Last update: April 10, 2012 11:13:23 AM E-mail Print


The Developed Merino Sheep and the Uniformity of its Fleece

M. L. Botha 


THE lack of uniformity in wool growing on the body folds of merino sheep has always been the cause of serious discrimination against the developed type. Accurate experimentation has proved that wool growing on the body folds "is stronger than that growing between folds. Evidence as to variability in length is lacking.

Length is one of the most important attributes in wool; the manufacturer desires good length in the spinning of high quality yarn, and length adds very materially to weight, on which basis the producer is paid. Therefore, it is highly desirable to have good and uniform length throughout the fleece.

During the judging of merino sheep at shows, the ringside observer often hears the judge's criticism. "Good length but should show better length on the folds ". The judge might well be asked whether the relatively small amount of wool on the crests of body folds is actually slower growing wool than that of the rest of the fleece. Such a variation, if it existed, would be as objectionable as the variation of fibre diameter in wools on and between body folds.

Differences in: length on and between body folds must be due to differences in rate of growth or to some other cause, and uneven shearing appears to be a most likely one. Developed sheep, and especially the excessively developed type, confront the shearer with great difficulty at shearing and it seems a likely explanation that the lack of length of wool on the body folds might be due to the shearer's inability to clip the wool uniformly short over areas on which folds occur.

Some preliminary observations were made at Grootfontein College of Agriculture to throw light on the subject of variation in length in fleeces grown by developed sheep. Three mature merino rams of the developed type were selected for the study. Sampling sites were prepared at the commencement of the growth period by clipping the wool close to the skin with special fine curved, pointed scissors. Sampling sites were selected on the forequarters - inclusive of the apron folds on the hindquarters of the sheep, provision being made for corresponding pairs of small samples on and immediately off folds. After an exact period of 365 days, the wool samples were taken from the sites in the exact manner employed in preparing the sites a year previously, care being taken to avoid double cuts. "

The following determinations were made on each of the 10 pairs of samples taken: - (1) staple length, (2) straight length, (3) coefficient 01 variation in straight length, (4) crimp ratio, that is, straight length: staple length, (5) fibre thickness, (6) coefficient of variation in fibre thickness, (7) number of crimps per inch, and (8) degree of medullation.

It is evident from the results that there is no significant difference in staple length, straight length and crimp ratio of the wool grown on, as opposed to off, folds. However, wool grown on folds is approximately 28 per cent more variable in straight length; that is, the mean straight length for the two positions is the same, but the wool on folds is less uniform in length. The results, therefore, do not support the contention that wool grown on folds grows more slowly than wool off folds, and a sheep lacking in length on its folds must be looked upon as lacking length in general. In these cases the apparent good length elsewhere can only be ascribed to faulty shearing.

The data also reveal that fold wool is stronger than the rest of the fleece by approximately 10 per cent and that the former exhibits about 57 per cent fewer crimps. These figures corroborate the findings of previous investigators who found that the wool on the folds is stronger and has fewer crimps than the wool of the rest of the fleece.

In respect of uniformity of fibre thickness and degree of medullation, no significant difference was established between samples grown on and off folds.

Further, the results of the study revealed that, judging by crimps per inch, the wool appeared finer than the measurements obtained by actual thickness measurements. This is not uncommon in the case of rams' wool.

In conclusion it can be stated that the wool growing on the apron and body folds of merino sheep is of the same staple length and straight length as the rest of the fleece, and any difference in length between wools grown on such adjacent regions must be ascribed to irregular sheering and not to a difference in growth rate. The wool on folds is more variable in straight length, it is stronger and it has fewer crimps per inch than the wool off the folds. 



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