Abstract

Brief periods cannot be measured with traditional autoradiographic methods on wool fibres because the labelled points overlap. A dose of [35S]cysteine was injected into 24 sites across the side of five Lincoln ewes. After 48 hours a second injection was administered to one site on each ewe, followed by an injection into another site every two hours until all 24 sites had been labelled twice. Three days later all 24 sites were injected again. Following autoradiography the distance between radiolabelled points was traced using a digitizer (50 fibres per site). A linear increase in length between points 1 and 2 was observed between sites (r2 = 0.920) and the regression equation showed the fibre increased in length by 29.2 µm per site (P < 0.01). However, a linear decrease in length was observed down (P < 0.001) but not along (P = 0.813) the midside over the period delineated by injections 1 and 3. Removing the effect of site gave growth rates that reflected the overall mean of 28.9 µm/hour for all sites. This method could be used to determine changes in growth rate over a few hours or the response to a growth factor, hormone or nutrient over a time course of several hours.

DR, Scobie

Proceedings of the New Zealand Society of Animal Production, Volume 64, Hamilton, 268-271, 2004