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Cry Wolf: Are Domesticated Horses Less Fearful Of Predators?

A study out of Poland sought to determine if domesticated horses responded to predators they have never encountered the same way their wild ancestors did: by fleeing. The research team hypothesized that horses would express anxiety when exposed to vocalizations of predators and that horses with Thoroughbred breeding would be more responsive to the cues as they are known for their sensitive nature.

Drs. Iwona Janczarek, Anna Stachurska, Witold Kędzierski, Anna Wiśniewska, Magdalena Ryżak and Agata Kozioł used 19 Polish horses in the study and concluded that the horses reacted more strongly to the growl of a leopard than the howl of a wolf, though they were unfamiliar with either predator. The scientists report that this may indicate that the horse is more afraid of a sound from an unknown predator that one known to their ancestors. The behavioral responses of the horses were less distinct then the physiological changes, the team noted.

The horses used in the study were between 6 and 10 years old; they were divided into three groups based on the amount of Thoroughbred in their pedigree: Six horses were 75 percent Thoroughbred; seven were half-Thoroughbred; and six were 25 percent Thoroughbred.

Individually, the horses listened to recordings of the gray wolf howling and a leopard growling for five minutes. The study team monitored salivary cortisol levels of the horses 10 minutes before and 10 minutes after the conclusion of the vocalizations. Each horse's heart rate was continually monitored through the test.

The study team hypothesized that the horses with more Thoroughbred in their breeding would react more strongly to the vocalizations since Thoroughbreds are known for their sensitivity. They were correct: the horses with more Thoroughbreds in their pedigree had stronger internal reaction to the predator's vocalizations. This suggests that the response is partially genetically coded and that the horses were more interested in the sounds rather than frightened by them.

This may also indicate that horses that are handled and trained by humans may be able to manage their emotions. Domesticated animals may not be able to coexist with predators like wolves being reintroduced into their environment and care should be taken to protect them.

Read the article here.

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Study: Mare Size Affects Birth Process

Drs. Christina Nagel, Maria Melchert, Christine Aurich and Jörg Aurich created a study to determine if the size of the mare affected the birthing process. The team used 23 pregnant mares and studied hormone and heart-related changes that occur in the mare and the fetus around birth. The groups consisted of six Shetland Pony (small); eight Haflinger (medium) and nine warmblood (large) mares.

They discovered that foal weight was approximately 10 percent of mare weight, no matter the size of the mare. Placenta weight was highest in Warmbloods; it did not differ between the small- and medium-sized mares. Progestins and cortisol were also highest in the larger mares. Progestin concentrations decreased as foaling got closer and cortisol increased as parturition was imminent in all sizes of horse studied.

Heart rates in all mares increased before foaling, but the most pronounced increase was in the small mares. Overall, the small mares foaled earlier than the larger mares.

Missed heartbeats during foaling occurred regularly in the larger mares, but only occasionally in the small- and medium-sized mares. The scientists report that this is most likely because of differences in heart efficiency. Small- and medium-sized mares occasionally had missed beats during the expulsive phase of foaling and the first two hours after delivery. The researchers suggest that this is an effect of breed, not size.

The team concludes that fit, athletic horses have highly efficient respiratory and cardiovascular systems; while at rest, these horses have reduced heart rates. Fetal heart rate also went down toward birth, with the most prominent reduction in full-sized horses.

The authors determined that mare of different sizes show both similarities and differences in cardiac and endocrine changes as the time for them to give birth nears. They note that late pregnancy puts substantial strain on the mare's cardiovascular system, but that mares are well adapted to these demands, no matter their size.

Read the full article here.

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Heart-Rate Variability May Indicate Outcome Of Colic Cases

Colic, a catch-all term for abdominal pain in horses, can be caused by a variety of reasons; it can be a life-or-death situation and requires immediate veterinary care. Colic is stressful for horses; horses that are actively colicking have an increased cortisol level and heart rate. A new study shows that heart-rate variability may be a key indicator in assessing the possible outcome of colic cases.

Drs. Heidrun Gehlen, Maria-Dorothee Faust, Remigiusz Grzeskowiak and Dagmar Trachsel of the Free University in Berlin, and Dr. Remigiusz Grzeskowiak of the University of Tennessee wanted to determine if horses showed varying stress levels with different types of colic, therefore warranting different treatment strategies.

The team used 43 horses admitted to two different equine hospitals for colic and categorized them into three groups: surgical, conservative (non-surgical) and euthanized. The scientists studied the blood tests and heart-rate variability of the horses at admission, 24 hours after admission and at discharge.

The team found that heart rate and cortisol levels decreased the day after admission and on the day of discharge in both the surgical and non-surgical groups of horses, indicating that they were not as stressed as they were during their intake into the hospital.

However, decreases in heart rate and cortisol levels were not seen in the horses that were ultimately euthanized. The difference in heart rate in the euthanized and non-euthanized horses was most obvious the day after admission.

The team concluded that heart-rate variability can offer treating veterinarians important information on the stress level of colicking horses and may be helpful in assessing the possible outcome. They suggest further studies be completed.

Read the full study here.

Read more at HorseTalk.

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Three Signs That Indicate Colic Is Critical

Colic is the No. 1 killer of horses in the United States. The term encompasses any equine abdominal pain and it is the most-common reason why horses require emergency veterinary care. Though many colic cases are resolved with simple, on-farm medical management, some cases are critical.

Drs. Adelle Bowden, Gary England, Marnie Louise Brennan, Tim Mair, Wendy Furness, Sarah Freeman and John Burford reviewed the clinical notes from 941 colic cases seen by two major equine clinics in England. The study team was able to identify three “red flags” that indicated that a colic case was critical. “Critical” in this case means that the colic required medical or surgical in-hospital care or resulted in euthanasia or death.

There are three red flags were: an increased heart rate, increasing age and abnormal mucous membrane color. The study team determined that of the 941 cases, 225 (23.9 percent) were critical; 18 percent of the critical cases were euthanized and 1 percent of the cases died.

The researchers note that these three “red flag” parameters should be an essential component of the colicky horse's initial assessment. The team suggests further research into the role a horse's age plays in critical cases; clarification is needed on if older horses are more likely to have critical conditions or if owners are more likely to choose euthanasia instead of treatment in older horses.

Read more at HorseTalk.

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