THE INHERITANCE OF PRODUCTIVITY IN FARM LIVE STOCK.
295
Throughout the adolescent and mature phases the changes in fleece-growth
that can follow alterations in nutritional level are very varied, and may be of some
magnitude. For example, in one case, which has been studied, of an Australian
Merino fleece, it was estimated that in terms of average fibre-volume per month,
the rate of production suddenly accelerated by over 100 per cent at one period of
the year [4]; and the wool-fibres are not the only products of the skin-and-follicle
system which make up the growing fleece [5].
But so far as wool-productivity is concerned, we are mainly involved in consi-
dering wool as an annual crop of some direct value to the farmer. For the most
part its course to the real consumer is peculiarly tortuous and prolonged, and
through the innumerable mixings which occur the individual fleece loses all its
identity. The cash value of the wool crop to the farmer is ordinarily some func-
tion of the weight of the raw wool, the proportion of grease and other non-wool
materials in the raw fleeces, and the estimated fitness of the amount of actual pure
wool present for particular manufacturing purposes. These three factors are
very variable, from one animal to another, from flock to flock between different
breeds, and according to locality and husbandry. Moreover, when the wool-using
industry is viewed, as a whole, it is readily appreciable that absolute uniformity
of the supply of raw material is not desirable of the inherent attributes of the
wool-fibres in the fleece which affect its manufacturing utility, length, soundness,
'quality' or fineness, uniformity, fineness to its particular type or breed, and general
character, may be mentioned, but of these only length and fineness are readily
measurable, and have, therefore, been studied most.
The most useful combination of these characters from the manufacturer's
point of view is not necessarily that which the farmer would consider optimal,
quite apart from other attributes of the fleece with which the latter is concerned.
For example, fleece-density, in part contributory to fleece-weight, is of more direct
interest to the breeder than to the user, in so far as it is involved in the rain-
coating action of the fleece. Yet it is apparently not always dissociable from the
length-fineness complex.
In view of such interrelations, it is perhaps not surprising that the majority
of investigators conclude that apart from questions of colour, the inheritance of
most fleece-characters is dependent upon multiple factors.
Apparently conflicting results have, however, been noted. For example,
whilst Hill [6] found the F 1 intermediate in wool-fineness in Hampshire-Ram~
bouillet crosses, Davenport and Ritzman [7] noted that the F 1 approached the
coarser-wooled Hampshire parental type; yet these investigators also describe
intermediate F 1 s in crosses involving South-down and Oxford rams and Ram-
bouillet ewes with a tendency to approach the finer-wooled parent. At the same
time, they record in the Oxford cross an F 1 wool-length type, whilst in the South-
down and Hampshire crosses, the F 1 had longer wool than either parental form.
Observations on Scotch Halfbred (Border Leicester ram × Cheviot ewe) also
M