|Livestock Research for Rural Development 32 (10) 2020||LRRD Search||LRRD Misssion||Guide for preparation of papers||LRRD Newsletter||
Citation of this paper
This study was conducted to evaluate the reproductive performance at estrus detection in post-partum anestrus cows following treatment with controlled internal drug release (CIDR) and Ovysynch or with Ovsynch protocol alone. Seventy (70) gyneco-clinically intact multiparous cows (40 Montbeliarde and 30 Holstein) were divided into two equal groups (35 cows each) in June when many cows (67%) were in anestrus. The cows in group 1 (n=35) were treated with Ovsynch alone. They were treated with inj GnRH 100 μg (Cystoréline) at day 0, inj PGF2α 25 mg (dinoprost) at day 7 and inj GnRH 100 μg at day 9 intramuscularly. The cows in Group 2 (n=35) were treated by Ovsynch plus CIDR protocol. The progesterone device (CIDR) was inserted on day 0 and removed at the time of PGF2 α injection on day 7. The cows that exhibited estrus were inseminated 12 to 18h after PGF2α injection in both protocols.
The estrus response for CIDR-treated cows was greater (80.0%) than for no-CIDR-treated cows (48.6%). The pregnancy rate at day 30 post insemination was lower for Ovsynch alone cows (31.4%) than for Ovsynch plus CIDR treated cows (57.1%). The protocols obtained conception rates of 71.4% (group 2) and 64.7% (group 1) with a statistical difference. Thus, the conception rate could be increased by controlled breeding using CIDR added to Ovysynch protocol in cows mainly in anestrus.
Keywords: cow, CIDR, conception rate, estrus, PGF2α, pregnancy rate, reproduction
The estimated number of cattle in Algeria is less than two million. Thus cattle occupies the third place after the sheep and goat herd, and represents 6% of the total national ruminant herd (MADRP 2016).
Three types of hormonal treatments can be used to synchronize heat in cattles (Ashit Kumar et al 2015): 1. prostaglandin-based treatments and F2α or its analogues, 2. others combining to GnRH and PGF2α and 3. Progestin-based treatments (a device that releases progesterone or norgestomet and/or PGF2α and eCG).
Thus a good knowledge of the physiological mechanisms explaining the effect of each treatment will facilitate the management of breeding cows via artificial insemination (AI). Almost all programs involve strategically timed treatment of prostaglandin F2α (PGF) and gonadotropin releasing hormone (GnRH) which the basic program is the “Ovsynch” regimen. Although the original studies using this combination were conducted and reviewed by Thatcher et al (1991), it was the comprehensive studies by Pursely et al (1997) that demonstrated the suitability of the basic “Ovsynch” protocol.
However, one of the major constrains of profitable dairy farming is the low pregnancy rate in cows Shamsuddin et al 2001). Low rates and accuracy of estrus detection also are major factors limiting in reproductive efficiency of dairy cows (Macmillan 2010; Paul et al 2011).
On the other hand, the productivity of cattle could be low because of poor nutrition witch the specific reasons for the decline have not been documented. These might be directly related to or exacerbated by environmental and management conditions (Alam et al 2006).
To increase the reproductive efficiency in dairy cows, various estrus synchronization protocols using Progesterone and implant or intravaginal device associated to PGF2α are the alternative strategy to bypass the critical problem of estrus detection and to increase pregnancy rates of dairy cattle under a variety of management systems (Jayaganthan et al 2016). However, the CIDR is an effective method that is convenient to use in case of poor heat detection on primiparous or multiparous cows particularly suitable for non-cycleous females. To my knowledge, no study has been edited on this subject in Algeria.
This study aims to assess the effect of Ovsynch alone and Ovsynch plus CIDR protocol (day 7) on the reproductive performance of cows in Algerian dairy cattle.
This study was conducted on a private dairy farm in Setif area (Algeria) at an altitude of 1 080 m.
