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CHAPTER 2.
GENERAL PRINCIPLES OF GENE FLOW
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mature weight, conception rate of ewes, milk yield, fat and protein content or yield,
somatic cell count, average litter size, wool production and productive life of ewes
are considered to be maternal traits (traits 8, 21, 22 and 26 to 35). Mature weight
is considered as maternal trait because there are maintenance costs in each reproductive cycle. Wool is repeatedly sheared. Productive lifetime may be understood
as a result of successive surviving in the individual reproductive cycles.
Several traits have direct and maternal components:
birth weight, weaning
weight, growth rate from birth till weaning and survival rate of lambs at birth
and until weaning (traits 1 to 3, 23 and 24). The direct component of growth traits
till weaning expresses the genetic potential of lambs for growth, the maternal component expresses the genetic potential of the dam for milk available to lambs. The
direct eect of the lamb survival rate expresses the health status of the lambs, the
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maternal eect is determined by the mothering ability of a ewe .
1 Maternal components of growth traits and survival rates till weaning will therefore be expressed
both on pure-bred and on cross-bred progeny.