{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,10]],"date-time":"2026-07-10T20:42:12Z","timestamp":1783716132314,"version":"3.55.0"},"reference-count":61,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2021,3,17]],"date-time":"2021-03-17T00:00:00Z","timestamp":1615939200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"CEVA Sant\u00e9 Animale","award":["None"],"award-info":[{"award-number":["None"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Animals"],"abstract":"<jats:p>In beef herds, increasing animal welfare, improving reproductive performance and easing animal management are key goals in farm economics. We explored whether delaying the removal of the intravaginal progesterone device by 24 h in heifers synchronized with a 5d Co-synch 72-h protocol could improve reproductive efficiency of fixed-time artificial insemination (FTAI). In experiment 1, we examined the total synchronization rate (TSR) in cycling Holstein heifers. Heifers (13.4 \u00b1 0.69 mo.) were randomly assigned to the standard 5d Co-synch 56-h protocol (5dCo56; n = 10), 5d Co-synch 72-h (5dCo72; n = 17), or the modified 5d Co-synch 72-h protocol, in which removal of the progesterone device was delayed by 24 h (6dCo48; n = 19). In experiment 2, 309 cycling beef heifers on 18 commercial farms were subjected to the 5d Co-synch 72-h or 6-d Co-synch 48-h protocol and conception rate (CR) studied. In experiment 1, the three protocols led no differences on TSRs of 80.0% (5dCo56), 88.2% (5dCo72), and 89.5% (6dCo48). In experiment 2, the CR from the beef heifers, observed during two consecutive reproductive seasons did not differ: 59.7% for 5dCo72 and 62.0% for 6dCo48 (p = 0.907). Therefore, delaying removal by 24 h provides satisfactory results without reducing reproductive efficiency of heifers.<\/jats:p>","DOI":"10.3390\/ani11030849","type":"journal-article","created":{"date-parts":[[2021,3,17]],"date-time":"2021-03-17T11:48:22Z","timestamp":1615981702000},"page":"849","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["Effects on Synchronization and Reproductive Efficiency of Delaying the Removal of the Intravaginal Progesterone Device by 24 h in the 5d Co-Synch Protocol in Heifers"],"prefix":"10.3390","volume":"11","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-0112-8543","authenticated-orcid":false,"given":"Aitor","family":"Fernandez-Novo","sequence":"first","affiliation":[{"name":"Veterinary Department, School of Biomedical and Health Sciences, Universidad Europea de Madrid, C\/Tajo s\/n, Villaviciosa de Od\u00f3n, 28670 Madrid, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sergio","family":"Santos-Lopez","sequence":"additional","affiliation":[{"name":"Animal Production Department, Veterinary Faculty, Complutense University of Madrid, 28040 Madrid, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5669-6014","authenticated-orcid":false,"given":"Jose Luis","family":"Pesantez-Pacheco","sequence":"additional","affiliation":[{"name":"School of Veterinary Medicine and Zootechnics, Faculty of Agricultural Sciences, University of Cuenca, Avda. Doce de Octubre, Cuenca 010150, Ecuador"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Natividad","family":"P\u00e9rez-Villalobos","sequence":"additional","affiliation":[{"name":"Veterinary Department, School of Biomedical and Health Sciences, Universidad Europea de Madrid, C\/Tajo s\/n, Villaviciosa de Od\u00f3n, 28670 Madrid, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ana","family":"Heras-Molina","sequence":"additional","affiliation":[{"name":"Animal Reproduction Department, SGIT (INIA), Avda. Puerta de Hierro s\/n, 28040 Madrid, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Juan Vicente","family":"Gonzalez-Martin","sequence":"additional","affiliation":[{"name":"Medicine and Surgery Department, Veterinary Faculty, Complutense University of Madrid, 28040 Madrid, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Susana","family":"Astiz","sequence":"additional","affiliation":[{"name":"Animal Reproduction Department, SGIT (INIA), Avda. 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