Effect of Sexual Experience, Location, Malnutrition, and Repeated Sampling on Concentrations of Testosterone in Blood Plasma of Gallus domesticus Roosters

Abstract

Five studies were conducted with mature White Leghorn roosters to study variables associated with concentrations of testosterone in blood sampled from a wing vein. Testosterone in blood plasma was unchanged 15, 30, or 45 min after collection of semen artificially whether or not roosters were trained for collection of semen. Likewise, cohabitation with hens for 7 to 8 hr was without effect. However, trained roosters had higher (P less than .05) plasma testosterone concentrations after 7 to 8 hr in a new location than untrained roosters. Furthermore, both groups in the new location had higher testosterone concentrations than the controls not translocated. Plasma testosterone was decreased (P less than .01) about 50% within 2 weeks by feeding a diet low in crude protein (2%) which decreased feed intake 33% and caused weight loss; those fed 12% crude proteins were unchanged. Variations in concentrations of testosterone among sequential samples of blood collected at 45 min intervals for 3 hr indicated random pulsatile releases of testosterone as reported for mammals. Sequential sampling at 15 min intervals for 1 to 2 hr revealed that the testosterone increases (up to 10 ng/ml) lasted for about 1 hr and that the returns to basal concentrations required about 1 to 1.5 hr. The interval between pulsatile releases may be as long as 3 hr in some roosters. These results indicate that roosters have spontaneous and pulsatile releases of testosterone as expected, because roosters release luteinizing hormone episodically during both light and dark cycles of the day.