TECHNICAL FIELD OF THE INVENTION

The invention relates to a poultry feed comprising biomass from bacteria in the Rhodospirilliceae family, preferably Rhodospirillum rubrum ( R . rubrum ), for lowering the cholesterol level and optionally improving colour in a poultry egg yolk. The invention also concerns such improved poultry eggs, methods for obtaining the poultry feed or such an improved poultry egg, and uses thereof.

BACKGROUND OF THE INVENTION

Eggs have been a staple food item in cultures around the world for many years. In fact, for many people, such as vegetarians, eggs are a vital part of their diet to ingest the necessary amounts of protein, lutein, zeaxanthin and vitamins that can only be obtained through animal products. However, there have been some health concerns raised over the past few decades about the high consumption of eggs.

In particular, nutritionists, dieticians and other medical professionals are concerned about the relatively high levels of cholesterol present in egg yolks. An average chicken egg contains more than 60% of the recommended daily intake of cholesterol. Consequently, regular consumption of eggs, and in particular the yolks, have been hypothesized to result in an increased plasma cholesterol level in the consumer. Increased plasma cholesterol is a well- known risk factor for cardiovascular disease. Therefore, currently it is recommended to eat a maximum of 2-6 egg yolks per week.

As a result, there is substantial interest from consumers, as well as healthcare professionals, in egg yolks that have a lower level of cholesterol.

Most of the methods to obtain eggs with a lower cholesterol level in the yolk available in the prior art focus on removing the cholesterol from the egg by using, for instance, solvent extraction. Such methods require cracking the egg open. This means that the egg then has to be used as an ingredient and can no longer be consumed as simply an egg.

Another factor that determines whether a consumer is more likely to consume an egg is the colour of the yolk. In a lot of countries, such as Germany, France, Italy, and the Netherlands, a darker, more intense orange, egg yolk colour is perceived as more appealing and is also considered a sign that the chicken that laid the egg was healthy.

Consequently, in order to achieve the desired egg yolk colour, canthaxanthin is often added as a colouring agent to poultry feed. The European Union (EU) has regulations in place for the amount of canthaxanthin that can be used in foodstuff since it was found that high dietary intake levels of canthaxanthin resulted in the deposition of colour crystals in the retina, which may damage the retina and impair sight. Therefore, a safer alternative for canthaxanthin to obtain the desired egg yolk colour would be desirable.

Therefore, a need still remains for an effective way to reduce cholesterol levels in egg yolks, while at the same time providing an effective and safe means to obtain the desired egg yolk colour.

DEFINITIONS

The term “biomass” as used herein has its conventional meaning and refers to a biological material produced by growth and/or propagation of living cells, such as microorganisms, which material may be harvested or collected from said cells and/or may be processed further. Biomass may contain whole cells, such as microbial cells, and/or parts thereof such as cell membranes, cell walls, intracellular contents, for example cellular fatty acids, as well as extracellular material including microbial products or by-products secreted by a cell, for example, secreted fatty acids or polysaccharides.

The term “cholesterol” as used herein has it conventional meaning and refers to the total cholesterol in a given sample, such as blood plasma or egg yolk dry matter, which includes both LDL- and HDL-cholesterol.

The term “poultry” as used herein has its conventional meaning and refers to any poultry animal, in particular any bird species or subspecies of any known breed or race, raised or ranched for the production of meat, eggs or other products, which animal can be domesticated. Examples of a poultry animal include a chicken, duck, turkey, goose, quail, ostrich or emu.

The term “poultry feed” as used herein has its conventional meaning and refers to food material given to domestic poultry animals, which is suitable for the particular species, subspecies, breed and/or race of poultry the feed is given to.

The term “ Rhodospirillaceae ” as used herein has its conventional meaning and refers to a family of purple non-sulphur bacteria capable of producing energy through photosynthesis. All members of this family can be found in the Deutsche Sammhing von Mikroorganismen und Zellkulturen GmbH database (Family: Rhodospirillaceae (dsmz.de)).

