Livestock Research for Rural Development 24 (11) 2012 Guide for preparation of papers LRRD Newsletter

Citation of this paper

Synchronization rate and factors affecting pregnancy rate after synchronization of estrus cycle and insemination of Gobra zebu (Bos indicus) in traditional area in Senegal

J Kouamo* and G J Sawadogo

* School of Veterinary Medicine and Sciences, University of Ngaoundere. PO BOX 454 Cameroon
EISMV-Laboratory of endocrinology and radio-immunology, PO BOX 5077 Dakar (Senegal)


The aim of the present study was to determine the success rate of artificial insemination (AI), risk factors on pregnancy rate and to propose solutions for the improvement of the AI in a traditional area in Senegal. Of 291 selected cows, 276 were synchronized with the vaginal spiral (PRID®), PMSG and PGF2a.

A synchronization rate of 99.3% was obtained. The synchronized cows detected in heat were inseminated with semen of selected Holstein and Montbeliard bulls. The pregnancy diagnosis was carried out at day 60 post AI by transrectal palpation and a total pregnancy rate of 44.3% was obtained. It was concluded that factors such as body condition score (BCS) at day 60 post-AI, sponges withdrawal -AI interval and bull semen influenced the pregnancy rate. A pregnancy rate of 58.8% was obtained for the cows with BCS of 3.5. The bulls Oxbow and Nirgiv presented a pregnancy rate of 100% and 83.8% respectively and the cows inseminated in the interval 54-56 hours after the spiral withdrawal, presented a pregnancy rate of 60%. These factors should be considered in further AI national program to increase pregnancy rate. 

Key words: cow, PGF2a, PMSG, success rate, Thies, vaginal spiral


Livestock play a significant role in the economic, social and cultural plan in Senegal. Thus, it constitutes an essential link of the economy through the generation of incomes and the satisfaction of the food needs for the rural populations. The local production of meat and milk remains very low. The dairy production is still in extensive system and the production of milk from zebu Gobra is 1.5 liters/day (Diop 1996). Indeed, the importations of dairy products in Senegal (mostly in powder) are increasing each year to more than 53 billion francs CFA ($106 lakh US) per year (Kouamo et al 2009a). 

To solve this problem, the development of reproductive techniques such as oestrus synchronization, artificial insemination (AI) and embryo transfer are directed to solve or minimize the effects of these limiting factors as well as to make possible the application of more intensive systems of production and to facilitate the genetic improvement of the productive characteristics of the herd. To date, AI is recognized as the best biotechnological technique for increasing reproductive capacity and has received widespread application in farm animals (Landiver et al 1985; Mukasa-Mugerewa 1989). The AI after synchronization was identified as the tool of choice for a better productivity of the local Gobra zebu in Senegal through a national campaign (Kouamo et al 2009b). Despite the wide application of AI and its success throughout the developed world, the success rate in Senegal is still low; 38.1 % (Hakou 2006); and 44.9 %  (Badji 2007) owing to a number of technical, financial, infrastructural, managerial and sanitary problems (Kouamo et al 2010). 

Therefore, this study has been taken to evaluate the synchronization rate, pregnancy rate and factors affecting the pregnancy rate after synchronization and AI.

Materials and methods

Selection of Gobra zebu  

The study was carried out in two departments of the region of Thies, at 40 km from Dakar. A total of 291 cows were selected on the basis of certain criteria. To be selected, Gobra zebu must be more than 3 years old, in good health (vaginoscopy examination), not pregnant (transrectal palpation) and have over 90 postpartum days. The appreciation of the body condition score (BCS) was made according to the method suggested by Vall et al (2002). All the selected cows were treated one month before the program of AI with Ivermectin (200 microgram/kg by subcutaneous injection) and Oxytetracycline injection 10% (10 mg/kg intramuscularly). A flushing was recommended to the farmers to optimize the fertility.  

Protocol of synchronization, artificial insemination and pregnancy diagnosis 

The following synchronization protocol was applied: sponge PRID®  containing 1.55g of progesterone and 10 mg of benzoate œstradiol (Progesterone Release Intra-vaginal Device ‘Ceva santé animale’) from day 0 to day 12; intra muscular (im) injection of 25 mg PGF2α at day 10; PRID® removal and im injection of 500 IU PMSG at day 12; insemination at day 14 after estrus detection. The estrus was detected early morning (5-8 hours) and early evening (17-18 hours). If the zebu stands still, definitely in heat and the farmers should informed the inseminator. The cows were inseminated by same inseminator (one service) with frozen semen (-196°C) of selected bulls (Montbeliard and Holstein) imported from France. At day 60 post AI, pregnancy diagnosis was made by transrectal palpation. 

