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The influence of stocking density on broiler chicken bone quality and fluctuating asymmetry

Journal Contribution - Journal Article

Because broiler chickens are juvenile animals
undergoing physical development, stocking density
during rearing may influence this development. Some of
these physical changes may cause welfare problems, for
example, decreased bone quality, which may lead to
fracture during catching and transport. Others do not
influence welfare directly but can be used as indicators
of the animal’s ability to cope with its environment
(e.g., fluctuating asymmetry). The present study evaluates
the effect of stocking density on bone quality and
fluctuating asymmetry. Birds were stocked at densities
of 2.4, 5.8, 8.8, 12.1, 13.6, 15.5, 18.5, and 21.8 birds/
m2 from 1 until 39 d of age. Increased stocking density
had a negative effect on some aspects of bone quality
(tibia curvature and shear strength). Tibias were
shorter at high density, possibly due to increased curvature.
Several other bone quality aspects (tibia weight,
torsion, and dyschondroplasia, and femur curvature
and epiphysis shape) remained unaffected. Middle-toe
length was the only character that showed a significant
increase with increasing density when each character
was analyzed separately. Nevertheless, a composite index
of fluctuating asymmetry, which combined data
on all 11 measured characters, tended to increase with
stocking density. Such increased fluctuating asymmetry
may indicate decreased welfare. However, one of the assumptions
of fluctuating asymmetry is that the animal
is subjected to the same environmental influences on
both sides. This assumption may not be fulfilled when
leg deformations occur, as these may lead to asymmetric
changes in bone growth by altering the division of
force over the 2 legs. In addition, leg deformations decrease
the accuracy of bone length measurements made
in a straight line. This raises some concerns on the applicability
of fluctuating asymmetry measurements on
broiler chicken legs, especially because stocking density
did not effect the asymmetry of the head.
Journal: Poult Sci
ISSN: 0032-5791
Volume: 91
Pages: 1759–1767
Publication year:2012
  • DOI: https://doi.org/ 10.3382/ps.2011-01859
  • Scopus Id: 84864094433