International Omega-3 Learning and Education Consortium for Health and Medicine

What are the omega-3 fatty acid requirements for the dog?

The National Research Council made the following requirements/recommendations for omega-3 dietary intakes in its 2006 publication for dogs ¹.

• The adequate intake (AI) during growth is 0.07% DM (dry matter) for α-linolenic acid (ALA), 0.03% DM for docosahexaenoic acid (DHA) and less than 0.03% DM for eicosapentaenoic acid (EPA). The recommended allowance (RA) is set for ALA only, which is 0.08% DM.
• For adult maintenance, the RA for ALA is set at a level of 0.044% DM when LA is provided at the 1.1% DM level. AI is set for DHA and EPA at a combined level of 0.11 g/1000 kcal.
• During gestation and lactation, the RA for ALA is increased to 0.08% DM. Although no official recommendations are set for DHA and EPA (eicosapentaenoic acid) at this stage, a modest amount of 0.05 - 0.10% DM is considered adequate. However, the safe upper limit (SUL) is set at 2.8 g/1000 kcal for DHA and EPA combined during gestation and lactation. No minimum requirement of these omega-3 fatty acids is set for any of the developmental stages.

Since the NRC ¹ specifies dietary requirements for different omega-3 fatty acids for the dog, how can these be assessed to insure that a dog food is providing an adequate amount? In other words, what test can be done to determine if the nutritional needs for the dog are being met from the dietary recommendations and dog food being fed? This is an important question because omega-3 fatty acids are necessary for pregnancy and lactation, developmental processes during puppy growth, optimal functioning of the immune system, control of inflammatory responses and general health status throughout the life cycle. So, how can omega-3 fatty acid sufficiency be determined in the dog, and what is the effective level of dietary intake for omega-3 fatty acids in the dog? Herein we propose that blood levels can be used as a biomarker of nutritional status for omega-3 fatty acids during various stages of the dog's life.

What are the omega-3 fatty acid deficiency symptoms observed in the dog?

Linoleic acid (LA) has long been recognized as essential for general health in dogs. When dogs are not getting a sufficient supply of this omega-6 fatty acid, it results in overt manifestations of deficiency, such as dermatitis, growth retardation, poor wound healing and reproductive impairment. However, it is hard to detect apparent symptoms of omega-3 deficiency. Omega-3 fatty acid deficiency is more apparent on the functional level of tissues and organs and is difficult to be observed by simple visual inspection. Special examinations with the aid of laboratory equipment are necessary to find out if the dog's omega-3 fatty acid status is deficient. It is well known that omega-3 deficiency in mammals affects mostly the neural system, especially the visual development at early stages of life ². Supplying omega-3 fatty acids, either by enriching the milk during lactation or by providing these fatty acids directly in the diet of the bitch or after weaning to the puppy, improves visual acuity in puppies ^3,4.

There are other health aspects that can also be improved with elevated dietary intakes of omega-3 fatty acids. However, this benefit is associated with the biochemical balance achieved from omega-3 fatty acids in controlling the potential actions of an excessive supply of omega-6 fatty acids. This is not an effect of reversing a specific deficiency symptom of omega-3 fatty acids but facilitating the capacity of individual cells and tissues to adapt to biochemical and physiological processes with hormones and products derived from both omega-6 and omega-3 fatty acids to support optimal health.

What are the benefits of omega-3 fatty acids for the dog?

From a limited number of publications focused on the effect of dietary omega-3 fatty acids in canine health or the relationship between tissue levels of omega-3 fatty acids and canine health conditions, it is clear to conclude that the general health benefit of the inclusion of omega-3 fatty acids in the canine diet is undeniable. The vast majority of research that has been published so far strongly supports this dietary practice. The health effects of omega-3 fatty acids are reported in investigations that utilized various sources of this group of fatty acids: vegetable oils (flaxseed oil or linseed oil, canola oil and soybean oil), oil seeds (flaxseed) or fish oil (menhaden oil). The implied health benefits from these publications focused mostly upon improved visual development in puppies ^3,4, dermatological benefits ^5,6,7,8, cardiovascular effect in lowering cholesterol levels ⁹ and the positive effect on dogs with chronic valvular disease ¹⁰ and their potential in positive behavioral modification ¹¹.

Are blood omega-3 fatty acid levels a biomarker for health assessment in dogs?

