Influence of the Dominant Follicle on the Superovulatory Response in Cattle

다국어 초록 (Multilingual Abstract)

Nine cows were superovulated by administration of 8 injections of Folltropin each (2.5 ml/injection, 1.75 mg/ml) i.m spread over 4 days, beginning on Day 10 of oestrous cycle, and 30 and 20 mg prostaglandin $F_{2{\alpha}}$ was given along with the 5th and 6th injections of Folltropin, respectively, to induce luteolysis. The animals were artificially inseminated 48, 60 and 72 h after the first prostaglandin $F_{2{\alpha}}$ injection. The number of corpora lutea was recorded by palpation per rectum and by ultrasonography on Day 6 (Day 0 = day of oestrus). The ovaries were examined daily by ultrasonography on Days 3-9 of the oestrous cycle for following the growth and regression of the largest follicle, which was considered the morphologically dominant follicle. The animals were classified into two groups depending upon the presence (n = 4) and absence of a dominant follicle (n = 5). There was a high correlation (r = 0.97, p < 0.001) between the number of corpora lutea observed by palpation per rectum and that determined by ultrasonography. Mean (${\pm}SEM$) number of corpora lutea determined by ultrasonography ($11.20{\pm}3.71$ vs $3.25{\pm}0.75$) and by palpation per rectum ($10.40{\pm}3.91$ vs $2.25{\pm}0.75$) was significantly higher (p < 0.05) in the nondominant group compared to that in the dominant group. There was no difference in the numbers of follicles 2-3 mm ($13.80{\pm}4.49$ vs $8.00{\pm}1.08$), 4-6 mm ($7.00{\pm}1.87$ vs $3.50{\pm}1.33$), and the total number of follicles ${\geq}2mm$ ($22.00{\pm}5.95$ vs $12.50{\pm}1.26$) between the two groups, one day prior to initiation of superovulation. There was, however, a significant (p<0.01) positive correlation between the number of corpora lutea with the numbers of follicles 2-3 mm (r = 0.83), 4-6 mm (r = 0.80) and the total number of follicles ${\geq}2mm$ (r = 0.89) observed one day prior to initiation of superovulation. The results of this study indicate that the presence of a dominant follicle adversely affects the superovulatory response in cattle.