The role of hydrolysed proteins - Veterinary Practice
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The role of hydrolysed proteins

Ian Williams in this second article in the series from Royal Canin on the latest knowledge on nutrients that can be of benefit to dogs and cats, looks at hydrolysed proteins

DIETARY allergy or intolerance are
often manifested by the same
clinical signs – dermatologic signs
(pruritus being the most prominent)
and gastrointestinal (GI) indicators –
from vomiting, variable stools, frank
enteritis, colitis and some reported
cases of inflammatory bowel

Cats and
dogs with such an
allergy or
can be
either by a
selected exclusion diet or a hydrolysed
diet. Hydrolysed diets offer the
advantage of being very practical to use,
easily available and affordable.

The diets are very well tolerated
from a digestive standpoint and may be
administered with no transition period.
They also contain appropriate amounts of highly digestible protein.
Diets manufactured with hydrolysed protein (e.g. soya, chicken heart and liver
and casein) have been available for some
years now and, following a number of
large-scale studies, they can be
recommended for use with a good
degree of certainty.

In general it is considered that only complex molecules,
such as water soluble glycoproteins, are
able to stimulate the immune system
and trigger an allergic response. Most
commonly, the glycoproteins are in the
range of 14 to 40kDa, although smaller
(10kDa) and larger (70kDa) compounds
may also be immunogenic.

Proteins that are incompletely or
poorly digested (e.g. into glycoproteins)
have more potential to incite an immune
response than do proteins which are
completely digested to free amino acids
and small peptides.

The principle of hydrolysed proteins
is that by enzymatically cleaving dietary
protein molecules into peptides, the
molecular weight is reduced to below
the threshold required to activate the
immune system.

Put another way, hydrolysed
proteins are proteins which
have been broken down from
the original, large protein
present in the raw ingredient,
into much smaller compounds
(polypeptides, oligopeptides
and single amino acids) by
using enzymes to break the
peptide links which hold the
building blocks of the protein

This enzymatic process
replicates the same process
which occurs within the body
as part of the natural digestive
process, and uses the same
enzymes that the body produces for this

Whilst hydrolysed proteins can be
used in diets for palatability purposes*
they are most useful when considering
the nutritional management of pets with
dietary allergies.

[*Hydrolysed animal proteins can be
used as a palatability enhancer,
specifically with poultry liver. This
process takes the aroma and taste of the
liver and concentrates these
characteristics into an extremely
appealing powder or liquid which can be
dusted onto the outside of the kibble.
In this instance, the hydrolysed animal
proteins form only a small part of the
diet and are added purely for palatability
reasons; they do not represent the main
protein source of the diet.]

In terms of allergies, pets unable to tolerate “standard” pet foods can be fed
a specific hydrolysed protein diet. For
these formulations, hydrolysed protein is
used as the main protein source of the
diet. Examples include soya protein
isolate and feather protein hydrolysate.

Using a hydrolysed protein can help
to reduce GI and/or dermatological
signs as the hydrolysed protein is unable
to crosslink receptors on mast cells,
therefore minimising degranulation and
release of histamine.

Hydrolysed diets have also proven
beneficial in the management of pets
with other issues such as chronic
enteropathies (e.g. inflammatory bowel
disease) and exocrine pancreatic

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