Two experiments evaluated using an estrous-detection patch to identify animals that are in standing estrus at split-timed AI (STAI) and the necessity of a gonadotropin-releasing hormone (GnRH) injection at STAI on a 7-Day CO-Synch + CIDR protocol. In experiment 1 (n=216) and in experiment 2 (n=101), multiparous lactating crossbred beef cows were stratified by age, BW, BCS, and post-partum interval to 2 treatment groups: CTRL=timed-AI (TAI) at 72h post CIDR removal, or TRT=STAI at 72 or 84h post CIDR removal. All females received GnRH plus a CIDR on d0, prostaglandin-F2α, CIDR removal, and an Estrotect estrous-detector patch on d7. At 72h post-CIDR removal, a patch score was assigned (PS1 <50% removed; PS2 ≥ 50% removed) to all females. Cows in the CTRL group were administrated a second GnRH injection at 72h TAI. Cows in the TRT group with a PS2 were not administrated GnRH at TAI. At 84h, the remaining TRT cows were given a second PS and cows with a PS1 received a GnRH injection and cows with a PS2 did not. Blood samples for Progesterone concentration were collected on d-11 and 0 to determine percent of cows cycling. Data were analyzed using Proc Genmod with treatment and AI technician as fixed effects, sire as a random effect, and BW, BCS, age, and PPI as covariates. In experiment 1, TAI pregnancy rates were similar (P=0.81) between the CTRL (40.8%) and TRT (43.4%) groups. Pregnancy rates tended to be greater (P=0.07) for cows with a PS2 (50.3%) compared with a PS1 (29.4%). However, by extending TAI to 84h in unresponsive cows, 82.0% of the TRT cows did not receive a second injection of GnRH at TAI. In experiment 2, TAI pregnancy rates were similar (P=0.80) between the CTRL (32.3%) and TRT (38.6%) groups. Pregnancy rates were greater (P=0.04) for cows with a PS2 (70.6%) compared with a PS1 (19.4%). By extending TAI to 84h in unresponsive cows, 37.1% of the TRT cows did not receive GnRH at TAI. Using a heat-detector can reduce the percentage of cows that require GnRH at TAI without compromising pregnancy rates.
| Identifer | oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-04072017-132758 |
| Date | 21 April 2017 |
| Creators | Demeterco, Danilo |
| Contributors | Walker, Ryon, Williams, Cathleen, Gentry, Glen, Keith, Ashley |
| Publisher | LSU |
| Source Sets | Louisiana State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lsu.edu/docs/available/etd-04072017-132758/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached herein a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to LSU or its agents the non-exclusive license to archive and make accessible, under the conditions specified below and in appropriate University policies, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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