Fixed timed artificial insemination (FTAI) through progestagen (CIDR) of 1^st, 2^nd, 3^rd and 4^th uses in bovine: II. Conception rate related to times of CIDR use, to the semen used, to artificial insemination technician and to farm management

P C H Melo, W G Vale^*/**, W Ernane, S T Rolim Filho, H F L Ribeiro, A N Reis^*, J S Sousa^* and A O A Silva^*

Universidade Federal Rural da Amazônia, Instituto da Saúde e Produção Animal, Setor de Reprodução Animal,
Av. Presidente Tancredo Neves nº 2501, Montese, CEP 66.077-530 - Belém, Pará, BRAZIL
wmvale@hotmail.com
* Central de Biotecnologia de Reprodução Animal – CEBRAN, Universidade Federal do Pará - UFPA,
Rua João Henrique de Carvalho, S/N, CEP 68.741-400 - Castanhal, Pará, BRAZIL
** Instituto de Biodiversidade e Florestas, Universidade Federal do Oeste do Pará – UFOPA,
Rua Vera Paz, Campus I – Tapajós, CEP 68035-110, Santarém, Pará, BRAZIL

Abstract

This study had the purpose of verifying the efficiency of fixed timed artificial insemination (FTAI) through the progesterone releasing device (CIDR ® Pfizer 1.9g P₄) of 1^st, 2^nd, 3^rd and 4^th uses in n=18665 Zebu females (Bos taurus indicus) and n=409 crossed Zebu x European (Bos taurus indicus x Bos taurus taurus) breeds in a total of n=19071 females. Among 19071 females subjected to FTAI, n=10797 became pregnant, representing an overall conception rate of (56.5%); the conception rates (CRs), according to the times of the CIDR uses and reproductive category, among n=19071 female submitted to FTAI, were for the multiparous at the 1^st, 2^nd, 3^rd and 4^th CDIR uses n=3563 (60.0%), n=1807 (56.7%), n=1560 (58.3%) and n=676 (59.2%) respectively; for nulliparous females at the 1^st, 2^nd, 3^rd and 4^th CDIR uses it was found n= 471 (56.7%), n=765 (53.1%), n=36 (51.4%) and n=203 (51.9%), respectively; for primiparous n=622 (51.0%), n=384 (47.4%), n=345 (47.3%), n=104 (46.2%) and for open females for 1^st n=110 (54.4%), for 2^nd n=94 (58.0) and 4^th use n=57 (64.0%),  respectively.

It was observed  a statistical significant difference (P <0.0002) among different groups; the average of highest and lower CR related to the semen used among 20 different sires was (56.6%) and varied from (67.7%) for the “sire I” whereas it was (41.8%) for “sire Q”, respectively; even though five sires showed CRs superior to (60.0%) whereas only two sires showed CRs lower as (50.0%); the CR related to the artificial insemination technician (AIT) showed that among 14 AITs which were used in this survey the higher and lower CR was obtained by the AIT #14 and #9 (76.4%) and (43.2%) respectively, although #4, # 5 and #3 AITs have obtained CRs upon (60.0%), (50.0%) and (40.0%), respectively; for stocking rate regarding the CR related to the farm management among the n=28 farms included in this study the higher farm #2 and the lower  farm #1 among the farms worked  obtained CRs of (77.0%) and (44.4%), respectively,  therefore 19 farms have got CRs upon (50.0 %).  It seems obvious that many factors were involved on this concern such as quality of pasture, stocking rate, mineral supplement and reproductive management, although such parameter were not submitted to statistical analysis. Indeed, this study suggests that the adoption of FTAI and the re-uses progesterone (CIDR ® Pfizer 1.9g P₄) is a feasible and economic technology to be used to increase beef production system activity inside the adaptations required among the so-called development sustainable achievement, actually one of the main challenges among the strategies aiming the increasing Brazilian cattle productivity in the Amazon region.  

