Well-being of mares undergoing ovum pick-up

Ovum pick-up (OPU) is an advanced assisted reproduction technique (ART) allowing the retrieval of oocytes from the ovary for subsequent in vitro embryo production (IVP). This procedure replicates biological conditions necessary for embryo development whilst offering significant reproductive advantages over natural mating. Originally developed for cattle, transvaginal ultrasound-guided OPU has been successfully adapted for equids, demonstrating variable oocyte recovery rates (7%–70%, averaging ~50%). This variability is largely influenced by operator experience and the protocols employed. The procedure involves ultrasound-guided transvaginal aspiration of ovarian follicles using a double-lumen needle. Using this approach, follicular fluid is aspirated and the follicles flushed to enable the retrieval of viable oocytes for subsequent in vitro maturation (IVM) and fertilization via intracytoplasmic sperm injection (ICSI). 

Currently, ovum pick-up is not permitted in Sweden because it is considered to be a painful, invasive procedure. However, to date, no scientific evidence has been presented to substantiate reports of mares being adversely affected by the procedure. 

It can be difficult to assess subtle signs of pain in horses; prey animals are adept at hiding signs of discomfort or weakness from predators. Indicators of compromised well-being include ”pain face” i.e. facial changes due to pain, specific behaviours associated with abdominal pain (stretching, looking at the abdomen, pawing), and changes in the activity time budgets, such as spending more time lying down, and not eating or not moving around as expected. These signs are individual and intermittent; they might be difficult to detect unless the horse is continuously kept under observation and baseline values are already known.  

Our hypothesis is that signs of discomfort will be detectable from videos made of the mares before and after the OPU procedure.