A prolonged change in body composition induced by endocrine
manipulation of the neonate
S.N. McCutcheon, I.T. Kadim, G.A. Wickham, R.W. Purchas
Department of Animal Science, Massey University, Private Bag,
Palmerston North, New Zealand.
Proceedings of the New Zealand Society of Animal Production 1994,
54: 51-54
The ability of endocrine manipulation of the neonate to effect prolonged
changes in body composition was examined. Treatment of lambs with
recombinant bovine somatotropin (rbST) at doses of 0.1 or 0.3 mg/kg
liveweight/day for 11 weeks from birth elevated circulating ST concentrations
(P<0.01) but had no effect on circulating concentrations of insulin-like growth
factor-1 or on liveweight gain compared with excipient-treated lambs.
However, at 8 months of age (5 months after cessation of treatment),
ultrasound backfat depths (Mean±SE) were significantly (P<0.05) higher in
lambs previously treated with excipient (3.4±0.3 mm) than in those treated with
rbST at 0.1 mg/kg (2.8±0.3 mm) or 0.3 mg/kg (2.5±0.3 mm). In a second
study, rats were treated with saline vs. 0.2 ug/g rbST vs. 0.4 ug/g rbST vs. 0.2
ug/g pituitary ovine prolactin (poPRL) vs. 0.4 mu/g poPRL for the first 21 days
of life. At 120 days of age they were euthanased, selected fat depots weighed
and the carcasses analysed for fat content. Neonatal treatment with rbST or
poPRL significantly (P<0.05) reduced weight of the subcutaneous scapular fat
depot (1.08±0.18 vs. 0.46±0.17 vs. 0.52±0.18 vs. 0.50±0.17 vs. 0.49±0.17 g)
and carcass fat content (5.88±0.27 vs. 5.03±0.26 vs. 4.58±0.27 vs. 5.28±0.26
vs. 4.70±0.26%) but did not influence weights of the subcutaneous abdominal,
genital or perirenal fat depots. These results suggest that endocrine
manipulation of the neonate may offer a means of producing desirable changes
in the composition of production animals while avoiding consumer resistance
to the use of hormonal growth promotants close to the time of slaughter.
Keywords: NZSAPAB;
Neonate; somatotropin; prolactin; body composition; fat deposition.
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