Wool growth as affected by nutrition and by climatic factors.

摘要: The weight, length and quality (fineness) of wool produced at different times the year under nutritional conditions has been determined over a period three years by clipping monthly intervals grown on delineated skin areas sheep. treatments consisted ( ) wet ewes, grazing pasture all year, subjected to high low levels feeding during ‘dry’, pregnancy lactation periods; b dry ewes lambs fed differentially winter spring; c in stalls diet constant composition rates sufficient maintain effective body weight (i.e. making allowance for increase fleece increase). A small number these was also increased environmental temperature winter. experiments have shown existence marked seasonal rhythm growth having maximum January (midsummer) minimum July (midwinter). Changes are caused sympathetic changes both diameter. At same level rate midwinter is about onethird that midsummer. demands reduce those delay rise production spring. Nutrition plays an important part determining time minimum. In sheep tends occur before midsummer when its best, but prevents expression early summer, so it generally occurs after weaning, therefore nutrition determines within limits magnitude fundamental cause remains obscure. Nutrition, can modify rhythm, exists strongly even variations due eliminated. solar radiation recently influence growth, particularly winter, though this undoubtedly one factor not only one. Temperature suggested elsewhere as possible cause, described do support theory any direct effect growth. It suggested, however, may be second factor.