics due to fetal shifting and increased fetal size, or abdominal discomfort can be a sign of more life threatening conditions such as uterine torsion or preparturient uterine artery hemorrhage. As with all signs of colic, evaluation by your veterinarian is indicated if your mare's colic signs do not resolve or increase in severity.  On the farm, your veterinarian may perform a physical, rectal, and/or ultrasonographic exam to determine if referral is indicated.

In the post foaling broodmare, causes of colic signs attributable to the reproductive tract include mild colic signs due to normal uterine contraction and involution, or more severe colic signs secondary to uterine artery rupture, uterine tears, invagination of a uterine horn or uterine prolapse. In the case of uterine artery rupture, the mare will often show signs of abdominal pain if the hemorrhage is limited to the broad ligament (soft tissue structure which suspends the uterus within the abdomen), as the hematoma dissects through the ligament itself. If she is bleeding freely into her abdomen however, she may not show signs of colic, rather exhibiting a high heart rate, anxiety, and increased respiratory rate consistent with blood loss. In these cases, a thorough physical exam, rectal palpation, abdominal ultrasonography, and abdominocentesis (analysis of a sample of the abdominal fluid) can be critical in determining whether or not the mare is actively hemorrhaging.

Uterine tears can present a diagnostic challenge, as they occur during foaling but do not necessarily cause signs of abdominal pain until the leakage of uterine fluid into abdomen causes signs of abdominal infection (septic peritonitis). In these cases, the mare often presents within the first few days after foaling for dullness and depression, fever, and high heart rate. The diagnosis of septic peritonitis is made using abdominal ultrasonography and abdominocentesis. Prompt surgical repair of these tears, often found at the tip of the uterine horn, limits the continued contamination of the abdomen and allows for intraoperative lavage of the abdomen with drain placement for post-operative lavages. Cases of invagination of the uterine horn are often diagnosed and treated on farm, but if they progress to uterine prolapse may necessitate referral for replacement under general anesthesia.

Lacerating or tearing the cervix during foaling is usually not painful and is commonly found later when the mare is spec'ed or when she is cultured. Manual examination of the cervix is required to definitively diagnose a cervical tear, which are usually repaired after the initial swelling from foaling has subsided (approximately three weeks after parturition).

It is important to note that just because a mare had an uneventful foaling does not mean that the foal didn't damage segments of the reproductive or gastrointestinal tract during parturition. In all cases of broodmare colic, evaluation by a veterinarian experienced in broodmare disorders and timely referral, if necessary, are critical to survival of both mare and foal.

Dr. Katy Dern is originally from Colorado and Montana. She attended Washington State University for her undergraduate work, and Colorado State University for her veterinary degree. Following graduation from CSU in 2012, she completed an internship at Peterson and Smith Equine Hospital in Ocala, followed by an internship at Rood and Riddle Equine Hospital. After her internships, Dr. Dern completed a three-year surgical residency at The Ohio State University, while also earning a Master's of Science Degree. She became board certified in equine surgery in 2018 and has been the surgeon at Rood and Riddle's Saratoga hospital since 2017. 

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PR Back Ring Keeneland November: From Weanlings To Winners

CLICK HERE TO READ THIS ISSUE OF THE PR BACK RING

The latest issue of the PR Back Ring is now online, ahead of the Keeneland November Breeding Stock Sale.

The PR Back Ring is the Paulick Report's bloodstock newsletter, released ahead of, and during, every major North American Thoroughbred auction. Seeking to expand beyond the usual pdf presentation, the Back Ring offers a dynamic experience for bloodstock content, heavy on visual elements and statistics to appeal to readers on all platforms, especially mobile devices.

