Viability of bovine embryos following exposure to the green filtered or wider bandwidth light during in vitro embryo production.

BACKGROUND Microscopic light during in vitro production (IVP) is a common stress factor compromising embryo development and viability. Many studies discussing detrimental effects of light have been conducted on in vivo matured/fertilized oocytes or on flushed embryos that were exposed to light only when cultured in vitro. The aim of this work was to examine the effects of light composition during all IVP steps on subsequent embryo development and quality. METHODS We compared the effects of a green pass filter of 498-563 nm wavelength, and a wider bandwidth of stereomicroscopic light on bovine embryo development rates, total cell counts and the presence of constitutive (Hsp73) and stress-inducible (Hsp72) forms of the Hsp70 protein. RESULTS The use of the green filter had no effect on embryo development rates, morphological quality or total cell counts on Day 7 or 8 of development compared with control group. However, Hsp72/73 protein levels revealed the protective effect of the filter against harmful blue and infrared regions of the light. The constitutive form Hsp73 was seen in both groups, but the inducible stress-response form Hsp72 was absent from the filter group embryos and appeared only in the group exposed to the stereomicroscopic light. CONCLUSIONS An easy to use and inexpensive green filter seems to reduce the stress caused by light during the IVP procedures without affecting either the accuracy of embryo monitoring or the need to increase the light intensity.