Maataloustieteellinen A ikakauskirja
Vol. 60: 554—556, 1988

Plasma progesterone concentration during oestrus cycle and
pregnancy in Finnsheep and other prolific sheep breeds

B. REKLEWSKA, Z. J. TYSZKA and R. NIZNIKOWSKI
Warsaw Agricultural University
ul. Przejazd 4, 05-840 Brwinow, POLAND

Abstract. The aim of the study was to evaluate the relationship between the litter size and
plasma progesterone (PP) concentration during the breeding season and pregnancy in some
prolific sheep breeds. Investigations were performed duringtwo consecutive reproductive cycles.
PP concentrations were determined in Finnsheep (n = 16), Polish Heath (n = 13), Friesian
(n = 10), Zelazna (n = 12) and Karakul (n = 14). Prolificacy was 3.14, 2.0, 2.0, 1.8 and
1.12, resp. Highly significant differences in PP levels during pregnancy were found between
the prolific breeds and breed with the lowest litter size. There was also a significant effect of
pregnancy stage on the PP concentration. Breed differences in PP levels during the oestrus
cycle were the most pronounced on the 10th day of the cycle. However, due to a considerable
variation within breeds they were statistically insignificant.

Index words: Finnsheep, Polish Heath, Karakul, Friesian, Zelazna, prolificacy, plasma progesterone

Introduction

Among different attempts of analysing the
variation in the ovarian activity, Wheeler and
Land (4) contributed to the accumulated
knowledge with their investigations concern-
ing genetic variation in the ovulation rate and
its relation to the luteal function, while others
tried to find out differences in plasma
progesterone (PP) levels during pregnancy be-
tween ewes carrying single or twin foetuses (1,
2). However, it is still not clear whether there
is a possibility to predict the litter size (LS)
on the basis of PP concentration either dur-

ing oestrus cycle or during pregnancy. Thus,
the aim of the present study was to evaluate
the relationship between the LS and the PP
during oestrus cycle and pregnancy.

Material and methods

Investigations were performed at Zelazna
Experimental Farm of Warsaw Agricultural
University during two consecutive breeding
seasons. All the animals were kept in the same
flock. PP concentration was determined us-
ing the direct RIA method (3). Blood samples

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JOURNAL OF AGRICULTURAL SCIENCE IN FINLAND



were taken by jugular veni puncture on every
second day of the oestrus cycle and at approx-
imately 3 weeks intervals during pregnancy in
Finnsheep (F, n = 16), Polish Heath (n = 13),
Friesian (n = 10), Zelazna (n = 12) and
Karakul (K) called also Astrakhan (n = 14).
Results of the investigations were analysed by
least-squares analysis of variance. The model
included main effects of season, breed, day
of the cycle, stage of pregnancy and LS ver-
sus PP concentrations.

Results and discussion

PP concentrations during oestrus cycle are
presented in table 1. The examined breeds var-
ied in their respective PP levels. The breed
differences were most clearly pronounced on
10th day of the cycle, with F having the
highest and K the lowest PP concentration.
Thus, the results obtained in this work sup-
port the observations of Wheeler and Land
(4) that the circulating PP concentration in the
middle of the luteal phase is related to the ovu-
lation rate. However, due to a large within
breed variation the differences in PP levels
during oestrus cycle between breeds were not
significant.

PP concentrations during pregnancy in re-
lation to LS are demonstrated in table 2. It
can be noted, that the presented PP levels
changed significantly depending on the stage
of pregnancy. A similar variation on PP con-
centration during pregnancy was described by
Basset et al. (1). There were also significant
differences in the PP levels depending on LS.
At all the examined stages of pregnancy the
lowest PP concentrations were found in ewes
carrying single foetuses, while the highest ones
in ewes carrying triplets.

It should be mentioned that the PP concen-
trations in ewes carrying quadruplets were
»out of range», i.e. lower than those found
in ewes with triplets. However, the number of
dams with quadruplets (n = 2) was too small
for drawing any conclusions. The available in-
formations concerning the relationship be-
tween on PP levels during pregnancy and LS Table

1.
Plasma

progesterone
concentrations

during
oestrous

cycle.

Breed

Days
of
the

cycle

I—2

3—4

5—6

7—B

9—lo

11—12

13—14

15

16

17—

x

s

xs
xs
xs
xs
xs
xs
xs
xs

Finnsheep
0.34
0.18

1.08
0.46

2.12
0.52

2.02
0.47

3.59
0.59

2.89
0.54

2.80
0.50

0.39
0.27

0.36
0.18

Friesian

0.30
0.21

1.43
0.53

1.21
0.61

1.25
0.54

0.96
0.68

0.49
0.42

0.62
0.58

0.52
0.31

0.70
0.21

Polish
Heath

0.59
0.16

0.75
0.41

1.37
0.47

0.87
0.42

1.15
0.53

1.24
0.49

1.23
0.45

0.52
0.24

0.33
0.16

Zelazna

0.59
0.18

0.47
0.44

0.88
0.51

1.24
0.45

1.25
0.57

1.28
0.53

0.89
0.48

0.44
0.26

0.38
0.17

Karakul

0.49
0.19

0.32
0.27

0.92
0.54

0.45
0.40

0.68
0.61

1.03
0.56

0.82
0.52

0.50
0.28

0.40
0.19

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Table 2. Average plasma progesterone concentrations in relation to the litter size and the pregnancy stage.

Litter size Days of pregnancy

1—25 26—50 51—75 76—100 101 125 126 Mean

Singles 2.70 3.33 3.85 3.30 1.81 5.26 2.52 BCD
Twins 3.82 4.16 4.78 4.28 2.64 6.39 2.85 A<
Triplets 4.98 5.87 8.17 4.97 3.41 7.88 3.29 AB
Quadruplets 2.95 2.28 1.43 3.37 2.53 3.46 3.07 A
Average 2.61 bcDF 2.91" EF 2.92 aEF 3.04 AEF 2.40BCFJF 3.73ABCDE

a, b, c, d, e, f P < 0.05
A, B, C, D, E, F P < 0.01

are limited to the comparisons of single and
twin pregnancies.

Conclusions

1. In general, results of these investigations
confirm the earlier findings concerning the
possibility of predicting LS on the basis of
PP levels during pregnancy.

2. Significant changes in the PP concentra-
tions during pregnancy may influence the

results of prediction. Thus, the stage of
pregnancy should be taken into account.

3. It is suggested, that the relationship be-
tween LS and PP level exists for LS with-
in the range from singles to triplets. How-
ever, the number of the quadruplets was
too small for drawing any conclusions.

4. The most pronounced breed differences in
PP concentration during oestrus cycle were
found in the middle of the luteal phase, but
they were statistically insignificant.

References

1. Bassft. J.M., Oxborrow, T.J., Smith. I.D. & Thor
burn. G.T. 1969. J. Endocr. 45: 449—457.

2. Shemesh, M., Ayalon. N. & Lindnfr, H.R. 1973. J.
of Anim. Sci. 36: 726—729.

3. Kokot. F. & Stupnicki, R. 1979. Metody radioim-

munologiczne i radiokompetycyjne stosowane w
klinice. PZWL.

4. Wheeler, A.G. & Land, R.B. 1977. Anim. Prod. 24:
363—376.

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