{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,22]],"date-time":"2026-09-22T19:02:28Z","timestamp":1790103748402,"version":"4.0.1"},"reference-count":47,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2026,9,19]],"date-time":"2026-09-19T00:00:00Z","timestamp":1789776000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Vet. Sci.","Veterinary Sciences"],"abstract":"<jats:p>This field study evaluated the effects of 400 and 500 IU equine chorionic gonadotropin (eCG) on oestrus response, fertility, and lambing performance in Ile-de-France ewe lambs and adult ewes under seasonal-transition field conditions. A total of 914 animals were assigned to four groups according to age category and eCG dose: ewe lambs receiving 400 IU (EL400, n = 173) or 500 IU eCG (EL500, n = 169), and adult ewes receiving 400 IU (AE400, n = 301) or 500 IU eCG (AE500, n = 271), following a 7-day intravaginal progesterone-based synchronization protocol. Oestrus rate did not differ among groups (p = 0.861), indicating that both doses were similarly effective in inducing behavioural oestrus, whereas the interval to oestrus onset showed significant main effects of both age category (p &lt; 0.001) and eCG dose (p &lt; 0.001), with no significant age \u00d7 dose interaction (p = 0.559). Using a 2 \u00d7 2 factorial analysis, significant main effects of age category were observed for outcomes including pregnancy rate following oestrus, overall pregnancy rate, and fecundity (p = 0.001, p = 0.009, and p = 0.004, respectively), with higher values in adult ewes than in ewe lambs regardless of eCG dose. In contrast, 500 IU eCG was associated with a greater overall litter size and multiple birth rate than 400 IU eCG (p = 0.039 and p = 0.033, respectively). The age \u00d7 dose interactions for litter size and multiple birth rate were not statistically significant (p = 0.058 and p = 0.071, respectively). The age \u00d7 dose interaction for lambing rate was also not statistically significant (p = 0.064). These results indicate that age category and eCG dose were associated with different aspects of reproductive performance. Under the specific seasonal-transition field conditions of this single-breed, single-farm study, selecting the eCG dose according to the reproductive objective may represent a practical management consideration.<\/jats:p>","DOI":"10.3390\/vetsci13090992","type":"journal-article","created":{"date-parts":[[2026,9,22]],"date-time":"2026-09-22T17:56:41Z","timestamp":1790099801000},"page":"992","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Effects of Age Category and eCG Dose on Reproductive Performance in Ile-de-France Ewe Lambs and Adult Ewes Under Seasonal-Transition Field Conditions"],"prefix":"10.3390","volume":"13","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8333-6500","authenticated-orcid":false,"given":"Muhammed Furkan","family":"Ciftci","sequence":"first","affiliation":[{"name":"Department of Obstetrics and Gynecology, Faculty of Veterinary Medicine, Selcuk University, Konya 42130, T\u00fcrkiye"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"},{"role":"software","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"formal-analysis","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"data-curation","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"},{"role":"funding-acquisition","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9877-8405","authenticated-orcid":false,"given":"Fatma","family":"Satilmis","sequence":"additional","affiliation":[{"name":"Department of Obstetrics and Gynecology, Faculty of Veterinary Medicine, Selcuk University, Konya 42130, T\u00fcrkiye"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"resources","vocabulary":"credit"},{"role":"data-curation","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"},{"role":"project-administration","vocabulary":"credit"},{"role":"funding-acquisition","vocabulary":"credit"}]}],"member":"1968","published-online":{"date-parts":[[2026,9,19]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Gebreselassie, G., Berihulay, H., Jiang, L., and Ma, Y. (2019). Review on genomic regions and candidate genes associated with economically important production and reproduction traits in sheep (Ovis aries). Animals, 10.","DOI":"10.3390\/ani10010033"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"82","DOI":"10.7831\/ras.10.0_82","article-title":"The reproductive traits of sheep and their influencing factors","volume":"10","author":"Ajafar","year":"2022","journal-title":"Rev. Agric. Sci."