{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,9]],"date-time":"2025-10-09T00:36:03Z","timestamp":1759970163948,"version":"build-2065373602"},"reference-count":26,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2025,1,8]],"date-time":"2025-01-08T00:00:00Z","timestamp":1736294400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Federal University of Western Par\u00e1"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Veterinary Sciences"],"abstract":"<jats:p>We aimed to evaluate the reproductive efficiency of Nelore cows in fixed-time artificial insemination (FTAI) programs with early resynchronization. A total of 468 Nelore cows were divided into two experimental groups: R30\u2014conventional resynchronization at 30 days (n = 234); R22\u2014early resynchronization at 22 days (n = 234). Both groups followed a synchronization protocol using intravaginal progesterone devices combined with the administration of steroids and gonadotropins. The R30 protocol involved resynchronization 30 days after FTAI, while the R22 protocol implemented early resynchronization 22 days after FTAI without prior pregnancy diagnosis. In both groups, one FTAI was followed by two resynchronizations. The results showed similar pregnancy rates between the groups, with the pregnancy rate in the 1st FTAI being 50.85% in the R30 group and 48.72% in the R22 group (p = 0.742). During the 1st resynchronization, the rates were 45.22% in the R30 group and 46.67% in the R22 group (p = 0.742). The cumulative pregnancy rate after the 1st FTAI, 1st, and 2nd resynchronizations was 80.77% in the R30 group and 82.91% in the R22 group (p = 0.643), with no significant difference observed. Follicular dynamics were also monitored, with ovulation occurring in 78.95% of cases in the 1st FTAI, 91.67% in the 1st resynchronization, and 88.98% in the 2nd resynchronization. The mean diameter of the ovulatory follicle was 13.64 \u00b1 3.48 mm, and the largest follicle diameter was significantly greater (14.47 \u00b1 2.76 mm) in cows that ovulated compared to those that did not (11.54 \u00b1 4.24 mm) (p &lt; 0.05), reinforcing the association between follicle size and the likelihood of ovulation. These findings indicate that both early and conventional resynchronization protocols perform similarly, with early resynchronization offering advantages in reducing the calving interval. Furthermore, the relationship between follicular diameter and ovulation confirms the importance of follicle size as an indicator of reproductive success.<\/jats:p>","DOI":"10.3390\/vetsci12010027","type":"journal-article","created":{"date-parts":[[2025,1,8]],"date-time":"2025-01-08T04:54:08Z","timestamp":1736312048000},"page":"27","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Reproductive Efficiency of Nelore Cows in Fixed-Time Artificial Insemination Programs with Early Resynchronization"],"prefix":"10.3390","volume":"12","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-3734-0837","authenticated-orcid":false,"given":"Larissa de Paiva Nunes","family":"Gon\u00e7alves","sequence":"first","affiliation":[{"name":"Postgraduate Program in Biosciences, Federal University of Western Par\u00e1 (UFOPA), Santarem 68040-255, PA, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0009-0002-7078-4341","authenticated-orcid":false,"given":"Alisson Jord\u00e3o","family":"Prado","sequence":"additional","affiliation":[{"name":"Postgraduate Program in Animal Science, Federal University of Western Par\u00e1 (UFOPA), Santarem 68040-255, PA, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Aline","family":"Pacheco","sequence":"additional","affiliation":[{"name":"Institute of Biodiversity and Forests\u2014IBEF, Federal University of Western Par\u00e1 (UFOPA), Santarem 68040-255, PA, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yana Eliza Feitosa de","family":"Almeida","sequence":"additional","affiliation":[{"name":"Institute of Biodiversity and Forests\u2014IBEF, Federal University of Western Par\u00e1 (UFOPA), Santarem 68040-255, PA, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6773-4450","authenticated-orcid":false,"given":"Pietro Sampaio","family":"Baruselli","sequence":"additional","affiliation":[{"name":"Department of Animal Reproduction, School of Veterinary Medicine and Animal Science, University of S\u00e3o Paulo, S\u00e3o Paulo 05508-000, SP, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9287-0465","authenticated-orcid":false,"given":"Welligton Concei\u00e7\u00e3o da","family":"Silva","sequence":"additional","affiliation":[{"name":"Postgraduate Program in Animal Science (PPGCAN), Institute of Veterinary Medicine, Federal University of Para (UFPA), Castanhal 68746-360, PA, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6742-3652","authenticated-orcid":false,"given":"Ant\u00f4nio Humberto