Original article
Changes in plasma testosterone, thyroxine
and triiodothyronine in relation to sperm production
and remex moult in domestic ganders
M Zeman
J
Košutzký
&jadnr; Mi&jadnr;ek
A
Lengyel
1
Slovak Academy of Sciences, Institute of Animal Physiology, 900 28 Ivanka pri Dunaji;
2
Poultry Research and Production Institute,
900 28 Ivanka pri Dunaji, Czechoslovakia
(Received 28 November 1989; accepted 31 May 1990)
Summary ― Changes
in plasma testosterone (T), thyroxine (T
), triiodothyronine (T
4
), semen out3
moult were studied in domestic ganders. A bimodal pattern in both plasma T and
sperm concentration was observed during the annual cycle. Ganders started to produce semen at
the end of January; maximum semen volume (0.32 ± 0.04 ml) and sperm concentration (148 ± 38 x
)
/mm were reached in March and a marked decrease was observed after mid-April, when the
10
3
moult of the remiges began. Plasma T
3
levels peaked in February (9.7 ± 0.6 nmol·I-! ) and this peak
coincided with maximum T concentrations (9.8-10.4 nmoi’i!).). Elevated levels of T
4 were found from
late February until mid-April (31.0-33.6 nmol·I-!). Plasma T concentration was low at all stages of
remex moult and regrowth. Decreased T
4 levels were found in ganders during remex regrowth from
the &dquo;brush&dquo; to half of the full primary growth stage. Higher plasma T
4 levels were found before and
after this stage of the moult. A reverse pattern was observed for T
3 concentrations.
put and
remex
testosterone / thyroxine / sperm concentration / semen volume / moult /
gander
Résumé ― Testostérone, thyroxine et triiodothyronine plasmatiques en relation avec la production spermatique et la mue chez le jars domestique. Les changements de concentration plasmatique de testostérone (T), de thyroxine (T
) et de triiodothyronine (T! ainsi que la production de
4
spermatozoïdes et la mue des rémiges ont été étudiés chez le jars domestique. La sécrétion de T et
la concentration des éjaculats en spermatozoïdes présente un profil bimodal au cours de l’année.
Les premiers spermatozoïdes sont observés à la fin du mois de janvier, leur production est maximale en mars (57 ± 17 x 10
/éjaculat) puis diminue en avril au moment où les rémiges commencent
6
à tomber. La concentration de T
3 est maximale (9,7 ± 0,6 nmolll) en même temps que celle de T
(9,8 ± 10,4 nmol/1). La concentration en T
4 augmente de la fin février à la mi-avril (31-34 nmoili). Les
concentrations plasmatiques de T sont faibles pendant la mue des rémiges; celles de T
4 passent par
un minimum aux stades 4-5 de la mue et présentent un profil inverse de celui des concentrations
plasmatiques de T
.
3
testostérone / thyroxine / concentration spermatique / mue /
*
Correspondence and reprints
jars
INTRODUCTION
The domestic goose shows the seasonal
pattern of reproductive activity which its
wild ancestor, the Graylag goose (Anser
anser) evolved in adapting to seasonal
changes of environmental conditions. This
reproductive strategy is convenient in the
traditional extensive breeding conditions
characterized by natural incubation of
eggs and parental care. However, the introduction of large-scale goose production
requires the artificial incubation of eggs
and a substantial increase of reproductive
performance, particularly an extension of
the reproductive period in the annual cycle. Endocrine mechanisms control the development of reproductive capacity, and
their study seems to be important in improving the reproductive performance in
this species of waterfowl.
In many avian
species of
mid and
high
latitudes, day length is the major environmental trigger in the initiation and synchronization of annual reproductive cycles.
