Five goats were injected with GH (15 mg/day), three goats received systemic infusions of insulin-like growth factor (IGF)-I (43 nmol/h) and four goats received systemic infusions of physiological saline (20 ml/h) on days 4–6 of a 10-day experimental period during mid-lactation.
Milk yield increased by an average of 24% in GH-treated goats by the time of the third injection. In contrast, milk yield of IGF-I-infused goats did not differ from saline-infused animals although two of three goats did show a small increase (12%) after 36 h of IGF-I infusion.
With GH and IGF-I treatments plasma IGF-I concentrations increased similarly, reaching maxima of 100–130 nmol/l within 24 h. Plasma IGF-I concentration was relatively constant in saline-infused goats at about 50 nmol/l throughout the experiment.
Total IGF-I bound to 50 kDa and 150 kDa binding proteins in plasma was increased by GH and IGF-I treatments but, in contrast to IGF-I, GH increased the proportion of IGF-I bound to 150 kDa binding protein.
In a second experiment, four goats received systemic infusion of IGF-I (43 nmol/h) and four goats received systemic infusion of physiological saline (20 ml/h). There was no evidence that milk yield was changed during IGF-I infusion. However, when those goats which had previously received IGF-I infusions were injected with GH, milk yield increased by 30%. While the increment in plasma IGF-I concentration during IGF-I infusion was similar to that obtained in the first experiment, the IGF-I response to GH injection was much greater, plasma concentrations rising to 230 nmol/l.
The data show a lack of milk yield response in goats whose plasma IGF-I concentrations were increased by IGF-I administration. Systemic infusion of IGF-I appears to be ineffective as a means of procuring a sustained increase in milk production.
Journal of Endocrinology (1989) 123, 33–39
Journal of Endocrinology is committed to supporting researchers in demonstrating the impact of their articles published in the journal.
The two types of article metrics we measure are (i) more traditional full-text views and pdf downloads, and (ii) Altmetric data, which shows the wider impact of articles in a range of non-traditional sources, such as social media.
More information is on the Reasons to publish page.
| Sept 2018 onwards | Past Year | Past 30 Days | |
|---|---|---|---|
| Full Text Views | 5 | 0 | 0 |
| PDF Downloads | 1 | 0 | 0 |
Online ISSN: 1479-6805
Print ISSN: 0022-0795
Strengthening biomedical communities
to advance science and health
CONTACT US
Bioscientifica Ltd | Starling House | 1600 Bristol Parkway North | Bristol BS34 8YU | UK
Bioscientifica Ltd | Registered in England no 3190519
