the best feeding option would be the natural , wild - type one , whereupon the bird grazes on greens and leaves and collects insects and worms in a wild , “ fight - or - flight ” environment . however , this method of production is not compatible with the growing need of an ever - expanding world population and economy . greens are essentially source of α - linolenic acid that is formed from linoleic acid in plant chloroplasts as a result of energy transfer from sunlight to chemical π - bonds . given that the lipid fraction of green leaves account for about 1 % of their total mass and that about 50 % fatty acids therein are α - linolenic acid , one can calculate that a normal 100 - g portion leaves provides 0 . 5 g α - linolenic acid . this is far from negligible when compared to the low concentration of this particular fatty acids in most edible seeds and oils , but total fat content (± 1 %) is much too low to sustain a continuous process of egg production ( an economically - viable way to produce healthy eggs at reasonable cost on a world - wide basis ). within the group of green lipids , fits a unique exception from seeds in the name of flax seeds . flax or linseeds are indeed an exceptional source of plant ω3 fatty acids otherwise found in much smaller amounts and higher ω6 : ω3 ratio in soya and canola seeds ( table 7 ). flaxseeds are also readily available at competitive world market price for feed ingredients . in this sense , flax seeds represent a unique source of green plant - type lipids which is contained within a seed in substantial quantities and at reasonable cost . huygebaert ( arch . geflügelk ( 1995 ) 59 ( 2 ), p . 145 - 152 ) has developed a mathematical model for the prediction of the fat composition in egg , in particular c16 - c18 , based on their respective contribution to total fat in the feed ( table 8 ). therefore , this models predicts for example that a concentration y of c16 : 0 fatty acids in the eggs can be obtained if the diet given to the poultry contains a concentration x 1 of dietary fat and a concentration x 2 of c16 : 0 fatty acids , the concentration y being calculated as follows : y = 26 . 60 − 1 . 462 x 1 + 0 . 191 x 2 + 0 . 0348 ( x 1 ) 2 − 0 . 0046 ( x 2 ) 2 + 0 . 028 x 1 x 2 this model has been shown to be valid for the continuous production of wild - type eggs as defined , if the feed composition given to poultry comprises 4 to 10 % ( w : w ) of total fat , seed ω6 and green ω3 plant - type fatty acids contributing to total fat content in steadily decreasing manner from 40 to 15 % and from 50 to 30 %, respectively , and ω6 : ω3 essential fatty acid ratio being in favour of the green ω3 plant type fatty acids and decreasing from 0 . 8 to 0 . 5 . more precisely , the fat composition ( ω6 : ω3 = polyunsaturated : saturated = 1 : 1 ) of the wild - type egg has been maintained constant for several months (& gt ; 18 months ) under a defined feeding regimen . groups of 30 , 000 isabrown birds were fed with a wild - type diet containing no animal fat , 35 . 5 % carbohydrates , 17 % protein , 12 % moisture , 10 . 25 % ash and 6 . 5 % fat for a total of 2 , 800 kcal metabolisable energy ( m . e .). the detailed composition of the feed is given in table 9 . vegetable oil is cold - pressed flax seed oil ( bs 6900 : sediment , max . 0 . 25 %; iodine value , min . 175 ; acid value , max . 4 mg koh / g , peroxide value , max . 10 , colour gardner , max . 13 ) stabilised with 0 . 4 % rendox ( kemin ) containing bha ( e320 ), ethoxyquin ( e324 ), citric acid ( e330 ), phosphoric acid ( e338 ), mono - & amp ; diglycerides of fatty acids ( e471 ), and enriched with 0 . 2 % dl - α - tocopherol ( roche ). the composition of fatty acids in egg yolk lipids can be modulated through dietary means . especially , the ω3 fatty acid of plant origin ( α - linolenic acid ) can be incorporated at the expenses of saturated and monounsaturated fatty acids in the triglyceride fraction . typically , regular eggs would contain almost undetectable level (& lt ; 1 %) of α - linolenic acid whilst free wandering birds grazing on greens and worms would almost incorporate 13 % of α - linolenic and show a balanced ω6 : ω3 ratio in the triglyceride fraction . nutritionally , this change into the birds diet does not affect the way these lipids are metabolised in the body since α - linolenic acid is usually burned and incorporated into tissues and cells membrane lipids at the same rate as monounsaturated fatty acids . a clear sign that this is indeed