is less than one-half the cost of maintenance on a practical ration in 

 winter quarters. 32 



Under normal conditions sheep may be grazed for seven months 

 of the year. However, on bright days during the winter months it is 

 highly desirable to have the flock turned out on pasture to graze and 

 exercise. 



While on pasture the sheep should be provided with shade, water 

 and salt. Sheep naturally graze when it is cool, and lie in the shade 

 during the hotter portion of the day. Trees are best for shade. Fresh 

 water and salt are necessities too often overlooked for sheep on pasture. 

 During early spring and late autumn, shelter that will protect the 

 sheep from cold rains will extend the period of pasturing by a month 

 or more without danger of losses. The two serious obstacles during 

 the summer months are parasites and the "sheep killing dogs." 



Internal Parasites in Sheep. 



In order that internal parasites may be controlled intelligently, 

 their life histories should be known. The most serious internal sheep 

 parasites in Pennsylvania are the stomach worms (Haetnonchus con- 

 tortus) and the worm causing nodular disease (Esophagostomum 

 columbianum). Another parasite associated with the pasturing sea- 

 son is "grub in the head," caused by the sheep gadfly (Oestrus ovis). 



The Stomach Worm. 



"It occurs in the fourth stomach, the place where the hay and 

 other coarse vegetable food of the host animal have finally become 

 converted into chyme, and where the worm can do the most damage 

 by irritation to the mucous membrane and by absorbing food that 

 should be utilized by the host animal. 



"The male Haemochus contortus (stomach worm) attains a 

 length of three-fourths of an inch (20 millimeters) and has at the pos- 

 terior end a clasping organ, known as a bursa, which has a very char- 

 acteristic bi-lobed structure. The female may attain a length of one 

 and one-fourth inches (30 millimeters), and is characterized by a 

 spiral striping due to the coiling of the two uterine branches around 

 the intestine. The worms are red. 



"The female produces a large number of eggs, which are passed 

 in the feces of the host animal. These eggs hatch in two days, if the 

 temperature and moisture conditions are favorable, and small em- 



32The Pennsylvania State College Annual Report, 1911-12, 1912-13, 1915- 



26 



