Evaluation of split-time artificial insemination following administration of a long or short-term progestin-based estrus synchronization protocol in beef heifers.
Theriogenology
; 133: 179-186, 2019 Jul 15.
Article
em En
| MEDLINE
| ID: mdl-31125868
ABSTRACT
Fixed-time and split-time AI were compared following the melengestrol acetate (MGA®) prostaglandin F2α (Experiment 1) and 7-d CO-Synch + controlled internal drug release (CIDR®) protocols (Experiment 2). Heifers in Experiments 1 (nâ¯=â¯524) and 2 (nâ¯=â¯456) were assigned within pen to balanced treatments based on weight and reproductive tract score (RTS; Scale 1-5). In Experiment 1, MGA® (0.5â¯mgâanimal-1âd-1) was fed for 14â¯d, and prostaglandin F2α (PG; 250⯵g im cloprostenol sodium) was administered 19â¯d after MGA® withdrawal. In Experiment 2, gonadotropin-releasing hormone (GnRH; 100⯵g gonadorelin acetate) was administered coincident with CIDR® (1.38â¯g progesterone [P4]) insertion. Inserts were removed after 7â¯d, and PG (250⯵g im cloprostenol sodium) was administered at CIDR® removal. In both experiments, estrus detection aids (Estrotect®) were applied at the time of PG administration. Estrous status was recorded at FTAI or STAI. Estrus was defined as removal of ≥ 50% of the grey coating from the Estrotect® patch. Heifers assigned to FTAI treatments received GnRH and were artificially inseminated at the standard time for FTAI for each protocol 72 or 54 h after PG administration for the MGA-PG or 7-d CO-Synch + CIDR® protocol, respectively. In the STAI treatments, only heifers that expressed estrus prior to the standard time of FTAI were artificially inseminated at that time. For heifers failing to express estrus, AI was postponed 24â¯h. Only heifers that failed to exhibit estrus by the delayed time received GnRH concurrent with AI. In both experiments, estrous response prior to the standard time of FTAI did not differ between treatments. Total estrous response was increased (Pâ¯<â¯0.01) among heifers assigned to STAI in Experiment 1 (88%, STAI; 72%, FTAI) and 2 (74%, STAI; 47%, FTAI). In Experiment 1, pregnancy rates resulting from AI were greater (Pâ¯<â¯0.04) for heifers assigned to STAI compared with FTAI (55% vs 46%, respectively). In Experiment 2, pregnancy rates resulting from AI were similar between treatments (48% and 46%, respectively; Pâ¯=â¯0.6). In summary, when compared with FTAI, STAI resulted in greater estrous response following both the MGA®-PG and 7-d CO-Synch + CIDR® protocols. The increased estrous response through use of STAI was associated with a corresponding increase in pregnancy rates to AI following the MGA®-PG protocol; however, a similar improvement in pregnancy rates was not observed following the 7-d CO-Synch + CIDR® protocol.
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Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Progestinas
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Bovinos
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Inseminação Artificial
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Sincronização do Estro
Tipo de estudo:
Guideline
Limite:
Animals
/
Pregnancy
Idioma:
En
Revista:
Theriogenology
Ano de publicação:
2019
Tipo de documento:
Article
País de afiliação:
Estados Unidos