Clinical Biochemistry of Domestic Animals (Sixth Edition) - UMK ...

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Chapter | 21 Clinical Reproductive Endocrinology
immunoassay technique for plasma progesterone an accuracy
of 100% to diagnose pregnancy in samples taken
between days 15 to 16 from a flock of 130 ewes (107
diagnosed pregnant and 24 diagnosed nonpregnant) was
reported (McPhee and Tiberghen, 1987).
A relatively marked increase in progesterone values
from 2 to 4 ng/ml (6 to 13 nmol/liter) to 12 to 20 ng/ml (38 to
64 nmol/liter) occurs between days 60 and 125 of pregnancy
(Stabenfeldt et al. , 1972 ). This increase is due to increased
progesterone production from the fetoplacental unit. The
contribution of the CL to progesterone concentrations
remains constant throughout pregnancy, thus the relatively
large difference in progesterone concentrations between
nonpregnant ewes with a CL present and ewes with fetus(es)
present could be used to minimize the relatively high falsepositive
forecasts observed for sheep at 17 days postbreeding.
The limitations are the same for the use of progesterone
analysis as a pregnancy test in sheep as discussed for cattle.
2 . Estrone Sulfate
In the pregnant ewe estrone sulfate produced from the
fetoplacental unit is detected in elevated concentrations
beginning at around day 70 after conception ( Tsang, 1978 )
( Fig. 21-6 ). Worsfold et al. (1986) determined estrone
sulfate concentrations in blood from ewes bred 85 days
previously and found the accuracy of the nonpregnant
versus pregnant interpretations was 44% and 88%, respectively.
A considerable overlap in estrone sulfate values
between ewes with single and multiple fetuses was found
and even at day 116 of pregnancy, estrone sulfate concentrations
overlapped between groups of ewes with single
and multiple fetuses. Because of this the authors conclude
that estrone sulfate concentrations could not be used as a
predictive tool for litter size ( Fletcher and Worsfold, 1988 ).
3 . Other Substances
Circulating pregnancy-associated glycoprotein 1 (ovPAG-1)
has been reported in sheep. A heat labile protein with a
molecular weight of around 8000 was found in sera of
sheep as early as day 6 of gestation ( Cerini et al. , 1976 ).
It has been demonstrated that the bovine pregnancyspecific
protein B (bPSPB) assay can be used for early detection
of pregnancy also in the ewe, as pregnant ewes have
a blood antigen that cross-reacts with antibodies to bPSPB
(ovPSPB, Ruder et al. , 1988 ). In a study comparing the
accuracy of detecting pregnancy with an ultrasonic device,
a real-time scanning instrument and a RIA for bPSPB in
ewes, it was concluded that the RIA for bPSPB detected
pregnancy earlier and more accurately than the ultrasonic
device and equally accurate as the real-time scanning
instrument ( Ruder et al. , 1988 ).
Ovine placental lactogen (oPL) has been demonstrated
in the peripheral blood of pregnant ewes ( Kelly et al. ,
1974 ). Increase in maternal oPL concentrations occurs
between 40 and 50 days of pregnancy, reaches maximum
concentrations between days 120 and 140, and declines as
parturition approaches ( Chan et al. , 1978 ). The determination
of oPL concentrations might be used as a basis for a
specific pregnancy test in the ewe.
C . Pig
1 . Progesterone
Luteal phase progesterone concentrations in the pig are
considerably higher than in cattle and sheep, namely, 20 to
50 ng/ml (64 to 159 nmol/liter), whereas concentrations at
estrus are below 0.5 ng/ml ( 1.6 nmol/liter) ( Stabenfeldt
et al. , 1969a ). The difference in progesterone values
between nonpregnant and pregnant animals 19 to 24 days
after service has been used as an early pregnancy test
( Robertson and Sarda, 1971 ). In the pig, progesterone
determination is usually performed on blood. Because of
the sensitivity of the assay systems and the concentration of
progesterone in blood in pigs during the luteal phase, analyses
can be performed on a small volume of blood (about
10 drops), allowing the sample to be obtained through a
small incision in an ear vein. The limitations associated
with using progesterone determinations as a pregnancy
test in the pig are similar to those previously discussed
for cattle. Progesterone analyses can be used to determine
ovarian activity in clinically anestrus gilts as well as to
establish the stage of the estrus cycle in gilts and subsequent
response to treatment. It is also possible to monitor
luteal phase activity in the sow through measurement
of fecal gestagens ( Hultén et al. , 1995 ; Moriyoshi et al. ,
1997 ).
2 . Estrone Sulfate
Previous studies of estrogen concentrations in urine revealed
a marked increase in estrogen between day 20 and 30 of
pregnancy in pigs ( Velle, 1958 ). Studies of blood concentrations
of estrone sulfate in pigs during pregnancy showed
patterns similar to those determined in urine ( Robertson
and King, 1974 ) ( Fig. 21-6 ). In early pregnancy in the
pig, it has been hypothesized that estrogen synthesized by
the early preimplantation embryo may be the messenger
for the maternal recognition of pregnancy ( Perry et al. ,
1976 ) and that the elevated estrone sulfate concentrations
in the maternal circulation during early pregnancy reflect
fetal synthesis. The determination of estrone sulfate in
early pregnancy in the pig is thus a specific pregnancy test
(Cunningham et al. , 1983 ). The index of discrimination
between estrone sulfate concentrations in blood of pregnant
versus nonpregnant pigs around 25 days after breeding is
very high as concerns pregnancy diagnosis. Sugiyama et al.
(1986) reported an accuracy rate of 98% in pigs between