A study on seasonal variation in fleece yellowing of selected Corriedale ewes

Abstract

An experiment has been described in which a study was made on the seasonal variation in fleece colour and fleece components of a selected group of Corriedale ewes. The effects of long term storage on greasy and scoured wool colour was also examined.

Predicted susceptibility to fleece discolouration was determined by incubation. Maximum incubated colour score was the most efficient means of differentiating resistant and susceptible sheep at all samplings.

Maximum incubated colour score was related to most greasy fleece components, but not closely enough to allow indirect selection to replace maximum incubated colour score as the most efficient means for separating the two groups.

The expected seasonal variation in greasy and clean fleece weight was observed, along with the variation in fleece colour, wax and suint content.

Two soxhlet extraction methods were used to separate wax and suint form the greasy fleece samples. The first method used organic solvent extraction followed by water extraction. The other method used water extraction followed by organic solvent extraction. There was no difference between the two methods in the total amount of wax and suint extracted, although there were differences in the relative amounts of wax and suint extracted.

The Resistant Group tended to have a higher clean yield than the Susceptible Group. The amount of wax in the fleece was similar for both groups, while the Resistant Group had a much lower suint content.

The storage of greasy wool resulted in increased greasy colour and changes in scoured colour. The scoured colour could not be predicted from the greasy colour.

A mechanism for fleece colouring has been postulated.