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RESEARCHES REGARDING ESTRUS INDUCTION

AND SYNCHRONIZATION IN SOWS AFTER WEANING 

Professor Liviu BOGDAN*, PhD

Professor Ioan GROZA*, PhD

Assistant Mihai CENARIU*, PhD

Lecturer Simona CIUPE*, PhD

Emoke PALL*, PhD Student

Anamaria PETREAN*, PhD Student

Sorana MATEI*, PhD Student*

Sidonia BOGDAN**, student

Abstract

The purpose of this paper was to improve the reproductive performances of sows after weaning in a private swine farm. The main 
objective was to implement modern reproductive biotechnologies (estrus synchronization, artificial insemination and early pregnancy 
diagnosis) in order to increase the economic efficiency of the reproductive sector of this farm. The biologic material used for the 
research was represented by 300 sows whose estrus was synchronized using three hormonal procedures (Regu-Mate administered 
collectively, Regu-Mate administered individually and PG600) as well as naturally, using stimulating boars. The results showed that the 
best methods of estrus induction and synchronization in sows use either Regu-Mate administered individually in fodder or PG600.

Key words: sows, estrus, synchronization, artificial insemination, pregnancy, weaning

Introduction

Swine breeding has developed as a necessity meant to ensure meat for consumption, therefore the 

main objective of this industry is to maximize production. Swine have the ability to produce a large 

number of offspring during a short period of time [1,4]. Thus, pigs may represent one of the most 

profitable species among the farm animals. Profitability of this sector is largely dependent on the 

reproductive performance [2,3]. Therefore, the main purpose is to wean as many good quality piglets 

from a sow as possible during a year, with as little expenses as possible [5,6]. The implementation of 

* University of Agricultural Sciences and Veterinary Medicine, Faculty of Veterinary Medicine, Department of Veterinary 
Reproduction, Obstetrics and Gynecology, 3-5 Manastur Street, 400372 Cluj-Napoca, Romania, tel. +40 264 596384 ext. 163, 
e-mail: medivetbogdan@yahoo.com

** University of Agricultural Sciences and Veterinary Medicine, Faculty of Veterinary Medicine
Cluj Veterinary Journal, 15(1)/2009, pp. 24-28



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new biotechnological methods for estrus induction and synchronization in reproduction programs 

allows the improvement of technological and economical parameters [7,8]. 

The purpose of this paper was to improve the reproductive performances of sows after weaning 

in a private swine farm. The main objective was to implement modern reproductive biotechnologies 

(estrus synchronization, artificial insemination and early pregnancy diagnosis) in order to increase 

the economic efficiency of the reproductive sector of this farm. 

Material and methods

The research has been carried out during November 2008 – May 2009 in a private swine farm 

from Mures County, Romania. The farm had a total of 8900 pigs out of which 800 were mother sows, 

165 awaiting sows and 13 boars, the rest being used for meat production. The boars belonged to the 

following breeds: White Duroc, Maxter, Pietrain and Great White, while the sows were mixed breeds 

between PIC and one of the previously mentioned boars. 

The average productive life of the sows was of 5-6 parturitions, with an average of 12 piglets/

parturition and 11.5-11.8 weaned piglets/sow. 

The biologic material used for the research was represented by 300 sows, 1-4 years of age, mixed 

breed between PIC and Great White, Duroc and Pietrain boars.

Estrus induction and synchronization was performed using three hormonal procedures (Regu-

Mate administered collectively, Regu-Mate administered individually and PG600 – figure 1) as well 

as naturally, using stimulating boars.

The sows were divided into four batches as follows:

Batch 1 made up of 75 sows whose estrus was induced using the collective administration of Regu-

Mate in the fodder;

Batch 2 made up of 75 sows whose estrus was induced using the individual administration of 

Regu-Mate in the fodder;

Batch 3 made up of 75 sows whose estrus was induced using PG600;

Batch 4 made up of 75 control sows.

Fig. 1. The hormonal products used

Semen collection was performed using the manual method, which is efficient and does not imply 

supplementary costs. The dilution of fresh semen was performed using the TriXcel dilution media 

that maintains the viability of spermatozoa for 7 days (figure 2). 



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Fig. 2. Semen collection and dillution

The optimum moment for insemination was chosen 24 

hours after the observation of the immobility syndrome. 

The sows were artificially inseminated (A.I.) twice (in the 

morning and in the evening) using 50 ml diluted semen/

dose, with a concentration of 3 billions spermatozoa/dose 

(fig. 3). The pregnancy diagnosis was performed 30 days after 

artificial insemination in all sows, using a Doppler device 

(fig. 4). 

Results and Discussions

Following estrus synchronization in batch 1, 67 sows 

(90%) showed heat symptoms after 5-8 days. The remaining 

8 sows (10%) did not show estrus signs during this period. 

