THE MORE COMMON AILMENTS OF SHEEP 393 



previous year the loss of lambs produced by the same 

 dams, though grazed on the same pastures, was serious. 

 It is true, nevertheless, as experiment has shown, that in- 

 fection is possible when both dams and lambs are con- 

 fined to the pens, but it is not likely to occur in any con- 

 siderable degree. When guarding against this disease, 

 preventive measures are greatly important. These in- 

 clude : (i) Using great care when introducing the founda- 

 tion stock on which the future flock is to be built; (2) 

 grazing lambs on new rather than old pastures while they 

 are young; (3) changing the pastures frequently; (4) 

 sustaining vigor in the lambs by feeding nourishing foods 

 to them; (5) giving food in racks and water in troughs 

 when practicable. When choosing the material on which 

 to found a flock, if the assurance is present that no indica- 

 tions of stomach worm have ever visited the flock, it is, 

 in a sense, certain that introductions from that flock will 

 not bring stomach worms with them, especially if the 

 flock is one that has been long established and has not 

 recently been reinforced from outside sources. It will 

 also be necessary to proceed in the same cautious manner 

 should materials be brought in subsequently from outside 

 sources to reinforce the flock. While introducing the 

 lambs to new pastures will not in itself be a guaranty 

 against invasion, it will lessen the hazard, and this will 

 be still further reduced if the pastures are grown from 

 cereals sown purposely to make them. The lambs do not 

 graze these so closely as they would old pastures, espe- 

 cially when the herbage is plentiful ; hence they are less 

 liable to invasion by the parasites. Such pastures are also 

 much less liable to be infested by the larvae. If the lambs 

 come quite early in the season, especially in northern 

 areas, they will be so far grown that they will be more re- 

 sistant to the sapping influences resulting from the pres- 

 ence of the worms. If the lambs are to be maintained 

 within the yards while the old sheep go out to the pas- 

 tures this process will be facilitated by giving the lambs 



