Crude protein

What it is

Crude protein is calculated from a feed's total nitrogen. Protein is assumed to be 16% nitrogen, so nitrogen × 6.25 = crude protein ^[1]. It is called "crude" because the figure doesn't distinguish true protein from non-protein nitrogen ^{[1, 2]}.

Quality as well as quantity

Lysine, methionine and threonine are essential amino acids for horses, and the requirements of growing horses are expressed partly as lysine ^[3]. Lucerne (alfalfa) and soybean products have a better amino acid balance than cereal grains, especially maize, or most grass hays ^[3].

Hay dried in poor conditions can have a large share of its protein bound to the cell-wall fibre (reported as ADF-CP), which is largely unavailable to the animal ^{[1, 2]}.

Common myths

The MSD Veterinary Manual states that excess protein as a cause of developmental orthopaedic disease is a myth disproved by research, and that protein does not cause excitable behaviour ^[3].

When intake is low

Horses eating less, for example during weight loss, may need a ration balancer to meet protein needs ^[3]. Restricted or soaked hay diets can be low in protein, so protein, minerals and vitamins need to be balanced with supplements ^[4].

See also lysine, methionine, threonine.