what are the factors which affect the quality of the wool

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 length, 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, such as burdock, that will stick in the wool.