DISEASES OF HORSES 97 



The appropriate treatment of osteomalacia in cattle is so effec- 

 tive that if osteoporosis were a similar manifestation of disease a sim- 

 ilar line of treatment should prove equally efficacious. However, 

 this is not the fact. On the other hand, the occurrence of oste- 

 omalacia on old, worn-out soil, or on land deficient in lime salts, or 

 from eating feed lacking in these bone-forming substances, or drink- 

 ing water with a lime deficiency, is in perfect accord with our knowl- 

 edge of the disease. But osteoporosis may occur on rich, fertile soil, 

 in the most hygienic stables, and in animals receiving the best of 

 care and of bone-forming feeds with a proper amount of mineral 

 salts in the drinking water. 



Cause. The cause of this disease still remains obscure, although 

 various theories have been advanced, some entirely erroneous, others 

 more or less plausible ; but none of these has been established. Thus 

 the idea that feeding fodder and cereals poor in mineral salts and 

 grazing in pastures where the soil is poor in lime and phosphates 

 will cause the disease has been entirely disproved in many instances. 

 Others have considered that the disease starts as a muscular rheuma- 

 tism which is followed by an inflammatory condition of the bones, 

 terminating in osteoporosis. The idea that the disease is contagious 

 has been advanced by many writers, although no causative agent has 

 been isolated. Numerous experiments have been made by inoculat- 

 ing the blood of an affected horse into normal horses without results. 



On some farms and in some stables bighead is quite prevalent, 

 a number of cases following one after another. On one farm of 

 thoroughbreds in Pennsylvania all the yearling colts and some of 

 the aged horses were affected during one year, and on a similar farm 

 in Virginia a large proportion of the horses for several years were 

 diseased, although the cows and sheep of this farm remained un- 

 affected. 



Symptoms. The commencement of the disease is usually unob- 

 served by the owner, and those symptoms which do develop are gen- 

 erally not well marked or are misleading unless other cases have 

 been noted in the vicinity. Until the bones become enlarged the 

 symptoms remain so vague as not to be diagnosed readily. The dis- 

 ease may present itself under a variety of symptoms. If the bones 

 of the hock become affected, the animal will first show a hock lame- 

 ness. If the long bones are involved, symptoms of rheumatism will 

 be the first observed, while if the dorsal or lumbar vertebrae are 

 affected indications of a strain of the lumbar region are in evidence. 

 Probably the first symptom to be noticed is a loss of vitality com- 

 bined with an irregular appetite or other digestive disturbance, and 

 with a tendency to stumble while in action. These earlier symp- 

 toms, however, may pass unobserved, and the appearance of an in- 

 termittent or migratory lameness without any visible cause may be 

 the first sign to attract attention. This shifting and indefinite lame- 

 ness, involving first one leg and then the other, is very suggestive, 

 and is even more important when it is associated with a tendency to 

 lie down frequently in the stall and the absence of a desire to get 

 up, or the presence of evident pain and difficulty in arising. 



