EFFECT OF UNILATERAL OVARIECTOMY, GONADOTROPIN STIMULATION AND IMMUNIZATION AGAINST A SYNTHETIC PEPTIDE OF THE INHIBIN ALPHA-SUBUNIT ON FOLLICULAR DEVELOPMENT AND OOCYTE RECOVERY IN CATTLE

Nulliparous Holstein cows were randomly distributed among 4 treatment groups to test the effects of treatments, including unilateral ovariec tomy, anti-inhibin immunization and gonadotropin stimulation on ovaria n follicle population and oocyte recovery. The Control treatment consi sted of intact cows (I-Control). Unilaterally ovariectomized cows were included in the 3 remaining treatments consisting of ovariectomy alon e (U-Control), cows immunized against a synthetic peptide of the alpha (c)-subunit of bovine inhibin (alpha(c)I; U-IH), and cows stimulated w ith FSH (Super-Ov(R); 75 units/female/week) and also immunized with al pha(c)I as in the previous treatment (U-IH/FSH). Oocytes were collecte d by transvaginal ultrasound-guided aspiration on a weekly basis from cows in each treatment for 5 consecutive weeks. Intact Control cows ha d a greater (P<0.05) number of follicles greater than or equal to 3 mm per female (4.7) than the U-Control and U-IH cows (2.6 and 2.9, respe ctively), and had a similar number of follicles as the U-IH/FSH treatm ent group (3.5). The numbers of follicles aspirated (2.7 to 3.6) and o ocytes recovered/cow (1.6 to 2.6) were similar for cows in the I-Contr ol, U-IH and U-IH/FSH treatment groups. Cows in the U-Control treatmen t group had a lower (P<0.05) number of aspirated follicles (2.0) and r ecovered oocytes (1.1) than the I-Control cows. Cows in the U-IH/FSH a nd U-IH treatments had follicles with larger (P<0.01) diameters (8.7 a nd 8.2 mm, respectively) than cows in the I-Control (6.6 mm) and U-Con trol(5.7 mm) treatments. In conclusion, unilateral ovariectomy did not result in compensatory increase of follicle number or size in the int act ovary; cows in the U-IH/FSH treatment group had a greater number o f follicles aspirated than the U-Control cows. In addition, the anti-a lpha(c)I immunization may have played a role in increasing the number and diameter of the follicles. None of the treatments evaluated in thi s study improved oocyte retrieval over that of the intact, nontreated cows.