Increasing day length in the spring induces
acceleration of gonadotropin secretion,
and this precedes and stimulates vernal increase in the gonadal activity of birds (Farner and Gwinner, 1980; Farner and Wingfield, 1980). Reproductive activity is
terminated by the development of long-day
refractoriness which results in an inhibition
of gonadotropin-releasing hormone synthesis and gonadal regression under long
photoperiod (Nicholls et al, 1988). The
mechanisms involved in the development
of long day refractoriness are still unclear
but the role of interactions between seasonally elevated sex hormones and thyroid
hormones, and between gonadotropins
and prolactin have been suggested (Assenmacher and Jallageas, 1980; Follett
and Nicholls, 1984; Nicholls et al, 1988;
Dawson, 1989). Geese are the only species of poultry regularly used in breeding
for several seasons. A study of endocrine
control of seasonal breeding could improve
their management and the benefits of their
breeding. However, such studies are rare
in geese (Kosutzky et al, 1982; Lazar,
1983; Peczely et al, 1985; Zeman et al,
1987) and most data about the endocrine
control of reproduction in waterfowl come
from studies on ducks (Jallageas and Assenmacher, 1974; Paulke and Haase,
1978). The objective of this study was to
establish the relationship between changes in semen production and plasma testosterone concentration and to evaluate the
relationships among semen output, primary remex moult and plasma concentrations of testosterone (T), thyroxine (T
) and
4
triiodothyronine (T
) in ganders.
3
MATERIALS AND METHODS
Ganders of a parent line of broiler breeder
geese Ivages were used. They were hatched in
March and studied in the following year, ie in
both trials during their first reproductive season.
The birds were housed in groups of 10 in pens
with a slatted floor (2.5 x 2 m) and an open concrete yard (2 x 3 m) supplied with a trough containing running water (2 x 1.5 m). A complete
goose feed (18.2% crude protein and 10.46 MJ
metabolizable energy/kg) was provided.
Experiment I
were exposed from 15 October
to 20 December to a short photoperiod of 8 h of
light and 16 h of darkness (LD 8:16) and restricted feed intake (180 g of feed per gander per d).
From 20 December the feed was provided ad
Thirty ganders
libitum and
day length
was
increased
gradually
by artificial light (incandescent 100 W bulbs providing a light intensity of 10-50 lx at the level of
the birds’ heads) to a regime of LD 12:12 at the
end of January. This light-dark cycle was held
until 21 March and then the
ganders
were ex-
posed to naturally increasing day length (47°
N, 17° 13’ E).
18’
Blood and
samples were taken at
the first 10 days of each
month at the same time of day (between 8.0010.00 h). The semen was collected by dorsosemen
monthly intervals in
abdominal massage. Semen volume was deter1 g) by weighing (Wilmined indirectly (1 ml
liams and de Reviers, 1981) and sperm concentration by a haemocytometer. Blood was taken
from the wing vein immediately (within 1 min) after semen collection because this treatment did
not significantly affect plasma testosterone concentration (Zeman, unpublished results). Heparinized blood was centrifuged at 2 500 g for
10 min; the plasma was removed and stored at
- 20 °C until assayed for testosterone.
=
Experiment II
Another 30 ganders were kept during the next
year under the same management conditions as
trial I, only the short photoperiod LD 8:16 lasted
from 15 November to 10 January. Blood and semen were collected more frequently (2-3
weeks) during the reproductive season (Janu-
ary-June) in the same
manner as in Experiment
1. The semen volume and sperm concentration
were determined.
The concentrations of hormones were
measured by radioimmunoassay. Thyroxine and
triiodothyronine were estimated from unextracted plasma using commercial RIA-kits (Institute
of Radioecology and Nuclear Technology Application, Kosice, Czechoslovakia). Testosterone
was determined by direct RIA with 125
1 tracer
(Zeman et al, 1986). Standards in all 3 methods
were made up in gander’s plasma from which
endogenous steroids and thyroid hormones
were removed (Abraham, 1977).
At the end of the reproductive season the
moult and the replacement of primary remiges
were recorded according to Herremans (1986).
A 10-step scale was used for the determination
of the stages of remex moult in which 0 old (1
week before a drop), 1
dropped, 2 pin, 3
tenths of the full-grown
brush, and 4-10
length. Under this system, each bird was individually examined at 2-3-d intervals and a moult
score of 1-10 was given for the 1st, 5th and
10th primaries. The global score was a mean
from these 3 primaries. In most cases all primaries were in the same stage of moult, as is usual
in Anseriformes.
=
=
=
=
=
Experimental values were analyzed by 2-way
analysis of variance as a randomized complete
block design (Sokal and Rohlf, 1969) with the
ages at the respective stages of feather moult
as
the fixed treatment effects and the individuals
constituting the randomly chosen blocks. Levels
of significance were determined by Duncan’s
multiple range test.
