Thermal effects of reproductive hormones on the sheep udder

The thermal effect of reproductive hormones on the sheep udder was tested in five ewes at the end of their breeding season. Radiotelemetry was used to provide continuous recordings of deep body temperature (Tb), udder skin temperature (Tud), and back skin temperature (Tbk) while the animals were held in a controlled-environment isolation chamber. Injections of estradiol (1.0 and 2.5 mg, im) resulted in an increase in Tud, but not in Tb, and only occasionally in Tbk. The amplitude of the rise in Tud varied from 0.4 to 3.8 degrees C and the rise persisted over 48 h following injection. Injections of saline, prostaglandin (PGF2alpha), or progesterone did not affect Tud, and injections of pyrogen (typhoid vaccine) elicited only an insignificant change in Tud concurrent with substantial increases in Tb and Tbk.