| dc.description.abstract | The effects of exogenous recombinant human growth
hormone (rhGH) were studied on Nile crocodiles 4 weeks
after hatching (group A) and at 9 months of age (group B).
They were kept under controlled laboratory conditions.
During the treatment period the animals were injected
(intramuscularly) with rhGH or saline (controls) twice a
week. The group A animals were treated with doses of 3.25
Jlg rhGH/g b.wt., twice weekly for 5 weeks. After 8 weeks
without treatment they were given doses of 1.30 Jlg/g for 3
weeks. The group B animals were treated with doses of
0.325 Jlg/g for four weeks and then sacrificed for blood and
tissue sampling.
Recombinant hGH stimulated growth, food uptake and
food conversion efficiency of the group A animals during the
first treatment period, however, within a week after the
last injection the treated crocodiles stopped eating and the
growth was arrested. When treatment was restarted, they
all died within 7 weeks, probably due to a secondary
immunological response.
Although the 9 month crocodiles were treated with
1/10 of the dose given to the hatchlings, the growth
stimulating effects of rhGH may have been more pronounced
in the older animals. Crocodiles seem to recognise the rhGH
as a foreign protein since antibodies to rhGH were present
in plasma after 4 weeks of treatment with rhGH.
It is concluded that rhGH increase growth in young
crocodiles by stimulating appetite and mechanisms involved
in protein synthesis. However, such therapy is not likely to
be of any practical use since the crocodiles seem to develop
hypersensitivity to the human growth hormone | en |
