COLLECTION OF OOCYTES FROM CATTLE VIA FOLLICULAR ASPIRATION AIDED BY ULTRASOUND WITH OR WITHOUT GONADOTROPIN PRETREATMENT AND IN DIFFERENT REPRODUCTIVE STAGES

Ultrasound-guided follicular aspiration was performed on 29 Holstein-F riesian cows/heifers twice weekly at 3- to 4-d intervals over a period of 2 consecutive estrous cycles (total 42 d). For visualization of th e ovaries and guidance of the aspiration needle, a 6.5 MHz fingertip p robe on a 62 cm probe carrier was inserted into the vagina. The dispos able aspiration needle was connected to a permanent rinse tubing syste m, thus ensuring minimum death of oocytes in the aspiration processs. After penetration of the vaginal wall, the needle was inserted into a follicle of the rectally fixed ovary. Cumulus oocyte complexes (COG) w ere aspirated at a pressure of 100 mm Hg. In the first experiment, the effect of an additional gonadotropin treatment 4 d prior to aspiratio n was investigated in 8 lactating cows. Following FSH-treatment, the n umber of aspirated follicles was higher (P < 0.05) than in the nontrea ted animals (10.6 +/- 0.7 vs 8.9 +/- 0.5). The number of recovered COC (7.0 +/- 0.6 vs 5.8 +/- 0.5), the recovery rate (COG per aspirated fo llicle) (66.6% vs 65.4%), the percentage of viable COC (56.8% vs 52.1% ), the cleavage rate upon in vitro maturation and in vitro fertilizati on (56.7% vs 59.8%) as well as the rate of morula/blastocyst formation (3.8% vs 2.9%) were similar in both groups. in the second experiment, follicles were aspirated in 4 lactating cows, 6 dry cows, 4 pregnant cows (first 35 d of pregnancy), and 4 heifers. The average number of a spirated follicles and recovered COC was higher (P < 0.05) in the firs t 2 groups (10.6 +/- 0.6 and 9.3 +/- 0.7 follicles; 7.2 +/- 0.5 and 6. 9 +/- 0.7 oocytes) than in the 2 other treatment groups (7.3 +/- 0.5 a nd 8.1 +/- 0.5 follicles; 5.0 +/- 0.4 and 5.7 +/- 0.5 oocytes). The pe rcentage of viable COC was higher (P < 0.05; 68.3%) in lactating anima ls than in all the other groups' (49.7, 52.5 and 57.4%, respectively). Similarly, upon invitro fertilization, cleavage rate was higher (P < 0.05; 63.4%) in lactating cows than in the other groups (43.7, 50.5, 5 5.1% respectively). A total of 21.5, 22.7, 11.9 and 13.5%; respectivel y, in the 4 groups of the in vitro fertilized oocytes reached the moru la and blastocyst stages. After transfer of a total of 48 embryos 22 p regnancies (45.8%) were established as detected on Day 65. We conclude that I) repeated aspiration of viable COC at short intervals is possi ble, 2) additional FSH-treatment does not increase oocyte yields, and 3) viable blastocysts can be produced from cattle at various reproduct ive phases irrespective of the reproductive phase.