The term “ Phaeospirillum ” as used herein has its conventional meaning and refers to a genus of the family Rhodospirillaceae . Within the genus Phaeospirillum two species are known: Phaeospirillum fulvum and Phaeospirillum molischianum. For nomenclature, see Imhoff JF, Petri R, Suling J, Int. J. System . Bacteriol. 1998, 48, 793-798 and Deutsche Sammlung von Mikroorganisms und Zellkulturen GmbH. Bacterial nomenclature: www.dsmz.de/bactnom/bactname.htm.

The term “Rhodospirillum ” as used herein has its conventional meaning and refers to a genus of the family Rhodospirillaceae . Within the genus Rhodospirillum , three species are distinguished: Rhodospirillum rubrum (Imhoff and Truper, 1992), Rhodospirillumcentenum and Rhodospirillumphotometricum. Furthermore, four officially unrecognized subspecies are known: Rhodospirillum salexigens, Rhodospirillum salimarum , Rhodospirillum sodomense, and Rhodospirillum tenue. For nomenclature, see Imhoff JF, Petri R, Suling J, Int. J. System . Bacteriol. 1998, 48, 793-798 and Deutsche Sammlung von Mikroorganisms und Zellkulturen GmbH. Bacterial nomenclature: www.dsmz.de/bactnom/bactname.htm.

The term “Rhodospirillum rubrum’ or simply “ R . rubrum’ as used herein, has its conventional meaning and refers to a spiral-shaped Gram-negative bacterium species, identified by E. von Esmarch (1887), named by H. Molisch (1907), and currently classified to the genus Rhodospirillum , which is the type genus of the family Rhodospirillaceae in the class Alphaproteobacteria. R. rubrum is a facultative anaerobe capable of using oxygen for aerobic respiration under aerobic conditions, as well as, after the exhaustion of oxygen. Under the anaerobic conditions R. rubrum is capable of synthesizing bacteriochlorophylls and carotenoids, which render R. rubrum pink-coloured, and thus becomes photosynthesis active. For the purposes of the disclosed herein methods and uses, any R. rubrum in general can be employed without limitation to any specific strain thereof. For purposes of nomenclature reference is made to Imhoff JF, Petri R, Suling J, Int. J. System . Bacteriol. 1998, 48, 793-798 and Deutsche Sammhing von Mikroorganismen und Zellkulturen GmbH. Bacterial nomenclature: www.dsmz.de/bactnom/bactname.htm. SUMMARY OF THE INVENTION

In a first aspect, the invention relates to a poultry feed comprising at least 0.05 wt% and less than 2 wt% of biomass from bacteria in the Rhodospirillaceae family, preferably from the genus Rhodospirillum , more preferably R. rubrum , based on the total weight of the feed.

Another aspect of the invention concerns a method for producing a poultry feed comprising at least 0.05 wt% and less than 2 wt% of biomass from bacteria in the Rhodospirillaceae family, preferably from the genus Rhodospirillum , more preferably R. rubrum , based on the total weight of the feed, comprising the steps of: a. growing bacteria; b. collecting biomass and optionally drying and/or grinding the biomass; c. providing conventional poultry feed; and d. mixing the poultry feed with the obtained biomass to obtain a feed with the desired weight percentage of biomass based on the total weight of the feed.

A further aspect of the invention relates to a method for obtaining a poultry egg with a reduced cholesterol content in the egg yolk comprising the steps of: a. feeding a poultry animal with the poultry feed according to the invention for a period of at least 3 weeks, preferably at least 6 weeks, more preferably at least 7 weeks; and b. harvesting the poultry egg from the poultry animal.

In another aspect the invention concerns a poultry egg obtained from, or obtainable by, the method according to the invention.

A related aspect of the invention relates to the use of the poultry egg obtained from or obtainable by the method according to the invention as a food product or food ingredient.

In yet a further aspect the invention relates to the use of bacteria from the Rhodospirilliceae family, preferably from the genus Rhodospirillum , more preferably R. rubrum , or biomass from bacteria from the Rhodospirilliceae family, preferably from the genus Rhodospirillum , more preferably R. rubrum , for preparing a poultry feed according to the invention.

Another aspect of the invention concerns the use of the poultry feed according to the invention for the production of poultry eggs, from a particular species, subspecies, breed or race of poultry animal, with a decreased cholesterol level in the egg yolk when compared to an egg yolk of a poultry egg, from the same species, subspecies, breed or race of poultry animal, not being fed with the poultry feed according to the invention.