Data collection and statistical analysis  

During the selection, synchronization, AI and pregnancy diagnosis, data were collected into two groups: intrinsic factors (Directly from the inseminated cow) and extrinsic or indirect factors. 

All the collected data were recorded and processed in Excel Microsoft table.  SPSS version 10.0 was used for the statistical analysis of the results. The test of Pearson Chi2 was used to find statistiical significance of differences (P< 0.05).


Synchronization rate  

A total of 276 cows were retained for synchronization on 291 selected cows (15 others absent or pregnant). 274 were detected on heat (synchronization rate=99.3) and inseminated and two lost the sponges.

Pregnancy rate

A pregnancy rate of 44.3% was obtained at day 60 post AI. The table 1 presents the pregnancy rate according to the two departments.  

Table 1. Result of the pregnancy diagnosis per transrectal palpation at day 60 post AI    

Departments of the region of Thies

Pregnant (%)

Sold after AI (%)

Total (%)


40 (43.4)

2 (2.1)

92 (100)


65 (44.8)

1 (0.6)

145 (100)

Total (%)

105 (44.3)

3 (1.3)

237 (100)

Intrinsic factors affecting the pregnancy rate 

The table 2 presents the effect of postpartum day and BCS on pregnancy rate

Table 2. Pregnancy rate according to the intrinsic factors

Intrinsic factors

Pregnancy rate  % (Total number of cows)

Days post partum (months)

(P = 0.657)



3 to 5

43.7a (110)

6 to 11

42.4a (26)

12 to 17

46.3a (55)

18 to 23

54.5a (11)

24 to 30

50a (35)

BCS at  day 60 post AI

(P = 0.010)




22.7c (25)


45b (105)


47.1b (84)


58.8a (20)

Age of the cow (years)

(P = 0.528) 



53.3a (12)

5 to 8

47.3a (92)


41.6 a (133)

a,bPercentage in the same row without common letter are different at P<0.05

Note: animals sold were considered non-pregnant

Extrinsic factors influencing the pregnancy rate  

The table 3 presents extrinsic factors affecting pregnancy rate. 

Table 3.  Pregnancy rate according to the extrinsic factors

Extrinsic factors

Pregnancy rate in % (Total number of cows)

Bull race (P = 0.458)


41.3a (94)


47.7a (143)

Departments (P = 0.915) 


43.48a (94)


44.83a (143)

Type of breeding (P = 0.668)


41.07 (181)


46.06 (56)

Principal activity of farmers (P = 0.697)


48.88a (91)


40.62a (97)


45.83a (49)

Ethnos group of farmers (P = 0.558)


35.71a (23)


49.15a (86)


45a (21)


41.79a (107)

Distance inseminator-farmer in km (P = 0.682)

0 –20

46.97a (43)

21 –40

40a (81)

41 –60

39.7a (113)

Interval sponge application – sponge withdrawal (days)

(P = 0.397)


49.16a (122)


40.35a (115)

Interval sponge withdrawal +PMSG injection –AI  in hours (P = 0.041)

51 –53

37.2b (44)

54 –56

60a (163)

57 –59

27.58b (30)

AI hours (P = 0.351)

16 –18

47.67a (87)

18 –20

44.27a (132)


35.29a (18)

a,b,c Percentage in the same row without common letter are different at P<0.05

Note: animals sold were considered non-pregnant

There were differences between bulls: Luksor (32.25%), Pinkfloyd (28.57%), Relans (52%), Roglin (50%), Romin (56.25%), Oranais (41.66%), Minister (46.66%), Darmio (50%), Galani (30.76%), Virnin (50%), Nirgiv (83.83%), Oxbow (100%), Rubistein (0%).


Synchronization of estrus 

By the use of estrus synchronization protocol with the combination of sponges, PMSG and PGF2α, the synchronization rate (99.3%) was high. Several authors suggested the combination of progestins and prostaglandins to increase the results. Prostaglandin has also been used as a co-treatment in effective progestogen-based synchronization protocols in cattle such as Kojima et al (2000), Lucy et al (2001), Wood et al (2001) and Islam (2011) for both natural mating and AI/timed AI situations. Duygu and Köker (2011) reported the use of intravaginal sponges impregnated with 45 mg FGA (melengestrol acetate) and 0.5 ml PGF2α combination is convenient for estrus synchronization during the breeding season. Lucy et al (2001) reported the use of progestins plus protaglandins could  increase  the  synchronization rate  by  approximately  30%,  and  pregnancy  rate  by approximately 20%, in both the anestrous and cyclic females. Hafez (1993) also reported 85% in estrus response in dairy cattle with prostaglandin and progesterone analogues. In the same conditions, similar results (91.8 to 100%) has been reported by Okouyi ( 2000), Diedhiou (2002), Kamga et al (2005), Tcheufo ( 2007), and Abonou (2007). 

