Prolapse of the oviduct is a common problem which results in 5% mortality of
female male-line breeding turkeys that have been selected for high meat yield.
Prolapse is rare in unselected traditional-line turkeys. Male-line turkeys are
characterised by large multiple ovulating ovaries compared to traditional-line
It was proposed that the large ovary of the male-line resulted in a high plasma
oestradiol concentration, which stimulated collagen degradation in the oviduct,
impairing the structural integrity of the oviduct and predisposing the male-line to
There was no disproportion in growth of the oviduct, ovary, uterus, vagina, sphincter
ani muscle or muscular cord of ventral ligament in the male-line compared to the
traditional-line. Histological investigation of the uterus, vagina, sphincter ani muscle
and muscular cord of ventral ligament from traditional-, male-line and prolapsed
male-line turkeys revealed no abnormalities that could be associated with prolapse.
The male-line had a lower vaginal collagen content than the traditional-line, while
male-line turkeys with prolapse had an even lower vaginal collagen content. No
differences were seen in the collagen content of the uterus between the different
groups. It was concluded that reduced vaginal collagen in the male-line impaired the
structural integrity of the vagina and predisposed the strain to prolapse.
The collagen of the prolapsed turkeys had fewer mature cross-links than the collagen
of the non-prolapsed turkeys that would substantially reduce the strength of the
tissue. This suggested that there may be increased collagen turnover in the prolapsed
The male-line had a lower plasma oestradiol concentration than the traditional-line,
and there was no significant difference in plasma progesterone concentration
between the two strains.
Administration of oestradiol increased plasma oestradiol concentrations but had no
effect on the vaginal collagen content in either strain. Progesterone administration
also had no effect on vaginal collagen content in either strain although plasma
progesterone was raised.
Ovulatory cycle changes in plasma concentrations of oestradiol, progesterone and
luteinizing hormone in traditional and male-line turkeys were compared. It was
concluded that male-line turkeys did not have higher concentrations of oestradiol or
progesterone at any time during the ovulatory cycle.
Incubation of ovarian follicles from traditional- and male-line turkeys to measure the
output of progesterone and oestradiol demonstrated that the multiple follicular
hierarchy of the male-line had a physiological and anatomical basis. Oestradiol
output was lower from male-line follicles compared to those from the traditionalline, even in the presence of luteinizing hormone. This was consistent with the lower
plasma oestradiol concentration of the male-line. Aromatase activity was also lower
in small follicles from the male-line than the traditional-line. The results suggest that
ovarian steroidogenesis is reduced in male-line turkeys.
Food restriction of male-line turkeys to reduce body weight at sexual maturity to 0.6
of ad libitum fed controls inhibited the onset of lay, but had no effect on the multiple
hierarchy, plasma oestradiol concentration or the vaginal collagen content of those in
lay. Delaying photostimulation of male-line turkeys by 5 weeks also had no effect on
the multiple hierarchy, plasma oestradiol concentration or vaginal collagen content
It was concluded that prolapse in male-line turkeys was associated with low vaginal
collagen and that this was not caused by high plasma concentrations of oestradiol.