Prevention and Treatment of Parasites. 109 



can be more highly recommended for the pre- 

 vention of stomach worms in sheep than the fre- 

 quent change of pasture, for sheep become infested 

 with these pests only by swallowing the worms 

 while grazing. If possible sheep should be changed 

 to fresh, clean pasture every two to three weeks 

 during June, July, August, and September, for dur- 

 ing warm weather otherwise clean pastures may 

 become infested in even less time by sheep graz- 

 ing thereon. Fields on which no sheep or goats 

 have grazed for a year, and plots which have been 

 plowed and cultivated since sheep grazed on them 

 are practically free from infection. Old blue 

 grass pastures are especially to be avoided. It 

 is thus clear that annual pastures, such as rape, 

 furnish clean pasture for the flock. In the warmer 

 sections it is necessary to begin changing to fresh 

 pasture earlier in the spring and to change more 

 frequently in the summer. This method requires 

 several separate, clean pasture lots, but flockmas- 

 ters who have followed this method have had little 

 trouble with parasites. 



In some cases it is impossible for the flockmas- 

 ter to change pastures as frequently as has been 

 recommended above. For such instances it is to 

 be hoped that some remedy may be found which 

 will be a sure preventative of stomach worms. 

 During the last few years some medicated stock 



