Reproduction in Domestic Animals - Facultad de Ciencias Veterinarias

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16 t h International Congress on Animal Reproduction 6 Workshop Abstracts presence of A. pyogenes or viral infection. The exotoxin of A. pyogenes, pyolysin (PLO), causes epithelial and particularly stromal cell death. Similarly, BoHV-4 is highly tropic for the endometrium, causing a rapid cytopathic effect in stromal and then epithelial cells. This tropism may be because viral replication is activated by prostaglandin E 2 , which is constitutively secreted by the stromal cells. Further exploration of the molecular mechanism of microbial infection and immunity will lead to greater understanding of how uterine disease impacts fertility, and provide insights to help develop new therapeutic approaches. This work was supported by the Wellcome Trust and BBSRC. Workshop 02 - Factors Affecting Pregnancy Rates in Estrus Synchronization Programs in Beef Heifers Moderator: Gabriel Bo (Argentina) WS02-1 Reproductive management of cycling and non-cycling Bos taurus beef heifers in the USA Lamb, G North Florida Research and Education Center, University of Florida, Marianna Estrus synchronization and artificial insemination (AI) are reproductive management tools that have been available to beef producers for over 30 years. Synchronization of the estrous cycle has the potential to shorten the calving season, increase calf uniformity, and enhance the possibilities for utilizing AI. Artificial insemination allows producers the opportunity to infuse superior genetics into their operations at costs far below the cost of purchasing a herd sire of similar standards. These tools remain the most important and widely applicable reproductive biotechnologies available for beef cattle operations in the USA. However, beef producers have been slow to utilize or adopt these technologies into their production systems. Several factors, especially during early stages of development of estrus synchronization programs, contributed to the poor adoption rates. Initial programs failed to address the primary obstacle in synchronization of estrus, which was to overcome the late onset of puberty in heifers. Additionally, these programs failed to manage the timing of ovulation precisely, resulting in more days over which detection of estrus was necessary. This ultimately precluded fixedtime AI (FTAI) with acceptable pregnancy rates. More recent developments focused on the control of both the corpus luteum and follicle waves in convenient and economical protocols to synchronize the timing of ovulation, facilitating FTAI. This new generation of estrus synchronization protocols uses two strategies which are key factors for implementation by producers because they: 1) minimize the number and frequency of handling cattle; and 2) eliminate the need for detection of estrus by employing FTAI. However, developing FTAI protocols in beef heifers has not been straightforward because of the inability to synchronize follicular waves reliably with gonadotrophin-releasing hormone (GnRH). For example, after an injection of GnRH at random stages of the estrous cycle, 60 to 90% of postpartum cows ovulated; whereas, only 48 to 60% of beef and dairy heifers ovulated in response to the same treatment. Therefore, most recent research continues to focus on inducing onset of puberty in noncycling heifers and enhancing synchrony of ovulation by incorporating progestin devices in GnRH-based protocols to facilitate FTAI and improve fertility in heifers. WS02-2 Why are pregnancy rates to fixed-time AI generally lower in Bos indicus than Bos taurus cattle McGowan, M*; Butler,S; Phillips, N School of Veterinary Science, The University of Queensland, Brisbane, Australia The recent developments in quantitative and molecular genetics which have led to improvements in our ability to select for a range of important production traits in beef cattle (carcass quality, fertility, health & welfare), have increased the need to develop practical and effective programs which efficiently disseminate selected genetics. As the major grazing rangelands for beef cattle are located in tropical and subtropical regions, development of artificial breeding programs which focus on maximizing the reproductive outcome in Bos indicus cattle, the genotypes most suited to these environments, is essential. However, most of the treatment protocols for synchronization of oestrus have been developed for Bos taurus cattle with the assumption being that usage in Bos indicus cattle will result in similar outcomes. Although some publications report similar reproductive outcomes, marked, frequently unexplained variation in response to hormonal treatments to synchronise oestrus, continue to be important factors limiting the widespread usage of this technology in extensively managed Bos indicus herds. Progestin and progesterone implants combined with prostaglandin F2α, oestrogen and gondaotrophin treatments are most commonly used for fixed-time AI (FTAI) of Bos indicus females. The reported responses to these treatments in terms of animals detected in oestrus between 48 to 72 h after implant removal, and animals diagnosed pregnant to FTAI vary considerably (44 to 98% and 37 to 62%, respectively). A series of recently completed studies conducted in northern Australia have shed some light on potential causes of the observed variation in response