Biomedical Engineering Reference
In-Depth Information
of making clinical assessments. However, in contrast to
corral breeding, production of macaques in harem groups
can result in decreased genetic diversity of offspring
produced and lower production rates. A strong veterinary
and animal care program is central to the production of SPF
macaques, and its importance should not be under-
estimated. Training programs for all personnel who have
contact with the animals should include discussion of the
routes of pathogen transmission, zoonotic potential of
pathogens, and use of personal protective equipment. In
addition, the importance of prompt reporting of clinical
problems is essential to prevent disease outbreaks in the
colony. Computerized medical, pathology, and demo-
graphic databases should be considered essential in colony
management to aid in the identification of disease trends
and housing, breeding, and pedigree data.
(
Hendrickx, 1967; Hendrickx and Kraemer, 1969; Pauer-
stein et al., 1978; Stevens, 1997; Chen et al., 1998
).
Cycle reading has been used to produce timed preg-
nancies in baboons for years at the facility with the world's
largest captive baboon breeding program, the Southwest
National Primate Research Center (SNPRC), Southwest
Foundation for Biomedical Research. Reading the baboon
cycle three times per week (usually Monday, Wednesday,
and Friday) produced accurate predictions of conception
within 2 days. Detection of pregnancy is best confirmed
indirectly by lack of sex skin swelling. Therefore, it is
possible to predict a pregnancy as early as 15 days (if the
cycle length is known and regular). The pregnancy can be
confirmed with ultrasound, which requires sedation but
does not require manual palpation of the uterus, which
might predispose to pregnancy loss. Ultrasound confirma-
tion of pregnancy is also appealing since the result is
instantly visible whereas chemical confirmation from
a blood or urine sample further delays the answer.
The baboon gestation period is about 6 months
(
Sunderland et al., 2008
) and most baboons deliver at
around 185 days' gestation. Pregnancy loss is most likely
in the first 90 days. Viable offspring that do not need
supportive care have been born as early as 155 days'
gestation. Pregnancies may extend 2 weeks past the due
date with no adverse events. Breech presentations are
occasionally observed but successful deliveries have been
accomplished with manual turning of fetus.
Baboons have a single discoid placenta similar to that of
humans. This anatomical similarity to humans is important
when measuring maternal-infant placental transfer.
Shearer
et al. (1995)
have demonstrated that baboons, like humans
and unlike macaques, have four IgG subclasses (IgG 1, 2, 3,
and 4). Maternal immunity is transferred to the fetus
through IgG subclasses so this trait is important in an
animal model used to test the efficacy of human vaccine
regimens designed to enhance placental transfer of
maternal antibodies to the fetus (
Ha et al., 2000a,b
).
Most baboon babies are born at night (
Sunderland et al.,
2008
), regardless of whether they are group or singly
housed. In most cases, the placenta is consumed immedi-
ately after delivery. Baboons generally continue to lactate
as long as the infant nurses. Success with surrogate mothers
has been limited (K.S. Rice, personal observation).
Baboons continue to cycle regularly for at least 15
years and usually well into their mid twenties. Docu-
mentation of a female baboon reaching menopause
(6 months acyclic with no vaginal bleeding) before the late
twenties or early thirties is rare (
Chen et al., 1998; Honore
and Tardif, 2009
).
Male baboons attain puberty, as determined by testic-
ular enlargement, between 5 and 6 years of age (
Beehner
et al., 2009
). Generally, males are not selected as breeders
until they are at least 6 or preferably 8 years old because to
Baboons
Baboons breed continuously throughout the year, which is
a major advantage when research protocols depend on
a regular, consistent supply of pregnancies or newborn
infants. The prominent perineal skin of the female baboon
enables reliable and inexpensive daily visual assessment of
ovarian function status and of pregnancy, which is valuable
for
reproductive
research
and
breeding
colony
management.
Female baboons in captivity generally reach puberty
between 3 and 4 years of age (as determined by observation
of the menstrual cycle). Females have a regular menstrual
cycle that is physically visible by the size and appearance
of skin in the perineal area, commonly called the “sex skin”
in nonhuman primates. The sex skin swells and shrinks
according to reproductive hormone levels. In an unpub-
lished study of 32 juvenile females, cycles were read
starting at 3 years of age, using the scoring system of
Hendrickx and Kraemer (1969)
. The average age of cycle
commencement was 3.6 years (K.S. Rice, unpublished
observations).
The average menstrual cycle length in baboons is 33
days, with follicular and luteal phases, just as in humans.
The correlation between sex skin turgescence and ovulation
has been well documented (see the section “Detection of
ovarian cycle phase” below) so that determining the onset
of the menstrual cycle in puberty, producing timed preg-
nancies in group-caged baboons, and identifying cycle
irregularities in the perimenopausal period are both feasible
and economical.
Endometriosis develops spontaneously in baboons, as in
humans. Although endometriosis is undesirable in
a breeding colony because it affects fecundity, the existence
of this condition in baboons demonstrates their physio-
logical similarity to humans and is thus a useful model for
testing agents meant
to inhibit endometrial growths
