広島大学農場における乳牛の分娩間隔が乳生産に及ぼす影響  [in Japanese] Effects of calving interval on milk production of dairy herd at Hiroshima University Farm  [in Japanese]

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Abstract

<p>広島大学農場のホルスタイン種乳牛の2000年度~2017年度の分娩-分娩間の乳生産量,泌乳,乾乳日数などの記録から,分娩間隔の影響を,産次(初産,2産,3産以上)ごとに検討した.分娩間隔の中央値前後で2つの分娩間隔区(CIG)(CI<sub>S</sub>, 分娩間隔<404日およびCI<sub>L</sub>, 分娩間隔≧404日)に分け,乳生産などへのCIGの効果を検定した.CI<sub>L</sub>でCI<sub>S</sub>より泌乳日数/分娩間隔比は低下しなかったが,初産と2産で乾乳前乳量低下の早期化による泌乳日数当たりと分娩間隔当たりの日乳量低下傾向を認め,分娩間隔延長による乳生産効率低下が示唆された.2011年3月に本農場に自動搾乳システムが導入され,同時に飼料給与システムが分離給与から混合給与に移行した後に,泌乳初期における乳量増加とともに体重変化の改善または維持が認められたものの,2産以上で乾乳期間と分娩間隔は延長した.分娩間隔延長への対策の重要性と,その要因のさらなる精査の必要性が示唆された.</p>

<p>Using the records of Hiroshima University Farm for the Holstein dairy herd from the year 2000 to 2017, we investigated the effects of the calving interval on the milk production, length of lactation and dry period, and body weight change of dairy cows in early lactation. The 232 records for periods from one calving to the next calving including the dry period were divided into three parity groups (first parity, second parity, and third or greater parity) and analyzed within each group. An automatic milking system (AMS) was introduced on the farm, and the feeding system was changed from separate feeding to partial mixed ration feeding in March 2011. The data sets for the periods during which the AMS was introduced were not included the data set used for the analyses. We compared the responses listed above between calving interval groups (CIG ; CI<sub>S</sub><404 d, CI<sub>L</sub>≧404) and between periods before and after the AMS introduction. An increase in the calving interval significantly elongated lactation period and dry period. However, the ratio of the lactation period to the calving interval did not decrease with increasing calving interval. The decrease in the milk yield at 45 days before dry off (45_day_Milk yield) with increasing calving interval suggested decreases in the milk yield during the later period of lactation, and seems to have caused the decrease in the milk yield per lactation day and the milk yield per calving interval. Those results indicated that an increase in the calving interval decreased the efficiency of the milk production and might seriously diminish the management efficiency of dairy farmers. The energy balance in the early lactation stage estimated from the body weight change, and the milk yield in early lactation period did not significantly differ between the CIGs for all parity groups. After the introduction of the AMS, the increase in the milk yield in early lactation did not result in an increase in body weight loss, probably due to the introduction of the partial mixed feeding system. However, the dry period and calving interval for the second or greater parity were elongated. Further research is required to investigate the factors that contribute to the calving interval elongation of dairy cows. To improve the milk production efficiency under the condition of calving interval elongation, factors affecting the decrease rate of the milk yield in the later lactation stage should be investigated.</p>

Journal

  • Nihon Chikusan Gakkaiho

    Nihon Chikusan Gakkaiho 90(2), 111-120, 2019

    Zootechnical Science Society of Japan

Codes

  • NII Article ID (NAID)
    130007662334
  • NII NACSIS-CAT ID (NCID)
    AN00195188
  • Text Lang
    JPN
  • Article Type
    journal article
  • ISSN
    1346-907X
  • NDL Article ID
    029764704
  • NDL Call No.
    Z18-348
  • Data Source
    NDL  J-STAGE  JASI 
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