Development of a simple, portable carbon dioxide incubator for in vitro production of bovine embryos

The objective of this study was to develop a simple and portable CO, incuba tor using effervescent granules (EG) and to examine the effect of negative and positive air pressure for in vitro maturation (IVM), fertilization (IVF ) and culture (IVC) of bovine oocytes, In experiment 1, cumulus-oocyte comp lexes (COCs) were matured (22 h), fertilized (5 h) and cultured (7 days) us ing 0.25, 0.5 or 1.0 g of EG per 0.6 1 added to maintain an optimum level o f CO2 (approximately 3, 6 or 12%, respectively) for in vitro production of embryos. Control oocytes, zygotes and embryos were cultured in a standard C O, incubator. The blastocyst production rates observed on Days 7 to 9 after insemination were 20.5 +/- 4.2%, 18.5 +/- 3.9% and 28.7 +/- 5.1% for the 0 .25 g EG, 0.5 g EG treatments and control, respectively. These rates were s ignificantly higher (P < 0.05) than that of the 1.0 g EG treatment (8.7 +/- 2.6%). The number of cells in the inner cell mass (ICM) and trophectoderm (TE) produced from blastocysts using the control procedure were 40.8 +/- 2. 9 and 81.2 +/- 5.3, respectively, and were higher (P < 0.05) compared to th e 0.50 g EG (34.6 +/- 2.9 and 66.8 +/- 5.7) and 1.0 g EG treatments (33.4 /- 3.4 and 67.2 +/- 7.3). In experiment 2, COCs were placed in a small box with 0.25 g of EG so that the effects on IVM, IVF and IVC of positive or ne gative air pressure could be compared. The blastocyst production rare obser ved in the negative air pressure treatment (29.6 +/- 4.6%) was higher (P < 0.01) than that of the positive air pressure treatment (6.2 +/- 1.5%) or th e normal treatment pressure (P < 0.05; 18.7 +/- 4.2%) but did not differ fr om that of the control (30.7 +/- 4.4%). These results indicate that this si mple type of incubator with negative air pressure can be successfully used for in vitro production of bovine embryos and could be used at the field le vel. (C) 1999 Elsevier Science B.V. All rights reserved.