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Colorado State University

1. Markwood, Matthew. Effect of delaying time of AI based on Estrotect patch status on pregnancy rates of beef heifers and nursing beef cows.

Degree: MS(M.S.), Animal Sciences, 2015, Colorado State University

Four studies were conducted to evaluate the efficacy of a delayed timed AI (TAI) protocol. The objective was to evaluate the use of Estrotect patch status to determine optimum TAI implementation. Experiment 1 was conducted with, 997 cows across 6 locations were administered a 7-d CO-Synch + controlled internal drug release (CIDR) estrous synchronization protocol. The experimental design was a 2 x 2 factorial; factors were patch status at 58 h post PGF2α injection (activated or inactivated) and time interval from PGF2α to TAI (58 or 76 h). Patch status was characterized at 58 h post PGF2α into 4 scores: 1 = 0% activated, 2 = 50% activated, 3 = 100% activated, and 4 = missing. Females with a patch status of 3 were considered to be activated and females with patch status of a 1 or 2 were considered to be not activated. Females with missing patches were removed. There was no treatment x location interaction for pregnancy rate (P = 0.96), so data were pooled across locations. There was a tendency (P = 0.07) for an interaction between the main effects for pregnancy rate. Pregnancy rate was greater (P < 0.01) in cows with activated patches at 58 h post PGF2α (67.0%) compared to those with inactivated patches (51.1%). There was no difference (P = 0.99) for pregnancy rate when comparing the 58 (59.9%) vs. 76 h PGF2α to TAI interval (58.7%). Pregnancy rates for cows with a patch status of 3 at 58 h post PGF2α were greater (P < 0.05) than cows with a patch status of 1 or 4 and tended (P = 0.09) to be greater than cows with a patch status of 2. Cows with a patch status of 1 tended (P = 0.06) to have increased pregnancy rates by delaying TAI to 76 h post PGF2α. Although, it was not different (P = 0.13), there was a 7.4 percentage point increase in pregnancy rates for cows with inactivated patches that received TAI at 76 vs. 58 h. Experiment 2 was conducted to evaluate delayed TAI on 1,682 heifers across 3 locations. The objective was to evaluate the use of Estrotect patch status at various recommended and delayed insemination times for a TAI protocol. Experiment 2a was implemented with 1,159 Bos taurus heifers synchronized using a 14 d melengestrol acetate (MGA) – PGF2α protocol. Estrotect patches were applied at the time of PGF2α injection and evaluated at the time of insemination. Heifers were subsequently assigned to 5 treatments: 1) recommended 72 h post PGF2α TAI with activated patches, 2) recommended 72 h post PGF2α TAI with inactivated patches, 3) 12 h delayed TAI with inactivated patches, 4)18 h delayed TAI with inactivated patches, and 5) heifers with missing patches. Experiment 2b was conducted with 449 Bos taurus heifers synchronized using a 14 d MGA – PGF2α protocol. Heifers were divided into 3 treatments: 1) recommended 72 h post PGF2α TAI with activated patches, 2) recommended 72 h post PGF2α TAI with inactivated patches, and 3) an 8 h delayed TAI with inactivated patches. Experiment 2c utilized 74 heifers synchronized with a 7-d CO-Synch plus CIDR protocol. All heifers had Estrotect patches… Advisors/Committee Members: Peel, Kraig (advisor), Ahola, Jason (advisor), Whittier, Jack (committee member), Hadrich, Joleen (committee member).

Subjects/Keywords: delayed insemination; timed artificial insemination; estrus detection aid; beef cattle

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Markwood, M. (2015). Effect of delaying time of AI based on Estrotect patch status on pregnancy rates of beef heifers and nursing beef cows. (Masters Thesis). Colorado State University. Retrieved from http://hdl.handle.net/10217/167051

Chicago Manual of Style (16th Edition):

Markwood, Matthew. “Effect of delaying time of AI based on Estrotect patch status on pregnancy rates of beef heifers and nursing beef cows.” 2015. Masters Thesis, Colorado State University. Accessed April 22, 2021. http://hdl.handle.net/10217/167051.

MLA Handbook (7th Edition):

Markwood, Matthew. “Effect of delaying time of AI based on Estrotect patch status on pregnancy rates of beef heifers and nursing beef cows.” 2015. Web. 22 Apr 2021.

Vancouver:

Markwood M. Effect of delaying time of AI based on Estrotect patch status on pregnancy rates of beef heifers and nursing beef cows. [Internet] [Masters thesis]. Colorado State University; 2015. [cited 2021 Apr 22]. Available from: http://hdl.handle.net/10217/167051.

Council of Science Editors:

Markwood M. Effect of delaying time of AI based on Estrotect patch status on pregnancy rates of beef heifers and nursing beef cows. [Masters Thesis]. Colorado State University; 2015. Available from: http://hdl.handle.net/10217/167051

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