Key words: Amazon, cattle, fertility, hormones, reproductive management

Introduction

Cattle ranching in the Amazon in the last decades have experienced unprecedented growth, with surprising results in view of its satisfactory profitability. This development generates increased income for the farmers, as well as jobs in the various production segments. On the other hand, in other regions of Brazil, the beef cattle production expansion has lost force, as areas that could be opened to livestock, were running out and / or being used in agriculture. In the specific case of Pará State in 2010, this flock peaked at 23 million cattle, and almost one million buffalo heads. This extraordinary growth of more than 30% is due, in large part to migration of livestock from other regions of the country to Pará state (Portal Amazon, 2007). Moreover with the advent of the use of hormonal treatments to improve the reproductive performance in Bos taurus indicus cattle it is possible to re-establishment of postpartum ovarian cyclicity in the bovine herds with a substantial increase of the reproductive efficiency (Baruselli et al 2003). Meanwhile the use of fixed timed artificial insemination (FTAI) has proved to be an excellent tool against high incidence of postpartum anoestrous that increases the calving to conception interval and, as consequence , negatively affects the fertility of females Zebu cattle in the tropical areas (Baruselli et al 2004, Barros 2007).

Among the hormones compounds used in FTAI, progesterone (P₄) is a steroid secreted by luteal cells of the corpus luteum, the placenta and the adrenal gland, and is transported in the blood, having the function of preparing the endometrium for implantation and maintenance of pregnancy, acting synergistically with estrogen to induce sexual behavior, with its high levels inhibit the heat and pulsating waves of LH (Hafez and Hafez 2004).

In treatments with progesterone or progestin, often is used melengestrol acetate (MGA) orally, progesterone and medroxyprogesterone acetate in the form of intravaginal devices (IVD) and norgestomet in the form of subcutaneous implants. In general, the progestins have similar effects of pharmacological agents to progesterone, used in the synchronization of estrus to prolong the luteal phase (Zilbelman  and Smith 1966). The use of estrogen (E2) at the beginning of treatment with progesterone, was of great importance to prevent the formation of persistent follicles and allow the development of a new follicular wave, resulting in a dominant ovulatory follicles ready for fertilization (Madureira 2000).

The artificially high concentrations of P₄ limits follicular growth, negative feedback to GnRH, inhibiting the release of LH (Hafez and Hafez 2004). The feedback mechanism of E2 and P₄, while independent of each other on LH secretion may be different (Stock  and Fortune 1993). However, when administered in combination, E2 enhances the ability of P₄ in the suppression of circulating LH (Stumpf et al 1993). Therefore, combining the effects of P₄, inhibition of frequency of LH pulses, with the effects of E2, as a luteolytic agent, is able to synchronize the emergence of a new follicular wave (Adams 1994).

In Brazil, different FTAI protocols have been developed using progesterone/progestagens releasing devices as well as the use of  GnRH plus PGF_2α protocols without monitoring estrus detection followed by AI 12 h later with fertility results up 50.0% of conception rates (Baruselli et al 2003, Baruselli et al 2004, Vale et al 2011). Furthermore, another alternative for the use of hormonal compounds based in progesterone/progestagens releasing like CIDR in FTAI is the possibility of the re-use of such devices which has a positive impact on the final production cost of this biotechnology (Pinto-Neto  et al 2009).  The conception rates in cows treated with P₄ implants and estradiol benzoate (EB) are around 50-64% with FTAI (Baruselli et al 2003, Carvalho 2004). Sá-Filho et al (2003), working with beef heifers using protocols with intravaginal  P₄ device associated with EB for FTAI found conception rates ranging from 46.0 to 64.0%. Lucy et al (2001) working with beef cows in anoestrus, cyclic  heifers  prepubertal, cycle heifers pubertal and milk cows found the following conception rates using  progesterone (CIDR ® Pfizer 1.9g P₄) 57.0% , 63.0%, 58.0%, 61.0% and 54.0% , respectively.

Thus the objective of this study was to evaluate the conception rate in cows submitted to artificial insemination in fixed time in farms located in southeastern Pará state, Brazil and the influence of factors such as CRs related to times of  CIDR uses, to  semen used, to artificial insemination technician, to the farms management. 

Materials and Methods

Location
This study was conducted in partnership with n=28 different commercial farms located in the municipalities of  Paragominas, Ulianópolis, Aurora do Pará, Thailand and Tome-Açu, in northeastern Pará State, Brazil. The technical operations such as selection of the females, synchronization, monitoring protocols, artificial inseminations and the final diagnosis were performed in the period from July 2009 to March 2010, The average annual temperature was 26° C range (19-38^o C) where the dry period lasted from July to December and a rainy season from January to June, with annual rainfall of 2250-2750 mm³ and relative humidity around 85%. (Portal Amazon 2007). 

