Follicular development and reproductive endocrinology during and after superovulation in heifers and mature cows displaying contrasting superovulatory responses

• Published in: Theriogenology Vol. 44; no. 4; pp. 479 - 497
• Main Authors: Desaulniers, D.M., Lussier, J.G., Goff, A.K., Bousquet, D., Guilbault, L.A.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.09.1995
• Subjects: AGE; aging; cattle; DESARROLLO EMBRIONARIO; DEVELOPPEMENT EMBRYONNAIRE; EDAD; ESTROGENOS; FEMELLE; FSH; GENISSE; gonadotropins; HEMBRA; HFS; HORMONAS; HORMONE; NOVILLA; OESTROGENE; OVAIRE; ovarian follicles; OVARIOS; PLASMA SANGUIN; PLASMA SANGUINEO; PROGESTERONA; PROGESTERONE; SECRECION; SECRETION; SUPEROVULACION; SUPEROVULATION; VACAS LECHERAS; VACHE LAITIERE; ovarian follicles; gonadotropins; cattle; aging; superovulation
• ISSN: 0093-691X; 1879-3231
• DOI: 10.1016/0093-691X(95)00220-3

To understand the causes for poor response to superovulation in mature cows of high genetic potential, endocrine and follicular events during and after superovulation were compared in heifers (<2 yr old) yielding large numbers of embryos and cows (9 to 13 yr old) known to be poor embryo donors. Follicular development was monitored by daily ultrasonography. Blood samples were taken 2 to 3 times a day for the measurements of P4, E2, FSH and LH by RIA. Intensive blood collections at 15-min intervals for 6 h were also performed during preovulatory and luteal phases. The number of embryos produced in the heifers (15.2 ± 2; mean ± SEM) and the cows (0.6 ± 0.4), was similar to the number of ovulatory follicles derived from ultrasonographic observations in the heifers (16.2 ± 3.7), but not in the cows (7.8 ± 2.8). Contrary to that observations in heifers, there was no increase in the number of 4- to 5-mm follicles in cows during superovulation. The number of larger follicles (>5 mm) increased during superovulation in both cattle groups, but it was significantly lower in cows than in heifers. During superovulation, the maximal E2 concentration was greater (P < 0.0001) in heifers than in cows. One cow showed delayed luteolysis during superovulation, while another had abnormally high FSH (>10 ng/ml) and LH (>3 ng/ml) concentrations following superovulation. All the cows had a postovulatory FSH rise which was not detected in the heifers. The results showed that attempts to improve superovulatory response in mature genetically valuable cows are hampered by a number of reproductive disorders that are not predictable from the study of the unstimulated cycle.