The objective of our study was to develop an effective method for coll
ecting and maturing equine oocytes. In Experiments 1 and 2, oocytes we
re collected from excised ovaries obtained via colpotomy. In Experimen
t 3, oocytes were collected from ovaries obtained after slaughter. Fol
licles were aspirated and flushed with various treatments to recover t
he oocytes, which were then cultured and stained to observe the stage
of meiosis. In Experiment 1, the aspiration treatments consisted of 0.
5 ml of modified Dulbecco's PBS with 0, 100 or 500 IU\ml hyaluronidase
. There was no increase (P>0.05) in oocyte recovery with the addition
of hyaluronidase. The oocytes were cultured in either TCM-199 or Ham's
F-10 medium containing 0.5 ug/ml FSH, 1 ug/ml LH, 1 ug/ml estradiol 1
7 beta, 250 uM Na-pyruvate and 10% estrual mare serum for 0, 24, 36 or
48 h. Maturation rates were higher (P<0.05) at 36 h for oocytes cultu
red in TCM-199 (79%) than for those in Ham's F-10 (21%). There was no
difference (P>0.05) in the percentage of maturation of oocytes between
the 2 media at 48 h of culture. In Experiment 2, a single aspiration
was performed with no flushing medium (dry aspiration) in 0.5 ml of PB
S or in PBS with 1000 IU/ml hyaluronidase. The oocytes were then cultu
red in TCM-199 for 24, 30 or 36 h. There was an increase (P<0.05) in o
ocyte recovery when follicles were flushed with PBS, with or without h
yaluronidase. There was also a difference (P<0.05) in the percentage o
f maturation of oocytes between 30 and 24 h (86 vs 48%), but no furthe
r increase was seen by 36 h (84%). In Experiment 3, follicles were asp
irated with PBS 5 to 6, 6 to 7 or 7 to 8 h after slaughter. The oocyte
s were cultured for 30 h in TCM-199 either with or without 100 IU/ml e
CG. There was no effect of eCG or time from slaughter on oocyte matura
tion or cumulus expansion (P>0.05).