COMMON AILMENTS OF CATTLE 161 



which were in the egg stage during the first treatment and thus 

 unaffected. 



257. Warbles. — Everyone is familiar with the lumps on the 

 cow's back caused by the warble fly, but few appreciate that these 

 lumps are just one phase of the effect of this fly. The warble or 

 heel fly lays its eggs on the heel. The eggs develop into grubs which 

 burrow into the skin and travel all through the body. After about 

 eight months they work up under the hide on the back and develop 

 further, producing irritation and pus formation, until they finally 

 emerge and drop off to change to mature flies and start the egg-lay- 

 ing process again. The grubs harm the animal all the time they 

 are in the body and hurt the value of the hide for leather. The 

 treatment consists of squeezing them out of the hide and killing 

 them so they will not develop into the egg-laying flies. If this 

 is done thoroughly for the entire herd, the pests can be got rid of. 



258. Wire in feed. — So many cases of death in cattle occur 

 from the swallowing of wires and other sharp objects which later 

 pierce the heart, that it seems worth while to emphasize the need 

 of preventive measures. The wires of label tags on the feed bags, 

 wire bristles out of the cleaning brush, nails, screws, tacks and 

 many other sharp objects have caused death through heart punc- 

 ture. Of course the thing to be done is to be constantly on guard 

 against such objects getting into the hay or feed that the animal 

 eats. 



259. Scours. — Both common and white scours have been dis- 

 cussed (63, 64) in connection with the rearing of calves. 



