Prolactin Secretion and Ovarian Function in Cycling and Non-Cycling African Female Elephants (Loxodonta africana)

Abstract

Reproduction of captive elephants in zoos has shown a low fecundity and requires improvement. One of reasons of low fecundity is ovarian dysfunction in many female elephants. To investigate whether prolactin has correlation with ovarian function in female elephants, serum concentrations of prolactin, progesterone and estradiol-17β in four African female elephants (one cycling female and three non-cycling female elephants) were measured. Cyclic pattern of prolactin and estradiol-17β were observed in a cycling female elephant, which tended to high during the follicular phase and low during the luteal phase. On the other hands, cyclic pattern of prolactin was not observed in non-cycling female elephants. One out of three non-cycling females (Mako) had the developed breast and showed significantly higher average levels of prolactin than those of the other female elephants. These results suggested that high concentrations of circulating estradiol-17β during the follicular phase stimulated prolactin secretion. These results also suggested that hyperprolactinemia in Mako was one of the causes of developed mammary glands and ovarian dysfunction.