{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T00:51:45Z","timestamp":1760230305180,"version":"build-2065373602"},"reference-count":28,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2022,7,22]],"date-time":"2022-07-22T00:00:00Z","timestamp":1658448000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Veterinary Sciences"],"abstract":"<jats:p>This study aimed to evaluate follicular dynamics and pregnancy rates in Nellore heifers submitted to fixed-time artificial insemination (FTAI) protocols associated with equine chorionic gonadotrophin (eCG) or follicle stimulating hormone (FSH). Nellore heifers (n = 259) were used, divided into two studies. Experiment I evaluated the ovarian follicular dynamics in 64 Nellore heifers submitted to different FTAI protocols (n = 32\/group) using either FSH or eCG. In Experiment II, the pregnancy rate was evaluated in 195 heifers submitted to FTAI protocols and divided into two groups: FSH (n = 97) and eCG (n = 98). In Experiment I, the ultrasound examination showed that the maximum diameter of the dominant and preovulatory follicles and the ovulation time were similar between the FSH and eCG groups (p &gt; 0.05). However, the ovulation rate was higher in the eCG group when compared to FSH (p = 0.014). In Experiment II, females that received eCG presented a higher pregnancy rate (58.1%) when compared to FSH (40.2%) (p = 0.012). The use of eCG in the FTAI protocol in Nellore heifers promoted a higher ovulation rate and increased pregnancy rate and may be the most suitable alternative to increase conception rates in animals that are raised in an extensive system under tropical conditions in the Amazon.<\/jats:p>","DOI":"10.3390\/vetsci9080377","type":"journal-article","created":{"date-parts":[[2022,7,25]],"date-time":"2022-07-25T04:52:47Z","timestamp":1658724767000},"page":"377","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Follicular Dynamics and Pregnancy Rate in Nellore Heifers Submitted to Fixed-Time Artificial Insemination Protocols (FTAI)"],"prefix":"10.3390","volume":"9","author":[{"given":"Filipe Prudente da","family":"Silva","sequence":"first","affiliation":[{"name":"Centro Universit\u00e1rio da Amaz\u00f4nia, Santar\u00e9m 68010-200, PA, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Kedson Alessandri Lobo","family":"Neves","sequence":"additional","affiliation":[{"name":"Laboratory of Animal Health (LARSANA), Federal University of Western Par\u00e1 (UFOPA), Rua Vera Paz, s\/n, Sal\u00e9, Santar\u00e9m 68040-255, PA, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Francisco R. A.","family":"Correa","sequence":"additional","affiliation":[{"name":"Centro Universit\u00e1rio da Amaz\u00f4nia, Santar\u00e9m 68010-200, PA, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"L\u00edlian K. X.","family":"Silva","sequence":"additional","affiliation":[{"name":"Centro Universit\u00e1rio da Amaz\u00f4nia, Santar\u00e9m 68010-200, PA, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Helder R.","family":"Batista","sequence":"additional","affiliation":[{"name":"Centro Universit\u00e1rio da Amaz\u00f4nia, Santar\u00e9m 68010-200, PA, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9287-0465","authenticated-orcid":false,"given":"Welligton C. da","family":"Silva","sequence":"additional","affiliation":[{"name":"Centro Universit\u00e1rio da Amaz\u00f4nia, Santar\u00e9m 68010-200, PA, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Nohora","family":"Mercado Caruso","sequence":"additional","affiliation":[{"name":"Departamento Productividad e Innovaci\u00f3n, Universidad de la Costa, CUC, Calle 58 n.55-66, Barranquilla 080001, Atl\u00e1ntico, Colombia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6742-3652","authenticated-orcid":false,"given":"Antonio 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, Santar\u00e9m 68040-255, PA, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2022,7,22]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"902","DOI":"10.1111\/rda.13446","article-title":"Organic or Conventional Dairy Farming in Northern Spain: Impacts on Cow Reproductive Performance","volume":"54","author":"Fouz","year":"2019","journal-title":"Reprod. Domest. Anim."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"109","DOI":"10.26605\/medvet-v13n1-2618","article-title":"Reproductive Efficiency and Reproductive Diseases of a Nelore Cattle Herd Raised in the West Region of Par\u00e1 State, Brazil","volume":"13","author":"Minervino","year":"2019","journal-title":"Med. Vet."