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Content archived on 2024-04-30

Blastocyst growth, development and viability: relevance to embryo loss and to advances in embryo-related biotechnology in cattle


A major problem faced by the EU cattle breeding industry is embryo loss which compromises reproductive efficiency, genetic improvement and the development and exploitation of embryo-related biotechnology. Fertilization rate is greater than 90%, calving rate is 55%, and 30% of embryos die at the blastocyst stage. Advances in molecular biology, genetic technology and germline manipulation are dependent on a supply of viable IVF embryos but only 25% reach blastocyst stage and, following freesing and transfer their survival rate is lower than those produced in-vivo. Despite its inherent importance, there is an acute lack of information on the development and viability of the cattle blastocyst. Some increment of embryo death prior to blastocyst stage arises from oocyte incompetence, but the critical period is between blastocyst formation and elongation.
The objective is to reduce the high level of embryonic mortality. This involves investigation and correlation of the cellular, biochemical, physiological and genetic mechanisms that control in-vivo and IVF cattle blastocyst development during formation (Days 7/8) and elongation (Days 13/16), in terms of a) differential expression of key genes controlling development, b) nutrient supply, energy metabolism and protein synthesis, c) role of growth factors and their mediation by signal transduction systems and, d) interaction between the blastocyst and uterine environment.
How these mechanisms are affected or modified by in-vivo and in-vitro environments and different developmental histories will be established. The approach is integrated because the methods proposed to study energy metabolism and amino acid uptake are non- invasive, allowing multiple assays on a single embryo and also allowing these embryos to be subsequently processed for analysis in the collaborating laboratories for, changes in gene expression, overall rate of protein synthesis, and the localization and quantitation of growth factor receptors and signal transduction components. The use of confocal microscopy will allow localization of multiple components of interest in a single embryo. These methodologies are particularly valuable for scarce biological material such as embryos.
The disciplines of molecular biology, biochemistry, immunocytochemistry, and cell physiology are applied to in-vivo and IVF embryos from 5 research institutes and an SME, in 5 countries of the EU. The approach is completely novel as it involves multiple assays on a single embryo, allowing correlation of several factors controlling blastocyst development. It will enable information derived from the gene mapping initiative to be placed in a functional context. The objective specifically addresses the priorities of the Biotechnology Workprogramme AREA 3, (3.2.1) on Animal Physiopathology in that, through studies on basic reproductive mechanisms, they aim to improve the reproduction and selection of farm animals.

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Teagasc - Agriculture and Food Development Authority
EU contribution
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31 Tuam

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Participants (5)