Response of Pre-pubertally Castrated Rams and Ewes to Artificial PhotoperiodChanges in Plasma LH and Prolactin

Abstract

Castrate rams and ovariectomized ewes were maintained in the presence of entire rams and ewes and subjected to successive periods of alternating 6 h light: 18 h darkness ('short' days) and 18 h light: 6 h darkness ('long' days) preceeded by a period of 12 h light: 12 h darkness ('constant' light days). Plasma concentrations of LH and prolactin were measured in the castrate animals in order to determine how LH and prolactin secretion responded to (i) the artificial light regime and (ii) corresponding periods of elevated or depressed testicular and ovarian activity in the entire rams and ewes.