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The role of hydrolysed proteins

01 February 2014, at 12:00am

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 disease.

Cats and dogs with such an allergy or intolerance can be managed either by a carefully 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 together.

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 purpose.

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 insufficiency.

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Overweight pets are more predisposed to developing diabetes mellitus. In the case of a diabetic pet, dietary management is of major importance along with appropriate medical care.

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