so is the fact that most α - linolenic acid , when present in the yolk triglyceride fraction , is located at position sn - 1 / 3 , characteristic of non - essential fatty acids , however , it provides a unique back - up source of ω3 fatty acids in fat depots for the synthesis of dha through the fatty acids cascade pathway . the major change associated with the presence of α - linolenic in the wild birds diet is the ratio inversion of the animal derived long - chain polyunsaturated fatty acids in the phospholipid fraction of the yolk . whilst regular feed contributes to the accretion of arachidonic acid at the expenses of docosahexaenoic acid ( aa : dha = 2 : 1 ), the wild - type feed favours the synthesis and deposition of docosahexaenoic acid ( aa : dha = 1 : 3 ). fatty acid and lipid compositions of wild - type eggs compared to those of standard eggs after 3 weeks induction on designer feed , wild - type eggs can be followed for their fatty acid pattern . a validation study ran on five groups of hens during 19 months has allowed to establish a specification for the wild - type egg ( table 10 ), as follows : during the same period , standard eggs available on the market and obtained from europe , the united states , south and east asia were collected and analysed according to the same procedure for their fatty acid and lipid contents . results show that standard eggs substantially deviate from wild - type egg ( table 11 ). in particular , standard eggs are extremely poor ( max . 1 %) in plant - type ω3 fatty acids and , as a consequence , they are also much richer in arachidonic acid . other eggs , often declared as ω3 docosahexaenoic acid enriched , were analysed in detail for their fatty acids distribution . these eggs are normally obtained from hens fed with a docosahexaenoic acid oil - enriched feed ( fish oil , algae , single cell oil , etc .) and their content of this specific fatty acid is relatively higher than in other eggs . it also turned out that such eggs exhibit a fatty acid composition reminiscent to that of standard eggs in terms of their low content in wild - type plant ω3 fatty acids ( max . 1 %) and their high content in domestic - type animal - derived ω6 long - chain fatty acids , not withstanding the additional fact that , when animal - derived ω3 fatty acids were summed up , they had less of these than the wild - type egg obtained with an exclusive vegeterian diet . wild - type eggs , naturally rich in ω3 fatty acids , may be assumed less stable than modern ω6 - rich eggs . nutritionists and consumers may raise more specific concerns towards fatty acids and cholesterol peroxidation in wild - type eggs . fatty acid changes with hen &# 39 ; s age . the influence of hen &# 39 ; s age on ω3 long - chain phospholipids content in wild - type eggs was followed on the life - cycle of two independent groups of 30 , 000 birds each . the data show that although a very slight trend down is observed , the effect of age on fatty acid composition in wild - type eggs is minor ( table 12 ). fatty acid changes with egg &# 39 ; s age . wild - type eggs were analysed for their fatty acid composition ( from fatty acid methyl ester ( fame ) spectrum analysis ) 3 and 9 weeks after being laid and stored at room temperature ( 21 ° c .). after 9 weeks , the yolk were barely separable from the white . the most obvious change upon storage is in the level of docosahexaenoïc acids (− 9 %/ 3 weeks , − 18 %/ 6 weeks and − 27 %/ 9 weeks at 21 ° c .). all other fatty acids were kept at a remarkable constant level ( table 13 ). fatty acid changes with processing temperatures . both wild - type and standard eggs were tested for their stability against oxidation during typical culinary practices , i . e ., boiling ( hard eggs ) and baking ( cake and baked custard ) ( tables 14 & amp ; 15 ) and compared . the rates of setting of the eggs upon boiling were also compared between standard and wild - type eggs . eggs were bored in order to have a hole in the shell at the apical side where the air chamber lies ( without perforing it ) and were boiled for various time ( 8 to 12 min .) in hot water ( min . 