The estrus synchronization after a Gonadotropin releasing hormone (GnRH) treatment at controlled internal drug releasing device (CIDR) insertion (CIDR® 1,9 g, Pfizer Animal Health, France) was investigated in an Algerian cattle farm.
70 postpartum anestrus cyclic multiparous cows (40 Montbeliarde and 30 Holstein cows) aged between 2 to 5 years were selected after thorough gyneco-clinical examination for their reproductive status as illustrated in the timelines in Figure 1. The Montbeliarde is the most represented in the population (57%) followed by the Holstein with 43%. The cows had body condition scores 2 to 3 (according to Campanile et al 2010) and were between the intervals of 55-90 days postpartum.
The study was conducted from June to September 2016. At the beginning, most of the cows (67 %) were in anoestrus.
They were dewormed using ivermectin, 100 mg S/C and supplemented with a mineral mixture for 20 days before initiating treatment. After selection, the cows were randomly distributed to two treatment groups as Ovsynch with or without CIDR consisting of 35 cows each group. They received the treatments during this period were inseminated (AI) at observed estrus.
The animals in treatment 1 (n=35, 22 Montbeliardes 13 Holsteins) were subjected to the Ovsynch protocol as described by Pursley et al (1995). The cows were administered intramuscularly with injection of GnRH (Cystoreline 100 μg i.m.) on day 0, injection of PGF2α (dinoprost 25 mg i.m.) on day 7 and a second injection of GnRH (Cystoreline 100μg i.m.) on day 9.
The animals in treatment 2 (n=35, 18 Montbeliardes 17 Holsteins) were subjected to the Ovsynch plus CIDR (Internal Drug Release Device, 1.9 g of progesterone, Pfizer Animal Health, France).
The treatments were similar to those used in group 1 except that a progesterone device (CIDR) was inserted on 0 day and removed at the time of PGF2α injection (dinoprost 25 mg i.m.) on 7 day followed by a second GnRH injection (100µg of Cystoreline) administered I/M on day 9) (Figure 1).
The estrus of the cows was synchronized with gonadotropin releasing hormone (GnRH) and prostaglandin F2α (PGF2α). The detection of estrus was based on visual observation. The animals were checked for estrus twice daily at least for 30 min each time.
The estrus signs were recorded (standing to be mounted, bellowing, redness, swelling of vulva and clear mucous discharge). The cows also were confirmed in estrus by the permeability of the cervix of the pistol on the day of insemination.
An artificial insemination (AI) at observed estrus was performed 12 to 18 h after the second GnRH injection or 48 and 72 hours after the CIDR removal in the both protocols as shown in Figure 1.
|Figure 1. Schematic representation of the Ovsynch protocol with or without CIDR|
The pregnancy was diagnosed by transrectal ultrasound at 30 days followed by a palpation per rectum on day 45 after the artificial insemination.
The reproductive performance variables recorded in this study were determined as follows:
i) Estrous response (percentage of females showing estrus among those treated),
ii) Conception rate (CR, percentage of females conceiving divided by those inseminated in the corresponding group),
iii) Pregnancy rate (PR, percentage of females diagnosed as pregnant divided by the total number of cows in the corresponding group).
The data were analyzed with the statistical software program (SAS Version 9.12). The objectives of this analysis were to test the effect of the treatment on estrus response, pregnancy and conception rates for the two treatments. Significant differences in reproductive performance of the cows tested between treatments were determined by Chi-square. The level of significance was set at p < 0.05.
A rectal palpation was carried out in all cows used in this study before PGF2α injection to control the luteal structure.The reproductive performance of synchronized cows as the estrus responses, pregnancy and conception rates are shown at Table1.
Table 1. Comparative efficacy of Ovsynch protocol with or without CIDR insertion observed in Algerian cattle
Estrus- synchronization protocol
(n = 35)
(n = 35)
Synchronized estrus response: n (%)
Conception rate: n (%)
Pregnancy rate per IA by USG: n (%)
The results were better with the CIDR protocol as compared to the Ovsynch protocol alone (Figure 2).
