Oocyte culture in the presence of the nonspecific competitive phosphodiesterase inhibitor caffeine has been reported to increase developmental capacity of oocytes in different mammalian species. Here, we evaluated the effects of caffeine supplementation during the final phase of in vitro maturation (IVM) on developmental rates and blastocyst cell numbers. Bovine ovaries were collected from a local abattoir. A total of 1142 cumulus-oocyte-complexes were obtained by slicing. Cumulus-oocyte complexes were either in vitro matured for 24 h (Standard) or matured for 20 h followed by additional culture for 6 h in fresh IVM medium supplemented with 10 mm caffeine (Caffeine 6 h). In vitro fertilization was performed for 19 h using frozen-thawed sperm from 2 different bulls. After IVF, presumptive zygotes were cultured in vitro for 8 days until the blastocyst stage. Cleavage and blastocyst rates were evaluated 3 and 8 days after IVF, respectively. Expanded blastocysts from the different treatments were submitted to differential staining. SAS/STAT software (SAS Institute Inc., Cary, NC, USA) was used to evaluate cleavage and blastocyst rates using the Glimmix procedure and blastocyst cell numbers were compared using the linear model procedure. Cleavage rates were lower using caffeine for bull B and blastocyst production decreased for bull A. Caffeine treatment increased inner cell mass (ICM) number for bull B and decreased trophectoderm (TE) and total cell numbers for bull A. However, similar TE and total cells were obtained for bull B (Table 1; P < 0.05). Results show that developmental competence can be affected by caffeine supplementation at the final phase of IVM probably due to oocyte-sperm interaction changes. Table 1. In vitro developmental competence of oocytes cultured with caffeine at the end of IVM

Bull	Treatment	Cleavage (%)	Blastocysts (%)	ICM (n)	TE (n)	Total cells (n)
A	Standard	77.6 ± 3.0a	36.2 ± 4.0a	40.7 ± 2.8ab	121.4 ± 3.0b	162.1 ± 3.5a
A	Caffeine 6 h	72.7 ± 1.9ab	24.2 ± 1.3b	41.9 ± 3.7ab	101.2 ± 4.0a	143.1 ± 6.2b
B	Standard	63.8 ± 3.0bc	29.4 ± 4.0ab	36.7 ± 2.3b	118.6 ± 4.5b	155.4 ± 5.1ab
B	Caffeine 6 h	55.9 ± 7.6c	28.4 ± 3.4b	49.7 ± 3.7a	110.6 ± 4.3ab	160.3 ± 5.3ab

¹Data are the mean ± SEM. Different superscripts represent significant difference, P < 0.05