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"69","DOI":"10.1071\/BI9880069","article-title":"Seasonality of reproduction in sheep and its control by photoperiod","volume":"41","author":"Ortavant","year":"1988","journal-title":"Aust. J. Biol. Sci."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"75","DOI":"10.1016\/j.domaniend.2011.11.003","article-title":"The role of kisspeptin and gonadotropin inhibitory hormone in the seasonal regulation of reproduction in sheep","volume":"43","author":"Smith","year":"2012","journal-title":"Domest. Anim. Endocrinol."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"155","DOI":"10.1016\/S0921-4488(03)00038-5","article-title":"Seasonality of reproduction in sheep","volume":"48","author":"Rosa","year":"2003","journal-title":"Small Rumin. Res."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"39","DOI":"10.5513\/JCEA01\/22.1.2939","article-title":"Induction and synchronization of oestrus in sheep and goats","volume":"22","author":"Skliarov","year":"2021","journal-title":"J. Cent. Eur. Agric."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"100","DOI":"10.1016\/j.smallrumres.2014.04.004","article-title":"Efficacy of various five-day estrous synchronization protocols in sheep","volume":"120","author":"Jackson","year":"2014","journal-title":"Small Rumin. Res."},{"key":"ref_8","first-page":"21","article-title":"Sheep reproductive management","volume":"14","year":"2021","journal-title":"Agro Product."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Santos-Jimenez, Z., Mart\u00ednez-Ros, P., Encinas, T., Morales-Cruz, J.L., Guerrero-Gallegos, H.Z., Gonzalez-Avalos, R., and Guillen-Mu\u00f1oz, J.M. (2022). Ovarian response and fertility after short-term progestagen\/eCG treatments are compromised in nulliparous sheep during non-breeding season. Vet. Sci., 9.","DOI":"10.3390\/vetsci9120663"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"173","DOI":"10.1530\/jrf.0.0730173","article-title":"Changes in pulsatile LH secretion after ovariectomy in Ile-de-France ewes in two seasons","volume":"73","author":"Montgomery","year":"1985","journal-title":"Reproduction"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"48","DOI":"10.1111\/rda.14257","article-title":"Effect of eCG dose on ovarian haemodynamics, hormonal profiles and prolificacy rate when oestrus was induced during low-breeding season in Beetal goats","volume":"58","author":"Sharif","year":"2022","journal-title":"Reprod. Domest. Anim."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"107365","DOI":"10.1016\/j.anireprosci.2023.107365","article-title":"Evaluation of the effect of melatonin implantation in rams and eCG dose in ewes synchronized by a CIDR-eCG protocol on reproductive performance of Lacaune sheep breed during non-breeding season","volume":"259","author":"Akbarinejad","year":"2023","journal-title":"Anim. Reprod. Sci."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"425","DOI":"10.5194\/aab-68-425-2025","article-title":"Effects of intravaginal progesterone devices and Booroola fecundity (FecB) gene on the ovarian responses and reproductive indices of Qezel ewes following estrus synchronization and laparoscopic insemination during the breeding season","volume":"68","author":"Eslami","year":"2025","journal-title":"Arch. Anim. Breed."},{"key":"ref_14","first-page":"1128","article-title":"Determination of the effect of different doses of eCG applications on reproductive parameters in primiparous Akkaraman Kangal sheep","volume":"11","year":"2023","journal-title":"Turk. J. Agric. Food Sci. Technol."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"288","DOI":"10.1080\/00288233.2013.842176","article-title":"Comparison between the reproductive performance of ewe hoggets and mature ewes following a progesterone-based oestrus synchronization protocol","volume":"56","author":"Mulvaney","year":"2013","journal-title":"N. Z. J. Agric. Res."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"379","DOI":"10.1111\/rda.14295","article-title":"Induction of ovulation using repeated doses of sulpiride, a dopamine antagonist, in ewe lambs","volume":"58","author":"Kivrak","year":"2023","journal-title":"Reprod. Domest. Anim."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"937","DOI":"10.2478\/aoas-2019-0033","article-title":"Genetic variability in the loci of FABP4, PPAR\u03b3 and SCD genes of sheep breeds raised for different purposes","volume":"19","author":"Kucharski","year":"2019","journal-title":"Ann. Anim. Sci."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"169","DOI":"10.5194\/aab-52-169-2009","article-title":"Effects of crossbreeding Hungarian Merino sheep with Suffolk and Ile de France on carcass traits","volume":"52","author":"Pajor","year":"2009","journal-title":"Arch. Anim. Breed."