The detection of estrus in our study for the both groups was taken as a response to the treatments after CIDR removal and the second GnRH injection. Regardless of the estrus-synchronization protocol an estrous response was detected in 45 out of the 70 cows treated. However by treatment group, cows that were subjected to Ovsynch alone protocol showed estrus 17 cows (48.6%), while cows that were subjected to Ovsynch plus CIDR protocol showed estrus 28 cows (80%). There was a statistical difference between the two programs.
The cows that responded to the synchronization treatment in both groups were inseminated 12 to 18 h after second GnRH injection.
The pregnancy rate (Table 1) was significantly higher (P<0.05) in CIDR treated group 57.1 % (20/35) as compared to no-CIDR-treated group 31.4% (11/35). This study recorded low pregnancy rate relative to conception rate in Ovsynch group alone.
However, highest synchronized conception rate were recorded in the both protocols (64.7% and 71. 4%) respectively in Ovsynch alone protocol and in Ovsynch plus CIDR group (Figure 2). However, the results revealed greater conception rate in the Ovsynch plus CIDR group than in the Ovsynch group.
Reproductive performance observed in Algerian cattle subjected to
Ovsynch protocol with (n = 35) or without (n = 35) CIDR insertion
In herds with estrus detection problems, the use of estrus synchronization might improve reproductive performance by eliminating the problems associated with estrus detection (Stevensen et al 1999). It has been also reported that approximately 50% of all estrus behaviors may be not detected during the postpartum period (Mialot et al 1999).
To this end, the signs of estrus should be observed three or four times daily and inseminations should be made once a day. The cows that responded in the current study to Ovsynch protocol were 48.6%. This result is comparable to those reported in several studies estimating that ≤ 50% of the cows were detected in estrus in dairy herds (Udin et al 2017; Kandiel et al 2012).
Despite the applications of different Ovsynch protocols, the percentages of cows showing estrus and fertility were still low because there was a relatively lower estradiol concentration around AI (Shamsuddin 2001).
Therefore, the reproductive performance of cows receiving the ovsynch treatment may be improved if progesterone is administered during the period between the GnRH and PGF2α injections to increase the estrous response and conception rate of cows (Xu et al 1997).
Such progesterone treatment is the key player in the estrus induction and potentiates the action of estrogen which is aided by the regressing CL by secreting some amount of progesterone.
On the other hand, the benefits of a timed artificial insemination (AI) system increase under conditions of poor estrous detection rate and poor conception rate.
The estrus response of CIDR treated cows in the present study was significantly (P<0.05) higher (80%) than that reported in Ovsynch alone protocol (48.6%). Few previous works have calculated the estrus response and reported highest estrus rates (Xu et al 2000; Dhami et al 2014).
It has been observed that the progesterone from the controlled internal drug release (CIDR) was sufficient to increase and maintain a progesterone concentration in blood >2 ng/ml in the absence of CL on ovary (Mann et al 2006; Hammam et al 2013; Suthar et al 2012).
Chebel et al (2010) demonstrated that the use of a CIDR insert for 7 days during a timed AI protocol increased the proportion of functional CL in anestrous cows after AI and pregnancy/AI compared to protocols without CIDR.
Additionally, the progesterone concentration during one estrous cycle affects the endometrial morphology in the subsequent cycle and may decrease the number of hypothalamic estradiol-17 β-receptors by negative feedback (Shaham-Albalancy et al 1997).
Xu et al (2000) studied the progesterone treatment at two times with 7 or 8 days of CIDR insertion. According to these authors, changing the synchronization program from 7 to 8 days altered the pattern of estrous response. Although a good estrus rates was recorded in the two protocols used but the distribution in the onset of estrus was more dispersed at the 7 days program that was preferred because it did not reduce the conception rate at the synchronized estrus (Xu et al 2000).