Here is what's inside this issue…

CLICK HERE TO READ THIS ISSUE OF THE PR BACK RING

  • Lead Feature, presented by Pyrois Media: Bloodstock editor Joe Nevills ranks the 20 best Keeneland November weanlings by on-track performance since 2014, a five-year span, ending with the 3-year-olds of 2021.
  • Stallion Spotlight presented by New York Thoroughbred Breeders, Inc.: Chris Bernhard of Hidden Lake Farm discusses Fog of War, a Grade 1-winning son of War Front whose first foals arrive in 2022.
  • Toast To Vino Rosso presented by Spendthrift Farm: Tanya Gunther of Glennwood Farm reflects on breeding Breeders' Cup Classic winner and Spendthrift Farm sire Vino Rosso, and spotlights the two Vino Rosso weanlings the consignment will offer in Book 1 of the Keeneland November Sale.
  • Lesson Horses presented by John Deere Equine Discount Program: Bernard McCormack of Cara Bloodstock describes what the first broodmare he owned taught him about life.
  • Ask Your Veterinarian presented by Kentucky Performance Products: Dr. Katy Dern of Rood and Riddle Equine Hospital explains why broodmares are so prone to colic, and the common causes.
  • Indiana Weanling Spotlight presented by Indiana Thoroughbred Alliance: Putting the spotlight on an Indiana-bred filly by the red-hot sire Not This Time, and the state-bred program where her buyer can reap the benefits.
  • Pennsylvania Leaderboard presented by Pennsylvania Horse Breeders Association: A rundown of Pennsylvania's leading stallion award incentive earners with five crops of racing age or fewer.
  • American Graded Stakes Standings presented by Muirfield Insurance: Catching up with the leading breeders by North American graded stakes winners following the Breeders' Cup.
  • First-Crop Sire Watch: Stallions whose first crops of weanlings are represented in the Keeneland November Sale, including the number of horses cataloged and the farm where the stallion is currently advertised.

CLICK HERE TO READ THIS ISSUE OF THE PR BACK RING

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Ask Your Veterinarian Presented By Kentucky Performance Products: Enteroliths Can Make A Rocky Road To Colic

Veterinarians at Rood and Riddle Equine Hospital answer your questions about sales and healthcare of Thoroughbred auction yearlings, weanlings, 2-year-olds and breeding stock.

Question: How common are enteroliths, and what causes them?

Dr. Katy Dern, Rood and Riddle Equine Hospital: While many of our colic patients make it clear within a few minutes of presentation to hospital that they will require surgery — high heart rate, unremitting pain in the face of sedatives and NSAIDS, or clinical signs of devitalized bowel – some patients make it more difficult to determine if surgery is indicated. Horses with enteroliths are often on that list.

Enteroliths are calculi (rocks) which form in the right dorsal colon and can cause partial or complete obstruction of the gastrointestinal tract. They are composed of struvite (magnesium ammonium phosphate hexahydrate) and form when mineral deposition occurs in concentric layers around a central nidus. Although this central nidus is sometimes a foreign body (rope or metallic object), in most cases it is indistinguishable from the rest of the calculi.

Dr. Kathryn Dern

Although we don't know exactly why some horses form enteroliths and some don't, we do know that there are certain risk factors for enterolith formation. A review of 900 cases of horses with confirmed enteroliths determined that Arabians, Morgans, and American Saddlebreds are at an increased risk for developing enteroliths. Enteroliths were also found to occur more frequently in horses in California and regions of the Southwest. From a management perspective, the most important aspects of this retrospective analysis and other studies were that most patients with enteroliths had a diet which consisted of more than 50 percent alfalfa hay, and there was a significantly increased incidence of enteroliths in horses which did not have daily access to pasture grazing.

If your horses are part of the “at-risk” population, we recommend ensuring that the majority of their diets consist of pasture or grass hay, avoiding alfalfa-based products. Although the exact role of alfalfa in the formation of enteroliths is unknown, it is suspected that the higher protein content can result in a more alkaline pH in the colon, favoring enterolith formation. Alfalfa hay also has higher levels of magnesium and phosphorus, both of which are components of the typical struvite enterolith.

Enteroliths usually form in the right dorsal colon, which has a large enough diameter to accommodate the calculi while still allowing feed to pass through the gastrointestinal (GI) tract. If the enterolith begins to move from the right dorsal colon into the transverse colon, or further abroad into the small colon however, it becomes lodged due to the smaller diameter of these parts of the GI tract. In some horses, the enterolith intermittently occludes the transverse colon, causing occasional mild colic signs which resolve with medical management (flunixin meglumine, intravenous fluids, etc). Once the enterolith becomes lodged in the transverse or small colon, it completely blocks the passage of feed material though the GI tract, causing colic signs.

Diagnosis of enteroliths in the patients with a history of chronic colic can be challenging. Abdominal radiographs (x-rays) are more reliable in diagnosing enteroliths which are in the large colon versus the small colon – presumably due to the increased diameter of the enteroliths in the large colon. Enteroliths cannot be imaged in an ultrasonographic examination and are rarely detectable on rectal palpation. For these reasons, a definitive diagnosis of enterolithiasis often requires surgery.