400 ml per egg ). at the end of the incubation , eggs were rapidly cooled in a large volume of cold water and stored one night in the fridge . the day after , the eggs were peeled and sliced in twice . the appearance of the yolk in standard and wild - type eggs was compared . no difference in rate of setting could be assigned at any time between the two types of eggs . wild - type and standard eggs were boiled , cooled , dried and peeled . the white was separated from the yolk and the cholesterol content in the yolk was determined . based on the weight of the different fractions ( intact egg , shell & amp ; membranes , albumen , yolk ), the amount of cholesterol in 100 - g egg edible portion of wild - type and standard eggs was calculated ( table 16 ). the cholesterol content of both standard eggs and wild - type eggs is around 375 ± 45 mg /%, of the edible part . in other words , the cholesterol of the wild - type eggs according to the invention is not changed as compared to the one of standard - type eggs . among the antioxidants present in eggs , vitamin e plays an essential role in stabilising the lipids against oxidation and rancidity . wild - type eggs , richer in sensitive ω3 fatty acids , are advantageously enriched with vitamin e in order to avoid peroxidation of cholesterol and other lipid fractions . designer feed is enriched with 0 . 2 % dl - α - tocopherol acetate in order to maintain 10 mg vitamin e per 50 - g edible egg ( table 17 ). the effect of changing dietary lipids on hen &# 39 ; s capacity to produce essential active enzymes and proteins for the protection of eggs against invasion by pathogens was tested by measuring the amount of lysozyme present in wild - type egg as compared to that in standard eggs ( table 18 ). 21 analyses on each type egg , from layers of 42 to 65 weeks of age for standard eggs and from layers of 32 to 55 weeks of age for wild - type eggs . as seen , the amount of lysozyme contained in the wild - type egg is similar to the one contained in standard eggs . egg lipids are made of fat store lipids ( triglycerides , tg ) and structural lipids ( phospholipids , pl and cholesterol , chl ). these occur in egg yolk in a constant specific ratio ( tg : pl : chl = 16 : 6 : 1 ). most fatty acids are concentrated in the triglyceride and the phospholipid fractions whilst cholesterol is almost totally ( 90 - 95 %) unesterified . fatty acids in the two fractions are not randomly distributed : essential fatty acids are mostly present at position sn - 2 of the triglyceride and the phospholipid fractions whilst non - essential fatty acids ( fa ) occur at position sn - 1 / 3 of the triglyceride fraction and at position sn - 1 of the phospholipid fraction . the distribution of fatty acids in egg yolk lipids drives their postpandrial influence on blood lipids . in the digestive tract , they are hydrolysed by pancreatic 1 , 3 - lipase and 2 - phospholipase to free fatty acids , sn - 1 , 3 monoglycerides and sn - 2 lysophospholipids , respectively . their reconstitution in the intestinal enterocytes results into the formation of triglycerides bearing essential fatty acids at position sn - 2 and , among others , long - chain polyunsaturated fatty acids at position sn - 1 , 3 . triglycerides with essential fatty acids at position sn - 2 are known to have hypocholesterolaemic effect in human whilst long - chain polyunsaturated fatty acids at position sn - 1 , 3 of blood triglycerides are directly available for tissue incorporation through their release by endothelial 1 , 3 - lipase . the bioavailability of egg yolk long - chain polyunsaturated fatty acids is similar to that of those from other animal tissues and must be very similar to that of endogenously produced long - chain polyunsaturated fatty acids . given that egg yolk long - chain polyunsaturated fatty acids are extremely bio - available for incorporation into tissue - and circulating cells membrane lipids and that their ω6 : ω3 ratio is susceptible to changes through dietary means , it is interesting to assess the influence of the bird &# 39 ; s diet on the healthiness of the eggs destined to human consumption . egg lipids contain small amounts ( less than 20 % of total fatty acids content ) of short and medium chain ( c12 - 16 ) fatty acids . their location at position sn - 1 / 3 of tg and sn - 1 of pl makes them available for direct energy production or for storage in adipose tissue . monounsaturated fatty acids and polyunsaturated fatty acids present at position sn - 2 of triglycerides contribute to the hypocholesterolaemic effect of egg lipids . long - chain polyunsaturated fatty acids located at position sn - 2 of pl &# 39 ; s are available for tissue incorporation . seen as a food lipid vector , egg is ranking high in the range of dietary fats ( dairy and meat produces , vegetable and fish oils ). fish oil is often reckoned as a