| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 2097943 | Theriogenology | 2010 | 8 Pages |
The objective of this study was to investigate the effect of the presence or absence of Corpus luteum (CL) on the follicular population during superstimulation in dairy cows (Holstein-Friesian cattle). Animals were divided into two groups as follows: (1) Growing CL group (G1): Cows (n = 7) received a total dose of 28 Armour units (AU) follicle-stimulating hormone (FSH) through the first 4 d (twice daily) after spontaneous ovulation (Day 0). (2) CL Absence group (G2): Cows (n = 10) received prostaglandin F2α (PGF2α) at 9 or 10 d after ovulation. After 36 h, all the follicles (larger than 5 mm) were aspirated (Day 0). The FSH treatment started 24 h after aspiration and continued for 4 d. The number of small (3 to <5 mm), medium (5 to <8 mm), and large (≥8 mm) follicles was examined on Days 1, 3, and 5 in all groups. Blood samples were collected daily for 5 d, and progesterone (P4), estradiol (E2), insulin-like growth factor-1 (IGF-1), and growth hormone (GH) in plasma were measured by enzyme immunoassays. The results showed that in G1, the P4 level increased gradually from 0.5 ng/mL at Day 1 to 2 ng/mL at Day 5, whereas in G2, the P4 level was completely below 0.5 ng/mL. All cows of the G2 group showed an increase of E2 at Day 3 or Day 4 followed by an increase of IGF-1 within 24 h, while GH increased concomitantly with the E2 increase in 8 of 10 trials. On the other hand, cows of the G1 group showed neither E2 nor IGF-1 increase. Moreover, at the end of the treatment, the number of follicles in the G2 group was significantly increased compared with that of the G1 group (22.8 ± 2.0 vs. 11.6 ± 2.0). In conclusion, low P4 level during FSH treatment enhanced multiple follicular growth and E2 secretion, which was followed by increase of IGF-1 and GH. Therefore, the absence of the CL may play a critical role in the superovulation response by controlling the number of growing follicles.
