Neuroendocrine control of growth hormone release in sheep:
Effect of dose and route of administration of growth hormone releasing
factor on plasma growth hormone levels
G.S. Spencer, J.J. Bass, S.C. Hodgkinson
MAF Technology, Ruakura Agricultural Centre, Private Bag,
Hamilton
Proceedings of the New Zealand Society of Animal Production.
1990, 50: 101-104
There has been considerable interest recently in the use of
growth hormone (somatotrophin) to enhance growth, carcass
leanness and milk yield in a number of species. Despite the similarity
of bovine and ovine growth hormone, the administration of exogenous
somatotrophin to lambs has produced disappointing results. Conceivably,
stimulation of endogenous GH secretion may be more beneficial, and in
this communication we present our preliminary results on the effective
doses and rates of administration of growth hormone releasing factor in
a study of the neuroendocrine regulation of growth hormone secretion in
sheep. Sheep were housed indoors on a complete pelleted diet and were
fitted with jugular vein catheters. Some sheep were also fitted with
cannulae placed in a lateral ventricle of the brain. Bovine GRF was
given at different doses to the sheep either intravenously
(iv), intracerebroventricularly (icv) or intramuscularly
(im) and plasma GH levels monitored. There was a dose-dependent
increase in GH levels when the GRF was given iv, with both 30 and
3 ug being effective, while im administration was only effective at 30
ug. Central administration (icv) was also effective at both
dose but did not stimulate GH release at 300 ng. Further studies are
required to elucidate the mechanisms underlying GRF stimulation of GH
release, but the efficacy of GRF as a growth promoter can be
investigated using intramuscular administration.
Keywords: NZSAPAB;
Sheep; GRF; GH; intravenous; intramuscular; intracerebral
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Last Updated 25-01-1997
