334 SHEEP FARMING IN AMERICA 



mained vacant long enough for the infection to have 

 disappeared, and would consequently again be ready 

 for use. By continuing this rotation from year to 

 year, not only would each crop of lambs be protected 

 from infection, but as reinfection of the infested 

 ewe flock is prevented at the same time, the para- 

 site would in a few years be entirely eradicated 

 from the flock and pastures. The result to be gained 

 is worth the effort where this plan is practicable. 



If such frequent rotation is not possible or prac- 

 ticable, a smaller number of pastures may be util- 

 ized, after the ewe flock has been treated with ver- 

 mifuges. The treatment may be given either before 

 or after the birth of the lambs. If before, the ewes 

 should be treated before pregnancy is too far ad- 

 vanced in order to avoid possible bad results from 

 the handling necessary in treatment. Probably the 

 best time for treatment is late in the fall or early 

 in the winter. The treated sheep should be placed 

 immediately on clean pasture in order to avoid re- 

 infection. The object of treating the ewes is to get 

 rid of the worms with which they are infested, and 

 thus remove the source from which the pasture be- 

 comes contamimnated. If it were possible by treat- 

 ment to entirely free the old sheep from stomach 

 worms, it is evident that the lambs would remain 

 free from infection, provided, of course, that the 

 flock were afterwards kept on clean pasture. Un- 

 fortunately, there is no vermifuge known which can 

 always be depended upon to remove all of the 

 worms, but it is possible to get rid of most of them, 



