Fiber Diameter

Fiber diameter is probably the most important factor for determining the quality of wool and its value. As the fiber diameter increases, it changes the way wool is used. Larger diameter fibers do not work well in the felting process, but because they are stronger and less likely to break during the carding and combing process, they are very well suited for carpets and rugs. Small diameter fibers or fine wool are best suited for clothing and textiles.

Fiber diameter is used to determine the wool grade. The American system began by visually appraising the wool fibers. This system is known by the blood grade because it starts with the Merino breed and the wool from other breeds is graded according to the percentage of Merino in the breed. Table 1 shows the various wool grades using both the American Blood Grade system and the ASTM (American Society for Testing and Materials) standard grade. The number corresponding to the ASTM grade related to the number of 560 yard lengths of yarn that can be spun from one pound of top (clean wool).

Table 1
Wool Grades

Table 2
Staple Length Requirements by Grade

Taken from American Sheep Industry Directory

Fiber Color

The whiteness of wool is very important if the fibers are not expected to be dyed or will be dyed a light color. Very white wool fleeces come from fleeces that have been skirted to remove any urine or feces stained wool. Producers who wish to market a very high quality wool keep their sheep covered year-round to prevent contamination and discoloration of the wool. The presence of colored fibers in wool has an affect on the price of that wool also due to limiting the uses for the wool.  These fibers can come from the sheep themselves, either dark fibers in the wool or from head, belly or legs. They may also come from stained wools. Colored wools from natural colored sheep are generally a specialized market for people who spin or weave by hand. Sold to a mainstream market, these wools are discounted because of their limited use in the dying process.

Cotted or Felted Fleeces

Occasionally, the wool fibers may become matted or felted together. This occurs when fine fibers have very little crimp. Cotted or felted fleeces are considered low quality because of the amount of waste produced during carding due to breaking the fibers when they are torn apart. Fine wool sheep that have very little crimp should be culled.

Improving Wool Quality

Wool quality can be affected by genetic and environmental influences. Genetic influences would be to select sheep with higher quality wool, while environmental influences might include nutrition, sheep management, and shearing management.

Genetic selection should consider which traits are more heritable or more likely to pass to the lambs. Traits that are highly heritable include variation in fiber diameter, face covering, staple legnth, crimps and skin folds. Traits that are moderately heritable include fleece weight, clean wool yield, fiber diameter, and fiber density. Another factor that relates to wool production is body weight because larger sheep have more surface area to produce wool. Thus, large sheep produce more wool than small sheep.

The environment can influence wool quality in a number of ways. First is the nutrition of the sheep. Ewes tend to be stressed during the last third of their pregnancy and while nursing lambs. This has a direct effect on the fiber diameter that is being produced. As the nutritional level of the ewe meets her needs or is above what her needs are, the fiber diameter remains constant. As the ewe becomes stressed in the latter stages of pregnancy and after lambing, that fiber diameter may decrease which creates weak areas that are susceptible to breaking. Two ways to minimiize a decrease in wool quality are to make sure ewes are eating a ration that meet their needs and to shear ewes prior to lambing. If the fibers do have weak areas, the weakness is closer to an end of the fiber than if the ewes had long wool at lambing and weren't sheared until after weaning. It is also a good practice to have ewes in short wool at lambing time as lambs are less likely to suckle wool tags instead of the teat.

As mentioned previously, feeding management will affect the quality of wool if large amounts of feed contaminate the wool. Feeders should be low enough for sheep to eat without pulling hay down on top of their heads. Also, when feeding avoid throwing hay over the backs of the sheep.

In addition to what the animals eat is the consideration of bedding materials. Animals should be bedded often enough to keep them clean. In addition, use materials that are clean, dry, and free from dust. Another consideration, especially if you use straw, is to look for weed seeds that will stick in the wool such as burdock.

Summary comments

Wool production is often overlooked in many operations. For the average person marketing their wool through a wool pool, special considerations for wool production may not be warrented. However, if you are raising wool sheep with high quality wool, you will want to take every precaution you can to maintain the highest quality of wool possible. When you find the correct market, wool production can be quite profitable.