From the 75 sows, 52 (69%) were diagnosed pregnant after 

the first insemination, 15 (20%) after the second insemination 

while 8 (11%) did not show estrus signs and therefore were 

eliminated from the batch. The results obtained for batch 1 

are shown in table 1:

Table 1. Results obtained for batch 1

No.
REGU-MATE collectively in fodder

Number of sows Percent
1. Number of sows/batch 75 100%
2. Sows in heat 67 90%
3. Sows that did not show heat signs 8 11%
4. Pregnant sows after first insemination 52 69%
5. Pregnant sows after the second insemination 15 20%

Following estrus synchronization in batch 2, 73 sows (97%) showed heat symptoms after 2-3 days. 

The remaining 3 sows (3%) did not show estrus signs during this period. 

From the 75 sows, 71 (94%) were diagnosed pregnant after the first insemination, 2 (3%) after the 

second insemination while 2 (3%) did not show estrus signs and therefore were eliminated from the 

batch. The results obtained for batch 2 are shown in table 2:

Fig. 3. A.I. of sows

Fig. 4. Pregnancy diagnosis



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Table 2. Results obtained for batch 2

No.
REGU-MATE individually in fodder

Number of sows Percent
1. Number of sows/batch 75 100%
2. Sows in heat 73 97%
3. Sows that did not show heat signs 2 3%
4. Pregnant sows after first insemination 71 94%
5. Pregnant sows after the second insemination 2 3%

Following estrus synchronization in batch 3, 74 sows (98%) showed heat symptoms after 2-3 

days. The remaining sow (2%) did not show estrus signs during this period. From the 75 sows, 71 

(81%) were diagnosed pregnant after the first insemination, 13 (17%) after the second insemination 

while 1 sow (2%) did not show estrus signs and therefore was eliminated from the batch. The results 

obtained for batch 3 are shown in table 3:

Table 3. Results obtained for batch 3

No.
PG 600 i.m.

Number of sows Percent
1. Number of sows/batch 75 100%
2. Sows in heat 74 98%
3. Sows that did not show heat signs 1 2%
4. Pregnant sows after first insemination 61 81%
5. Pregnant sows after the second insemination 13 17%

In batch 4 (control), 67 (90%) sows showed estrus signs 5-10 days after weaning. The remaining 

8 sows (10%) did not show estrus signs during this period.

From the 75 sows, 52 (69%) were diagnosed pregnant after the first insemination, 15 (20%) after 

the second insemination while 8 (11%) did not show estrus signs and therefore were eliminated from 

the batch. The results obtained for batch 4 are shown in table 4:

Table 4. Results obtained for batch 4

No.
CONTROL

Number of sows Percent
1. Number of sows/batch 75 100%
2. Sows in heat 67 90%
3. Sows that did not show heat signs 8 11%
4. Pregnant sows after first insemination 52 69%
5. Pregnant sows after the second insemination 15 20%

After delivery and weaning of the resulted piglets belonging to the four batches, the following 

results have been obtained (table 5):

Table 5. Results obtained after delivery and weaning

No. Delivered piglets Average/sow Weaned piglets Average/sow
1. Batch 1 624 12 468 9
2. Batch 2 994 14 710 10
3. Batch 3 793 13 610 10
4. Batch 4 624 12 468 9



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Conclusions

After performing the research, the following conclusions were drawn:

1. The best results for estrus induction and synchronization were obtained in batch 2 and 3 where 

individual administration of Regu-Mate and PG600 were used.

2. The number of piglets delivered was also bigger in these two batches, as well as the number of 

weaned piglets.

3. Synchronization of estrus cycle leads to a short service-period and therefore to a larger number 

of deliveries/productive life of a sow.

4. Estrus synchronization also allows the decrease of boar number used for semen collection and 

therefore the number of artificial inseminations. 

5. Delivery monitoring avoids the inherent accidents during parturition (dystokia, large fetuses, 

female exhaustion). 

References

1. Bogdan L. M.: Biotehnici în reproducţia animalelor domestice, Ed. Academic Press, Cluj-Napoca, 
2000;

2. Bogdan L.M.: Reproducţie, obstetrică, terapie şi însămânţări artificiale la animale, Ed. AcademicPres 
Cluj-Napoca, 2001;

3. Cardenas H., HERRICK J.R., POPE W.F. : Increased ovulation rate in gilts treated with dihydrotestosterone, 
Reproduction, vol. 123, 2002;

4. Groza I., Muntean M.: Elemente de fiziologia reproducţiei la animale, Ed. Academic Press, Cluj-Napoca, 
2002;

5. Groza I., Morar I., Andrologie Veterinară, Ed. Gryphon, Braşov, 2004;
6. Michel R. Muirhead, Thomas JL. Alexander: Managing Pig Health and the Treatment of Disease, The 

Word Renound Book, 2002;
7. Wise T., Klindt J., Howard H.J., Conley A.J., Ford J.J.: Endocrine relationships of Meishan and White 

composite females after weaning and during the luteal phase of the estrous cycle, vol. 79, 2001;
8. Yen H.W., Ford J.J., Zimmerman D.R., Johnson R.K.: Follicular development and maturation in gilts 

selected for an index of high ovulation rate and high prenatal survival, Departament of Animal Science, 
University of Nebraska, U.S. Meat Animal Research Center.