Different conception rates in dairy cows and heifers after synchronized estrus ranging from 30% to 75% were recorded in the Ovsynch program (Kandiel et al 2012; Udin et al 2017).
This study showed good conception rates for the both groups with a slight superiority in favors of the CIDR treated group (71.4%) compared to the no CIDR treated (64.7%) with a statistical difference.
The result recorded in the Ovsynch program is in accordance with previous reports. On the other hand, other reviews founded lower conception rates compared to our result (Ali et al 2012; Mohd Alyas et al 2013; Raste Garnia and Anvari Savojbolghi 2010; Kawate et al 2004). Lower conception rates were also reported with Ovsynch in non-cycling cows and heifers by Nak et al (2011) and Jayaganthan et al (2016).
On the other hand, Vasconcelos et al (1999) reported greatest conception rates in dairy cows that began the Ovsynch protocol between the days 5 and 12 of the estrous cycle. The conception rate for cows in the Ovsynch plus CIDR group in our present study is in line with the findings of Jayaganthan et al 2016 and Kawate et al 2004. This result was greatest to that documented in other works (Bhoraniya et al 2012; Dhami et al 2014; Patel et al 2013).
Several previous works reported higher conception rate in the Ovsynch plus CIDR group than in the Ovsynch group (Ali et al 2012; Jayaganthan et al 2016; Mohd Alyas et al 2013; Rastegarnia and Anvari Savojbolghi 2010).
On the other hand, other workers also recorded higher conception rate in Ovsynch plus CIDR treated cows compared to Ovsynch treated group but without significant differences between the two protocols (Sakase et al 2005; Schafer et al 2007).
The variations in the conception rate of different workers might be due to differences in breed, climate, nutrition, management and different CIDR protocols (Jayaganthan et al 2016). But the reasons for the reduced conception rate cows in Ovsynch group as compared to cow in CIDR treated group could not be determined in the present study. It is possible that providing exogenous progesterone by the inclusion of a CIDR device improved the conception rates of the Ovsynch protocol in postpartum cows (Revah and Butler 1996).
Previous studies have shown that progesterone concentration in the late luteal phase before insemination is positively associated with conception rate (Xu et al 2000). These observations further supported the previous observations on the use of similar protocols in anestrus cows by many workers (Bhoraniya et al 2012; Chaudhari et al 2012; Dhami et al 2014; Ramakrishnan et al 2012).
The pregnancy rate is the product of estrus detection and conception rates (Shamsuddin et al 2001). In a previous study, the pregnancy rates after the Ovsynch studies in dairy cows varied from 27 to 40% (Neglia et al 2003; Taşal et al 2005). Pursley et al (1997) reported a pregnancy rate of 35.1% and 37.8% in heifers and cows respectively.
The pregnancy rate recorded in the Ovsynch group cows was 31.4% that is in the ranges of the authors stated. It was similar to that reported in recent reviews (Gokhan Dogruer 2010; Kandiel 2012; Kasimanickam et al 2008). However, this result is greater as compared to the findings of Caraba and Velicevici (2013) and Buhecha et al (2016).
On the other hand, higher pregnancy rates were reported by other recents works in the Ovsyynch protocol (El-Zarkouny 2004; Akbarabadi et al 2014; Jayaganthan et al 2016). Such low pregnancy rates relative to conception rates recorded in this study could perhaps be the consequence of the reduced fertility of an aged follicle/oocyte induced by estradiol injection (Pursley et al 1997).
In present study, the pregnancy rate in CIDR-treated cows and inseminated following detected estrus was significantly higher as compared to no-CIDR-treated group (57.1% vs 31.4%, P<0.05). Different studies showed an acceptable pregnancy rate after the use of a 7-d CIDR protocol in combination with GnRH and prostaglandin F2α as was reported by Crane et al (2006) and El-Zarkouny et al (2004).
It has been reported that the addition of progesterone to the Ovsynch protocol improved pregnancy (Stevensen et al 2006).
