Collection of oocytes and production of blastocysts in vitro from individual, slaughtered cows.

On four occasions ovaries from a total of 35 cows were collected separately at the abattoir where they had been killed. The age of 20 of these cows was recorded. Oocytes from these ovaries were collected separately and were submitted to in vitro maturation, in vitro fertilization and in vitro culture procedures. Ovaries of 34 randomly chosen cows were pooled and treated as the control. Ova from individual cows were cultured in 10 microliters droplets and those from pooled ovaries were cultured in groups of 50 in 50 microliters droplets of oviductal cell-conditioned medium. The 35 cows treated individually supplied 493 oocytes (mean 14.1 oocytes per cow) with high individual variation (SD = 10.0; range = 0-38) and 47 expanded blastocysts (9.5% of oocytes; mean 1.3 blastocysts per cow; range = 0-6). Among these cows, 16 produced one or more blastocysts. Considerable variation in average development rates was detected over the four replicate experiments (11.3, 4.0, 9.0 and 13.5%). The 34 cows treated as the control supplied 397 oocytes (mean 11.7 oocytes per cow) and 44 expanded blastocysts (11.1% of oocytes; mean 1.3 blastocysts per cow) with high variations between replicates (11.1, 4.0 and 18.1%). No difference was observed between individual and pooled ovaries regarding either the number of oocytes, the rate of blastocyst formation, or the number of blastocysts per cow. No effect of age was detected.(ABSTRACT TRUNCATED AT 250 WORDS)