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Session: Physiology and Endocrinology II: The Estrous Cycle, Breeding, and Embryo Transfer

292 - Evaluation of Two Beef Cow Fixed-time AI Protocols That Utilize Pre-synchronization

Monday, June 27, 2022

1:35 PM – 1:50 PM CT

Location: Oklahoma City Convention Center, 301 A/B

Presenting Author(s)

Jaclyn N. Ketchum, n/a

PhD Student
Texas A&M AgriLife Research, Overton, TX; Department of Animal Science, Texas A&M University, College Station, TX
overton, TX

Author(s)

Lacey K. Quail, MS

Graduate Student
Texas A&M AgriLife Research, Overton, TX; Department of Animal Science, Texas A&M University, College Station, TX
Overton, Texas
Kaitlin M. Epperson

Doctoral Graduate Student
Texas A&M AgriLife Research, Overton, TX; Department of Animal Science, Texas A&M University, College Station, TX
overton, Texas
Chloey Guy, MS

Research Assistant
Texas A&M AgriLife Research Center, Overton
Overton, Texas
Jerica J J Rich, PhD

Assistant Professor
Arkansas State University College of Agriculture, Jonesboro, AR
Jonesboro, AR
Saulo Menegatti Zoca, PhD

Post-Doctoral Research Associate
South Dakota State University Department of Animal Science, Brookings, SD
Brookings, South Dakota
AK

Adalaide Kline

South Dakota State University Department of Animal Science, Brookings, SD
Brookings, SD
TA

Taylor Andrews

New Mexico State University Department of Animal and Range Sciences, Las Cruces, NM
Las Cruces, NM
Julie Walker

Extension Beef Specialist
South Dakota State University Department of Animal Science, Brookings, SD
Brookings, SD
Pedro Fontes, PhD

Assistant Professor
University of Georgia
Athens, GA
Sandy Johnson, PhD

Professor, Extension Beef Specialist
Kansas State University Northwest Research & Extension Center, Colby, KS
Colby, KS
MO

Megan P. Owen

Assistant Professor of Animal Science
Texas A&M University Commerce
Commerce, TX
KH

Kelsey M. Harvey

Mississippi State University
Prairie, Mississippi
AS

Adam F. Summers

Assistant Professor of Animal Science, Cattle Physiology
New Mexico State University Department of Animal and Range Sciences, Las Cruces, NM
Las Cruces, NM
GP

George A. Perry, n/a

Associate Professor
Department of Animal Science, Texas A&M University; Texas A&M AgriLife Research; Texas A&M AgriLife Research and Extension Center Overton
Overton, Texas

Abstract: Pre-synchronization has been evaluated as a method to improve synchrony of ovulatory follicles before fixed-time AI (FTAI). The objective was to compare FTAI results in beef cows from two protocols that utilize pre-synchronization. Blood samples were collected on d-14 (d0=CIDR removal) to determine progesterone concentration at the start of synchronization (P4start: ≥1ng/mL=high, < 1ng/mL=low). In a subset (n=1,032), an additional blood sample was taken between d-21 and -29 to determine cyclicity. Cows (n=1,119), from 21 herds, were grouped by days postpartum and age and randomly assigned to one of two protocols. Cows assigned to the PG 6-day CIDR protocol (PG6d) received prostaglandin F2α (PG) on d-9, CIDR insertion and GnRH on d-6, and CIDR removal and PG on d0. Cows assigned to the 7&7 Synch protocol (7&7) were administered PG and CIDR insertion on d-14, GnRH on d-7, CIDR removal and PG on d0. For both protocols, FTAI occurred coincident with GnRH 66 h after second PG. Pregnancy was determined by transrectal ultrasonography 30-40 d following FTAI. The GLIMMIX procedure of SAS (9.4) was used to detect differences in estrus response and pregnancy success with herd included as a random variable. Estrus response (0 to 66 h) was influenced by treatment (P< 0.01; PG6d=60±5% and 7&7=74±4%), Body Condition Score (P< 0.01), cycling status (P=0.03), P4start (P< 0.01), and a P4start by treatment interaction (P< 0.001; PG6d-highP4=62±6%, PG6d-lowP4=58±6%, 7&7-highP4=84±3%, 7&7-lowP4=60±6%). Pregnancy success was influenced by estrus expression (P< 0.01; estrus=38±4% and no estrus=62±6%), and a treatment by P4start interaction (P=0.04; PG6d-highP4=58±5%, PG6d-lowP4=39±7%, 7&7-highP4=49±5%, 7&7-lowP4=55±8%) but was not influenced by treatment (P=0.45; PG6d=49±4% and 7&7=52±4%). In conclusion, effectiveness of pre-synchronization method depends on a cows’ physiological status at the beginning of the protocol. The 7&7 protocol increased estrus response compared to PG6d, but there was no difference in pregnancy success.