Front Matter

Chapter 4 The Role of Nutrition in Canine Performance and Rehabilitation 89

(EPA) in particular (Figure 4.9). AA is a precur-
sor to the normal production of eicosanoids—
prostaglandin E 2 (PGE 2 ) and leukotriene B 4
(LTB 4 )—through the cyclooxygenase and lipox-
ygenase enzymes, which are involved in the
inflammatory response as well as maintenance
of mucosal integrity. Therefore, if EPA or its
slightly longer omega‐3 counterpart docosahex-
aenoic acid (DHA) is substituted for AA in the
diet there is less production of the pro‐inflam-
matory eicosanoids such as PGE 2 and LTB 4
(see Figure  4.9). This results in less cartilage
degradation due to lower metalloprotease and
local cytokine production, allowing for better

glycosaminoglycan and collagen production

(Budsberg & Bartges, 2006). This supplementa-

tion of long‐chain omega‐3 fatty acids results in

improved clinical outcomes in osteoarthritis

(Fritsch et al.; 2010; Roush et al., 2010). The form

of omega‐3 fatty acid used is important since

the shorter chain omega‐3 fatty acid, often sup-

plemented as alpha‐linolenic acid (flaxseed oil),

may not exert the same anti‐inflammatory effects

as the longer chain omega‐3 fatty acids (EPA,

DHA) found in marine oils (Bauer, 2006). The

dose of fish oil in these cases may be more than

what is traditionally used in over‐the‐counter

commercial dog foods. Evidence suggests that

Seed/vegetable oil

18:3n-3 (ALA)

20:4n-6 (AA) 20:5n-3 (EPA)

22:4n-6

22:4n-6 (DHA)

Animal sources

Marine sources

Cell type-

dependent

synthase

activities

Thromboxane A 2 Thromboxane A 3

Prostaglandin E 3

Inert to mild

vasodilation

Pro-inflammatory

vasodilation

Leukotriene B 4

Leukotriene B 5

Prostaglandin E 2

18:2n-6 (LA)

D6 and D5 desaturase and

elongase enzymes produce

intermediates leading to AA

and EPA

Figure 4.9 Schematic of omega‐3 (right column) and omega‐6 (left column) sources and their elongation and
conversion into bioactive molecules during the inflammatory response. Note that the omega‐3 fatty acids become odd‐
series eicosanoids (i.e., PGE 3 ), which are inert and that can inhibit the pro‐inflammatory actions of the omega‐6 fatty
acid‐generated eicosanoids designated by even numbers (i.e., PGE 2 ). LA, linoleic acid; ALA, alpha‐linolenic acid; AA,
arachidonic acid; EPA, eicosapentaenoic acid; DHA, docosahexaenoic acid.