Our pregnancy results are consistent with the results from previous studies. They were similar to those reported by Akhiro et al (2008) and Jayaganthan et al (2016).
According to Moreira et al (2000), one of the advantages of CIDR for pregnancy rate was probably due to the preventive effect against early ovulation in case that it was initiated by the Ovsynch protocol.
Stevenson et al (2006) also reported that overall pregnancy rates for lactating dairy cows treated Ovsynch plus CIDR were 10 and 5% higher than those treated with Ovsynch at days 28 and 56 after timed AI, and respectively more anestrous cows conceived.
On the other hand, it has been also reported that the pregnancy rates of cows treated with Ovsynch plus PRID were 11% higher than those of cows treated with Ovsynch alone but without significant differences (Walsh et al 2007). However, Martinez et al (2002) also reported that the addition of progestin resulted in significantly improved pregnancy rates in heifers but not in cows.
El-Zarkouny et al (2004) reported that anoestrus dairy cow treated with Ovsynch plus CIDR had a higher pregnancy rate than anestrous cows treated with Ovsynch alone. However, cycling cows receiving Ovsynch plus CIDR had a pregnancy rate similar to that of cycling cows receiving Ovsynch alone.
Akhiro et al (2008) indicated that one reason of the higher pregnancy rate in CIDR treated group was probably due to existence of a CL on day 0. Furthermore, the plasma progesterone concentrations in CIDR treated cows remained elevated for 7 days to the time of CIDR removal. Perhaps these elevated progesterone concentrations increased the conception rates (Kawate et al 2004; Sakase 2005).
Authors thank Professor Daniel Tainturier, Head of the Department of Reproductive Pathology, ONIRIS, Nantes (France) for his collaboration in the improvement of this manuscript. They would also like to thank the staff of the farm for the facilities provided.
Akbarabadi M A, Shabankareh H K, Abdolmohammadi A and Shahsavari M H 2014 Effect of PGF2α and GnRH on the reproductive performance of postpartum dairy cows subjected to synchronization of ovulation and timed artificial insemination during the warm or cold periods of the year. Theriogenology, 82: 509-516.
Alam M G S, Azam M S, Khan M J 2006 Supplementation with urea and molasses and body weight, milk yield and onset of ovarian cyclicity in cows. Journal of Reproduction and Development, 52: 529-535.
Ali R, Shukla S P and Nema S P 2012 Hormonal induction of ovarian cyclicity and conception rate in postpartum anestrus buffaloes. Indian J. Field Vet., 7(4): 44-46.
Alnimer M A, Alfataftah A A and Ababneh M M 2011 A comparison of fertility with a cosynch protocol versus a modified ovsynch protocol which included estradiol in lactating dairy cows during the summer season in Jordan. Anim. Reprod., 8: 32-39. Direct Link
Ashit Kumar P, Ton Yoisungnern and Napolean Bunaparte 2015 Hormonal treatment and estrus synchronization in cows: A mini-review. J. Adv. Vet. Anim. Res., 2(1): 10-17. http://bdvets.org/JAVAR DOI: 10.5455/javar.2015.b45
Bhoraniya H L, Dhami A J, Naikoo M, Parmar B C and Sarvaiya N P 2012 Effect of oestrus synchronization protocols on plasma progesterone profile and fertility in postpartum anoestrus Kankrej cows. Trop. Anim. Health Prod., 44: 1191-1197.
Campanile G, Baruselli P S, Vecchio D, Prandi A, Neglia G, Carvalho N A, Sales J N, Gasparrini B and D’Occhio M J 2010 Growth, metabolic status and ovarian function in buffalo (Bubalus bubalis) heifers fed a low energy or high energy diet. Animal Reproduction Science, 122 (1-2): 74-81. https://doi.org/10.1016/j.anireprosci.2010.07.005
Caraba I and Velicevici S 2013 Using Ovsynch protocol versus co synch protocol in dairy cows. Scientific Papers: Animal Science and Biotechnologies. 46(2): 63-65.