Animals

In the present study n=18662 Zebu females (Bos taurus indicus) and n=409 crossed Zebu x European (Bos taurus indicus x Bos taurus taurus) were bred and raised in extensive management. Four reproductive category were used: nulliparous females n=2730, lacting primiparous n=2981, lacting multiparous n=12907,  cows and open cows n=453.  The postpartum females had at least 30 days calved. All animals were subjected to a gynecological clinical examination and evaluated according to their body condition scoring (BCS), within a variation of 1.75 to 5.0 on a scale of 1.0 (very thin) to 5.0 (obese) at intervals of 0.25 points according to  Houghton et al (1990). 

Hormonal treatments

All animals were synchronized by the same protocol recommended by Pfizer Animal Health Program, which consisted of: day zero (D0) was held to introduce the device to intravaginal progesterone (CIDR ® Pfizer 1.9g P₄)  and this was the 1st, 2nd, 3rd or 4th use, randomly distributed among the animals. Then it was carried out applying 2 ml of estradiol benzoate (2.0 mg Estrogin Farmavet ® BE) via intramuscular (IM). On day seven (D7) was applied 2.5 ml tromethamine dinoprost (Lutalyse Pfizer ® 5mg PGF_2a) IM. On day nine (D9) was held on removal of the (CIDR ® Pfizer 1.9g P₄) followed by an IM application of 0.3 ml of estradiol cypionate (ECP ® 5mg Pfizer E2). On day 11 (D11), artificial insemination was performed in all animals. The reuse the implants was performed with a wash with ethanol 70% for 5 minutes and subsequent washing with water to remove excess alcohol following the drying at room temperature of  22^o C (Pinto-Neto et al 2009). 

Reproductive management

The females were inseminated after hormonal protocol of 11 days duration and females presenting to the return-rate was used a second conventional artificial insemination however the non-pregnant animals were further subjected to natural breeding. It was used semen from n=20 sires randomly selected from a semen bank composed of 81 sires, purchased from commercial artificial insemination stations. Conception diagnosis was performed by ultrasonography and rectal palpation between 30 and 45 days after FTAI. The FTAIs were performed by 34 artificial insemination technicians with previous experience in FTAI and supervised by a Veterinarian however for statistical analysis only 14 technicians were evaluated. In the process semen of thawing it   was employed defroster electronics, to facilitate and standardize the process. All animals were followed individually, and their data recorded in an Excel spreadsheet.

Statistical analysis

The results were analyzed using Statistical Analysis System program version 8.0 (SAS 1996). The original data were subjected to chi-square test, with significance level of 5% (P <0.05). It was compared conception rates (CRs) between variables such as artificial insemination, semen, reproductive category (nulliparous, primiparous lactating, multiparous and open cow without calf), number of uses of the CIDR, the CR related to semen used, to artificial insemination technician and the farms management. 

Results and discussion

Conception rate in related to the times of CIDR uses

The conception rate (CR) in relation to the times of usage was 58.2%, 54.5%, 55.9%  and 56.3% for the first, second, third and four uses, respectively, with statistical significance  difference (P <0.0002) among the results, as shown in Table 1.

Comparing the times of the CIDR utilization and total CR, it was found a statistical significance difference between the first and second use (P <0.0001) and between first and third use (P = 0.0229). Probably the no existence of statistical difference between first and fourth use (P = 0.1403), was due the low numerical representation of the fourth use, compared to first. Anyhow with the use of CIDR, is expected to occur blocking the release of GnRH, thereby preventing the secretion of LH, which will accumulate in the pituitary. According to Savio et al (1993), plasma progesterone concentrations above 1 ng / ml are sufficient to suppress the release of endogenous LH. At the time of CIDR removal, progesterone levels fall, causing the hypothalamic-pituitary resume its activity, releasing LH and allowing ovulation to occur. However for Meneghetti and Vasconcelos (2008), the efficacy of CIDR (P₄ 1.9g) in relation to fertility of heifers and beef cows when used for nine consecutive days can be used four times, totalling 36 days of use.

Furthermore, comparing the conception rate within each category, it was observe that there was significant difference (p< 0.05) in animals that were used CIDR-1^st , 2^nd , 3rd and 4^th use, as shown in Table 2. For primiparous females, the CRs of 1^st , 2nd and 3rd use, 51.0%, 47.4% and 46.2% , respectively, were lower than those found by Favacho (2009), which reported 54, 9%,  50.3% and 50.6%  for the 1^st, 2^nd and 3^rd  CIRD uses , respectively.