When measuring the level of omega-3 fatty acids in the blood of dogs, it generally reflects what was fed to the dog. This is probably true as well for most other tissues in the body. The primary omega-3 essential fatty acid (EFA) in the diet is the 18 carbon ALA. Once ingested, it can be readily absorbed and used in the body for fuel, incorporated into tissue lipids or metabolized to longer, more unsaturated omega-3 fatty acids, such as EPA, docosapentaenoic acid (DPA) or DHA. The derivatives of ALA, especially EPA and DHA, are usually referred to as a group called long chain (LC) omega-3 polyunsaturated fatty acids (PUFA). Most mammals (with the exception of felines as they are a group of strict carnivores) have the ability to convert ALA to its longer chain derivatives, albeit the ability to accomplish this varies among different species. In dogs, it has been shown that puppies can convert dietary sources of ALA to DHA during the early neonatal period ^3,12; however, they lose most of this capability thereafter ¹². In adult dogs, the conversion from ALA to EPA and DPA seems effective as reported by Bauer et al. ¹³. However, along with the increases in EPA and DPA in plasma of dogs fed a flaxseed diet that supplied ALA, no accumulation of DHA was found throughout the feeding period of 84 d ¹³. The investigators of this research speculate that the conversion of DPA to DHA is limited in the liver, and DPA made in the liver is transported to the target tissue to be used for DHA synthesis. One such organ is the neural system, where it was shown that neuronal cells convert DPA to DHA and a hallmark characteristic of brain and nerves is the abundance of DHA ¹⁴. It is probably true that tissues have varying capacities in producing fatty acids from precursors to enrich their lipid pools. It is also true that tissues differ in degree for incorporating different fatty acids into its lipid pool. One study did not see a change in omega-3 fatty acids levels in skin over a 10 wk period of feeding flaxseed oil (114 mg ALA/kg body weight) or an EPA-DHA oil (50 mg + 33 mg/kg body weight) to dogs afflicted with atopic dermatitis ⁶. However, this finding of no change in the omega-3 content of skin is most likely an exception rather than a general rule for fatty acid enrichment of tissue lipids.

Although there is some evidence showing a positive correlation between tissue levels of omega-3 fatty acids and health benefits, we still need more quantitative data for omega-3 tissue levels and specific conditions in the dog. There may also be variations on how different breeds of dogs metabolize omega-3 fatty acids. For example, two breeds of dogs (Boxers vs. Doberman Pinschers) demonstrated different fatty acid profiles in plasma. Boxers had a higher ALA level in plasma than Doberman Pinschers, while Doberman Pinschers had higher total omega-6 fatty acids and higher total PUFA levels in the plasma than Boxers ¹⁵. The relationship between fatty acid and arrhythmias may also be different, as a weak, but significant positive correlation between the number of ventricular premature complexes (an indication of arrhythmogenic cardiomyopathy) and total omega-3 fatty acids was found in Boxers but no such relationship was found in Doberman Pinschers ¹⁵. Research by Hall et al. ¹⁶ and Bauer et al. ¹⁷ may help answer this question to some extent as they studied how the tissues in dogs respond to dietary supplies of omega-3 fatty acids. Hall et al. showed that feeding approximately 175 mg DHA/kg BW/d is required to attain maximum plasma levels of DHA at 6.7 g/100 g fatty acids under the experimental condition in healthy female geriatric beagles (7 - 10 y) ¹⁶. Bauer's research went even further in mathematically defining the relationship between dietary levels of omega-3 fatty acids and projected tissue concentrations of omega-3 fatty acids. Specifically, Bauer's research tried to quantitatively predict the relationships between dietary fatty acids (energy% of LA and ALA in diet) and the concentration of omega-3 fatty acids in plasma phospholipids (as of % total EPA + DPA) ¹⁷. Bauer's equation acknowledges the concept of a competitive and saturable hyperbolic relationship between PUFA content in diet and tissue PUFA accumulation in dog tissues. However, in this early attempt, nowhere is DHA mentioned in the calculation, which leaves a gap as to what would happen in lieu of this most important omega-3 fatty acid. Regardless of the limitations of the effort, to answer the question "What would be the omega-3 status targets for good health in the dog?", it is possible that by adopting the NRC recommendations and the predictive power of Bauer's research result, a generalized blood omega-3 fatty acid concentration could be estimated that may represent an omega-3 fatty acid state that is suitable for good health in dogs.

Summary

With the undeniable benefit of feeding DHA and other omega-3 fatty acids to dogs, finding an easy and accurate method to assess the omega-3 status has become an important issue for every dog owner. Blood levels of omega-3 fatty acids have been shown to be closely associated with dietary supply of these fatty acids. Measuring the omega-3 fatty acid blood concentration could be a viable means of evaluating if a dog is sufficiently supplied with omega-3 fatty acids.

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