vitamin A, especially in cattle, sheep, swine, and poultry; 
vitamin D for all classes except those exposed to sunshine 
throughout the year; niacin, riboflavin, pantothenic acid, and 
vitamin He Under prolonged droughts vitamin A deficiency in 
beef cattle results in lowered calf crops, anasarca or edema 
in the meat, blindness, and deaths. 
Mineral deficiencies may occur from lack of enough calciun, 
phosphorus, magnesium, iron, cobalt, copper, iodine, manganese, 
sodium, or chlorine. These deficiencies are generally associated 
with the soils and the crops grown in them,and thus with geo- 
graphical areas. Various forms of anemia may be traced to lack 
of iron, cobalt, and copper; poor skeletal development, including 
broken bones, to insufficient calcium and phosphorus; and goiter 
in farm animals largely to lack of iodine. Low reproduction and 
slow growth result from a lack of several mineral nutrients. 
Meat, milk, egg, and wool production are likewise decreased, 
Lack of feeds containing sufficient available carbohydrates 
and fats to yield energy and heat to maintain body functions also 
belongs in this category. Similarly, the protein content of the 
feed may be inadequate and lead to poor growth and low fertility. 
Because poultry and swine, especially, require specific amino 
acids, deficiency of any one of these acids may result in poor 
production. 
The disorders caused by excesses of feed constituents include 
those due to selenium, arsenic, lead, fluorine, molybdenum, and 
iodine. Some elements eiodine, for example =- are needed in 
minute amounts, but excesses may be toxic. 
These miscellaneous nutritional disorders apply not only to 
livestock and poultry, but also to rabbits and fur-bearing animals. 
Some are much more likely to suffer than others. Development of 
exact feeding standards for all the essential nutritional factors 
could do much to eliminate the losses. No good estimate of pre- 
sent losses can be made. Perhaps a 5= or even 10=-percent improve- 
ment in production is not unreasonable through elimination of 
these miscellaneous nutritional disorders. 
Intsrnal Parasites of Livestock and Poultry 
Table 2 
Livestock losses due to internal parasites occur in all parts 
of the country and in all seasons. However, the climate has 
much to do with the type, spread, and intensity of parasites, 
especially the weather from season to season. In general warmth, 
moisture, and shade favor parasitism. Control measures are based 
largely on taking advantage of the destructive effects of unfavor- 
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