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Serum IGF-1 concentration in pigs divergently selected for daily food intake or lean growth rate
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Serum IGF-1 concentration in pigs divergently selected for daily food intake or lean growth rate
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Cameron, N.D., McCullough, E., Troup, K., Penman, J.C. and Pong-Wong, R.
Divergent selection over seven generations for daily food intake (DFI) and for two lean
growth rate (LGA and LGS) selection criteria in pigs produced correlated responses in
serum insulin-like growth factor-1 (IGF-1) concentration. IGF-1 at 6 weeks of age
responded to selection on DFI (158 v. 104 mg/l, s.e.d. 22; control 136 mg/l) while
selection on LGA (198 v. 153 mg/l, s.e.d. 13; control 192 mg/l) and LGS (214 v. 178
mg/l)
altered IGF-1 at 90 kg. There were 342 animals in the study, with an average of 46 pigs
in each selection line and 72 pigs in the control line. Animals were performance tested
from 30 to 90 kg on an ad-libitumi feeding regime. Responses to selection indicated that
IGF-1 at 6 weeks of age may be a useful physiological predictor of genetic merit for DFI
during performance test, with the realised response providing an estimate of 0.38 (s.e.
0.11) for rAhIGF, where hIGF2 is the heritability of IGF-1 and rA is the genetic correlation
between DFI and IGF-1. Segregation analysis detected a major gene effect (54 mg/l, s.e.
4) on IGF-1 measured at 6 weeks of age with an allele frequency of 0.45 (s.e. 0.10).
However, the perceived benefit of incorporating IGF-1 in a selection criterion will be
over-estimated if the infinitesimal model is assumed and a major gene is segregating in
the population, as genetic variation arising from the major gene effect will inflate the
polygenic variance. It would be pertinent for breeding companies to determine if a gene
of large effect on IGF-1 was segregating within their nucleus populations, before using
IGF-1 at 6 weeks of age as a physiological predictor of genetic merit for daily food intake
during performance test.
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