412 ANIMAL BIOCHEMISTRY 



TABLE 16-3. Per Cent Composition of the Common Oil Meals 



Dry Crude Crude Crude N-free 



feeding purposes. These meals (Table 16-3) are characterized by 

 their high protein contents and are important as concentrates for 

 supplementing the normally lower protein levels of grain rations. 



Soybean meal or cake has become our most important high protein 

 supplement. Total production exceeds 5,000,000 tons annually, more 

 than twice the production of cottonseed meal. Heated soybean meal 

 is an excellent protein supplement for most forms of livestock, but 

 the raw meal is not used very efficiently by non-ruminants because 

 of the presence of a trypsin inhibitor (page 146). Soybean protein 

 possesses superior biological properties, owing to a better distribution 

 of essential amino acids than is found in most plant proteins. Soy- 

 bean meal is low in calcium and lower in phosphorus than are cotton- 

 seed meal and the wheat by-products. 



Cottonseed meal is a by-product of the cotton industry, which oc- 

 cupies an important economic place in the southern United States. 

 Cotton is grown for the fiber, but the cottonseed meal and cake, se- 

 cured in the production of cottonseed oil, furnish a protein supple- 

 ment second in value only to soybean meal. The production of 

 meal averages 2,500,000 tons annually. Cottonseed meal contains 

 a toxic substance called gossypol, which varies in amount, depending 

 upon climatic and soil conditions. Cattle are able to ingest large 

 amounts of cottonseed cake without showing ill effects, but other types 

 of livestock are more susceptible. Fortunately much of the gossypol 

 present in cottonseed is inactivated by the heating processes employed 

 during the oil extraction and solvent stripping of the meal. Gossypol 



