Recent advances in ovulation synchronization and superovulation in ...

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Abstracts. II International Symposium on Animal Biology of Reproduction, Nov. 19-22, 2008, São Paulo, SP, Brazil. Recent advances in ovulation synchronization and superovulation in buffalo P.S. Baruselli 1 , N.T. Carvalho 2 1 Department of Animal Reproduction, FMVZ-USP, São Paulo, SP, Brazil 2 Buffalo Experimental Farm, APTA, Vale do Ribeira, SP, Brazil. Introduction Associated to the enhancement in reproductive efficiency, techniques used to achieve genetic improvement make possible to obtain herds with better productive characteristics, such as growth rate, carcass quality, milk yield, food conversion and precocity, among others. Thus, multiplication of superior animals by using reproductive biotechniques [artificial insemination (AI) and embryo transfer ET)] can provide greater economic return. Moreover, increased reproductive rates associated to genetic improvement must be the main objective of farmers to improve buffalo productivity and farms income. Therefore, the objective of this presentation is to discuss some strategies that have been tested to increase the AI and ET responses in buffalo. Recent advances in protocols for fixed-time AI in buffalo Artificial insemination in buffalo has limited use worldwide due the difficulties in the estrus detection and in finding an adequate moment for this procedure (Baruselli et al., 2007). Therefore, an alternative to increase the number of buffalo that are inseminated is the use of protocols that allow the AI without the need of estrus detection, usually called fixed-time AI (FTAI). Follicular wave development can be controlled by treatments with GnRH or estradiol and progestogen/progesterone in combination. Treatment of buffalo with GnRH in combination with prostaglandin F2α (PGF2α) 7 d later and a second GnRH 48 h after PGF2α (known as Ovsynch) has resulted in acceptable pregnancy rates after FTAI in cycling buffalo during the breeding season (Baruselli et al., 1999, Berber et al., 2002). FTAI protocols using progestin devices, estradiol and eCG have resulted in synchronous onset of a new follicular wave, synchronous ovulation and consistent pregnancy rates in anestrous buffalo during the off breeding season. (Baruselli and Carvalho, 2003). The combination of these protocols permits the use of AI throughout the year, obtaining conception and calving even in anestrus buffalo during the off breeding season. Recent advances in protocols for superovulation in buffalo Bovine embryo transfer has been applied widely around the world. This technology increases the number of offspring obtained from donors with high genetic value and is used to disseminate desirable genetics around the world. However, buffalo embryo transfer present low efficiency compared to bovine, making difficult the use of this important technique by buffalo farmers (Drost et al., 1983; Baruselli, 1994; Zicarelli, 1994). In our trials buffalo present acceptable follicular response during superovulation (10 to 15 follicles ≥ 8 mm), moderate ovulation rate (~ 60%) and CL yield (5-10) but, in contrast, a low embryo recovery rate (20 to 30%) is observed (Baruselli, 2000). Our results provide strong evidence that low embryo recoveries in buffalo may be explained by a failure of oocyte to entry the oviduct after superovulation. It was also observed that buffalo presented, in average, ovulation rates of 62.8%, which is similar to the one found for bovines (Stock et al., 1996). This result suggests that the low efficiency of MOET is probably not related to follicular response or to ovulation during superstimulation treatment. The calving of buffaloes produced by in vitro embryo production showed that it is possible to obtain an IVF protocol to this species (Neglia et al., 2004; Sá Filho et al., 2008). References Baruselli PS. 1994. Buffalo J Suppl, 2:53-60. Baruselli PS, Carvalho NAT. 2003. Bubalus Bubalis, 27:17-192. Baruselli PS, Carvalho NAT, Gimenes LU, Crepaldi GA. 2007. Ital J Anim Sci, 6:107-118. Baruselli PS, Madureira EH, Visintin JA, Barnabe VH, Barnabe RC, Amaral R. 1999. Rev Bras Reprod Anim, 23:360-362. Baruselli PS, Madureira EH, Visintin JA, Porto-Filho R, Carvalho NAT, Campanile G, Zicarelli Z. 2000. Theriogenology, 53:491.(abstract). Berber RCA, Madureira EH, Baruselli PS. 2002. Theriogenology, 57:1421-1430. Drost M, Wright Junior JM, Cripe WS, Richter AR. 1983. Theriogenology, 20:549-585. Gasparrini B. 2002. Theriogenology, 57:237- 256. Neglia G, Gasparinni B, Brienza VC, Di Palo R, Zicarelli L. 2004. Vet Res Commun, 28:233-236. Sá Filho MF, Carvalho NAT, Gimenes LU, Torres Junior JR; Nasser LFT, Tonhati H, Garcia, JM, Gasparrini B, ZIcarelli L, Baruselli PS. 2008. Anim Reprod Sci. (in press). Stock AE, Ellington JE, Fortune JE. 1996. Theriogenology, 45:1091-1102. Zicarelli L. 1994. Buffalo J Suppl, 2:17-38. E-mail: barusell@usp.br. Anim. Reprod., v.6, n.1, p.195, Jan./Mar. 2009 195
