The development of oocytes of differing quality retrieved using transvaginal
follicular aspiration (TVFA) and following DNA injection was examined. Eight cows
were subjected to twice weekly TVF A for 16 wk. Oocytes retrieved were graded and
placed in an in-vitro maturation, fertilization and co-culture (IVMIIVFIIVC) program.
Two thirds of oocytes were injected with DNA. Good quality oocytes from slaughtered
cows (SH) were obtained once monthly and processed the same way. Good quality
TVF A oocytes had a higher mean development score than poor quality oocytes, but not
different from that of good quality SH oocytes. Good quality TVF A oocytes produced
more viable embryos (31.7% blastocysts) than poor quality oocytes or SH oocytes (12.8%
and 20.4% blastocysts, respectively). Embryo development following injection of DNA
was the same for oocytes for each source-quality group (TVF A-good, 8.4; TVF A-poor,
5.5; SH-good, 6.3 % blastocysts). Development of good quality TVFA oocytes increased during the last 9 wk of the 16 wk collection period. Poor oocyte development increased
slightly to 9 wk and then decreased. Development of TVF A oocytes injected with DNA
did not vary during the experiment. However, development of controls increased from
a mean score of2.50 at wk 1 to 4.17 at wk 16. Oocytes from TVFA produced more PCR
positive blastocysts (95.0%) than SH oocytes (61.5%). More calves were born from the
transfer of embryos injected with DNA from TVF A oocytes (3/5) than from SH oocytes
(116), although not statistically significant. One calf was PCR positive in bone-marrow,
but was negative in other tissues. The use of oocytes obtained by TVF A may improve
the efficiency of producing transgenic cattle.
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