In:
Journal of Animal Science, Oxford University Press (OUP), Vol. 100, No. Supplement_3 ( 2022-09-22), p. 139-140
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, & lt; 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 & lt; 0.01; PG6d=60±5% and 7 & 7=74±4%), Body Condition Score (P & lt; 0.01), cycling status (P=0.03), P4start (P & lt; 0.01), and a P4start by treatment interaction (P & lt; 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 & lt; 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.
Type of Medium:
Online Resource
ISSN:
0021-8812
,
1525-3163
DOI:
10.1093/jas/skac247.257
Language:
English
Publisher:
Oxford University Press (OUP)
Publication Date:
2022
detail.hit.zdb_id:
1490550-4
SSG:
12
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