Horse Species: Equine Advancements

Past studies investigating testicular heat stress due to exercise or insulation in the stallion have utilized thermistor probes to measure scrotal surface temperatures (SST). Although such devices are effective, a more efficient measurement of testicular thermal stress would be subcutaneous scrotal temperature (SQST). The objective of this study was to utilize a thermal sensory device to measure SQST in the stallion during exercise and correlate it with subcutaneous neck (SQNT), rectal (RCT), and ambient temperatures (AMBT), as well as % humidity (HUM), and temperature-humidity index (THI). Thermal sensory microchips (Digital Angel, Inc., St. Paul, MN) were surgically implanted into the subdermis of the necks and scrotums of 8 miniature stallions. Stallions were assigned to a non-exercised (Non-Ex; control; n = 4) or exercised (Ex; n = 4) group. A motorized equine exerciser was used to work stallions 30 min/d for 4 d/wk during a 12-wk period from July–October. Temperatures (SQST, SQNT, RCT, and AMBT) were recorded before exercise, immediately after intense exercise, and 1 and 2 h post-exercise. Humidity data was obtained later to determine THI. Data were not normally distributed; therefore, a Spearman′s Rank Order correlation analysis was used. No deleterious effects were observed from implantation of thermal sensory microchips. Subcutaneous scrotal and RCT showed the highest correlation (R = 0.761). Scrotal temperature was also correlated to SQNT, AMBT, and THI (P < 0.0001) (Table 1). Thermal sensory microchips are a safe and effective way to measure SQST to monitor testicular heat stress.