How to produce more embryos

Biotechnology researchers of the PCC (Philippine Carabao Center) have found what influence the maturation under incubator condition of eggs from ovaries of slaughtered buffaloes so that these can be successfully fertilized and developed into embryos that are ready for transfer to recipient animals.

A series of studies was conducted at the PCC Satellite Embryo Biotechnology Laboratory in India and at the PCC headquarters in Nueva Ecija by Danilda H. Duran, Dr. Peregrino G. Duran, Dr. Eufrocina P. Atabay, Dr. Edwin C. Atabay and Dr. Libertado C. Cruz with the collaboration of Japanese biotechnologists Dr. Y. Takahashi and Dr. Y. Kanai.

The results of the studies were presented during the recent 2007 annual convention of the Philippine Society of Animal Science and won the best paper award.

To determine the capability of oocytes to mature under incubator condition and be fertilized into embryos, the researchers ranked the oocytes that they collected at the Frigorifico Allana Limited slaughterhouse in India into five based on the density of the cumulus cells surrounding each oocyte.

Danilda Duran, who is pursuing a doctor of philosophy program in Japan under a fellowship from the JSPS (Japan Society for the Promotion of Science), said oocytes surrounded by five layers of cumulus cells have the best maturation and development into embryos under incubator condition. This was followed by those with three to four layers of cumulus cells, less than three layers, no cumulus cells, and those surrounded by expanded cumulus cells.

Since only 20 percent of the collected oocytes were surrounded by five layers of cumulus cells and the developmental potential of these oocytes did not significantly differ from those with three to four layers, the researchers put the two types of oocytes together and further classified them based on the granulation of the ooplasm or interior portion of the egg.

The study showed that whether the ooplasm is evenly granulated (homogeneous) or unevenly granulated (heterogeneous), development into mature embryos is not significantly affected. However, oocytes with loose cumulus cells and heterogeneous ooplasm mature faster (18 to 22 hours) inside the incubator to yield more embryos at the blastocyst stage after fertilization in the incubator. 

On the other hand, oocytes with homogeneous ooplasm and surrounded by compact cumulus cells mature longer (22 to 24 hours) inside the incubator to yield more embryos that are ready for transfer to recipient animals.

Based on size, ooplasms that are 120 to 139 micrometers had the best developmental potential (32 percent), followed by bigger oocytes (20 percent), indicating that they have already weakened.

Thus, Danilda Duran said the oocytes must be classified and separated based on their morphology and quality to optimize the production of embryos that are ready for transfer to recipient animal. – Sosimo Ma. Pablico