Date of Award

1993

Degree Type

Thesis

Degree Name

Bachelor of Applied Sciences Honours

Faculty

Faculty of Science and Technology

First Advisor

Dr I Adams

Second Advisor

Dr A C Schlink

Abstract

This project was part of a larger CSIRO experiment which was examining the factors involved in the development of tender wool. In order to understand the effect of nutritional variations on wool quality, changes in cellular activity and morphology within the wool follicle were examined. Six sheep with a history of producing low staple strength wool (< 25 N/ktex) and six sheep with a history of producing high staple strength wool (> 30 N/ktex) were selected. The experiment ran for 18 weeks, for the first 10 weeks the sheep were fed a restricted ration to achieve a weight loss of approximately 175g/day. From weeks 11 to 18, the sheep were fed an iso-energetic ration containing low or high protein. The sheep were weighed weekly and colchicine treated skin biopsies were collected at 0, 2, 10, 11, 12 and 18 weeks, embedded in paraffin and serial sectioned. The work carried out for this Honours project involved assessing wool follicles from these sheep to determine the stage of the growth cycle, the mitotic rate and the area of the follicle bulb. Although group differences were not evident between the different diets and staple strengths, this study demonstrated a high correlation between the number of mitotically active cells in the follicular bulb, the area of the follicular bulb, live-weight of the sheep, clean wool weight and fibre diameter (r = 84.5%, p = o.ooo). It was found that after ten weeks on restricted ration the live-weight, mitotic counts of follicular bulb cells and follicle bulb areas for all groups decreased from pretreatment. When followed by a change of diet from the restricted ration to the iso-energetic ration for eight weeks the live-weights, mitotic counts and follicle bulb areas in all groups increased to be higher than pretreatment. This study found that restricted food intake resulted in decreased cell division in the follicle bulb which is concomitant with decreased follicle bulb area. This was accompanied by a decrease in wool production and a shift toward the telogen stage of the growth cycle. Follicles in telogen stage of the growth cycle were identified for the first time in the Merino sheep. This suggests that follicles are less active, that is, have less cell division on the restricted ration but that the mitotic activity rises again on a higher energy ration, irrespective of staple strength history or low or high protein ration.

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