Doctor of Philosophy / Department of Animal Sciences and Industry / Jeffrey S. Stevenson / Two experiments assessed pregnancy outcomes (pregnancy per AI; P/AI) after 5-d
Ovsynch-56 Resynch (RES; GnRH injection 5 d before [GnRH-1; d 0] and 56 h (GnRH-2) after
the last PGF2α [PGF] injection on d 6 given 24 h after first PGF injection on d 5, and TAI on d 8)
with and without a 5-d progesterone insert. In Exp. 1, only 76% of 1,023 nonpregnant cows
enrolled on d 34 post-AI had high (≥1 ng/mL) progesterone. The RES-CIDR cows with low
progesterone at treatment initiation had greater P/AI than RES-CON (37.7 vs. 29.4%), whereas
RES-CIDR cows with high progesterone had lesser P/AI than RES-CON (27.4 vs. 34.3%)
suggesting that supplemental progesterone is progesterone-dependent. In Exp. 2, 381 cows were
enrolled in similar treatments on d 31 with RES on d 41post-AI plus a third treatment including
PG-3-G (Pre-PGF on d 31, Pre-GnRH on d 34, and RES on d 41. The P/AI was similar among
treatments but was greater in cows starting RES on d 41 when progesterone was low (44%) than
high (33%).Experiment 3 determined LH and ovulatory responses in cows enrolled in two
treatments before AI: 1) Pre10 (n = 37): PGF-1 and PGF-2 given 14 d apart (Presynch); or PG3G
(n = 33): PGF given concurrent with the PGF-2, 3 d before GnRH-1 followed in 7 d by Ovsynch
[injection of GnRH (GnRH-2) 7 d before PGF (PGF-3) and GnRH-3 at either 56 or 72 h after
PGF-3] that was initiated 10 d after PGF-2 for Pre10 or 7 d after GnRH-1 of PG3G. The GnRH-
1 increased incidences of LH surges and ovulation in PG3G compared with Pre10. The LH in
serum of Pre10 was greater than that of cows receiving PG3G after GnRH-2. Following GnRH-
3, cows receiving GnRH at 72 h had increased incidence of spontaneous LH surges before
GnRH-3. The P/AI for PG3G vs. Pre10 and for 56 vs. 72 h was similar, but the Pre10-72 h
treatment combination was less than all other treatment combinations. Release of LH is protocol
dependent and flexibility of GnRH timing is an advantage for PG3G before first-service TAI.
| Identifer | oai:union.ndltd.org:KSU/oai:krex.k-state.edu:2097/18266 |
| Date | January 1900 |
| Creators | Pulley, Stephanie Leeann |
| Publisher | Kansas State University |
| Source Sets | K-State Research Exchange |
| Language | en_US |
| Detected Language | English |
| Type | Dissertation |
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