THE INHERITANCE OF PRODUCTIVITY IN FARM LIVE
                                             STOCK

                                           IV. WOOL

                                        J. E. NICHOLS

                        (Wool Industries Research Association)

The general title of these papers suggests a wider field for consideration than
that simply of the inheritance of wool-characters, which has been reviewed recently
by Miller [1]. In the first place, it is to be remembered that the fleece, as a covering
during life, contributes to the hardiness of the animal in its ability to survive
the rigours and changes of environment, and is, therefore, concerned in the other
activities of the sheep, for meat-production, for breeding surplus stock, in some
countries for milk, and so on. It is an agent, though indirect, in promoting the
efficiency of the sheep as a producer of those commodities which the sheep-breeder
hopes will be profitable to him. Herein it gives rise to problems in productivity
rather remote from those occurring in the other animal products dealt with in these
articles.

Fibre-growth is a more intimate function of the sheep's activity than is, say,
milk-production of the cow's and egg-production of the hen's. It begins in early
foetal life and ends only at death. There would thus appear to be three different
primary sets of environmental conditions to which it is exposed, viz. (1) the rela-
tively constant foetal environment, during which, however, the follicles inter se are
affected by the sequence and density of their development [2], (2) the early post-
natal, representing a change in life-habit towards (3) the post-weaning, quite
independent life, in which the animal attains maturity, becomes a functional
ruminant, and so exposed to all the exigencies of nutritional environment inciden-
tal to free-grazing animals.

The changes that occur with general development are obvious in many breeds.
Many Merino lambs are born hairy; the birth-coat hairs are shed or lost, and
leave the growing lamb with a fleece of practically pure wool. The lambs of some
of our Down breeds, especially the Suffolk, are more or less darkly coloured at
birth; by shedding and replacement, the relatively pigment-free adult coat is
acquired; from maturity onwards we find other changes in fleece character.
Recent work on time or age changes, from birth to maturity is pervaded with the
idea that definite relationships exist between natal and adult coats, and that
selection for desirable adult fleece-characters can be exercised early in life [3].
It is clear that not only is the follicle-population variable in time, but also the forms
of the fibre-product are alterable.

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