NUTRITION

Van der Merwe L . L . BVSc Hons MMed ( Vet ) Small Animal Medicine , Department of Companion Animal Clinical Studies ( Outpatients ), Faculty of Veterinary Science , Lieselvdmvet @ gmail . com

This article summarises the most salient and practical aspects of the oxidative stress in the body and what mechanisms the body employs to minimise it .

Oxidative stress is a by-product of the daily metabolic functions which enable life . The majority of complex life on earth requires oxygen for its existence but oxygen is also a highly reactive molecule that damages living organisms by producing reactive oxygen species ( ROS ). Inflammatory disease , ageing , congestive heart failure , liver disease , stress , cancer and exercise can all increase oxidative stress . It is often unclear if oxidants trigger the disease , or if they are produced as a secondary consequence of the disease .

Changes associated with ageing may be physiological ( changes in body composition , metabolic rates and special senses ) or pathological . Several recommendations for alterations in nutrient intake in older dogs have been made . ( Table 1 )

Organisms contain a complex network of antioxidant metabolites and enzymes that work together to prevent oxidative damage to cellular components such as DNA , proteins and lipids . Oxidants can damage cells by starting chemical chain reactions such as lipid peroxidation , or by oxidizing DNA or proteins . Damage to DNA can cause mutations and possibly cancer , if not reversed by DNA repair mechanisms , while damage to proteins causes enzyme inhibition , denaturation and protein degradation . In general , antioxidant systems either prevent these reactive species from being formed , or remove them before they can damage vital components of the cell .

Antioxidants are substances which have the ability to scavenge ROS and reduce the overall number of oxidants in a system . It is now accepted that the various antioxidant mechanisms in a system act synergistically . The major antioxidant systems in the body in include the enzymatic antioxidants superoxide dismu-

Table 1 : Nutritional changes in senior pets

Recommendations for alterations in nutrient intake in older dogs ( and cats ) Nutrient Alteration Rationale

Protein

Increased - unless there is evidence of disease requiring protein reduction

Protein requirements of older dogs increase with age because of increased protein turnover . In cats protein absorption is decreased .

Fat Increased or decreased Senior dogs should have no alteration in fat digestibility with age .

Long chain omega-3-fatty acids

No alterations / increase

Inconclusive evidence but long chain fatty acids may be beneficial in delaying the onset and progression of several physiological ageing processes

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Issue 06 | DECEMBER 2017 | 40