Certain protective components, including protein and peptide hydrolysate fractions and substances that reduce undesirable enzymatic degradation, may stabilise the endogenous components of semen during storage.

Under this model, NOVUM does not need to supply β-NGF as the primary active reproductive signal. Rather, the semen itself provides naturally occurring β-NGF and other seminal factors. 

The role proposed for NOVUM is to modify the storage environment in a manner that reduces loss or degradation of these endogenous components. 

Hydrolysates work by providing physico-chemical protection: the peptides and amino acids they contain form a buffer around the cell membrane of the sperm cell and scavenge free radicals. 

As they have no pharmacological, immunological or metabolic effect on the body itself (they are added to the sperm in vitro), the product is therefore not regarded as a  veterinary medicinal product. 

The addition of peptidase (or protease) inhibitors to prevent the body’s own enzymes from breaking down proteins does not change its legal status to that of a veterinary medicinal product. This is because there is no therapeutic effect on the living animal, and peptidase inhibitors are not pharmaceutical substances.