292 Evaluation of two Beef cow Fixed-Time AI Protocols That Utilize pre-Synchronization. (21st September 2022)

• Record Type: Journal Article
• Authors: Ketchum, Jaclyn N; Quail, Lacey K; Epperson, Kaitlin M; Guy, Chloey; Rich, Jerica J J; Zoca, Saulo Menegatti; Kline, Adalaide; Andrews, Taylor; Walker, Julie; Fontes, Pedro; Johnson, Sandy; Owen, Megan P; Harvey, Kelsey M; Summers, Adam F; Perry, George A
• Is Part Of: Journal of animal science. Volume 100(2022)Supplement 3
• Page Start: 139
• Page End: 140
• Publication Date: 2022-09-21
• Subjects: beef cattle -- estrous synchronization -- pre-synchronization; Livestock -- Periodicals; Livestock; Electronic journals; Periodicals; 636.005
• DOI: 10.1093/jas/skac247.257
• Languages: English
• ISSNs: 0021-8812

Abstract

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.