RESULTS
Experiment I
A bimodal pattern of plasma testosterone
concentration was found in ganders submitted to a modified light regime during the
annual cycle (fig 1High plasma T levels
were determined in December and January. Thereafter the concentration decreased dramatically and low levels were
found from March to July. The second an-
nual peak of concentration of this androgen was observed during August and September, while low levels were recorded in
October and November.
Sperm concentration also showed a bimodal pattern during the annual cycle of
ganders. Spermatozoa were found at first
in January and maximum sperm concentration was determined at the beginning of
April. After this peak, sperm concentration
decreased and no spermatozoa were
found in July and August. A second, autumnal, reproductive period lasted from
September to November and the peak of
sperm concentration was found in October. The changes in testosterone levels
preceded those in sperm production by
about 2-3 months.
Experiment //
Concentrations of plasma T were low in
December and maximum concentrations
were found in January and mid-February
(fig 2). Thereafter, concentrations decreased (P < 0.05) and minimal levels
were found in mid-May. The increase in
plasma T was followed by a rise in plasma
3 levels (fig 2) with maximum values at
T
the beginning of February. Plasma T
4 increased from February to mid-March and
high until May. The decrease of plastestosterone concentration and the increase in the 4
T levels preceded a drop in
semen quality and primary moult. The
marked decline in semen volume and
was
ma
sperm concentration was accompanied by
the onset of primary moult in a group of
ganders (fig 3). Individual birds ceased to
produce semen a week before the primaries were dropped. The sequence of remex
moult was ascendant (from the apex of the
wing towards the body) and the primaries
dropped from both wings almost simultaneously in 1-2 d, even though some vari-
ability in the temporal pattern of
moult
remex
observed. The moult and replacement of remiges lasted approximately
6-7 wk. During this period the ganders did
not produce spermatozoa and their copulatory organs had regressed. The moult of
contour-feathers occurred earlier than that
of the primaries; however, it was not evaluated in detail.
was
A more precise relationship between
hormone levels and primary moult was
found when the hormone concentrations
(from periodical samplings) were arranged
according to the actual stages of the primary moult and regrowth (fig 4). Plasma
testosterone concentrations were low in all
sets (< 3 nmol/1), ie from ganders 1 week
before the primary moult to ganders with
fully-renewed primaries
DISCUSSION
The absolute levels and biphasic pattern of
plasma testosterone concentrations found
during the annual cycle in ganders correspond with our previous results (Košutzký
et al, 1982, 1984) and with those of Peczely et al (1985). These findings suggest the
existence of an inherent biphasic testicular
cycle profile in ganders, as already found
in extensive studies of hormonal changes
during the sexual cycle in drakes (Jallageas and Assenmacher, 1974; Balthazart
and Hendrick, 1976; Paulke and Haase,
with no significant
differences among these groups. Initial
stages of primary replacement (stages 37) were characterized by decreased plasma T
4 levels, but these increased again to
initial values during the final stages of primary growth. Low plasma T
3 levels were
found in ganders at the beginning and at
the termination of primary moult. Significantly (P < 0.01) increased T
3 levels were
measured in stages 3-7 of primary re-
The peak in plasma T concentration in
experimentI was already determined in
December, ie before the photoperiod was
artificially increased. Moreover, high testis
growth.
weight
1978).
was
found in
ganders kept
under
the
man
same
et
lighting regime
in
January (Ze-
al, 1987). Both these findings sug-
gest that the photoperiod LD 8:16 was sufficient for the development of gonads at
this phase of the gander’s annual cycle, as
found in some wild birds (Gwinner and
Ganshirt, 1982; Sharp et al, 1986b). Owing to less frequent blood sampling it is impossible to determine whether the T peak
in experiment II occurred before or after
the beginning of the day length increase.
Nevertheless, it was not found exactly at
the same time of year as in experiment I.
We suppose that sexual development is
initiated after termination of photorefractoriness. Applied photoperiod and other environmental conditions together with the age
of the birds, their previous life history and
nutrition determine the rate of subsequent
sexual development as well as the onset
and duration of the reproductive period.
Therefore, a variation in these factors may
account for differences in the exact timing
of the reproductive cycle in different years.
On the other hand, a modification of environmental conditions and nutrition may be
a way of controlling the temporal pattern of
the annual reproductive cycle in goose
farming.