Çevik M, Selçuk M and Dogan S 2010 Comparison of Pregnancy Rates after Timed Artificial Insemination in Ovsynch, Heatsynch and CIDR-Based Synchronization Protocol in Dairy Cows. Kafkas Univ Vet Fak Derg16 (1): 85-89. KVFD-2009-451
Chaudhari C F, Suthar B N, Sharma V K, Dabas V S, Chaudhari N F and Panchasara H H 2012 Estrus induction and fertility response in delayed pubertal Kankrej heifers treated with Norgestomet ear implant. Vet. World, 5: 453-458.
Chebel RC, Al-Hassan M J, Fricke P M, Santos J E, Lima J R, Martel C A, Stevenson J S, Garcia R, Ax R L 2010 Supplementation of progesterone via controlled internal drug release inserts during ovulation synchronization protocols in lactating dairy cows. J Dairy Sci, 93:922-931.
Crane M B, Bartolome J, Melendez P, de Vries A, Risco C and Archbald L F 2006 Comparison of synchronization of ovulation with timed insemination and exogenous progesterone as therapeutic strategies for ovarian cysts in lactating dairy cows. Theriogenology, 65:1563-1574.
Dhami A J, Panchal M T, Hadiya K K, Patel J A and Shah R G 2014 Use of controlled breeding techniques under field conditions for estrus synchronization and conception in anoestrus crossbred cows and buffaloes. Proceedings 2nd Annual Meeting of SVSBT and National Seminar on Biotechnological Approaches to Challenges in Animal Health and Production. Veterinary College, DUVASU, Mathura, UP, India, March 6-7. p 86.
El-Zarkouny S Z, Cartmill J A, Hensley B A, Stevenson J S 2004 Pregnancy in dairy cows after synchronized ovulation regimens with or without presynchronization and progesterone. J Dairy Sci 2004, 87:1024-1037.
Hammam A M, Abdel-Gawad E M M, Ali A H and Amer H A 2013 Effect of CIDR-ovsynch regimen as a pharmacological agent on fertility, blood and hormonal patterns of cross breed cows. Glob. J. Pharmacol., 7(4): 383-389.
Iwakuma A, Narahashi T, Kitahara G, Ohkubo M and Kamimura S 2008 Efficacy of Intravaginal Progesterone Administration as an Additional Treatment on Two Types of Timed AI Protocols in a Commercial Herd of Holstein Heifers. J. Vet. Med. Sci. 70(3): 243–249.
Jayaganthan P, Vijayarajan A, Prabaharan V, Rajkumar R, Sivakumar A and Raja 2016 Effect of Ovsynch plus CIDR protocol in Management of repeat breeding crossbred Jerzey cows. International Journal of Science, Environment ISSN 2278-3687 (O) and Technology, Vol. 5, No 6, 3707 – 3712. ISSN 2278-3687 (O)
Kandiel M M M, Bassuoni L A, Sosa G A , Moustaf M A and Ghallab A M 2012 Comparative Efficacy of Ovsynch and Heatsynch Protocols Assessed by Transrectal Ultrasonography and Serum Progesterone in Egyptian Buffalo Heifers. Theriogenology 2(3):173-183.
Kawate N, Itami T, Choushi T, Saitoh T, Wada T, Matsuoka K, Uenaka K, Tanaka N, Yamanaka A, Sakase M, Tamada H, Inaba T and Sawada T 2004 Improved conception in timed-artificial insemination using a progesterone-releasing intravaginal device and Ovsynch protocol in postpartum suckled Japanese Black beef cows. Theriogenology. Volume 61, Issues 2–3, 399–406.
Lucy M C, Billings H J, Butler W R, Ehnis L R, Fields M J, Kesler D J, Kinder J E, Mattos R C, Short R E, Thatcher W W, Wettemann R P, Yelich J V and Hafs H D 2001 Efficacy of an intravaginal progesterone insert and an injection of PGF2α for synchronizing estrous and shortening the interval to pregnancy in postpartum beef cows, peripubertal beef heifers, and dairy heifers. J. Anim. Sci. 79: 982–995.
