Omega-3 in poultry diets

Including omega-3 fatty acids in poultry diets could help boost bone strength. John Tarlton from the University of Bristol Vet School takes a look.

Certain types of omega-3 fatty acids are widely recognised as having an important role to play in reducing the risk of osteoporosis and heart disease in humans. However, recent research suggests that poultry might also benefit from higher levels in their diet.

Omega-3 fatty acids are a type of essential unsaturated fat which cannot be made by the body and must be obtained from the diet. Unsaturated fatty acids in this group include docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and alpha-linolenic acid.

The omega-3 recommended intake rate for an adult has been set at 450mg/day, although most scientists regard this as inadequate. It is believed that actual average intakes may be only 200mg/day or lower. Dietary intake of omega-3 fatty acids, found in fish oil and some vegetable oils, has been linked with the reduced incidence of a number of human disorders. These include osteoporosis, a bone-wasting disease that can lead to an increased risk of suffering fractures.

Other diseases claimed to be alleviated by increased omega-3 intakes are heart disease, colitis and rheumatoid arthritis. The widespread increase of these afflictions in modern Western societies has been associated with the relatively high dietary intake of omega-6, which is approximately 10 times that of omega-3.

Omega-3 and poultry

There is strong evidence to indicate that a hen’s natural, free-foraging diet is also rich in omega-3, derived from wild leafy plants, such as purslane. In studies, it was found that eggs from free-roaming hens contained much higher levels of omega-3 than eggs from conventionally housed birds.

It is no surprise that omega-3 fatty acids – commonly found in fish oils, linseed and marine algae – are beneficial for hens, as well as for humans. Their inclusion in poultry diets at the correct rate has been shown to significantly reduce cases of bone breakages.

Welfare continues to pose a serious problem for the poultry industry, and public perception of management systems is of growing concern to consumers.

Studies as part of a DEFRA-funded project have shown that large numbers of hens in free-range and barn systems systems incur bone breakages during their lifetime. In cases where additional environmental enrichment includes extra perches, rates may be even higher. This research could set alarm bells ringing in relation to the European-wide conventional cage ban, which is due to come into force in 2012. It seems that in some regards, non-cage housing systems could further contribute to the birds’ suffering.

The cost of bone breakages

The financial implication of birds succumbing to bone breakages due to osteoporosis is an issue producers should consider.

Fractures of the sternum (keel) are common in layers. These cause extreme pain and prevent important behaviours, often leading to an increase in infection rates.

Movement constraints due to fractures may last for many weeks, resulting in restricted access to food, water, and perches, to some extent wiping out the welfare benefits of non-cage housing systems. There is an urgent need for research to identify possible ways of alleviating this potential welfare problem.

Most nutritional strategies for preventing osteoporosis in laying hens have focused on enhancing calcium absorption or retention. But trials using calcium, vitamin K or fluoride added to the diet have met with limited success and evidence suggests that the problem is becoming more widespread.

A programme aimed at preventing structural bone problems by maximising peak bone mass and bone quality, may have an increased chance of success. It is possible that omega-3 in the diet could have an important role to play in this element of research.

It is also thought that the ratio of omega-3 and omega-6 in rations may be manipulated to the birds’ benefit. Omega-6 fatty acids are contained in soyabean, maize and safflower oil. The two fatty acid groups have differing effects on bone metabolism.

The understanding of the relationship between fatty acids and bone biology is somewhat limited. There is mounting evidence that osteoporosis is linked to an imbalance in dietary fatty acid intake in a number of species.

In general, studies have shown omega-3 to support bone formation, and so to reduce signs of osteoporosis, and omega-6 to promote bone resorption – a loss of bone tissue, which also releases calcium into the blood.

Adding omega-3 fatty acids to laying hen diets can bring producers a price premium for the eggs.

In particular, observations in broilers suggest that excessive consumption of omega-6 leads to increased bone loss. However, this effect may be reversed by increasing omega-3 consumption. Therefore, a higher dietary intake of omega-3 and a reduced omega-6 may increase bone mass and reduce the incidence and severity of osteoporosis. The principle can also be applied to laying hens.

Preliminary indications show that an omega-3 diet can reduce bone breakages by up to 40%, with a corresponding increase in bone strength. This work has now been extended, to examine these benefits in a controlled, on-farm study. The work has been funded by the Biotechnology and Biological Sciences Research Council, in collaboration with Noble Foods.

The link with human diets

The Scientific Advisory Committee on Nutrition has recommended doubling the average dietary intake of omega-3 for humans. The enrichment of eggs to increase human dietary omega-3 levels is well established and increasing in popularity.

One example is the omega-3 supplemented egg, which was marketed by Noble Foods, under the brand name "Columbus Eggs". They were produced to appeal to consumers who are aware that they should be eating more oily fish, but either do not like the taste, or simply cannot afford to buy it. The hens were fed a special GM-free, vegetarian diet, based on linseed oil.

The formulation has since been changed, to include higher concentrations of EPA, a long chain omega-3, with the eggs are marketed under the "Goldenlay" brand. The makers claim they can help to maintain a healthy heart and blood circulation, as well as easing the symptoms of rheumatoid arthritis.

It is also claimed that the eggs may even give protection against some forms of cancer, and improve brain function. It is believed that one large Goldenlay omega-3 egg contains one-third of the recommended daily amount of omega-3.

Richard Scragg, of feed specialists, Optivite blames the shortage of omega-3 fatty acid in poultry feed on the increasing reliance on adding energy to rations by using vegetable fats, which are high in omega-6.

It is possible to test feed for omega-3 content. The optimum inclusion rate and cost will vary, depending on the type of poultry, diet and whether producers are trying to improve performance, or increase the omega-3 level in eggs or meat.

Supplementing the diet with the essential omega-3 fatty acids will have a positive influence on many aspects of poultry production. These include an increase in feed conversion and growth rates, as well as the enhancement of the omega-3 content of meat and eggs. Independent trial work, as part of a government-backed LINK project at the Roslin Institute, has supported these theories.

Adding omega-3 fatty acids to laying hen diets can bring producers a price premium for the eggs. There is growing public awareness of the benefits, and eating eggs and meat from poultry fed on omega-3 enriched diets is considered to have a positive effect on health.