The Importance of Prolactin for Initiation. of Lactation in the Pregnant Ewe

Gow, C. B.; McDowell, GH; Jenkin, Graham

doi:10.1071/bi9830357

Cited by 9 publications

(8 citation statements)

References 29 publications

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“…Heat exposure did not cause an increase in prolactin concentrations beyond that already achieved by continuous lighting. The observed concentrations were within the range (100-280 p.g/l) that has been reported for lactating ewes (Barry 1980;Gow et al 1983).…”

Section: Mild Heat Exposuresupporting

confidence: 79%

Effects of Mild Heat Exposure and Suppression of Prolactin Secretion on Gastro-intestinal Tract Function and Temperature Regulation in Sheep

Gj¹,

Barry²

1986

Aust. Jnl. Of Bio. Sci.

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The effects of mild heat exposure (30�C; 30% relative humidity), and of the suppression of prolactin secretion under such conditions, were studied in anoestrous ewes given daily 791 g dry matter of a pelleted mixture of lucerne hay and oat grain (3: 2). 51Cr-EDTA, 103Ru-phenanthroline and lignin were used to determine mean retention times (MRT) in the gastro-intestinal (01) tract by a continuous infusion-total sampling procedure.

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Section: Mild Heat Exposuresupporting

confidence: 79%

Effects of Mild Heat Exposure and Suppression of Prolactin Secretion on Gastro-intestinal Tract Function and Temperature Regulation in Sheep

Gj¹,

Barry²

1986

Aust. Jnl. Of Bio. Sci.

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“…Previous work in dairy cows and sheep given bromocriptine to suppress the periparturient surge in circulating prolactin concentrations had similarly indicated a delay in lactogenesis, Present address: SmithKline Beeoham Pharmaceuticals, Welwyn Garden City AL7 1EY, UK. but with the subsequent lactation yield recovering only slowly towards controls (Schams et al 1972;Johke & Hodate, 1978;Akers et al 1981a, b;Gow et al 1983;Johke, 1986).…”

mentioning

confidence: 98%

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

Forsyth

Lee

1993

Journal of Dairy Research

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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. Davis et al. (1983) reported that goats treated with the dopamine agonist bromocriptine (5 mg daily from 4 d before to 4 d after parturition) showed a delay in lactogenesis, but that over 21 weeks post partum their total milk yield was 32% greater than in the previous year. Control goats showed no change in yield. An effect of this magnitude was of great interest, comparable to the increase in milk yield achieved by giving regular injections of bovine growth hormone (somatotropin, BST) to lactating ruminants (Bauman et al. 1985;Hart, 1988). Previous work in dairy cows and sheep given bromocriptine to suppress the periparturient surge in circulating prolactin concentrations had similarly indicated a delay in lactogenesis, Present address: SmithKline Beeoham Pharmaceuticals, Welwyn Garden City AL7 1EY, UK.

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“…Prostaglandin, however, is a potent luteolysin in many mammals (Liggins, 1982) and in five often animals in this study progesterone concentrations fell after the peak of PGFM. In eutherian mammals other than the rat, the prepartum prolactin peak is important for lactogenesis rather than luteolysis (Schams, Reinhardt & Karg, 1972;Gow, McDowell & Jenkin, 1983). Similarly, in the tammar, lactogenesis occurs immedi¬ ately after birth, but neither lactogenesis nor birth are dependent on progesterone withdrawal (Findlay, Ward & Renfree, 1983;Ward & Renfree, 1984).…”

Section: Discussionmentioning

confidence: 98%

Prostaglandin in the peripheral plasma of tammar wallabies during parturition

Lewis¹,

Fletcher²,

Renfree³

1986

Journal of Endocrinology

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Tammar wallabies (Macropus eugenii) were observed for 7 days, 24 h/day, at the expected time of birth in two consecutive breeding seasons. Blood was collected from the lateral tail vein 1-2 days before birth, then at 10- to 20-min intervals in the peripartum period and less frequently to 30-h post partum. Plasma was assayed for the prostaglandin metabolite 13,14-dihydro-15-oxo-prostaglandin F2 alpha (PGFM), progesterone and LH. An assay for PGFM was validated which allows direct measurement in 100 microliter unextracted plasma with a sensitivity of 0.14 nmol/l (50 pg/ml). There was a short-lived peak of PGFM immediately before or at birth (7.15 +/- 2.52 nmol/l; 2536 +/- 892 pg/ml) which declined to less than 0.28 nmol/l (100 pg/ml) within 2-h post partum. Progesterone concentrations declined about the time of birth, coincident with the peak of PGFM, and reached levels observed in lactationally quiescent animals by 16-h post partum, which was also the time of the LH peak. The transient prostaglandin pulse was detected only by frequent sampling and suggests that, as in other mammals, prostaglandin is important in parturition.

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The Importance of Prolactin for Initiation. of Lactation in the Pregnant Ewe

Cited by 9 publications

References 29 publications

Effects of Mild Heat Exposure and Suppression of Prolactin Secretion on Gastro-intestinal Tract Function and Temperature Regulation in Sheep

Effects of Mild Heat Exposure and Suppression of Prolactin Secretion on Gastro-intestinal Tract Function and Temperature Regulation in Sheep

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

Prostaglandin in the peripheral plasma of tammar wallabies during parturition

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