Abstract :
The oocyte recovery rate has a pivotal role to play in in vitro embryo production. For many
years, the aspiration technique was used on abattoir material as an inexpensive method of
collecting oocytes for in vitro procedures. Only moderate numbers of oocytes were however
harvested when using the aspiration method. This study was designed to introduce a
new oocyte recovery method from the ovaries of slaughtered ewes. Ovaries were obtained
from an abattoir and transported to the laboratory within a period of 1–2 h, at 37 ◦C. In
this study, two experiments were carried out. In Experiment 1, the oocyte recovery was
via the centrifuge ‘ORC’ (new technique). The first step was the incision of the entire surface
of each ovary. Thereafter ovaries were placed in modified Falcon tubes (MFT’s). The
MFT’s were filled with 3 mL of a pre-incubated oocyte washing medium and centrifuged
at 750
×
g for 3 min. In Experiment 2 (control groups), all visible follicles were aspirated
using an aspiration pump, set at flow rates of 10, 15 and 20 mL H2O/min, using a disposable
20 gauge needle. The ORC technique significantly (P < 0.05) improved the oocyte recovery
rate (6.8
±
0.3 oocytes/ovary), compared to the aspiration technique (2.3
±
0.4, 2.3
±
0.2
and 3.8
±
0.1 oocytes/ovary respectively). When using the ORC technique the proportion of
usable oocytes and the meiotic resumption rates were 92.2% and 79.0
±
1.7%, respectively.
By employing the aspiration pump set at the flow rates of 10, 15 and 20 mL H2O/min, the
proportion of usable oocytes were 95%, 86.4% and 75.2%, and the meiotic resumption rate
was 79.9
±
0.2%, 68.4
±
1.0% and 64.3
±
0.2%, respectively (P < 0.05). The oocytes were considered
usable in those with at least one cumulus cell layer and a homogeneous cytoplasm.
Results showed that by using the ORC technique the oocyte recovery rate was significantly
higher, compared to the aspiration technique. However there was no decrease recorded in
the meiotic division resumption rate and the proportion of good quality oocytes. Thus using
the ORC technique for oocyte recovery from slaughtered ewe ovaries increased the oocyte
recovery rate dramatically, without any significant deterioration in the meiotic competence
and oocyte quality. Additionally, using the ORC technique can lead to saving time for oocyte
collection, to maturation and subsequent embryo production.