of Bos indicus heifers. When 300 cycling disease-free Brahman heifers weighing 289±30 kg, were randomly assigned to be treated with oestradiol benzoate (ODB) and intravaginal implants (8 day insertion) varying in progesterone content (0.78g, 1.56g, 1.9g) followed by ODB treatment (Day 9) and FTAI 48 to 54 hours after implant removal, the overall pregnancy rate was 35%. However, the pre- and post-AI progesterone profiles of a random samples of 10 heifers from each group indicated that 32% (n=30) had plasma progesterone concentrations of 1ng/ml. Consideration should be given to investigating the role of hormonal treatments in inducing suboptimal preovulatory follicular and corpus luteum development in Bos indicus cattle. WS02-3 Fixed-time artificial insemination in cycling and noncycling Bos indicus beef heifers Baruselli, PS 1 *; Sales, JNS 1 ; Crepaldi, GA 1 ; Sá Filho, MF 2 ; Carvalho, JBP 3 ; Bo, GA 4 1Animal Reproduction Department, FMVZ/USP, São Paulo-SP, Brazil; 2FIRMASA-IATF, Campo Grande-MS, Brazil; 3 Vale do Paraíba Regional Station-Apta, Av. Prof. Manoel Cesar Ribeiro, No. 320, Caixa Postal 7, Pindamonhangaba, SP, Brazil; 4 Instituto de Reproducción Animal Córdoba, J.L. de Cabrera 106, X5000GVD Córdoba, Argentina Fixed-time artificial insemination (FTAI) protocols have generally yielded poor results in B. indicus heifers. It was hypothesized that follicular growth in Bos indicus heifers might be suppressed by circulating progesterone concentrations during the treatment protocol. It is speculated that lower steroid hormone clearance rates in Bos indicus cattle may account for the higher circulating progesterone concentrations during progesterone treatment resulting in reduced LH pulsatility and follicular growth rates. A series of experiments were designed to determine if synchronization of follicle wave emergence and ovulation with estrogen and subluteal progesterone concentrations during growth of the ovulatory follicle would improve the synchrony of ovulation and pregnancy rates following FTAI. Treatment with PGF at the start of progestin treatment resulted in decreased circulating progesterone concentrations and increased the follicular growth rates, dominant follicle diameters and ovulation rates. In comparison to CIDR, norgestomet ear implants resulted in increased dominant follicle growth rates leading to ovulatory follicles with larger diameters. Dose and estradiol ester were important factors in synchronizing follicle wave emergence. A dose of 2.5 or 5 mg estradiol valerate resulted in a longer and more variable interval from treatment to follicular wave emergence than 2 mg of estradiol benzoate (EB), which affected preovulatory dominant follicle size
16 t h International Congress on Animal Reproduction Workshop Abstracts 7 following progestin removal. Interestingly, satisfactory ovulation rates occurred in both cycling and non-cycling heifers treated with norgestomet ear implants, 2 mg EB at implant insertion and 1 mg EB 24 h after implant removal. Treatment with eCG at implant removal also increased dominant follicle growth rate, preovulatory follicle diameter, ovulation rate, and pregnancy rates in Bos indicus heifers that were FTAI. Nevertheless, conception rates in heifers that ovulated after treatment was lower in non-cycling than in cycling heifers which may be related to the immaturity of the hypothalamopituitary axis and the reproductive tract. An alternative in non-cycling heifers may be to use a priming treatment with a progesterone releasing device 20 to 40 days prior to initiating synchronization treatments. Data suggest that FTAI in Bos indicus heifers can be successful providing follicle wave emergence is synchronized and methods that result in increased ovulatory follicle growth, such as reduced progesterone concentrations and treatment with eCG are employed. Workshop 03 - Factors Influencing the Embryo Quality Moderator: Li Ning (China) Xiuchun Tian (USA) WS03-1 Modifications in oocyte maturation and/or embryo culture to improve quality of pig somatic cell cloned embryos Zhang, Y 1,2 , Zhang, K 1,3 , Wie, H 1 , Li, J 4 , Li, Q 1 , Dai, Y 1 & Li, N 1 * 1State Key Lab of Agrobiotech., China Agr. Univ., Beijing 100094, China; 2College of Anim. Sci. Tech., Anhui Agri. Univ., Anhui 230036, China; 3Department of Animal Sciences, University of Florida, FL 32611-0910, USA; 4Dept. of Genet. Biotech., Facul. of Agr. Sci., Univ. of Aarhus, Tjele, 8830, Denmark Somatic cell nuclear transfer (SCNT) is regarded as a tool with great potential in agriculture, medicine and basic research. For pigs, the efficiency of producing viable offspring from cloned embryos is poor. Suboptimal oocyte maturation and/or embryo culture are major bottlenecks limiting commercialization of pig SCNT. Oocytes are crucial starting material for SCNT therefore we examined effects of oxygen tension, leptin addition during IVM on development of SCNT embryos. Blastocyst rates and total cell number per blastocyst of SCNT embryos from oocytes matured under low (7%) O2 tension were significantly higher than those of embryos from oocytes matured under higher (20%) O2 tension (blastocyst rates: 16.3±0.9% vs. 6.5±0.6%, total cell number per blastocyst: 38.4±2.0 vs. 30.4±2.2%, respectively; P
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Reproduction in Domestic Animals - Facultad de Ciencias Veterinarias

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