Growth-promoting and metabolic actions of recombinant ovine placental
lactogen and bovine growth hormone in young lambs
S.H. Min, D.D.S. Mackenzie, B.H. Breier, S.N. McCutcheon, P.D.
Gluckman
Department of Animal Science, Massey University, Palmerston North,
New Zealand.
Proceedings of the New Zealand Society of Animal Production 1994,
54: 59-62
It has been shown previously that ovine placental lactogen (oPL) has a
growth-promoting effect in the growth hormone (GH)-deficient dwarf rat.
However, this effect has not been verified in an homologous system using
animals with an intact somatotrophic axis. To examine the effects of oPL in
the sheep, we injected lambs with recombinant oPL (0.1 mg/kg liveweight/day,
n=16) or saline (n=16) for 21 days commencing on day 3 of life and compared
their effects on body growth and energy intake with those in lambs treated with
the same dose of recombinant bovine growth hormone (bGH, n=16).
Circulating concentrations (ng/ml) of hormones in saline- vs bGH- vs oPL-
treated lambs at day 20 of treatment were (mean±SE): oPL, <0.5 vs <0.5 vs
12.8±0.5; GH, 10.8±5.0 vs 48.4±5.0 vs 12.6±5.0, P<0.001; insulin-like growth
factor-I (IGF-1), 267.6±14.4 vs 302.4±14.2 vs 291.7±14.4. Average daily gain
(kg/day) during treatment was significantly (P<0.05) greater in oPL-treated
lambs (0.28±0.01) than in saline-treated (0.25±0.01) or bGH-treated
(0.24±0.01) lambs. Similarly, there were significant (P<0.05) increases in
total energy intake (over the 21 day treatment period) during treatment with
oPL (112.5±3.5 MJ ME), compared with bGH (102.0±3.5 MJ ME) or saline
(102.0±3.5 MJ ME) treatment. It is concluded that oPL is somatogenic in
young lambs. This effect may be mediated by stimulating voluntary feed
intake rather than by elevating circulating concentrations of IGF-I.
Keywords: NZSAPAB;
Ovine placental lactogen; bovine growth hormone; lambs; growth;
voluntary intake.
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Last Updated 25-01-1997
