Larger follicles may result in an earlier ovulation. Administering hCG when follicles smaller than 35 mm are present will have little or no effect. There should be a follicle of approximately 35 to 40 mm present at this stage, and if so, hCG may be administered. Palpations should be increased to as often as every 6 hours in the period commencing 24 hours after this. It is important to assess the mare to ensure that ovulation did indeed occur at the anticipated time.
Mares are notorious for proving even the experienced palpator wrong.
Palpation should be used to detect ovulation, and this may then be followed with ultrasound to evaluate the uterine environment, as discussed above, or if there is any doubt as to whether the mare did indeed ovulate. The hormones used in manipulation of the mare are the same hormones that are present in humans, and they can be absorbed through the skin if spilled. All asthmatics, regardless of gender, and pregnant women, must be particularly careful when handling prostaglandin. Progesterone or Regumate must be handled extremely carefully by all women to avoid significant disruption of menstrual cycles.