},{"key":"ref_19","first-page":"223","article-title":"Growth, feedlot performance and carcass characteristics of Karakas and crossbred lambs (F1) (Ile de France \u00d7 Akkaraman (G1) \u00d7 Karakas) under rural farm conditions in Turkey","volume":"34","author":"Gokdal","year":"2004","journal-title":"S. Afr. J. Anim. Sci."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"9","DOI":"10.1016\/j.smallrumres.2012.08.001","article-title":"Introduction of sheep meat breeds in extensive systems: Lamb carcass characteristics","volume":"109","author":"Iglesias","year":"2013","journal-title":"Small Rumin. Res."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"66","DOI":"10.1186\/2193-1801-3-66","article-title":"Production traits in F1 and F2 crosses with naturalized hair breed Santa In\u00eas ewes","volume":"3","author":"McManus","year":"2014","journal-title":"SpringerPlus"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"1157","DOI":"10.2298\/BAH1103157M","article-title":"Effect of the short-term progestagen treatments plus PMSG prior ram introduction on the estrus synchronization and the fertility of Ile de France ewes","volume":"27","author":"Metodiev","year":"2011","journal-title":"Biotechnol. Anim. Husb."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"51","DOI":"10.46897\/livestockstudies.1589212","article-title":"The effects of different doses of eCG injection on reproductive parameters in nulliparous Merino ewes during the non-breeding season","volume":"64","author":"Akbulut","year":"2024","journal-title":"Livest. Stud."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"740","DOI":"10.1111\/rda.14344","article-title":"Reproductive performance of European-breed ewes in different seasons of the year under mid-latitude","volume":"58","author":"Heinzen","year":"2023","journal-title":"Reprod. Domest. Anim."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1095\/biolreprod.111.092817","article-title":"The interaction between photoperiod and nutrition and its effects on seasonal rhythms of reproduction in the ewe","volume":"86","author":"Menassol","year":"2012","journal-title":"Biol. Reprod."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"311","DOI":"10.1016\/S0093-691X(03)00215-2","article-title":"Ultrasound and endocrine evaluation of the ovarian response to a single dose of 500 IU of eCG following a 12-day treatment with progestogen-releasing intravaginal sponges in the breeding and nonbreeding seasons in ewes","volume":"61","author":"Barrett","year":"2004","journal-title":"Theriogenology"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"e20230092","DOI":"10.1590\/1984-3143-ar2023-0092","article-title":"Use of new recombinant proteins for ovarian stimulation in ruminants","volume":"20","author":"Baruselli","year":"2023","journal-title":"Anim. Reprod."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"106034","DOI":"10.1016\/j.smallrumres.2019.106034","article-title":"Investigation of ram effect and eCG usage in progesterone based oestrous synchronization protocols on fertility of ewes following fixed time artificial insemination","volume":"183","author":"Nakafeero","year":"2020","journal-title":"Small Rumin. Res."},{"key":"ref_29","first-page":"407","article-title":"The efficacy of three different estrus synchronization protocols on reproductive performance in Chinese Hu sheep","volume":"56","author":"Qu","year":"2022","journal-title":"Indian J. Anim. Res."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"2","DOI":"10.1016\/j.smallrumres.2013.12.022","article-title":"Breeding ewe lambs successfully to improve lifetime performance","volume":"118","author":"Kenyon","year":"2014","journal-title":"Small Rumin. Res."},{"key":"ref_31","first-page":"87","article-title":"Effect on fertility of PMSG applications in different doses in addition to flushing in Kivircik ewes","volume":"31","author":"Koyuncu","year":"2018","journal-title":"Mediterr. Agric. Sci."},{"key":"ref_32","first-page":"231","article-title":"Natural and artificial insemination in sheep-a review","volume":"64","author":"Bancheva","year":"2021","journal-title":"Sci. Pap. Ser. D Anim. Sci."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"1177","DOI":"10.1071\/AN22417","article-title":"Embryo development and survival in peripubertal ewe lambs","volume":"63","author":"Juengel","year":"2023","journal-title":"Anim. Prod. Sci."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"281","DOI":"10.1017\/S0003356100006899","article-title":"A comparison of plasma prolactin, LH and progesterone concentrations during oestrus and early pregnancy in ewe lambs and ewes","volume":"57","author":"Davies","year":"1993","journal-title":"Anim. Sci."