Do Different Sheep Breeds Affect Dye Color?

While working with my own wool yarn which is a mixture of Columbia, Hampshire and Dorset, I have begun dying some fleece for a friend who raises Tunis sheep. I noticed that her fleece was not taking some colors as well as my yarn, so I at first thought it was something I was doing differently. I decided to do a test, and cooked a pot of chestnut burrs. I prewashed both the fleece and yarn in the same pot, and placed it into the dyepot. My yarn was instantly a medium golden brown, while the fleece never would get darker than a dark gold, or very light golden brown. When dying with purple basil, her wool took the color much better than my yarn. In the past I assumed that different results were caused by something else, but now I am wondering if anyone else has had similar experiences? Basil purple is a beautiful color, by the way!