Lice are spread from one animal to another through direct contact. Control methods for all these parasites are often species specific. Timing of the control method is also often critical. For example, if using fly tags, put them in early in the season to take full advantage of the time frame when the tag is effective. In some cases a combination of control methods may be tried such as tags, backrubbers, dust bags, manure sprays and feed additives.
Some flies build up rapid resistance to the active ingredient in many insecticides.
It would be advisable to keep track of the type of chemicals used for fly control and vary their use from year to year. Also keep in mind what your neighbor does for fly control. If you do a good job and your neighbor does not, you will wind up controlling a lot of his or her flies. Every spring, beef cattle undergo the natural effect of shedding hair. This is a natural occurrence.