{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,11]],"date-time":"2026-09-11T08:21:11Z","timestamp":1789114871952,"version":"build-2803163510"},"reference-count":35,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2025,8,25]],"date-time":"2025-08-25T00:00:00Z","timestamp":1756080000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Instituto Nacional de Innovaci\u00f3n Agraria","award":["CUI N\u00b0 2338934"],"award-info":[{"award-number":["CUI N\u00b0 2338934"]}]},{"name":"Vice-Rectorate for Research at the \u201cUniversidad Nacional Toribio Rodr\u00edguez de Mendoza de Amazonas\u201d","award":["CUI N\u00b0 2338934"],"award-info":[{"award-number":["CUI N\u00b0 2338934"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Veterinary Sciences"],"abstract":"<jats:p>The performance of estrus synchronization protocols may be influenced by stressful environmental conditions, even in tropically adapted cattle. This study evaluated the efficacy of two synchronization protocols for fixed-time artificial insemination (FTAI) in crossbred Gyr dairy cows and their relationship with heat stress under Peruvian tropical conditions. Multiparous lactating cows under semi-intensive systems were synchronized and divided into two groups: the conventional protocol (PC9) and the prolonged proestrus protocol (J-Synch6). Estrus manifestation, pregnancy rate, and their association with the temperature\u2013humidity index (THI) were analyzed across seven phases of the FTAI program (73 days). In PC9 cows, no significant effect of the number of hours in each heat stress category according to THI was found. Conversely, in J-Synch6 cows, more hours in Category 0 (THI &lt; 72) during Phases 1 to 4 (follicular emergence to preovulatory follicle) had a positive effect on the estrus manifestation, whereas in Phase 3 (follicular growth), higher exposure to Category 3 (THI \u2265 83) had a negative effect on estrus manifestation. Both protocols demonstrated similar estrus and pregnancy rates, although heat stress affected estrus rates in J-Synch6, but not pregnancy. The choice of protocol should account for heat stress risks during specific periods of the year to maximize success.<\/jats:p>","DOI":"10.3390\/vetsci12090804","type":"journal-article","created":{"date-parts":[[2025,8,25]],"date-time":"2025-08-25T08:53:46Z","timestamp":1756112026000},"page":"804","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Efficacy of Two Estrus Synchronization Protocols in Crossbred Gyr Dairy Cows and Their Relationship with Heat Stress in the Peruvian Tropics"],"prefix":"10.3390","volume":"12","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-9179-9078","authenticated-orcid":false,"given":"Ronald W.","family":"V\u00e1squez-Tarrillo","sequence":"first","affiliation":[{"name":"Agricultural Experimental Station El Porvenir, Instituto Nacional de Innovaci\u00f3n Agraria, Juan Guerra 22400, Peru"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5919-8408","authenticated-orcid":false,"given":"Jos\u00e9 E.","family":"Hern\u00e1ndez-Guevara","sequence":"additional","affiliation":[{"name":"Facultad de Zootecnia, Universidad Nacional Agraria de la Selva, Tingo Mar\u00eda 10131, Peru"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Benjam\u00edn A.","family":"Depaz-Hizo","sequence":"additional","affiliation":[{"name":"Agricultural Experimental Station El Porvenir, Instituto Nacional de Innovaci\u00f3n Agraria, Juan Guerra 22400, Peru"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6193-0776","authenticated-orcid":false,"given":"Gustavo","family":"Ampuero-Trigoso","sequence":"additional","affiliation":[{"name":"Direcci\u00f3n de Desarrollo Tecnol\u00f3gico Agrario, Instituto Nacional de Innovaci\u00f3n Agraria, Lima 2791, Peru"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0008-9605-018X","authenticated-orcid":false,"given":"Annie Y.","family":"Pocl\u00edn-Rojas","sequence":"additional","affiliation":[{"name":"Agricultural Experimental Station El Porvenir, Instituto Nacional de Innovaci\u00f3n Agraria, Juan Guerra 22400, Peru"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Marisol","family":"Rojas-Reategui","sequence":"additional","affiliation":[{"name":"Agricultural Experimental Station El Porvenir, Instituto Nacional de Innovaci\u00f3n Agraria, Juan Guerra 22400, Peru"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Gleni T.","family":"Segura Portocarrero","sequence":"additional","affiliation":[{"name":"Facultad de Ingenier\u00eda Zootecnista, Agronegocios y Biotecnolog\u00eda, Universidad Nacional Toribio Rodr\u00edguez de Mendoza de Amazonas, Chachapoyas 01001, Peru"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4421-7589","authenticated-orcid":false,"given":"Jorge D.","family":"Juarez-Moreno","sequence":"additional","affiliation":[{"name":"Facultad de Zootecnia, Universidad Nacional Agraria de la Selva, Tingo Mar\u00eda 10131, Peru"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3146-5372","authenticated-orcid":false,"given":"Hurley A.","family":"Quispe-Ccasa","sequence":"additional","affiliation":[{"name":"Direcci\u00f3n de Desarrollo Tecnol\u00f3gico Agrario, Instituto Nacional de Innovaci\u00f3n Agraria, Lima 2791, Peru"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,8,25]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1009","DOI":"10.1007\/s11250-019-01866-6","article-title":"Dairy science and health in the tropics: Challenges and opportunities for the next decades","volume":"51","author":"Nally","year":"2019","journal-title":"Trop. 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