Progress 09/01/06 to 08/31/07
OUTPUTS: We have shown that embryo transfer with insulin-like growth factor-1 (IGF-1) treated embryos can result in pregnancy rates in heat stressed cows that are equivalent to those achieved using AI in cool weather. We have also established that IGF-1 protects embryos from direct effects of elevated temperature on development and delineated the role of apoptosis and signaling pathways in this effect. We have tested effects of bovine somatotropin and gonadotropin releasing hormone (GnRH) on fertility of heat-stressed cows and, for GnRH, embryo transfer recipients, and shown these are without effect. We have also shown that acceptable pregnancy rates can be achieved using embryo transfer using embryos produced by fertilization with sexed semen. We have characterized some of the cellular changes caused by heat shock that disrupt embryonic development including elucidating developmental changes in regulation of heat-shock induced apoptosis. This information has been transmitted to
producers via extension meetings (national and state), publications in Hoard's Dairyman and elsewhere, a CD available to dairymen, and through a website called the Dairy Reproduction Cookbook. We have also made the information available to veterinarians at veterinary and scientific meetings and via review articles in scientific publications.
PARTICIPANTS: The following students received degrees as a result of work for this project: Carlos Moises Franco, M.S., 2005, Animal Sciences. Thesis: Strategies to enhance fertility in dairy cattle during summer including use of cryopreservation of in vitro produced embryos. Present position: Owner, Embogen, San Carlos, Bolivia. Dean Jousan, Ph.D., 2006, Animal Sciences (Animal Molecular and Cell Biology), Dissertation: Insulin-like Growth Factor-I and Apoptosis as Determinants of Preimplantation Bovine Embryonic Development. Present position: Assistant Professor, Mississippi State University. Jeremy Block, Ph.D., Animal Molecular and Cell Biology, 2007. Ph.D. Dissertation, Effect of insulin-like growth factor-1 on development and post transfer survival of bovine embryos produced in-vitro. Current position: Postdoctoral Research Associate, University of Florida; co-owner, Embogen, Inc. Luis Augusto de Castro e Paula, Ph.D., Animal Molecular and Cell Biology, 2007. Dissertation
title: Role of oxygen and sphingomyelin metabolism in actions of heat shock on the oocyte and embryo. Current position: Research Scientist, EMBRAPA, Campo Grande, Brazil.
TARGET AUDIENCES: dairy farmers, dairy veterinarians, reproductive biology and animal science researchers
We have been successful in developing procedures for improving pregnancy rate in heat-stressed dairy cows through the use of embryo transfer. Pregnancy rates achieved in heat stressed cows using embryo transfer are equivalent to those achieved using AI in cool weather. This result represents the first solution to the problem of heat-stress induced infertility in dairy cattle. As a direct result of our research, embryo transfer is now being used in the field to improve fertility in heat-stressed cows and two commercial companies provide this service (Transova and Embogen).
- Brad, A.M., and Hansen, P.J. (2007) The block to apoptosis in bovine two-cell embryos involves inhibition of caspase-9 activation and caspase-mediated DNA damage. Reproduction 134, 789-797.
- de Castro e Paula, L.A. and Hansen, P.J. (2007) Interactions between oxygen concentration and glucose concentration that modulate actions of heat shock on bovine oocytes during in vitro maturation. Theriogenology 68, 763-770.
- Hansen, P.J. (2007) To be or not to be - determinants of embryonic survival following heat shock. Theriogenology, 68S, S40-S48.
- Hansen, P.J. (2007) Exploitation of genetic and physiological determinants of embryonic resistance to elevated temperature to improve embryonic survival in dairy cattle during heat stress. Theriogenology, 68S, S242-S249
- Block, J., Wrenzycki, C., Niemann, H., Herrmann, D., and Hansen, P.J. (2008) Effects of insulin-like growth factor-1 on cellular and molecular characteristics of bovine blastocysts produced in vitro. Mol. Reprod. Dev. 75, 895-903.
- Jousan, F.D., Oliveira, L.J., and Hansen, P.J. (2008) Short-term culture of bovine preimplantation embryos with insulin-like growth factor-I prevents heat shock-induced apoptosis through activation of the phosphatidyl 3-kinase/Akt pathway. Mol. Reprod. Dev. 75, 681-688.
- Loureiro, B., Brad, A.M., and Hansen, P.J. (2007) Heat shock and tumor necrosis factor-α induce apoptosis in bovine preimplantation embryos through a caspase-9 dependent mechanism Reproduction 133, 1129-1137.
- Block, J., and Hansen, P.J. (2007) Interaction between season and culture with insulin-like growth factor-1 on survival of in-vitro produced embryos following transfer to lactating dairy cows. Theriogenology 67, 1518-1529.
- Block, J., Fischer-Brown, A.E., Rodina, T.M., Ealy, A.E., and Hansen, P.J. (2007) The effect of in vitro treatment of bovine embryos with IGF-1 on subsequent development in utero to Day 14 of gestation. Theriogenology, 68, 153-161.
- Niasari-Naslaji, A., Hansen, P.J., and Thatcher, W.W. (2007) Successful cryopreservation of in vitro derived bovine blastocysts in microcapillary pipette tips. Iranian J. Vet. Res. 8, 1-7.
- Jousan, F.D., de Castro e Paula, L.A., Block, J., and Hansen, P.J.(2007) Fertility of lactating dairy cows administered recombinant bovine somatotropin during heat stress. J. Dairy Sci. 90, 341-350.
- Jousan, F.D. and Hansen, P.J. (2007) Insulin-like growth factor-I promotes resistance of bovine preimplantation embryos to heat shock through actions independent of its anti-apoptotic actions requiring PI3K signaling. Mol. Reprod. Dev. 74, 189-196.
- Franco, M., Thompson, P.M., Brad, A.M., and Hansen, P.J. (2006) Effectiveness of administration of gonadotropin-releasing hormone at day 11, 14 or 15 after anticipated ovulation for increasing fertility of lactating dairy cows and non-lactating heifers. Theriogenology, 66, 945-954.
- Franco, M., Block, J., Jousan, F.D., de Castro e Paula, L.A., Brad, A., Franco, J.M., Grisel, F., Monson, R.L., Rutledge, J.J., and Hansen, P.J. (2006) Effect of transfer of one or two embryos and administration of gonadotropin releasing hormone on pregnancy rates of heat-stressed dairy cattle . Theriogenology, 66, 224-233.