337 THE ONSET AND DURATION OF OVULATION IN DAIRY COWS SUPEROVULATED FOLLOWING SYNCHRONIZATION OF FOLLICLE WAVE WITH CIDR AND ESTRADIOL BENZOATE
K. Kishida A , T. Nishisouzu A , S. Aoki A , M. Iwata A , O. Dochi A and H. Koyama ADepartment of Daily Science, Rakuno Gakuen University, Ebetsu, Hokkaido, Japan. email: dochi@rakuno.ac.jp
Reproduction, Fertility and Development 16(2) 288-289 https://doi.org/10.1071/RDv16n1Ab337
Submitted: 1 August 2003 Accepted: 1 October 2003 Published: 2 January 2004
Abstract
Determining the optimal time for AI of superovulated cattle is important for yielding acceptable fertilization rates. The objectives of this study were to determine the interval to onset, and the duration of ovulation in dairy cows superstimulated with FSH following synchronization of follicular wave emergence with a CIDR and estradiol benzoate (EB). Holstein (n = 8) and Jersey (n = 1) cows received an intravaginal progesterone insert (CIDR-B, InterAg, Hamilton, New Zealand) combined with an injection of 2 mg EB at a random stage of the estrous cycle (Day 0). Superstimulatory treatments were initiated on Day 6 with a total dose of 24 or 36 mg FSH (Antrin, Denka, Kawasaki, Japan) via twice-daily i.m. injections in decreasing doses for 4 days. At 72 h after the first FSH injection, 30 mg PGF (Pronalgon F, Pharmacia, Tsukuba, Japan) was administered, and CIDR-B were removed at 80 h. Transrectal ultrasonography of ovaries was performed at 3-h intervals from 40 to 77 h after the PGF injection. The numbers of ovulations were counted as previously described (Purwantara et al. 1994 Anim. Reprod. Sci. 37, 1–5). All detected follicles were counted and classified as small, medium, or large (diameter 2–4 mm, 5–9 mm, or ≥10 mm, respectively). The number of ovulations recorded after each scanning was defined as the change in the number of large- and medium-sized follicles observed since the previous scanning. Data were analyzed using ANOVA. Results are presented in Table 1. There were two patterns of ovulations: one was a concentrated pattern of ovulations (ovulatory period <10 h); the other was a prolonged pattern of ovulations (ovulatory period >10 h). In cows with a high superovulatory response (≥14 ovulations), the onset of ovulation was earlier (P < 0.05) and the duration of the ovulatory period was longer (P < 0.05) than in cows with lower (≤8 ovulations) responses. In conclusion, concentrated and prolonged ovulation patterns were seen in dairy cows superstimulated after synchronization of the follicle wave with a CIDR and EB. In cows with a large number of follicles, the onset of ovulation tended to be earlier and the duration of the ovulatory period longer than in cows with fewer follicles.
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