{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,24]],"date-time":"2026-07-24T12:10:27Z","timestamp":1784895027421,"version":"3.55.0"},"reference-count":39,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2021,7,23]],"date-time":"2021-07-23T00:00:00Z","timestamp":1626998400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Israeli Milk Assembly","award":["820-0335"],"award-info":[{"award-number":["820-0335"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Animals"],"abstract":"<jats:p>We examined gonadotropin-releasing hormone (GnRH) administration at onset of estrus (OE), determined by automatic activity monitoring (AAM), to improve fertility of dairy cows during the summer and autumn. The study was performed on two dairy farms in Israel. The OE was determined by AAM recorded every 2 h, and a single im dose of GnRH analogue was administered shortly after OE. Pregnancy was determined by transrectal palpation, 40 to 45 d after artificial insemination (AI). Conception risk was analyzed by the GLIMMIX procedure of SAS. Brief visual observation of behavioral estrus indicated that about three-quarters of the events (n = 40) of visually detected OE occurred within 6 h of AAM-detected OE. Accordingly, the GnRH analogue was administered within 5 h of AAM-detected OE, to overlap with the expected endogenous preovulatory LH surge. Overall, pregnancy per AI (P\/AI) was monitored over the entire experimental period (summer and autumn) in 233 first, second or third AI (116 and 117 AI for treated and control groups, respectively). Least square means of P\/AI for treated (45.8%) and control (39.4%) groups did not differ, but group-by-season interaction tended to differ (p = 0.07), indicating no effect of treatment in the summer and a marked effect of GnRH treatment (n = 58 AI) compared to controls (n = 59 AI) on P\/AI in the autumn (56.6% vs. 28.5%, p &lt; 0.03). During the autumn, GnRH-treated mature cows (second or more lactations), and postpartum cows exhibiting metabolic and uterine diseases, tended to have much larger P\/AI than their control counterparts (p = 0.07\u20130.08). No effect of treatment was recorded in the autumn in first parity cows or in uninfected, healthy cows. In conclusion, administration of GnRH within 5 h of AAM-determined OE improved conception risk in cows during the autumn, particularly in those exhibiting uterine or metabolic diseases postpartum and in mature cows. Incorporation of the proposed GnRH treatment shortly after AAM-detected OE into a synchronization program is suggested, to improve fertility of positively responding subpopulations of cows.<\/jats:p>","DOI":"10.3390\/ani11082194","type":"journal-article","created":{"date-parts":[[2021,7,25]],"date-time":"2021-07-25T22:06:21Z","timestamp":1627250781000},"page":"2194","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":7,"title":["Administration of GnRH at Onset of Estrus, Determined by Automatic Activity Monitoring, to Improve Dairy Cow Fertility during the Summer and Autumn"],"prefix":"10.3390","volume":"11","author":[{"given":"Zvi","family":"Roth","sequence":"first","affiliation":[{"name":"Department of Animal Sciences, Faculty of Agriculture, Food and Environment, The Hebrew University, Rehovot 76100, Israel"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yaron Z.","family":"Kressel","sequence":"additional","affiliation":[{"name":"Department of Animal Sciences, Faculty of Agriculture, Food and Environment, The Hebrew University, Rehovot 76100, Israel"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3371-2904","authenticated-orcid":false,"given":"Yaniv","family":"Lavon","sequence":"additional","affiliation":[{"name":"Israel Cattle Breeders Association, Caesarea 38900, Israel"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0193-8733","authenticated-orcid":false,"given":"Dorit","family":"Kalo","sequence":"additional","affiliation":[{"name":"Department of Animal Sciences, Faculty of Agriculture, Food and Environment, The Hebrew University, Rehovot 76100, Israel"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"David","family":"Wolfenson","sequence":"additional","affiliation":[{"name":"Department of Animal Sciences, Faculty of Agriculture, Food and Environment, The Hebrew University, Rehovot 76100, Israel"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2021,7,23]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1139","DOI":"10.1016\/S0093-691X(03)00126-2","article-title":"Heat stress and seasonal effects on reproduction in the dairy cow\u2014A review","volume":"60","author":"Scaramuzzi","year":"2003","journal-title":"Theriogenology"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"22","DOI":"10.1071\/RD14311","article-title":"Genetic variation in resistance of the preimplantation bovine embryo to heat shock","volume":"27","author":"Hansen","year":"2015","journal-title":"Reprod. 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