196 Abstracts. II International Symposium on Animal Biology of Reproduction, Nov. 19-22, 2008, São Paulo, SP, Brazil. Current status of germ cell transplantation and testis graft in vertebrates L.R. França Laboratory of Cellular Biology, Department of Morphology, ICB, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil. 31270-901. Spermatogonial transplantation involves the removal of stem cells from a donor testis and their replacement into a recipient largely deprived or lacking endogenous spermatogenesis, where these transplanted cells grow to form mature fertile sperm with genetic characteristics of the donor. Since spermatogonial transplantation from mouse-tomouse was first reported by Brinster and colleagues in 1994, many important developments in this fascinating methodology such as interspecies transplants, transplants from cryopreserved and cultured spermatogonial stem cells have been made. In this regard, this technique has been shown a powerful approach to studying the biology of spermatogonial stem cells and their microenvironment, the stem cell niche. Also, several important functional questions regarding Sertoli-germ cell interactions and the role of the Sertoli cell and germ cells during spermatogenesis have now been answered. Transplantation of cultured spermatogonial stem cells is now opening exciting possibilities for in vitro multiplication of male germ cells and transfection or retroviral transduction has shown that it is now possible to produce transgenic mice. By freezing and storing testicular tissue, it should be possible to preserve indefinitely the genetic stocks of valuable farm animals, endangered species and unique experimental animals, until a suitable recipient can be found that will maintain the germ line. Also, because many cases of male infertility have proved intractable to therapy, spermatogonial transplantation has also potential clinical applications to address human infertility. For instance, if the testis of infertile individuals contains at least spermatogonial stem cells, it might be possible to transplant these cells into a host testis of the same or different species to obtain sufficient sperm of donor origin to achieve a pregnancy using ICSI. Another potential clinical use of spermatogonial transplantation technique is the replacement of the germ line in patients whose endogenous stem cells had been eliminated (or damaged) as a result of gonadotoxic chemo-or radiotherapeutic treatment.The spermatogonial transplantation efficiency is still relatively poor and presents limitations related to the preparation of donors, recipients, and the quality of germ cell development after transplant. Also, although germ cells from rabbits, dogs, large domestic animals (boar, bull and horse), primate (baboon) and humans into nude mice were able to colonize the testis at different degrees, no spermatogenesis of the donors occurred. These results suggest that the success of transplantation might be positively related to the degree of phylogenetic proximity of species during evolution. To bypass this limitation, recent investigation grafting small pieces of testis tissue from several species into nude mice hosts showed that male germ cells could be propagated and produce fertile spermatozoa. This approach created a totally new scenario in this field allowing, for instance, the production of transgenic domestic animals. However, regardless of its limitation germ cell transplantation has been proved to be an extraordinary and powerful technique to investigate reproductive biology and stem cell biology in mammals and, more recently, in other vertebrates such as fish. Financial support: CNPq and FAPEMIG E-mail: lrfranca@icb.ufmg.br Anim. Reprod., v.6, n.1, p.196, Jan./Mar. 2009
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