However, for  multiparous females, the results here obtained for 1^st CIDR use,  60.0% of CR  are similar to those reported  by Colazo et al (2004), who obtained 60.2%, again using CIDR. Besides, it was only observed statistical difference in the use of CIDR, within the category of multiparous, which may have occurred due to the largest numerical representation of this category compared to the others. This category of multiparous, had the best rates on the 1^st  and the 4^th  uses of CIDR diverging concepts, but this may have occurred due to much higher numerical representation of the 1^st compared to 4^th , respectively.

Moreover, according to the results of the present work, the multiply CIDR uses for up to four times is quite feasible to obtain satisfactory CRs (Bartolomeu 2003). Indeed it can be also considered that, nulliparous, primiparous and open cows have almost the same pregnancy rate independent of the  uses of the CIDRs, Table 2.  

On the whole, comparing the use of the devices on the overall conception rates, it can be observe that there was a statistical significant difference between the 1^st and 2^nd uses (P <0.0001) and between one and three uses (P = 0.0229). Therefore probably the absence of statistical difference between 1^st and 4^th uses (P = 0.1403), was due the low numerical representation of the 4^th use, compared to 1^st use. 

Conception rate as a function of semen used 

In relation to semen used, it can be observed that the “sire Q” obtained the lowest conception rate of 41.8% whereas  the “sire I” showed the highest  conception rate of 67.7%, with a high significant statistical difference (P <0.0001), which can be seen in Figure 1.

Monard (2008) evaluated the influence of variation found semen used 47.3 to 77.7% in the pregnancy rate as well as showing significance found in this work. Evaluating two semen used for artificial insemination in fixed time Costa (2009) found significant differences between them, and reported a CR of 62.2 and 49.4 per cent for the first and second sire, respectively, showing that semen quality may influence the pregnancy rate in a FTAI program.

The difference in the CR according to semen used may occur due the low quality management of some frozen semen batches during the cryopreservation process at laboratory level as well as by the negligence of the inseminator thawed semen. According Celeghini (2005) the low fertility associated with IA has been attributed to processes occurring during the freezing of semen, which causes damage to sperm. Attention should be paid to the semen that you are using since it has great influence on pregnancy rate. 

Conception rate in accordance with artificial insemination technician efficiency 

In assessing the artificial insemination technicians (AITs) efficiency involved to FTAI, it was not found any statistical difference (p <0.0001) between the indices of the same individual.  However the AITs  # 14 and  # 9 showed the higher and lowest performance with 76.4% and 43.2% of CRs, respectively, as shown in Table 3.

This difference may have occurred for several reasons: the experience of the AIT, attachment and commitment that the company has with artificial insemination programs (Fernandes et al  2001), skills and professional responsibility of the personal involved in the FTAI program (ASBIA 2010), fatigue of the AIT, hygiene at the time of insemination  (Diniz 1996), education level of the AIT (Murta et al 2001), among other factors. 

Favacho (2009), in his work using nine AITs, also found significant variation in CRs among these individuals, with the highest rate of 64.4% and the lowest pregnancy rate, 37.6%, results lower than those obtained in the present work. That being so, the findings observed in this study are satisfactory, since most of inseminators individual index showed more than 50% of CRs. 

Conception rates related to farms management

This study evaluated n=28 farm management and found significant differences between groups (P <0.0001). In the farm  # 2  and # 1 it was found the highest and lowest CRs  77.0% and 44.1%, as shown in Figure 2. On this concern it can be speculated that  such differences were due the fact that each farm have its own peculiarities and differences in  soil quality, management, manpower, semen, and grazing animals. 

Favacho (2009), comparing conception rates among different retreats in the same property, found a significant difference in CRs (P <0.05), where the retreat with best  and lower conception  rates showed  of 65.7% and 41.3%, respectively, suggesting that CRs could be related to the management of individual farming system and the amount of vegetation or shaded areas. Indeed, if within the same farm, there are differences in CRs among the different retreats,  it can be also acceptable to consider normal the differences among CRs among the different  farms  used in this work. 

Conclusion

Under the conditions of this study, it can be concluded that:

• The protocol used for synchronization was efficient, since the conception rates were similar to the ones mentioned in the literature.

  
  

• The reuse of CIDR is an important measure for reducing the cost of FTAI, being a feasible alternative to improve the cost benefit of FTAI.

  
  

• In general it can be considered that semen, artificial insemination technician and farm management can significantly influence the conception rates using FTAI.

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Received 4 December 2011; Accepted 6 March 2012; Published 2 April 2012

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