luteolysis till the first observed oestrous symptoms was 56 and 60 h in one female and Ž
. Ž
69 h in another. The average duration of standing behaviour oestrus was 27 h range: .
24–30 h . General interest in the observer, and lifting of the tail in response to touching the perineal regionrvulva, were seen for a somewhat longer period, usually 3–6 h prior
to and after the standing behaviour. No vaginal discharge or swelling of the vulva was observed during oestrus.
4. Pregnancy
The gestation period in reindeer and caribou is reported to be approximately 225–235 Ž
. days
Skjenneberg and Slagsvold, 1968; Bergerud, 1975; unpublished results .The reproductive endocrinology of pregnancy is poorly investigated. Only a few animals
have been blood-sampled repeatedly throughout pregnancy, and detailed individual hormone profiles for hormones other than progesterone are not available. Progesterone
concentrations show great variation during pregnancy, both within and between animals ŽMcEwan and Whitehead, 1980; Rehbinder et al., 1981; Blom et al., 1983, Ropstad et
. al., 1999 . Generally there is an increase from conception until around 1–3 months of
pregnancy after which the concentration stabilises or a slight decrease is seen. Prior to parturition a further increase in progesterone takes place. Progesterone detected during
early pregnancy is probably secreted by the corpus luteum. However, during later pregnancy progesterone secretion most likely occurs both in the ovaries and the
Ž .
foeto-placental unit Sjaastad et al., 1990 . 4.1. Pregnancy diagnosis
For use in population studies measurement of plasma progesterone and pregnancy Ž
. specific proteins PSPB has proven efficient for pregnancy diagnosis when performed
Ž .
in January or later in pregnancy Russell et al., 1998; Ropstad et al., 1999 . Although reindeer are seasonally polyoestrous, it is unlikely that a large proportion of high
progesterone concentrations at this stage originate from corpora lutea of the oestrous Ž
. cycle Ropstad et al., 1999 . In early stages of pregnancy, progesterone has proven
Ž .
superior to PSPB in pregnancy diagnosis Russell et al., 1998 . Preliminary results indicate that rectal ultrasound investigation can be useful for early pregnancy diagnosis.
When rectal ultrasound was performed in later stages of pregnancy the agreement with progesterone was good for positive diagnoses but not for negative diagnoses. This
probably reflects a high rate of false negative diagnoses by the ultrasound method rather
Ž .
than false positives in the progesterone analysis Ropstad et al., 1999 . 4.2. Cloprostenol treatment during pregnancy
In other cattle, prostaglandin can be used to cause luteolysis and induce abortion, and Ž
. have been used to control pregnancy in extensive production systems Roche, 1976 .
It is questionable, however, whether the use of cloprostenol can be a useful method Ž
for induction of abortion in pregnant reindeer Ropstad and Lenvik, 1991; Ropstad et al.,
. 1996b . Treatment may be unreliable and can cause undesirable side effects. Preliminary
data indicate that resumption of cyclic ovarian activity after induced abortion by Ž
. cloprostenol is not common Ropstad et al., 1996a; Ropstad, 1998 .
5. Factors affecting reproduction