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"479","DOI":"10.1016\/j.anireprosci.2004.04.025","article-title":"The Use of Hormonal Treatments to Improve Reproductive Performance of Anestrous Beef Cattle in Tropical Climates","volume":"82\u201383","author":"Baruselli","year":"2004","journal-title":"Anim. Reprod. Sci."},{"key":"ref_4","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":"2017","journal-title":"Anim. Reprod."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"s45","DOI":"10.1017\/S175173111800054X","article-title":"Review: Using Artificial Insemination v. Natural Service in Beef Herds","volume":"12","author":"Baruselli","year":"2018","journal-title":"Animal"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1050","DOI":"10.1111\/rda.13468","article-title":"Effect of Oestrous Resynchronization on the Reproductive Efficiency of Zebu Cows","volume":"54","author":"Faleiro","year":"2019","journal-title":"Reprod. Domest. Anim."},{"key":"ref_7","first-page":"1","article-title":"Fixed Timed Artificial Insemination (FTAI) through the Progesterone (CIDR) of 1st, 2nd, 3rdand 4thuses in Bovine. I. Conception Rate Related to Reproductive Category, Related to Body Condition Scoring (BCS), Related to Calf Withdrawal and Use of ECG","volume":"23","author":"Vale","year":"2011","journal-title":"Livest. Res. Rural. Dev."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"624","DOI":"10.1111\/rda.13150","article-title":"Effect of Body Condition Score and Reuse of Progesterone-Releasing Intravaginal Devices on Conception Rate Following Timed Artificial Insemination in Nelore Cows","volume":"53","author":"Pereira","year":"2018","journal-title":"Reprod. Domest. Anim."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"179","DOI":"10.1016\/j.theriogenology.2009.02.010","article-title":"Fixed-Time Artificial Insemination with Estradiol and Progesterone for Bos indicus Cows I: Basis for Development of Protocols","volume":"72","author":"Meneghetti","year":"2009","journal-title":"Theriogenology"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"490","DOI":"10.1016\/j.theriogenology.2013.11.004","article-title":"Different Circulating Progesterone Concentrations during Synchronization of Ovulation Protocol Did Not Affect Ovarian Follicular and Pregnancy Responses in Seasonal Anestrous Buffalo Cows","volume":"81","author":"Carvalho","year":"2014","journal-title":"Theriogenology"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"455","DOI":"10.1016\/j.theriogenology.2011.02.022","article-title":"Importance of Estrus on Pregnancy per Insemination in Suckled Bos indicus Cows Submitted to Estradiol\/Progesterone-Based Timed Insemination Protocols","volume":"76","author":"Santos","year":"2011","journal-title":"Theriogenology"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"940","DOI":"10.21451\/1984-3143-AR2018-0020","article-title":"Evolution of Fixed-Time AI in Dairy Cattle in Brazil","volume":"15","author":"Vasconcelos","year":"2018","journal-title":"Anim. Reprod."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"681","DOI":"10.1016\/j.theriogenology.2009.04.026","article-title":"Strategies to Improve Fertility in Bos indicus Postpubertal Heifers and Nonlactating Cows Submitted to Fixed-Time Artificial Insemination","volume":"72","author":"Peres","year":"2009","journal-title":"Theriogenology"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"3127","DOI":"10.2527\/jas.2013-7404","article-title":"Comparison of Three CIDR-Based Fixed-Time AI Protocols in Beef Heifers","volume":"92","author":"Bridges","year":"2014","journal-title":"J. Anim. Sci."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"775","DOI":"10.1111\/rda.12368","article-title":"Influence of Temperament Score and Handling Facility on Stress, Reproductive Hormone Concentrations, and Fixed Time AI Pregnancy Rates in Beef Heifers","volume":"49","author":"Kasimanickam","year":"2014","journal-title":"Reprod. Domest. Anim."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"106751","DOI":"10.1016\/j.anireprosci.2021.106751","article-title":"Effects of ECG and FSH in Timed Artificial Insemination Treatment Regimens on Estrous Expression and Pregnancy Rates in Primiparous and Multiparous Bos indicus Cows","volume":"228","author":"Bottino","year":"2021","journal-title":"Anim. Reprod. Sci."