The second peak in plasma T is accompanied by the second, autumnal, reproductive period in the annual reproductive cycle
of ganders and the second egg-laying period in geese (Grom, 1971; Lazar, 1983);
this is not observed in wild birds. The annual profile of testosterone differs partly
from that found under a natural photoperiod (Kosutzky et al, 1982; Péczely et al,
1985) by its peak amplitude and duration
of high plasma T levels. One of the reasons for a relatively short duration of high
peak levels could be the fact that the ganders were kept without females. High T
levels in males during the egg-laying stage
are stimulated by sexual behavior of females in some species of passerines
(Moore, 1982; Wingfield et al, 1989) and
ganders (Rosinski, 1989; personal
communication).
also in
Semen volume and sperm concentration were found to be highly variable and
their range corresponded with our previous
results (Zeman et al, 1985). There was a
phase-shift between annual rhythms in semen output and plasma T concentration.
Maximum sperm output was preceded by
maximum plasma T levels in both vernal
and autumnal reproductive periods. During
vernal reproductive season culmination
(March-April), plasma T levels represented
only 30-40% of the peak values determined in January and February. Mean testis weight in April represented approximately 50% and in May 20% of the
maximum testis weight found in February
(Zeman et al, 1987). These results show
that in spite of the decrease in plasma T
levels, viable spermatozoa were produced
by ganders for 3-4 months afterwards.
The high plasma T levels seem to correspond to behavioral activities occurring at
the beginning of the reproductive period in
water-fowl (aggressive behavior, formation
of pairs, territorial defense) rather than to
the process of spermiogenesis. The local
mechanisms in seminiferous tubules were
probably sufficient for maintaining the intratubular androgen concentrations essential
for normal spermatogenesis in mammals
(see Amann, 1983 for a review) and probably also in birds (Sharp et al, 1977) in
spite of low T levels in peripheral circulation.
Plasma T
4 levels in ganders
3 and T
nmol/I
and
22.1-36.4
nmol/I resp)
(2.7-9.7
were similar to those reported for other
species of Anseriformes (Jallageas
et al,
1978; John and George, 1978; Campbell
and Leatherland, 1980) and for immature
domestic geese (Lazar et al, 1981).The
role of the thyroid gland in the development of long day refractoriness (Dawson,
1984; Nicholls et al, 1984) and in the periodic
replacement of plumage in birds (see
Payne, 1972, for review) has been suggested. An involvement of sex and thyroid
hormones in the control of moult was established largely in studies using pharmacological doses of exogenous hormone administration (Payne, 1972). ,Moreover, significant correlations between spontaneous
changes in plasma sex and thyroid hormones and the feather moult were found in
Barheaded geese (Dittami and Hall, 1983)
and in laying hens (Herremans et al, 1988;
1989). In our experiment, the increase in
plasma T
4 levels was recorded from midFebruary to mid-March, ie during the period of a marked drop of plasma T levels,
and remained high throughout the breeding season. In mallards, plasma T
Q also
begins to increase after plasma T levels
fall (Haase and Paulke, 1980; Sharp et al,
1986a). Increased levels of plasma T
44
found during the breeding season are in
accordance with findings in Canadian
geese (John and Georg, 1978) and indicate an involvement of the thyroid gland in
the control of metabolic processes and
overall activity connected with reproduction. The peak in plasma T
3 may be associated rather with the low temperature prevailing during this period.
Because no clear relationship between
plasma levels of T, T
4 and remex moult
,T
3
was evident on a temporal basis, this relationship was analyzed by relating hormone
concentrations to individual stages of remex moult. By this approach low plasma T
levels were revealed at all stages of primary moult and regrowth. This finding corresponds with the classical antimoult role
of testosterone (Payne, 1972) and suggests that the decrease of circulating androgen levels is a prerequisite to the onset
of feather moult. This result physiologically
parallels the drops in progesterone, necessary to induce moulting in laying hens as
documented by Herremans et al (1988,
1989). The lowest T
4 levels were found in
ganders during the regrowth of primaries
(stages 3-7), when plasma T
3 levels were
increased. On the other hand, high plasma
T
4 levels and low T
3 concentrations were
found before the moult and again during
the final stages of primary replacement
(stages 8-10). This inverse relationship
clearly suggests that the rate of peripheral
conversion of T
4 to T
3 may be important
for feather growth.
ACKNOWLEDGMENTS
We thank E Decuypere and M Herremans for
valuable comments concerning the manuscript.
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Michal Zeman