Plant proteins

The bulk of the protein of ruminants comes from  plant sources. The protein content of plant varies considerably from  one type to another. Even within  the same plant, there is considerable variation from one stage of maturity to another or from one part of the plant to another. Proteins in plants are primarily  associated with  the tissues which are actively metabolizing such as leaves, centers of growth  and the seeds. Eventhough they are not especially high in protein by comparison with other feedstuffs, the vegetative portions of many plants supply an extremely large portion of the protein in the total ration of livestock, simply because these portion of feeds are consumed in large quantities. Needed protein not provided in these feeds is commonly obtained from one or more of the oilseed by-products –soybean meal, cottonseed meal, groundnut meal, safflower meal, sunflower meal, rapeseed meal linseed meal, sesamum meal and coconut meal. The protein content and feeding value of these products vary according to the seed from which they are produced, the amount of hull and/or seed coat included and the method of oil extraction used. Sometimes the unprocessed seed is used to provide both a source of protein and a concentrated source of  energy. The oil  bearing seeds are especially high  in  energy because of  the oil  they contain.

Additional  plant  proteins  are obtained  as by-products  from  grain  milling,  brewing  and distilling  and starch production.  Most of these industries use the starch from  grains and seeds, then dispose of the residue which  contains a large portion  of the protein of the original plant seed.