},{"key":"ref_17","first-page":"206","article-title":"Horm\u00f4nios Hipofis\u00e1rios e Seu Papel Na Foliculog\u00eanese Pituitary Hormones and Their Role in Folliculogenesis","volume":"4","author":"Saraiva","year":"2010","journal-title":"Rev. Bras. Reprod. Anim"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"12","DOI":"10.1016\/j.anireprosci.2011.02.007","article-title":"Fixed-Time AI Protocols Replacing ECG with a Single Dose of FSH Were Less Effective in Stimulating Follicular Growth, Ovulation, and Fertility in Suckled-Anestrus Nelore Beef Cows","volume":"124","author":"Sales","year":"2011","journal-title":"Anim. Reprod. Sci."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"182","DOI":"10.1016\/j.anireprosci.2009.10.004","article-title":"Equine Chorionic Gonadotropin Improves the Efficacy of a Progestin-Based Fixed-Time Artificial Insemination Protocol in Nelore (Bos indicus) Heifers","volume":"118","author":"Penteado","year":"2010","journal-title":"Anim. Reprod. Sci."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"17","DOI":"10.1016\/j.theriogenology.2010.07.005","article-title":"Neither Plasma Progesterone Concentrations nor Exogenous ECG Affects Rates of Ovulation or Pregnancy in Fixed-Time Artificial Insemination (FTAI) Protocols for Puberal Nellore Heifers","volume":"75","author":"Pegorer","year":"2011","journal-title":"Theriogenology"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"177","DOI":"10.1111\/rda.12268","article-title":"Use of Equine Chorionic Gonadotropin to Control Reproduction of the Dairy Cow: A Review","volume":"49","year":"2014","journal-title":"Reprod. Domest. Anim."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"1801","DOI":"10.5897\/AJAR2016.11801","article-title":"Climate Conditions in the Eastern Amazon: Rainfall Variability in Belem and Indicative of Soil Water Deficit","volume":"12","author":"Martorano","year":"2017","journal-title":"Afr. J. Agric. Res."},{"key":"ref_23","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_24","first-page":"2319","article-title":"Pregnancy Rates in Timed Artificial Insemination in Nelore Cows (Bos Taurus Indicus) Using Estradiol Benzoate or Estradiol Cipionate as Ovulation Inducers Associated WitheCG or FSHp","volume":"9","author":"Neves","year":"2016","journal-title":"IOSR J. Agric. Vet. Sci. Ver I"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"642","DOI":"10.1016\/j.theriogenology.2013.06.008","article-title":"Timed Artificial Insemination Should Be Performed Early When Used Norgestomet Ear Implants Are Applied for Synchronizing Ovulation in Beef Heifers","volume":"80","author":"Penteado","year":"2013","journal-title":"Theriogenology"},{"key":"ref_26","first-page":"199","article-title":"Efeito Do ECG Ou Benzoato de Estradiol Associado Ao Norgestomet Na Taxa de Concep\u00e7\u00e3o de Vacas de Corte Submetidas \u00e0 IATF No P\u00f3s-Parto","volume":"46","author":"Rossa","year":"2009","journal-title":"J. Vet. Res. Anim. Sci."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"73","DOI":"10.5380\/avs.v20i1.39101","article-title":"Efici\u00eancia Da Gonadotrofina Cori\u00f4nica Eq\u00fcina (ECG) e Do Desmame Tempor\u00e1rio (DT) Em Protocolos Para a Insemina\u00e7\u00e3o Artificial Em Tempo Fixo (IATF) Em Vacas Nelore, Previamente Tratadas Com Progesterona (P4) e Benzoato de Estradiol (BE)","volume":"20","author":"Souza","year":"2015","journal-title":"Arch. Vet. Sci."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"210","DOI":"10.1016\/j.theriogenology.2009.02.010","article-title":"Fixed-Time Artificial Insemination with Estradiol and Progesterone for Bos indicus Cows II: Strategies and Factors Affecting Fertility","volume":"72","author":"Meneghetti","year":"2009","journal-title":"Theriogenology"}],"container-title":["Veterinary Sciences"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2306-7381\/9\/8\/377\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T23:54:37Z","timestamp":1760140477000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2306-7381\/9\/8\/377"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,7,22]]},"references-count":28,"journal-issue":{"issue":"8","published-online":{"date-parts":[[2022,8]]}},"alternative-id":["vetsci9080377"],"URL":"https:\/\/doi.org\/10.3390\/vetsci9080377","relation":{},"ISSN":["2306-7381"],"issn-type":[{"type":"electronic","value":"2306-7381"}],"subject":[],"published":{"date-parts":[[2022,7,22]]}}}