The loss of two sponges might be due to traditional breeding; the animals taken to the pasture daily (the sponges would be withdrawn by the spines, the branches of trees or any other object).  

Pregnancy rate  

The overall first service pregnancy rate (44.3%) obtained in this study, is lower than the recommended 60% (Gaines 1989) indicating the inefficiency of AI service, in this study, which could be associated to several factors. The current figure is also lower than previously reported values of 71.8-82.2% in Debre Zeit (Bekana 1988), 46.7% (Samsson 2001), 46.7% (Belachew 2003), 54.3% and 54.9% obtained respectively by Abonou and Tcheufo (2007) in Senegal.   

However, it lies within the range of 22-45% reported by Tegegne (1989), Shiferaw et al (2003) and Badji (2007) in tropical area. Such differences may be attributed to factors associated with timing of insemination, feeding management, efficiency of heat detection, early embryonic mortality and presence of ovarian cyst which are all known to negatively affect fertility.  

In rural area, animals are considered as a great income source to solve certain urgent problems. The three inseminated cow which have been sold by the farmers were declared to be dead. It was after further investigations, we found that inseminated cows were sent to a slaughterhouse. In traditional areas, this situation is currently observed; sometimes the sold animals are pregnant and there affect considerably the results and the success rate (Kouamo et al 2008). 

Intrinsic factors affecting the pregnancy rate 

In this study, the numbers of post partum day and the age don’t affected the pregnancy rate. However, Hanzen (1996) obtained the best pregnancy rate between 70 and 90 day of postpartum and decreased during previous periods. Moreover, Steveson et al (1983) also note an increase of the fertility during the postpartum. Humblot (1988), Weller et al (1992) and Dieng (1994) observed a reduction of the fertility with the age, due to the increasing of later embryonic mortalities with the age. The differences might be due to efficiency of estrus synchronization protocol on older cows and extended post partum periods (post partum anestrus). 

There was no effect of BCS at the selection and the day of AI. However, cows with BCS of 3.5 at day 60 post AI presented higher pregnancy rate (58.8%) than others. Grimard et al (2003) reported that the effectiveness of the AI depends on the BCS of the inseminated cows. Poor nutrition main cause of reduced fertility in cattle, grazing in subtropical/tropical areas (Bó et al 2003). Investigations on postpartum reproduction in cattle indicated that body condition score (BCS) is a useful indicator of energy status and rebreeding potential (DeRouen et al 1994). Other studies also demonstrate the effect of BCS on ovarian cyclicity and pregnancy rates in beef cows (D’occhio et al 1990, Viscarra et al 1998). Rasby et al (1992) reported that restricted nutrition has a negative influence on LH release while Rekwot et al (2004)  showed that cows supplemented with 600 g of cotton seed daily resumed cyclicity than the controls (136 ± 8 days versus 107 ± 5 days, P < 0.05). Baruselli et al (2003a) and Cutaia et al (2003b) also demonstrated a significant effect of BCS on conception rates in animals submitted to fixed-time AI (FTAI) in cows bred in Brazil and in Argentina, with a 2.5 score on a scale of 1–5, being the minimum acceptable BCS for successful estrus synchronization in Bos indicus cattle.  

Extrinsic factors affecting the pregnancy rate 

Some factors not affected the pregnancy rate might be due to past experience of AI campaign and training received by farmers on feed and nutrition, estrus detection and reproduction management before starting this study 

On the other hand, a pregnancy rate of 60% was observed with inseminated cows between 54-56 h after the sponge withdrawal. This is in agreement with the recommendations of Diop (1996) which advises to carry out inseminations 57.5±3.5 hours after the sponge withdrawal. Diskin et al (2001) reported that after the treatment by synchronization, approximately 85% of the cows expressed heat between 36h and 60h so we recommend AI towards the end of the period of heats. 

The bulls Oxbow and Nirgiv presented better pregnancy rate compared to others. However, they should be tested in a large scale during the national AI campaign to confirm their efficiency, and the abusive use is not recommended to avoid consanguinity in the herds.  



The authors thank Professor Louis Joseph PANGUI (EISMV-Dakar), Director of the EISMV, Doctor Dramé of AFRIVET Clinic and Thies farmers for providing facilities on the field and in laboratory.  


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Received 18 July 2012; Accepted 4 October 2012; Published 6 November 2012

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