EFFECTIVENESS OF EARLY PREGNANCY DIAGNOSTICS IN SHEEP DEPENDING ON ULTRASOUND EXAMINATION METHOD APPLIED

Piotr Ślósarz, Agnieszka Frankowska, Sebastian Dobrzyński, Anna Frąckowiak
Department of Sheep, Goat and Fur Animals Breeding, Agricultural University of Poznan, Poland

ABSTRACT

The aim of the study was to compare the effectiveness of pregnancy diagnostics in sheep and the diagnosis of the number of embryos on the basis of two ultrasound methods: trans rectum in sheep lying in the dorsal position (with a Pie Medical Scanner 100LC apparatus equipped with a 8 MHz probe) and trans cutem in standing sheep (with an Aloka SSD210DXII apparatus with a 3.5 MHz probe). The transrectal ultrasound examination made it possible to positively diagnose pregnancy in 89% ewes as early as 16 days after service, while a definite confirmation of pregnancy in all examined sheep was possible on day 19. In contrast, the diagnosis of pregnancy in all examined sheep via abdominal integuments was possible only on day 41 of pregnancy. The determination of the number of developing embryos in case of twin pregnancy with the trans rectum method was possible as early as day 22 after service (83%), and on day 27 the accuracy of diagnosis increased to 92%. In case of the transcutaneous examination the accuracy of assessment of the number of embryos was much lower, amounting to 33 on day 27% of pregnancy and maximum 83 on day 41%.

Key words: pregnancy diagnosis, sheep, ultrasound.

INTRODUCTION

Ultrasonography is a non-invasive technique of image diagnostics, used in breeding practice with increasing frequency, also to diagnose pregnancy in sheep [1, 9]. In recent years, thanks to the improved quality of the ultrasound diagnostic equipment and probe miniaturization, the method of trans rectum examination has also been developing, making it possible e.g. to study ovarian activity, to assess losses of embryos/fetuses and to monitor their development [2, 4, 5, 8]. The aim of this study was to compare the effectiveness of pregnancy diagnosis in sheep and the diagnosis of the number of embryos on the basis of two ultrasound examination methods: trans rectum in sheep lying in the dorsal position and transcutaneous in standing sheep.

MATERIAL AND METHODS

A total of 13 ewes of the prolific sheep line 09 were examined being in their 2^nd and 3^rd breeding season. In order to compare the stage of the sexual cycle and to facilitate a precise determination of the age of the embryo / fetus the sheep were subjected to estrus synchronization using ChronoGest^® method, and next they were serviced in the group service system in groups of 3 – 4 ewes per 1 ram. A total of 9 ewes conceived in the analyzed group of ewes in their first estrus after synchronization and they had a total number of 24 lambs. Ultrasound examinations were performed 8 times on day 16, 19, 22, 27, 33, 41, 55 and 68 after service. Each time sheep were examined using two methods: trans rectum in sheep immobilized in the dorsal position using a Pie Medical Scanner 100LC apparatus with a 8 MHz linear probe (method 1) and trans cutem in the right popliteal fossa in the standing position using an Aloka SSD210DXII apparatus with a 3.5 MHz linear probe (method 2). In all sheep the confirmation or exclusion of pregnancy in successive testing periods was assessed along with the determination of the number of developing embryos / fetuses.

Results of studies were analyzed statistically using the SAS ver. 6.12. package, although due to the relatively small number of examined animals and the primarily descriptive character of the data, the analysis was limited to the presentation of mean values and the frequencies of individual cases.

RESULTS AND DISCUSSION

In the conducted experiment the ultrasound transrectal examination (method 1) made it possible to detect pregnancy in 88.9% ewes as early as day 16 after service, while the definite confirmation of pregnancy in all examined sheep was possible already on day 19 (Table 1, Fig. 1). This result is consistent with the investigations conducted by Schick and Inskeep [6] and Kaulfuss et al. [3], who found that the trans rectum method makes it possible to detect pregnancy as early as day 15, while 100% accuracy is obtained between day 18 and 21 after conception. For comparison in case of transcutaneous examination (method 2) the first indications of pregnant sheep occurred on day 22 (for 44.4% ewes), while the detection of pregnancy in all examined sheep was possible only on day 41 of pregnancy (Table 1, Fig. 2).

Table 1. Percentage of sheep in which pregnancy was detected in successive examination dates Number of pregnant sheep = 9

Examination method	Date of examination (days of pregnancy)
	16	19	22	27	33	41	55	68
Method 1 trans rectum	88.9	100	100	100	100	100	100	100
Method 2 trans cutem	0.0	0.0	44.4	55.6	55.6	100	100	100

Fig. 1. Image of pregnancy on day 19. On the left the trans rectum method – a large bladder (A) and a forming embryo (between arrows). On the right the trans cutem method – image not very clear, difficult to interpret

Fig. 2. Image of pregnancy on day 41. On both images a fetus may be seen (between arrows), differences in image quality are distinctly visible (A – the head of the fetus, B – the trunk)

Table 2 presents the effectiveness of the detection of the number of embryos / fetuses in successive periods of pregnancy. In the conducted examinations no twin or triple pregnancies were detected, whereas 6 ewes had twins and 3 sheep had quadruplets. In case of twin pregnancy, a relatively precise determination of the number of embryos using the trans rectum method was possible as early as day 22 after conception (83.3%), and on day 27 the effectiveness increased to 91.7% (Table 2). In a more advanced pregnancy increasing dimensions of fetuses made it more difficult to observe them on the screen of the ultrasound scanner (Fig. 3) and the effectiveness of the detection of the number of fetuses was lower. A similar trend was observed in earlier studies [7]. In case of a quadruple pregnancy an appropriate accuracy of assessment of the number of embryos using method 1 was obtained on day 27 after service (83.3%), while the highest effectiveness was obtained on day 33 of pregnancy (91.7%). The results indicate that the precision of the estimation of the number of embryos diminishes along with their increasing number, as it was shown e.g. by Kaulfuss et al. [3].

