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Testicular temperature must be below body temperature for normal spermatogenesis in bulls. Infrared thermography provides a non‐invasive, non‐contact imaging technique to determine normal and abnormal thermal patterns in bulls and other animals [5]. Thermography utilizes sensitive infrared imaging to produce a color photograph that portrays variations in surface temperature that reflect the temperature of tissues immediately beneath the skin. The normal thermogram of the scrotum in all species is a left and right symmetric pattern with a constant decrease in temperature gradient from the base to the apex (Figure 18.3). In bulls a temperature gradient of 4–6 °C from base to apex is considered normal. A gradual decrease from base to apex with concentric color bands is consistent with normal function of the vascular counter‐current heat‐exchange mechanism of the testes. An excessively cool or excessively warm area as evidenced by thermographic color is consistent with testicular disease or injury [6, 7] (Figure 18.4).

Figure 18.3 Normal thermographic pattern of bull scrotum.

Figure 18.4 Thermograph of scrotum of bull with unilateral pathology. Note decreased temperature on left side of scrotum.