Serum neuropeptide Y (NPY) and leptin concentrations
Domestic Animal Endocrinology (in press)
Responses in serum NPY and leptin concentrations after six generations of divergent selection
on components of efficient lean growth in pigs were measured. At 90 kg liveweight, log transformed serum NPY
concentration was increased (6.31 v 5.72, s.e.d. 0.09 log(pmol/l)) with selection for low food
conversion ratio (LFC) or (5.80 v 5.37 log(pmol/l)) for high lean growth rate (LGA) but not (6.26 v
6.14 log(pmol/l)) with divergent selection on daily food intake (DFI). However, selection for high
DFI was associated with increased serum leptin concentration (3.06 v 2.45, s.e.d. 0.21 ng/ml HE)
as was selection for low LFC (3.04 v 2.46 ng/ml HE), but there was no response with divergent
selection for LGA (2.70 v 2.74 ng/ml HE). The response in serum leptin concentration to selection
on DFI was consistent with the observations in db/db mice and human studies that high fat
deposition was associated with increased leptin-resistance. The high correlations between
successive serum NPY concentrations (0.80 s.e. 0.11) suggest that changes in body composition
with time are unrelated to serum NPY concentration. The low correlations of serum NPY
concentration with energy or lysine intake implied that the value of serum NPY concentration to
provide information on the responses to selection at a physiological level or as a physiological
predictor of genetic merit, in an animal breeding framework, were limited. Serum NPY and, to a
lesser extent, serum leptin concentrations were insensitive to dietary differences in digestible
lysine : energy and indicated that studies using a genetic resource population of animals may be
more powerful than studies using nutritional treatments to examine aspects of function and
expression of NPY and leptin in pigs.
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