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Bromocriptine treatment of periparturient goats: long-term suppression of prolactin and lack of effect on lactation

Published online by Cambridge University Press:  01 June 2009

Isabel A. Forsyth  and
Philip D. Lee
Isabel A. Forsyth
Affiliation:
Department of Cell Biology, AFRC Institute of Animal Physiology and Genetics Research, Cambridge Research Station, Babraham, Cambridge CB2 4AT, UK
Philip D. Lee
Affiliation:
Department of Cell Biology, AFRC Institute of Animal Physiology and Genetics Research, Cambridge Research Station, Babraham, Cambridge CB2 4AT, UK
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Summary

British Saanen dairy goats (n = 10) were treated with bromocriptine or vehicle from day 147 of pregnancy to day 4 post partum, a treatment duration of 8·8±1·7 d (mean ± SEM). The periparturient prolactin surge was abolished by this treatment, but there were no significant effects on plasma growth hormone or insulin concentrations. Lactogenesis was delayed in the bromocriptine-treated goats, milk yields being significantly depressed (P < 0·01) for the first week of lactation. Yields had recovered to control values by day 10 when prolactin concentrations were still significantly depressed. Mammary gland biopsies were taken on day 4 post partum from five animals in each group. Using this tissue, no significant differences could be shown in mammary morphology or DNA synthesis, but the RNA:DNA ratio was significantly reduced (P < 0·05). After week 1, there were no significant differences between bromocriptine-treated and control goats in milk yield, milk composition, udder volume, time of peak yield or persistence. The goats given short-term bromocriptine treatment at parturition showed prolonged effects on prolactin secretion, their seasonal prolactin rise being severely blunted (P < 0·001). A normal lactation is therefore not prevented in goats by a delay in lactogenesis, suppression of prolactin at parturition or the resulting prolonged depression of circulating prolactin. Goats in established lactation given bromocriptine for 8 d showed, by contrast, a rapid recovery of plasma prolactin concentrations within 5 d post treatment. Milk yield declined significantly (P < 0·03) compared with pretreatment values during and for 1 week after bromocriptine but then began to recover, with no significant change in vehicle-treated goats.

Type
Original Articles
Information
Journal of Dairy Research , Volume 60 , Issue 3 , August 1993 , pp. 307 - 317
Copyright
Copyright © Proprietors of Journal of Dairy Research 1993

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