GROWTH OF WOOL.

New Zealand Herald, Volume LXIX, Issue 21132, 15 March 1932, Page 14

GROWTH OF WOOL.

TESTS IN AMERICA. EFFECT OF NUTRITION. The result of a small scale test designed to determine " the influence of the plane of nutrition upon various factors related to wool production," conducted at the University of California by Professor J. F. Wilson, has lately been made available. Three purebred Romney Marsh wethers were used in the experiments. These at the age of six months were closely shorn and started on a fattening ration consisting of good quality lucerne hay, a grain mixture of rolled oats and rolled barley and pasture. At the end of six months the animals were again closely shorn and then put on a. maintenance ration, comprising chiefly sufficient good hay and a little grain to keep them at a j uniform weight. They were held on this for six months as a preparation for the sub-maintenance diet period of another six months, the idea being to make the transition from plenty to poverty not too sudden. The sub-maintenance period lasted six months, and was preceded and followed by shearing, while the foddur during it consisted of poor quality lucerne hay, limited in quantity to a point which caused the sheep gradually to lose weight. Critical Comparison. At the close of the la6t six months the wool produced while the sheep were on the fattening and 011 the sub-maintenance ration was critically compared, with the object of ascertaining how the two divergent nutritional periods had affected its growth in all phases. The wool from the second, or nffiintenance period, was ignored. On the point of weight of fleece it was found the wool produced during the fattening period was about 343 per centheavier in average grease weight and 319 per cent, heavier in scoured weight than that grown in the last six months. The difference between the grease and scoured weights indicates that the fattening ration, in addition to increasing the production of pure wool fibre, acted as a stimulus to the'sebaceous glands in the production of yolk, a factor 'which is often noticed in Australia when sheep are on rich feed. As might be expected there was a very considerable difference in the appearance of the two sets of fleeces. The first was not only more bulky than the third, it was loftier, coarser in diameter of fibre, much more lustrous, and better crimped. Careful measurements showed that the average length of staple was 172 per cent, greater, and that the mean breaking stress was 206 per cent, higher. Uniform Diameter. It was also found that the diameter of the fibre of the sheep while on the fattening ration was more uniform and greater in the mean than when on the sub-maintenance diet. This raises the question, whether the difference in length, 172 per cent., plus the difference in diameter, accounts for the 319 per cent, variation in scoured weight. Professor Wilson thinks it hardly probable, and deduces the theory that the actual number of fibres per fleece decreased when the sheep were on the reduced diet. The limit of elongation of the fibres was not greatly affected, but the character of the elongation showed a marked contrast. The fibres produced during the fattening ration period, after stretching rapidly for a time, 6lowed down in their rate of elongation, and showed greater resistance to further stretching before rupture. The total growth of wool was 4.3 in. in the first six monthe and 2.5 in. in the third test period.