good source of ω3 long - chain polyunsaturated fatty acids . however , two - third of long - chain polyunsaturated fatty acids in fish oil are associated with the sn - 2 position of the tg which makes them less bio - available and more susceptible to be diluted in fat depots and thus more prone to oxidative deterioration . it has been recommended to take large amount of vitamin e supplements together with fish oil . as compared to regular eggs that are almost totally depleted of the wild - type plant linolenic acid ( linolenic acid ( lna )& lt ; 1 %; ratio linoleic acid : α - lineolenic acid ( la : lna )& gt ; 30 : 1 ), wild - type eggs supply these two essential fatty acids in a balanced ratio ( la : lna = 1 : 1 ) and contribute to the endogenous synthesis of long - chain polyunsaturated fatty acids via the fatty acids biological cascade in the liver . the absence of α - linolenic acid in the regular diet of layers also leads to the preferential accretion of arachidonic acid in egg yolk phospholipids (( ω6 : ω3 lc - pufa = 2 : 1 ) whilst this ratio is inverted in wild - type eggs ( ω6 : ω3 lc - pufa = 1 : 3 ). direct incorporation of dietary long - chain polyunsaturated fatty acids in tissues and circulating cells is - thus in favour of ω3 long - chain polyunsaturated fatty acids with the wild - type eggs . it is known that the effect of ω3 fatty acids on serum cholesterol concentration is similar to those of other unsaturated fatty acids ( monounsaturated and ω6 polyunsaturated ), i . e ., when they replace c12 - 16 saturated fatty acids at the sn - 2 position of triglycerides , they lower serum cholesterol . ω3 long - chain polyunsaturated fatty acids have an added benefit of consistently lowering serum triglyceride concentration through reduction of chylomicron and vldl secretion by the intestine and the liver , respectively . when fed to selected groups of people , the eggs according to the invention have been shown to indeed contribute to the improvement of : ( a ) circulating cell membranes fatty acid composition ( ω3 : ω6 long - chain polyunsaturated fatty acids ratio ), ( b ) blood lipid distribution ( no statistical change in blood cholesterol level , improved distribution within blood lipoproteins — hdl / ldl balance , substantial reduction in the amount of fat circulating in the blood ), ( c ) blood pressure ( 5 to 10 % reduction in both cystolic and diastolic pressure ) and , even ( d ) breast milk lipid composition ( 60 % and 300 % increase in α - linolenic acid and docosahexaenoic acid , respectively , with no substantial changes in other fatty acids ). finally , through this feeding practice of the chicken , it has been feasible to readjust the ω6 : ω3 ratio in eggs so that they present a balanced fatty acid composition comparable to the original “ wild - type food ” available to early man . as a lipid source , the egg according to the invention thus belongs to the minor family of ω3 - rich fats and oils and lies in between those from vegetable and fresh water fish origins ( table 19 ). the eggs according to the invention and river fish deliver a minimum of 70 % unsaturated fatty acids ( the healthy one ), equal amounts of both ω6 and ω3 polyunsaturated fatty acids ( ω6 : ω3 = 1 : 1 ) and substantial amounts of animal - derived ω3 long - chain polyunsaturated fatty acids in a favourable ratio ( ω6 : ω3 = 1 : 3 ) ( table 20 ). furthermore , the eggs according to the invention are also characterised by advantageous organoleptic properties in terms of freshness and flavour . they are rich in vitamins and antioxidants and are produced from layers effectively maintained immunised against salmonella infections through the diet according to the invention they receive , said diet being rich in oligosaccharides naturally present in green and leaves . ω3 fatty acids : fatty acids having first unsaturation on carbon 3 from the terminal methyl , as known by the man skilled in the art ω6 fatty acids : fatty acids having first unsaturation on carbon 6 from the terminal methyl , as known by the man skilled in the art
the present invention is related to an egg obtained from a domesticated bird , in particular a layer , having a lipid fraction balanced in ω6 and ω3 fatty saturated fatty acids according to the ratio of polyunsaturated / saturated fatty acids = 1 : 1 ± 10 %. the present invention is also related to a feed composition of exclusive vegetarian origin and suitable for poultry and a method for obtaining such egg from said poultry animals .