Biomedical Engineering Reference
In-Depth Information
Detailed descriptions of pregnancy, pregnancy
management, and lactation are provided in the main
sections “Basic reproductive biology” and “Housing,
husbandry, and population management for breeding.”
Species of macaques vary in the seasonality of their
breeding seasons. Pigtailed macaques (Macaca nemistrina)
and cynomolgus macaques (Macaca fasicularis) are not
known to show any seasonality and can conceive
throughout the year (
Ha et al., 2000a,b
). However, rhesus
macaques (Macaca mulatta) and Japanese macaques
(Macaca fuscata) show distinct seasonality with regard to
breeding. The breeding season for rhesus colonies in North
America is most commonly between October and February
(
Eaton et al., 1981; Ehardt and Bernstein, 1986
). Although
rhesus macaques do not typically ovulate outside these
months, they will continue to have menstrual cycles that
may be more irregular than during the breeding months. As
females age, they may cease to menstruate altogether
during the nonbreeding months. See the section “Repro-
ductive senescence” above for more details on reproductive
aging. Throughout the breeding season, the number of
ovulations varies for each individual rhesus female and has
been shown to be directly related to the female's body
weight, social rank, and mean luteal progesterone level
(
Takahata, 1980; Garcia et al. 2009, 2010; Du et al., 2010
).
In captivity, female macaques generally reach puberty
between 2 and 4 years of age and will deliver their first
offspring on average a year later. The menstrual cycle of
macaques is generally 26
e
30 days (
Blakley et al., 1981;
Walker et al., 1983
). Outward indications of ovarian
activity such as changes in sexual behavior, perianal
swelling, and alterations in inguinal and facial sex skin
coloration may aid in assessing the stage of the cycle
depending on the species involved (
Carpenter, 1942; Zinner
et al., 2004; Engelhardt et al., 2005; Bradley and Mundy,
2008; Dubuc et al., 2009
) Pubertal macaques also may have
large variations in their intermenstrual cycles (
Resko et al.,
1982
). Male macaques generally reach puberty at 3.5 years
of age; however, they normally do not contribute signifi-
cantly to breeding until 2 years later (
Chambers et al., 1982;
Honjo et al., 1984
). The age at which individual animals
reach sexual maturity is governed by various factors, of
which the animal's nutritional status and the social ranking
of its dam are thought to be most important.
The gestational period in macaques is generally
165
e
170 days. Most pregnancies result in the delivery of
one fetus; the incidence of twinning is very uncommon
(
Bercovitch et al., 2002; Sugiyama et al., 2011
). Normally,
infants are delivered at night and the female consumes the
placenta. Labor is reported to last 5
e
7 hours, and prior to
delivery, the female may show signs such as increased
grooming, restlessness, and alteration in eating and
sleeping patterns (
Goodlin and Sackett, 1983
). In addition,
there may be a decrease in the female's body temperature
prior to parturition (
Ruppenthal and Goodlin, 1982
).
Complications such as dystocia have been reported in many
macaque species and have been associated with the age and
parity of the dam along with the percentage of the dam's
previous pregnancies that resulted in caesarean section
deliveries (
Stockinger et al., 2011
). Unfortunately, cases of
dystocia may be difficult to detect, as most animals give
birth at night when staff are not usually present to observe
the births. Indications of dystocia include infants with
facial bruising or edema, presence of protruding limbs at
the vaginal orifice, and weakness or collapse of the dam. In
instances where there are clinical indications that the
delivery has been unsuccessful, medical intervention must
be taken immediately in order to save the life of the dam
and fetus. Treatments may vary from manual extraction of
the fetus and placenta if it is lodged in the vaginal canal to
delivery of the fetus by caesarean section. Should ultra-
sound examination indicate that the fetus is no longer
viable, it may be prudent to initiate fluid therapy and
supportive care to stabilize the dam prior to performing
surgery.
Additional complications associated with parturition in
macaque colonies include neonatal abandonment by
mothers. Retrospective analysis of reproductive perfor-
mance in a captive colony of Japanese macaques suggested
that the most important factor involved in abandonment
was parity of the dam followed by her social rank. In this
study, neonates were 90 times more likely to be abandoned
by a primaparous than by a multiparous mother. Also,
abandonment was six times more likely to occur by a low-
ranking female than by a high-ranking female (
Schino and
Troisi, 2005
). A correlation between the age of the dam and
the incidence of an infant dying before 30 days of age has
also been demonstrated. The incidence of death was found
to be higher for offspring born to either primaparous or
aged females (
Gagliardi et al., 2007; Schino and Troisi,
2005
). Studies have also examined the relationship between
the body condition of a primaparous female at time of first
conception and the time required to recover from preg-
nancy and lactation and also the effect on the postnatal
development of the infant. Results from work carried out at
the Caribbean Primate Center imply that the body condition
of the female at first conception directly correlates with the
growth and development of her infant and also with the
time needed to recover reproductive capabilities post-
partum (
Mas-Rivera and Bercovitch, 2008
). Females with
higher body mass index (BMI) prior to conception had
a more rapid recovery after parturition.
In recent years an increased emphasis has been placed
on studying the role that physiological factors may play in
the relationship between dams and their offspring, the
reproductive success of the dams, and the temperament and
success of the offspring. Studies have suggested that
glucocorticoids in breast milk and biogenic amines may
