Accelerometry and infrared thermography show potential for assessing ovarian activity in domestic cats (Felis catus)

Abstract

Accurate and reliable monitoring of ovarian activity is challenging in many felids as current methods are either invasive or not amenable to real-time assessments. This 45-day study assessed whether accelerometry and infrared (IR) thermography can be used to address these limitations. Intact female domestic cats (n = 12) were given 0.088 mg kg^-1 day^-1 altrenogest (progestin) orally for 37 days to suppress follicular growth. On Day 40, cats were given 75 IU eCG im to induce follicular growth and 50 IU hCG im 80 h later to induce ovulation. Cats were ovariohysterectomised 30-31 h after the hCG treatment. Actical® accelerometers were fitted to the cats' collars and activity monitored continuously from the start of the altrenogest treatment until ovariohysterectomy. Infrared images of the perivulvar, perianal, and gluteal area were taken of each cat on Day 30 and daily from Days 36-45 of the study. Perivulvar temperature (PVT), PVT relative to gluteal temperatures (PVT-GT), and PVT relative to perianal temperature (PVT-PAT) were recorded for each image. Blood samples were collected on Days 0, 10, 30, and 40, immediately prior to the hCG treatment, and at the time of ovariohysterectomy. Serum oestradiol and progesterone concentrations indicated complete ovarian suppression by Day 30 and, together with morphological assessment of the ovaries, confirmed the induction of follicular growth and ovulation in all cats. Daily activity counts differed among cats (P < 0.001), so the daily activity counts of each cat were converted to a proportional change from the average daily activity count from Days 30-39 (defined as the 'proportional daily activity'). Proportional daily activity counts increased after the stimulation of follicular growth with eCG, with peak levels (2.03 ± 0.29-fold higher than pre-treatment levels; P = 0.006) occurring three days after the eCG treatment. The PVT-GT showed the greatest sensitivity to detect subtle changes in body temperature, increasing from early to late follicular growth (1.96 ± 0.33 °C increase from Day 41-43; P < 0.001) and decreasing after hCG-induced ovulation (1.24 ± 0.41 °C decrease from Day 43-45; P = 0.01). In conclusion, both accelerometry and IR thermography show potential as non-invasive, real-time methods for assessing ovarian activity in cats, but further research is required to determine if these methods could be used to monitor natural/non-stimulated oestrous cycles.

Keywords: Accelerometry; Felid; Infrared; Oestrus detection; Perivulvar temperature; Physical activity.