Table 2. Detectability of the number of embryos / fetuses (%) in successive dates of examination

Type of pregnancy (number of fetuses)	Examination method	Date of examination (days of pregnancy)
		16	19	22	27	33	41	55	68
Twins (n = 12)	method 1 trans rectum	66.7	75.0	83.3	91.7	83.3	83.3	50.0	41.7
	method 2 trans cutem	0.0	0.0	0.0	33.3	50.0	83.3	83.3	83.3
Quadruplets (n = 12)	method 1 trans rectum	16.7	66.7	66.7	83.3	91.7	50.0	75.0	50.0
	method 2 trans cutem	0.0	0.0	0.0	0.0	25.0	41.7	75.0	75.0
Total n = 24	method 1 trans rectum	41.7	70.8	75.0	87.5	87.5	66.7	62.5	45.8
	method 2 trans cutem	0.0	0.0	0.0	16.7	37.5	62.5	79.2	79.2

Fig. 3. Image of pregnancy on day 68. On the left the trans rectum method – a fragment of a fetus may be seen with a distinct outline of the chest and the heart (the arrow). On the right the trans cutem method – the fetus is seen whole (between arrows), but organs may not be identified

In case of transcutaneous examination the assessment of the number of developing fetuses was possible only at the end of the first month of pregnancy (Table 2), while the assessment accuracy in that period was distinctly lower than in case of the trans rectum method. In turn, towards the end of the second month of pregnancy the effectiveness of detection of the number of fetuses using this method was similar or higher than in the trans rectum method, probably due to the bigger scanning width of the 3.5 MHz probe and the position of fetuses in the uterus.

CONCLUSIONS

Results of the examinations show that ultrasound transrectal examination of sheep may be useful in very early diagnostics i.e. in the first month of pregnancy. In turn, to examine sheep in advanced pregnancy in the field the transcutaneous method proves to be accurate enough; it is also less labour-consuming and less stressful for animals.

ACKNOWLEDGEMENTS

The study was supported by grant no. 2 P06Z 035 30 from the Polish Ministry of Education and Science.

REFERENCES

1. Garcia A., Neary M.K., Kelly G.R., Pierson R.A., 1993. Accuracy of ultrasonography in early pregnancy diagnosis in the ewe. Theriogenology 39, 847-861.

2. Gonzales de Bulnes A., Moreno Santiago J., Sebastian Lopez A., 1998. Estimation of fetal development in Manchega dairy ewes by transrectal ultrasonographic measurements. Small Rum. Res. 27, 243-250.

3. Kaulfuss K.H., Uhlich K., Brabant S., Blume K., Strittmatter K., 1996. Die ultrasonographische Trächtigkeitsdiagnostik (B-Mode) beim Schaf. Teil 1, Verlau-fsuntersuchungen im ersten Trächtigkeitsmonat [Real-time ultrasonic pregnancy diagnosis in sheep. Part 1: Frequent examinations during the first month of pregnancy]. Tierärztl Prax 24, 443-452 [in German].

4. Kaulfuss K.H., Giucci E., Süss R., Wójtowski J., 2006. An ultrasonographic method to study reproductive seasonality in ewes isolated from rams. Reprod. Domestic Anim. 41 (5), 416-422.

5. Mufti A.M., Wani G.M., Wani N.A., Buchoo B.A., Khan M.Z., 2000. Prenatal development of ovine fetus. Small Ruminant Res. 38, 87-89.

6. Schrick F.N., Inskeep E.K., 1993. Determination of early pregnancy in ewes utilizing transrectal ultrasonography. Theriogenology 40, 295-306.

7. Slosarz P., Steppa R., Gadek A., 1999. Proba wykorzystania ultrasonografii transrektalnej do wczesnej diagnostyki ciaży u owiec [The application of ultrasound technique for early pregnancy diagnosis in sheep]. Med. Wet. 55, 686-688 [in Polish].

8. Slosarz P., Frankowska A., Mis M., 2003. Transrectal ultrasonography in diagnosing the ovulation rate in sheep. Ani. Sci. Pap. and Rep. 21 (3): 183-189.

9. Tischner M., Wierzchos E., 1990. Ultrasonograficzne rozpoznawanie ciaży u owiec [Ultrasonic diagnosis of pregnancy in sheep]. Med. Wet. 46, 108-110 [in Polish].

 

Accepted for print: 9.05.2007

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Piotr Ślósarz
Department of Sheep, Goat and Fur Animals Breeding,
Agricultural University of Poznan, Poland
Złotniki, Słoneczna 1, 62-002 Suchy Las, Poland
Phone: 061 8125520
email: pslo@au.poznan.pl

Agnieszka Frankowska
Department of Sheep, Goat and Fur Animals Breeding,
Agricultural University of Poznan, Poland
Złotniki, Słoneczna 1, 62-002 Suchy Las, Poland
Phone: 061 8125520

Sebastian Dobrzyński
Department of Sheep, Goat and Fur Animals Breeding,
Agricultural University of Poznan, Poland
Złotniki, Słoneczna 1, 62-002 Suchy Las, Poland
Phone: 061 8125520

Anna Frąckowiak
Department of Sheep, Goat and Fur Animals Breeding,
Agricultural University of Poznan, Poland
Złotniki, Słoneczna 1, 62-002 Suchy Las, Poland
Phone: 061 8125520

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