},{"key":"ref_35","first-page":"309","article-title":"Induction of accessory corpus luteum in goats and sheep: From physiological basis to reproductive effects","volume":"45","author":"Fonseca","year":"2021","journal-title":"Rev. Bras. Reprod. Anim."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"491","DOI":"10.1071\/RD04035","article-title":"Nutritional and environmental effects on reproduction in small ruminants","volume":"16","author":"Martin","year":"2004","journal-title":"Reprod. Fertil. Dev."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"53","DOI":"10.1186\/2049-1891-5-53","article-title":"Conceptus elongation in ruminants: Roles of progesterone, prostaglandin, interferon tau and cortisol","volume":"5","author":"Brooks","year":"2014","journal-title":"J. Anim. Sci. Biotechnol."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"106938","DOI":"10.1016\/j.domaniend.2025.106938","article-title":"Insights into improving embryo survival in sheep","volume":"92","author":"Reader","year":"2025","journal-title":"Domest. Anim. Endocrinol."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"403","DOI":"10.1016\/j.cytogfr.2007.06.010","article-title":"Interferon-tau, a type 1 interferon involved in maternal recognition of pregnancy","volume":"18","author":"Roberts","year":"2007","journal-title":"Cytokine Growth Factor. Rev."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"skac123","DOI":"10.1093\/jas\/skac123","article-title":"Ruminant conceptus-maternal interactions: Interferon-tau and beyond","volume":"100","author":"Mathew","year":"2022","journal-title":"J. Anim. Sci."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"446","DOI":"10.1111\/rda.12930","article-title":"Administration of exogenous hormones in ovulatory and embryonic response in Pelibuey sheep","volume":"52","year":"2017","journal-title":"Reprod. Domest. Anim."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"479","DOI":"10.1016\/0093-691X(85)90054-8","article-title":"Effect of PMSG dosage on the reproductive performance of adult ewes and ewe lambs bred at a progestagen-PMSG synchronized estrus","volume":"24","author":"Ainsworth","year":"1985","journal-title":"Theriogenology"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"130","DOI":"10.1016\/j.theriogenology.2016.04.024","article-title":"Intrinsic determinants and predictors of superovulatory yields in sheep: Circulating concentrations of reproductive hormones, ovarian status, and antral follicular blood flow","volume":"86","author":"Bartlewski","year":"2016","journal-title":"Theriogenology"},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"143","DOI":"10.1590\/S1413-95962002000300006","article-title":"Effect of estrus synchronization and artificial insemination on reproductive performance of Merino sheep","volume":"39","author":"Simonetti","year":"2002","journal-title":"Braz. J. Vet. Res. Anim. Sci."},{"key":"ref_45","first-page":"249","article-title":"Reproductive response at Ile de France ewes after 5 days progestagen treatment plus or without pregnant mare serum gonadotropin (PMSG)","volume":"63","author":"Metodiev","year":"2020","journal-title":"Sci. Pap. Ser. D Anim. Sci."},{"key":"ref_46","first-page":"517","article-title":"Comparative data about estrus induction and pregnancy rate on Lacaune ewes in non-breeding season after melatonin implants and intravaginal progestagen","volume":"55","author":"Berean","year":"2021","journal-title":"Indian J. Anim. Res."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"28","DOI":"10.1016\/j.anireprosci.2015.01.010","article-title":"Successful induction of oestrus, ovulation and pregnancy in adult ewes and ewe lambs out of the breeding season using a GnRH+ progesterone oestrus synchronisation protocol","volume":"155","author":"Martinez","year":"2015","journal-title":"Anim. Reprod. Sci."}],"container-title":["Veterinary Sciences"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2306-7381\/13\/9\/992\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,9,22]],"date-time":"2026-09-22T18:11:34Z","timestamp":1790100694000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2306-7381\/13\/9\/992"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,9,19]]},"references-count":47,"journal-issue":{"issue":"9","published-online":{"date-parts":[[2026,9]]}},"alternative-id":["vetsci13090992"],"URL":"https:\/\/doi.org\/10.3390\/vetsci13090992","relation":{},"ISSN":["2306-7381"],"issn-type":[{"value":"2306-7381","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,9,19]]}}}