Bovine Serum Prolactin, Growth Hormone, and Triiodothyronine Levels during Late Pregnancy and Early Lactation

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  • JOHKE Tetsu
    Department of Physiology, National Institute of Animal Industry
  • HODATE Kouichi
    Department of Physiology, National Institute of Animal Industry

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  • 乳牛の血清プロラクチン,成長ホルモンおよびトリヨードサイロニンの妊娠末期から泌乳初期における変化
  • ニュウギュウ ノ ケッセイ プロラクチン セイチョウ ホルモン オヨビ トリヨ

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Abstract

Changes of serum prolactin (PRL), growth hormone (GH), and triiodothyronine (T3) levels in Holstein dairy cows during late pregnancy and early lactation were determined by radioimmunoassays. The cows calved in September. Mean serum PRL ranged 9.9ng/ml to 12.4ng/ml during the 3rd to 7th day prepartum. It increased to a peak value of 87.3ng/ml on the day of parturition from 57.5ng/ml on the day before calving, and decreased to 13.9ng/ml within 3 days postpartum. During the 2nd to 30th day prepartum, serum GH varied between 2.4 and 4.0ng/ml and increased to 8.0ng/ml on the day of calving. During a week postpartum, serum GH ranged from 5.2 to 8.2 ng/ml. Mean serum GH during a week postpartum was higher than that of prepartum (P<0.001). Mean serum T3 level during 5 days prepartum varied 104.2 to 108.8ng/dl and decreased to 93ng/dl on the day of calving. During 5 days postpartum, mean T3 level varied 73.0 to 83.8ng/dl. Contrary to GH, mean serum T3 level during 5 day postpartum was significantly lower than that of prepartum (P<0.001).

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