MORPHOLOGY AND LOCATION OF ATTACHED FOLLICULAR CUMULUS OOCYTE COMPLEXES IN HORSES, CATTLE AND LLAMAS

Morphology and location of the attached cumulus-oocyte complex (COG) w ere studied in slaughter-house ovaries in horses (49 follicles, 9 to 4 4 mm), cattle (68 follicles, 6 to 18 mm), and llamas (38 follicles, 3 to 14 mm). The expected point of ovulation was marked, using the ovula tion fossa in mares and the center of the projecting follicular surfac e in cattle and llamas. A follicle was dissected from an ovary, and ti ssue was removed from the follicle until the COC became visible by tra nsillumination. However, most llama follicles protruded prominently fr om the ovarian surface so that dissection was not required to locate t he COG. The COC was more readily recognized from the external follicul ar surface in mares and llamas than in cattle, primarily because of a dark oocyte. Compact COC's projected into the antrum with a smooth dom e-shape in horses. The COC's in cattle were also dome-shaped but were more irregular and a few contained prominent processes. The mean diame ter of the isolated follicle was calculated from 3 planes,except that in llamas the follicles were spherical so that the 3 dimensions were i dentical. The angle between a straight line connecting the expected ov ulation site and the opposite pole and a straight line from the ovulat ion site to the COC was defined as the COC-location angle. This angle was chosen because it is unaltered by size of a sphere (45 degrees for a COC at the equator). The mean (+/-SEM) COC-location angle differed (P<0.01) among horses (39.9+/-3.3), cattle (50.0+/-2.5), and llamas (6 4.8+/-2.1). In mares, the locations of the COC's did not differ from e quality between follicular hemispheres, but in cattle and llamas the C OC's were located with greater frequency (P<0.05) in the hemisphere co ntaining the expected ovulation site (cattle, 65%; llamas, 91%).