THE UNIVERSITY OF MANITOBA STUDIES ON OVINE PLACINTAL ...

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vrhich continued to the tr4rentieth day of prêgnancy (Nist¡ender
et 41, 1968). Àt days 123-!28, no maternal blood LH was
detected (Foster et aL, L972).
(e) Follicle-StÍmulatjìg Hormone, FSH:
The only figures found for FSH in pregnancy
were those of Chamley et aI (1924). To the nearest inte¡¡er,
values were: day 42, 34 ng/mLi day 91, 72 ng/ml-¡ day 126,
59 ng/nJ,¡ day 147 (parturitÍon), 35 ng,/nl.
(f) Prolactin:
Leve1s in the blood of pregnant, e.rÀres ranged
between 20 and 80 nglml during the first 20 days. At 2 days
prepartum â sharp ¡jss bega¡,, reaching 400 ngrlml on the day
of parturition $rith wide but smaller flucÈuations for g
days (Davies et al, I97l-). comparable results showed 20_40
ng/nI up to 80 days, an increase from 50 to 1OO ng,/ml within
1-0 days of part.urition, and. a terminal peak of 100 ng,/m1
representing a mean for seven etrres (Kann et al , I9Z4).
(iii) Possible Mechanisms for Maintenance of Corpus Lutum
Function in Early pregnancy:
1. lt has been shov¡n that when embryos of ewes are transferred
to synchronous recipients at any tÍme up to day l2,pregnancy
can ensuei v¡hereas, when they are transferred after this time,
the corpus luteun is not maintained beyond day I5r(ie. the
time of IuÈeaL regression in the normal estrous cycle ) and
consequently r pregnâncy does not foLlor¡, (Ror4rson et aI , 19 6? ) .
Thus r^re can say that the maternal- organism recognizes t.he
presence of an embryo by, or before, day 12 and by this time