{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,8]],"date-time":"2026-01-08T23:44:53Z","timestamp":1767915893592,"version":"3.49.0"},"reference-count":0,"publisher":"Oxford University Press (OUP)","issue":"2","license":[{"start":{"date-parts":[[1979,11,1]],"date-time":"1979-11-01T00:00:00Z","timestamp":310262400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/academic.oup.com\/pages\/standard-publication-reuse-rights"}],"content-domain":{"domain":["reproduction-online.org"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[1979,11,1]]},"abstract":"<jats:p>Summary. Yorkshire gilts in 18 h cool-white fluorescent light with 6 h dark daily and those in 9\u00b70\u201310\u00b78 h natural light exhibited puberty earlier (165 and 175 days: P &amp;lt; 0\u00b705) and had more corpora lutea (13\u00b75 and 12\u00b76: P &amp;lt; 0\u00b705) than those reared in complete darkness (200 days and 11\u00b73 respectively).<\/jats:p>\n                  <jats:p>Weekly samples of plasma showed significant fluctuations of progesterone which confirmed the different times of the first overt oestrus (puberty). In all 3 groups total oestrogen concentrations showed a peak at about 135 days. The correlation between oestrogen and progesterone values changed from a positive to a negative value at about 135 days of age. It is suggested that the oestrogen peak marks a time of change in sensitivity of the reproductive system to hormonal feedback.<\/jats:p>","DOI":"10.1530\/jrf.0.0570447","type":"journal-article","created":{"date-parts":[[2004,3,20]],"date-time":"2004-03-20T03:12:46Z","timestamp":1079752366000},"page":"447-451","update-policy":"https:\/\/doi.org\/10.1530\/rep\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":8,"title":["Plasma oestrogen, progesterone and other reproductive responses of gilts to photoperiods"],"prefix":"10.1093","volume":"57","author":[{"given":"R. R.","family":"Hacker","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"G. J.","family":"King","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"B. N.","family":"Ntunde","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"R.","family":"Narendran","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"286","published-online":{"date-parts":[[1979,11,1]]},"container-title":["Reproduction"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/academic.oup.com\/reproduction\/article-pdf\/57\/2\/447\/64934420\/jrf_57_2_031.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/academic.oup.com\/reproduction\/article-pdf\/57\/2\/447\/64934420\/jrf_57_2_031.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,1,8]],"date-time":"2026-01-08T18:17:14Z","timestamp":1767896234000},"score":1,"resource":{"primary":{"URL":"https:\/\/academic.oup.com\/reproduction\/article\/57\/2\/447\/8290162"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1979,11,1]]},"references-count":0,"journal-issue":{"issue":"2","published-print":{"date-parts":[[1979,11,1]]}},"URL":"https:\/\/doi.org\/10.1530\/jrf.0.0570447","relation":{},"ISSN":["1470-1626","1741-7899"],"issn-type":[{"value":"1470-1626","type":"print"},{"value":"1741-7899","type":"electronic"}],"subject":[],"published-other":{"date-parts":[[1979,11,1]]},"published":{"date-parts":[[1979,11,1]]}}}