In the patients with persistent colic signs in which the enterolith has become permanently lodged in the bowel, timely surgical intervention is important. In these cases, the enterolith compresses the bowel wall, decreasing the blood supply and potentially causing weakened areas or areas of necrosis (tissue death), which can lead to fatal rupture of the transverse or small colon. To avoid this tragic outcome, surgery is recommended in horses with persistent pain in the face of sedation and analgesia (flunixin meglumine, etc).

Once in surgery, the location of the enterolith is determined and a pelvic flexure enterotomy is performed to completely empty the contents of the large colon. This procedure involves making a small incision in the bowel wall through which to empty the contents, and then instilling fluid into the large colon to help “flush” the enterolith to a location from which it can be safely removed. Multiple incisions are often required to both evacuate the contents of the colon and to remove the enterolith. If the enterolith is lodged in the small colon, an incision will be made into the wall of the small colon to facilitate enterolith removal. In some cases, the enterolith has compressed the bowel wall so severely that tissue death (necrosis) has occurred – in these cases the devitalized area of bowel needs to be removed.

Post-operative management involves intravenous antimicrobials, intravenous fluids, and a gradual refeeding program to ensure that the lining of the colon has time to recover from trauma and irritation caused by the enterolith. Fortunately, survival after surgical removal of enteroliths is high, with reports ranging from 92 percent to 96 percent. As with many colic cases, prompt referral and timely surgical intervention are the keys to a good outcome.

Dr. Dern is originally from Colorado and Montana. She attended Washington State University for her undergraduate work, and Colorado State University for her veterinary degree. Following graduation from CSU in 2012, she completed an internship at Peterson and Smith Equine Hospital in Ocala, followed by an internship at Rood and Riddle Equine Hospital. After her internships, Dr. Dern completed a three-year surgical residency at The Ohio State University, while also earning a Master's of Science Degree. She became board certified in equine surgery in 2018 and has been the surgeon at Rood and Riddle's Saratoga hospital since 2017. 

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PR Back Ring Fasig-Tipton October Sale: The Centuries-Long Legacy Of Normandy Farm

CLICK HERE TO READ THIS EDITION OF THE PR BACK RING

The latest issue of the PR Back Ring is now online, looking ahead to The Fasig-Tipton Kentucky Fall Yearling Sale.

The PR Back Ring is the Paulick Report's bloodstock newsletter, released ahead of, and during, every major North American Thoroughbred auction. Seeking to expand beyond the usual pdf presentation, the Back Ring offers a dynamic experience for bloodstock content, heavy on visual elements and statistics to appeal to readers on all platforms, especially mobile devices.

Here is what's inside this issue…

CLICK HERE TO READ THIS EDITION OF THE PR BACK RING

  • Lead Feature presented by WestWin Farm: Myra Lewyn looks back on the legacy of Normandy Farm, the home Man o' War's sire and dam, and how the farm's former residents have shaped today's racing and breeding landscape in the latest Kentucky Farm Time Capsule.
  • Stallion Spotlight presented by New York Thoroughbred Breeders, Inc.: Sean Feld of Climax Stallions discusses Mr. Monomoy, a Grade 2-winning resident of Waldorf Farm in New York, whose first foals arrive in 2022.
  • Ask Your Veterinarian presented by Kentucky Performance Products: Dr. Katy Dern of Rood and Riddle Equine Hospital explains the rock-like enteroliths that can build up in a horse's colon and lead to colic.
  • Pennsylvania Leaderboard presented by Pennsylvania Horse Breeders Association: A look at the 2-year-olds who are earning their connections the most money in Pennsylvania-bred and -sired incentives, led by the impressive maiden winner For the Dreamers.
  • American Graded Stakes Standings presented by Muirfield Insurance: A rundown of the leading breeders by North American graded stakes winners, headed up by a close race between global powers Godolphin and Juddmonte Farms.
  • First-Crop Sire Watch: Stallions whose first crops of yearlings are represented in the Fasig-Tipton October catalog, including the number of horses cataloged and the farm where the stallion is currently advertised.

CLICK HERE TO READ THIS EDITION OF THE PR BACK RING

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