{
    "abstract": "The primary objective of this study was to investigate the effects of abnormal ovarian cycles during the pre-service postpartum period on subsequent reproductive performance of high-producing Holstein cows. The study was conducted in a commercial dairy farm with approximately 150 lactating cows, in a subtropical region of Japan. Animals were kept in free-stall barn, and fed a total mixed ration. Cows that calved from June 2001 to July 2002 were included in the study. Milk samples were collected twice weekly from 2 to 11 weeks postpartum, and progesterone concentrations in skim milk were determined by ELISA. After a voluntary waiting period of 40 days, cows detected in estrus were bred by artificial insemination (AI). Pregnancy was confirmed by palpation per rectum 40-70 days after AI. Out of a total of 91 cases, 39 (42.9%) had normal ovarian cycles (ovulation within 45 days after calving, followed by normal ovarian cycles), 32 (35.2%) had prolonged luteal phase (i.e. luteal activity for >20 days), and 12 (13.2%) had anovulation or delayed first ovulation (i.e. first ovulation did not occur until >45 days after calving). The remaining (8.8%) had other types of abnormalities. When compared with cows with a normal ovarian cycle, prolonged luteal phase cows had a lower 100 days AI submission rate, conception rate and pregnancy rate (84.2% versus 56.3%; P<0.05, 50% versus 16.7%; P<0.05 and 42.1% versus 9.4%; P<0.01, respectively), and longer intervals to first AI and to conception ( 67+/-6 days versus 98+/-7 days and 95+/-9 days versus 136+/-11 days; P<0.01 for each). Similarly, when compared with cows with normal ovarian cycles, those with anovulation had lower 100 days conception rate and pregnancy rate (50% versus 0%; P<0.05 and 42.1% versus 0%; P<0.01, respectively), and longer intervals to first AI and to conception ( 67+/-6 days versus 93+/-12 days; P<0.05 and 95+/-9 days versus 155+/-14 days; P<0.01, respectively). Survival analysis of the data for calving to conception interval showed that cows with prolonged luteal phase or anovulation were getting pregnant at a slower rate, and took longer to get pregnant than the cows with normal resumption of ovarian cyclicity postpartum. In conclusion, abnormal ovarian cycles during the pre-service period postpartum adversely affected reproductive performance, including AI submission rate, pregnancy rate, interval to first AI, and calving to conception interval in high-producing Holstein cows.",
    "authors": [
        {
            "affiliation": "Animal Science Laboratory, Graduate School for International Development and Cooperation (IDEC), Hiroshima University, 1-5-1 Kagamiyama, Higashi-Hiroshima 739-8529, Japan.",
            "firstname": "Hemanta Kumar",
            "initials": "HK",
            "lastname": "Shrestha"
        },
        {
            "affiliation": null,
            "firstname": "Toshihiko",
            "initials": "T",
            "lastname": "Nakao"
        },
        {
            "affiliation": null,
            "firstname": "Toshihiko",
            "initials": "T",
            "lastname": "Suzuki"
        },
        {
            "affiliation": null,
            "firstname": "Tsuneo",
            "initials": "T",
            "lastname": "Higaki"
        },
        {
            "affiliation": null,
            "firstname": "Masashi",
            "initials": "M",
            "lastname": "Akita"
        }
    ],
    "conclusions": null,
    "copyrights": null,
    "doi": "10.1016/j.theriogenology.2003.09.007",
    "journal": "Theriogenology",
    "keywords": [],
    "methods": null,
    "publication_date": "2004-03-24",
    "pubmed_id": "15036985",
    "results": null,
    "title": "Effects of abnormal ovarian cycles during pre-service period postpartum on subsequent reproductive performance of high-producing Holstein cows.",
    "xml": "<Element 'PubmedArticle' at 0x788503572610>"
}