Hamad","family":"Minervino","sequence":"additional","affiliation":[{"name":"Laboratory of Animal Health (LARSANA), Federal University of Western Par\u00e1 (UFOPA), Rua Vera Paz, s\/n, Sal\u00e9, Santarem 68040-255, PA, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jucelane Salvino de","family":"Lima","sequence":"additional","affiliation":[{"name":"Postgraduate Program in Animal Science, Federal University of Western Par\u00e1 (UFOPA), Santarem 68040-255, PA, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6784-5380","authenticated-orcid":false,"given":"Kedson Alessandri Lobo","family":"Neves","sequence":"additional","affiliation":[{"name":"Institute of Biodiversity and Forests\u2014IBEF, Federal University of Western Par\u00e1 (UFOPA), Santarem 68040-255, PA, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2025,1,8]]},"reference":[{"key":"ref_1","unstructured":"Figueiredo, J.R., Gon\u00e7alves, P.B.D., and Freitas, V.J.F. (2008). Biot\u00e9cnicas Aplicadas \u00e0 Reprodu\u00e7\u00e3o Animal, Roca. [2nd ed.]."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"119023","DOI":"10.34117\/bjdv7n12-593","article-title":"Estudo retrospectivo das taxas de prenhez obtidas com uso de protocolos de insemina\u00e7\u00e3o artificial em tempo fixo (IATF) em vacas suplementadas com horm\u00f4nio liberador de gonadotrofina (GNRH)\u2013Mini Revis\u00e3o","volume":"7","author":"Oliveira","year":"2021","journal-title":"Braz. J. Dev."},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Silva, F.P.d., Neves, K.A.L., Correa, F.R.A., Silva, L.K.X., Batista, H.R., Silva, W.C.d., Mercado Caruso, N., and Minervino, A.H.H. (2022). Follicular Dynamics and Pregnancy Rate in Nelore Heifers Submitted to Fixed-Time Artificial Insemination Protocols (FTAI). Vet. Sci., 9.","DOI":"10.3390\/vetsci9080377"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1083469","DOI":"10.3389\/fvets.2023.1083469","article-title":"Animal welfare and effects of per-female stress on male and cattle reproduction\u2014A review","volume":"10","author":"Viana","year":"2023","journal-title":"Front. Vet. Sci."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"364","DOI":"10.21451\/1984-3143-AR2019-0050","article-title":"Challenges to increase the AI and ET markets in Brazil","volume":"16","author":"Baruselli","year":"2019","journal-title":"Anim. Reprod."},{"key":"ref_6","first-page":"82","article-title":"Ressincroniza\u00e7\u00e3o em bovinos de corte","volume":"5","author":"Marques","year":"2012","journal-title":"Simp\u00f3sio Int. Reprodu\u00e7\u00e3o Anim. Apl."},{"key":"ref_7","first-page":"308","article-title":"Evolu\u00e7\u00e3o e perspectivas da insemina\u00e7\u00e3o artificial em bovinos","volume":"43","author":"Baruselli","year":"2019","journal-title":"Rev. Bras. Reprodu\u00e7\u00e3o Anim."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"284","DOI":"10.1016\/j.theriogenology.2013.09.027","article-title":"Resynchronization with unknown pregnancy status using progestin-based timed artificial insemination protocol in beef cattle","volume":"81","author":"Marques","year":"2014","journal-title":"Theriogenology"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"175","DOI":"10.1016\/j.livsci.2008.11.004","article-title":"Validation of body condition score as a predictor of subcutaneous fat in Nelore (Bos indicus) cows","volume":"123","author":"Ayres","year":"2009","journal-title":"Livest. Sci."},{"key":"ref_10","first-page":"58","article-title":"Efici\u00eancia reprodutiva de vacas Nelore submetidas a tr\u00eas diferentes estrat\u00e9gias reprodutivas em uma esta\u00e7\u00e3o de monta de 64 dias","volume":"1","author":"Crepaldi","year":"2017","journal-title":"Reprodu\u00e7\u00e3o Anim. SBTE"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"619","DOI":"10.1016\/j.theriogenology.2013.05.029","article-title":"Resynchronization of estrous cycle with eCG and temporary calf removal in lactating Bos indicus cows","volume":"80","author":"Campos","year":"2013","journal-title":"Theriogenology"},{"key":"ref_12","first-page":"450","article-title":"Pregnancy rate of Nelore cows submitted to resynchronization starting 14 or 22 days after prior FTAI","volume":"13","author":"Penteado","year":"2016","journal-title":"Anim. Reprod."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"152","DOI":"10.1111\/rda.13084","article-title":"Effect of oestrous synchrony between embryo donors and recipients, embryo quality and state on the pregnancy rate in beef cattle","volume":"53","author":"Rodrigues","year":"2018","journal-title":"Reprod. Domest. Anim."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"558","DOI":"10.21451\/1984-3143-AR999","article-title":"Timed artificial insemination: Current challenges and recent advances in reproductive efficiency in beef and dairy herds in Brazil","volume":"14","author":"Baruselli","year":"2018","journal-title":"Anim. Reprod."