MADRP 2016 Minister for Agriculture, Rural Development and Peach 12 Boulevard Colonel Amirouche. Algiers Algeria Email: firstname.lastname@example.org
Macmillan K L 2010 Recent advances in the synchronization of estrus and ovulation in dairy cows. Journal of Reproduction and development, 56: S42-S47.
Mann G E, Fray M D, Lamming G E 2006 Effects of time of progesterone supplementation on embryo development and interferone-ƭ production in the cows. Veterinary Journal, 171: 500-503.
Martinez M C, Kastelic JP, Adams G P, Cook B, Olson W O and Mapletoft RJ 2002 The use of progestins in regimens for the fixed-time artificial insemination in beef cattle. Theriogenology, 57: 1049-1059.
Mialot J P, Laumonnier G, Ponsartc C, Fauxpoint H, Barassion E, Ponter A A, Deletang F 1999 Postpartum subestrus in dairy cows: Comparison of treatment with prostaglandin F2α or GnRH+prostaglandin F2α + GnRH. Theriogenology, 52, 901-911.
Moreira F, de la Sota R L, Diaz Tand Thatcher W 2000 Effect of day of the estrous cycle at the initiation of a timed artificial insemination protocol on reproductive responses in dairy heifers. J. Anim. Sci., 78,1568-76.>Moreira F, de la Sota R L, Diaz Tand Thatcher W 2000 Effect of day of the estrous cycle at the initiation of a timed artificial insemination protocol on reproductive responses in dairy heifers. J. Anim. Sci., 78,1568-76.
Nak Y, Tuna B, Nak D, Karakas E and Simsek G 2011 The effects of Ovsynch, Ovsynch with progestin and progestin plus double TAI on pregnancy rates in unobserved oestrus dairy cows and heifers. Kafkas Univ. Vet. Fakul. Derg., 17(6): 917-922.
Neglia G, Gasparini B, Di Palo R, De Rosa C, Zicarelli L and Campanile G 2003 Comparison of pregnancy rates with two estrus synchronization protocols in Italian Mediterranean Buffalo cows. Theriogenology, 60, 125-133.
Patel K R, Dhami A J, Hadiya K K, Savalia K K and Sarvaiya N P 2013 Effect of CIDR and Ovsynch protocols on estrus response, fertility and plasma progesterone and biochemical profile in true anoestrus crossbred cows. Indian J. Anim. Prod. Manag., 29(3-4): 50-58.
Paul A K, Alam M G S and Shamsuddin M 2011 Factors that limit first service pregnancy rate in cows at char management of Bangladesh. Livestock Research for Rural Development, 23: 57. http://www.lrrd.org/lrrd23/3/paul23057.htm (Accessed on August 2, 2014)
Pursley J R, Mee M O and Wiltbank M C 1995 Synchronisation of ovulation in dairy cows using PGF2alpha and GnRH. Theriogenology, 44 915-923.
Pursley J R, Wiltbank M C, Stevenson J S, Ottobre J S, Garverick H A and Anderson L L 1997 Pregnancy rates per artificial insemination for cows and heifers inseminated at a synchronized ovulation or synchronized estrus. J Dairy Sci, 80, 295-300.
Ramakrishnan A, Dhami AJ, Naikoo M, Parmar BC and Divekar BS 2012 Estrus induction and fertility response in postpartum anoestrus Gir cows. Indian J. Anim.Reprod., 33: 37-42.
Rastegarnia A A R and Anvari Savojbolghi H 2010 Effect of CIDR-Based (CIDR Synch) Protocol, for Timed Artificial Inseminations, and on the Conception Rate of Dairy Cows. Journal of Veterinary Clinical Research Fall, Volume 1, Number 4 (4); Page(S) 243 to 252.
