Effect of experimentally induced fever on mammary blood flow in lactating goats.

The effect of artificially induced fever on normal mammary blood flow (MBF) was studied in conscious lactating goats in a thermoneutral environment. Fever was induced either by intravenous (i.v.) injection of LPS or by intracerebroventricular (i.c.v.) infusion of PGE2. The increment stage of fever was always accompanied by a fall in MBF, shivers and miosis. There was a positive correlation between the intensity of temperature increase and MBF decrease. Once fever was established or during the decrement stage of fever, MBF returned to control levels and often increased far above pre-injection values. These specific circulatory changes observed in the lactating udder of the goat might contribute to the genesis and lysis of fever. MBF might play an important role in the pathogenesis of fever in the lactating goat. The effect of centrally induced fever was studied on the biphasic MBF pattern normally occurring during experimentally induced LPS mastitis. PGE2 was infused i.c.v. practically simultaneously with the intramammary administration of LPS. In most experiments fever occurred earlier than during control mastitis. The biphasic MBF-curve was strongly altered, MBF peak I being inhibited. Fever increment during control mastitis could be one of the factors limiting the duration of MBF peak I and fever decrement could induce peak II.