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"82","DOI":"10.1016\/j.livsci.2017.01.011","article-title":"Development and validation of an objective method for the assessment of body condition scores and selection of beef cows for timed artificial insemination","volume":"197","author":"Pfeifer","year":"2017","journal-title":"Livest. Sci."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"70","DOI":"10.1017\/S1751731114000585","article-title":"Physiological and practical effects of progesterone on reproduction in dairy cattle","volume":"8","author":"Wiltbank","year":"2014","journal-title":"Animal"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"107028","DOI":"10.1016\/j.anireprosci.2022.107028","article-title":"Influence of body condition score and its change after parturition on pregnancy rates to fixed-timed artificial insemination in Bos indicus beef cows","volume":"243","author":"Carvalho","year":"2022","journal-title":"Anim. Reprod. Sci."},{"key":"ref_18","first-page":"1","article-title":"Escores de condi\u00e7\u00e3o corporal (ECC) relacionados \u00e0 taxa de prenhez em f\u00eameas bovinas submetidas a insemina\u00e7\u00e3o artificial em tempo fixo (IATF)","volume":"6","author":"Padilha","year":"2023","journal-title":"Arq. Bras. Med. Veterin\u00e1ria"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"3825","DOI":"10.5433\/1679-0359.2021v42n6Supl2p3825","article-title":"Estrus expression and pregnancy rates in primiparous and multiparous Nelore heifers subjected to timed artificial insemination with strategic use of gonadotropin-releasing hormone","volume":"42","author":"Bonato","year":"2021","journal-title":"Semin. Ci\u00eancias Agr\u00e1rias"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"422","DOI":"10.1590\/S1516-35982010001300047","article-title":"Fatores nutricionais associados \u00e0 reprodu\u00e7\u00e3o da f\u00eamea bovina","volume":"39","author":"Sartori","year":"2010","journal-title":"Rev. Bras. Zootec."},{"key":"ref_21","first-page":"193","article-title":"Compara\u00e7\u00e3o da taxa de prenhez entre novilhas, prim\u00edparas e mult\u00edparas da ra\u00e7a Nelore submetidas \u00e0 insemina\u00e7\u00e3o artificial em tempo fixo","volume":"37","author":"Grillo","year":"2015","journal-title":"Braz. J. Vet. Med."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"3867","DOI":"10.5433\/1679-0359.2013v34n6Supl2p3867","article-title":"Fixed-time artificial insemination using injectable progesterone: Ovarian follicular dynamics and pregnancy rates of Nelore cows (Bos indicus) with and without a corpus luteum","volume":"34","author":"Morotti","year":"2013","journal-title":"Semin. Ci\u00eancias Agr\u00e1rias"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"3859","DOI":"10.5433\/1679-0359.2013v34n6Supl2p3859","article-title":"Ovarian follicular dynamics of Nelore (Bos indicus) cows subjected to a fixed-time artificial insemination protocol with injectable progesterone","volume":"34","author":"Morotti","year":"2013","journal-title":"Semin. Ci\u00eancias Agr\u00e1rias"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"510","DOI":"10.1016\/j.theriogenology.2012.02.031","article-title":"Effects of two estradiol esters (benzoate and cypionate) on the induction of synchronized ovulations in Bos indicus cows submitted to a timed artificial insemination protocol","volume":"78","author":"Sales","year":"2012","journal-title":"Theriogenology"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"e1413","DOI":"10.31533\/pubvet.v17n7e1413","article-title":"Avalia\u00e7\u00e3o do di\u00e2metro folicular no momento da IATF sobre a taxa de prenhez de vacas Nelore","volume":"17","author":"Neto","year":"2023","journal-title":"Pubvet"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"25","DOI":"10.5380\/avs.v21i1.41561","article-title":"Rela\u00e7\u00e3o entre o di\u00e2metro do fol\u00edculo no momento da insemina\u00e7\u00e3o artificial em tempo fixo e a taxa de gesta\u00e7\u00e3o em vacas Nelore","volume":"21","author":"Cavalieri","year":"2016","journal-title":"Arch. Vet. Sci."}],"container-title":["Veterinary Sciences"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2306-7381\/12\/1\/27\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,8]],"date-time":"2025-10-08T10:24:34Z","timestamp":1759919074000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2306-7381\/12\/1\/27"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,1,8]]},"references-count":26,"journal-issue":{"issue":"1","published-online":{"date-parts":[[2025,1]]}},"alternative-id":["vetsci12010027"],"URL":"https:\/\/doi.org\/10.3390\/vetsci12010027","relation":{},"ISSN":["2306-7381"],"issn-type":[{"type":"electronic","value":"2306-7381"}],"subject":[],"published":{"date-parts":[[2025,1,8]]}}}