Revah I and Butler W R 1996 Prolonged dominance of follicles and reduced viability of bovine oocyte. J. Reprod. Fertil.106:39–47.
Sakase M, Seo Y, Fukushima M, Noda M, Takeda K, Ueno S, Inaba T, Tamada H, Sawada T and Kawate N 2005 Effect of CIDR-based protocols for timed-AI on the conception rate and ovarian functions of Japanese black beef cows in the early postpartum period. Theriogenology, 64: 1197- 1211.
Schafer D J, Bader J F, Meyer J P, Haden J K, Ellersieck M R, Lucy M C, Smith M F and Patterson D J 2007 Comparison of progestin based protocol to synchronize estrus and ovulation before fixed-time artificial insemination in postpartum beef cows. Journal of Anim. Sci., 85: 1940-1945.
Shaham-Albalancy A, Nyska A, Kaim M, Rosenberg M, Folman Y and Wolfenson D 1997 Delayed effect of progesterone on endometrial morphology in dairy cows. Anim. Reprod. Sci. 48:159–174.
Shamsuddin M, Bhuiyan M MU, Sikder T K, Sugulle A H, Alam M G S and Galloway D 2001 Constraints limiting the efficiency of artificial insemination of cattle in Bangladesh. In “radioimmunoassay and related techniques to improve artificial insemination programmes for cattle reared under tropical and subtropical conditions”. Proceeding of a final research co-ordination meeting organized by the joint FAO/IAEA. Division of nuclear techniques in food and Agriculture and held in Uppsala, Sweden. 9-28 p.
Stevenson J S, Pursley J R, Garverick H A, Fricke P M, Kesler D J, Ottobre J S, Wiltbank M C 2006 Treatment of cycling and noncycling lactating dairy cows with progesterone during ovsynch. J Dairy Sci, 89, 2567-2578.
Suthar V S, Burfeind O, Bonk S, Dhami A J and Heuwieser W 2012 Endogenous and exogenous progesterone influences body temperature in dairy cows. J. Dairy Sci., 95(5): 2381-2389.
Taşal I, Ataman M B, Aksoy M, Kaya A, and Karaca Fand Tekeli T 2005 Estimation of early pregnancy by electrical resistance values of vaginal mucosa in cows and heifers. Rev Med Vet, 156, 91-94.
Thatcher W W, Macmillan K L, Hansen P J and Drost M 1991 Concepts for regulation of corpus luteum function and ovarian follicles to improve fertility. Theriogenology, 31: 149-164.
Udin Z, Rahim F, H and Yellita Y 2017 Effect of Ovsynch and Co-synch on Follicle Size and Conception Rate Indifferent Postpartum of Simmental Cows. Asian J. Anim. Vet. Adv 12 (2): 115-122. ISSN 1683-9919 DOI: 10.3923/ajava.2017.115.122
Vasconcelos J L M, Silcox R W, Rosa G J M, Pursley J R and Wiltbank M C 1999 Synchronization rate, size of the ovulatory follicle, and pregnancy rates after synchronization of ovulation beginning on different days of the oestrous cycle in lactating dairy cows. Theriogenology, 52:1067-78. https://doi.org/10.1016/S0093-691X(99)00195-8
Walsh R B, Leblanch S J, Duffield T E, Kelto D F, Walto J S and Leslic K E 2007 The effect of a progesterone releasing intravaginal device (PRID) on pregnancy risk to fixed-time insemination following diagnosis of non-pregnancy in dairy cows. Theriogenology, 67, 948-956.
Xu Z Z and Burton L J 2000 Estrus Synchronization of Lactating Dairy Cows with GnRH, Progesterone, and Prostaglandin F2α. Livestock Improvement Corporation Ltd. Journal of Dairy Science, Vol. 83, No. 3, 471–476.
Xu Z Z, L J Burton and Macmillan K L 1997 Reproductive performance of lactating dairy cows following estrus synchronization regimens with PGF2α and progesterone. Theriogenology 47:687–701.