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New Study Shows Some Mares Find Rectal Ultrasounds Uncomfortable
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New Study Shows Some Mares Find Rectal Ultrasounds Uncomfortable

While trans-rectal exams are quite a normal thing in the breeding industry, nobody has ever tried to extensively establish its psychological effects on an animal’s welfare, until now.

A team of university researchers from Germany, in collaboration with counterparts from Switzerland, have published findings of a study they recently conducted looking into the levels of stress that are experienced by pregnant and lactating mares when they undergo the routine trans-rectal ultrasound examinations. They found out that non-lactating thoroughbred mares often perceive these exams as a modest temporary stresser.

The study, dubbed “Influence of Trans-Rectal & Trans-Abdominal Ultrasound Examination on Salivary Cortisol, Heart Rate, & Heart Rate Variability in Mares," involved 25 thoroughbred broodmares and was published in Theriogenology.

According to study author and lead researcher Hanno Schönbom, who is also an assistant at the reproductive medicine unit in the University of Veterinary Medicine in Hannover, Germany, his team noted that there was a significant rise in stress levels when a trans-rectal ultrasound was performed on a pregnant, non-lactating mare. A notable rise in the concentration of salivary cortisol and heart rate variability, which are two key parameters indicative of acute stress, were observed.

However, trans-abdominal ultrasounds, which are effective without clipping but with application of isopropyl alcohol, showed no similar increases in the level of cortisol. With this in mind, the research team recommends that whenever possible, an abdominal ultrasound should replace the rectal one. Generally, this is most appropriate after 90 days of gestation.

On the other hand, both pregnant and non-pregnant lactating mares did not show signs of experiencing increased stress levels during a trans-rectal exam. This supports previous research on mammals -- including humans -- that lactation often causes an attenuation of stress parameters in otherwise stressful situations.

Nevertheless, this does not mean that lactating mares will always have lower stress levels than non-lactating ones. The study found out that baseline stress levels (i.e. the normal equine stress levels at rest) were roughly the same for both lactating and non-lactating mares. Further still, Schönbom’s team recommends that vets should avoid taking the trans-rectal route altogether whenever possible, for modesty and ethical reasons.


Image source: annettevet.wordpress.com

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