A further aspect of the invention relates to the use of the poultry feed according to the invention for the production of poultry egg yolks with an improved egg yolk colour.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the nature of present disclosure, reference is made to the following detailed description taken in conjunction with the accompanying figures, in which:

Figure 1 shows the cholesterol level reduction over time in the egg yolk of eggs from laying hens being fed a chicken feed comprising 0.05wt% R rubrum biomass based on the total weight of the feed. After 7 weeks treatment cholesterol reduction is 0.5933 x 7 = 4.15 g, which equals a cholesterol level reduction of 18%.

Figure 2 shows the cholesterol level reduction over time in the egg yolk of eggs from laying hens being fed a chicken feed comprising 0.5wt% R. rubrum biomass based on the total weight of the feed. After 7 weeks treatment cholesterol reduction is 0.3467 x 7 = 2.42 g, which equals a cholesterol level reduction of 11%.

Figure 3 shows the cholesterol level reduction over time in the blood plasma of laying hens being fed a chicken feed comprising 0 05wt% R. rubrum biomass based on the total weight of the feed.

Figure 4 shows the cholesterol level reduction over time in the blood plasma of laying hens being fed a chicken feed comprising 0.5wt% R rubrum biomass based on the total weight of the feed.

Figure 5 shows the cholesterol level reduction over time in the blood plasma of laying hens being fed a chicken feed comprising 2wt% R. rubrum biomass based on the total weight of the feed.

Figure 6 shows the cholesterol level increase over time in the blood plasma of laying hens being fed a chicken feed comprising no R. rubrum biomass (control) based on the total weight of the feed.

Figure 7 shows a photograph of a colour assessment of egg yolks with a BASF colour fan (Lucantin® yellow) in eggs from laying hens being fed a chicken feed comprising (as indicated) 0 wt%, 0.05 wt%, 0.5 wt%, or 2 wt% of A. rubrum biomass based on the total weight of the feed. DETAILED DESCRIPTION

It is known from W02004052380 that inclusion of the bacteria from the genus Rhodospirillum can lower the cholesterol level in blood and plasma of special mouse models.

Along these lines, Chinese patent document CN 1 274 584 discloses a preparation of Rhodospirillum for lowering blood lipid, and a Japanese patent document JP 08 205819 discloses a food supplement or probiotic (beverage for health) also containing Rhodospirillum.

European patent EP 1 569 667 granted to ezCol B.V. discloses a preparation comprising the membrane fraction of Rhodospirillum for use as a medicament, notably for lowering plasma cholesterol in humans.

In W02008056450 it was disclosed that the use of photosynthetic bacteria in animal feed to obtain animal products with a lower cholesterol level. In one of their Examples they use Rhodopseudomonas capsulata in chicken feed at 0.01 wt%, 0.02 wt% and 0.04 wt% based on the total weight of the feed and observed a decrease in the cholesterol level in the obtained egg yolks.

In W02008115055 it was furthermore discovered that the use of bacteria from the genus Rhodospirillum and Phaeospirillum in animal feed led to animal products, such as milk, meat and eggs, with a lower cholesterol level. It was further disclosed that the higher the content of the bacteria, the higher the reduction of the cholesterol level. However, with regard to eggs, W02008115055 appears to teach that the higher the dose of R rubrum , the better the effect on lowering the cholesterol level in yolk, suggesting that 5 wt% R rubrum is preferred.

The presently disclosed methods, uses, and related products as obtainable therefrom stem from a surprising observation that supplementation of poultry feed with biomass from bacteria in the Rhodospirillaceae family, preferably from the genus Rhodospirillum , in particular R rubrum , equal to or exceeding 2 wt% based on the total weight of the feed, results in increased egg yolk cholesterol contents, contrary to the desirable effect as disclosed in W02008115055. Additionally, the data presented herein shows that the optimal supplementation amounts with bacteria from this family, in particular A. rubrum , to achieve the desired effects, lie in ranges much lower than the ones contemplated in W02008115055.

Namely, the inventors have surprisingly observed that a poultry feed comprising at least 0.05 wt% and less than 2 wt% of biomass from bacteria in the Rhodospirillaceae family, preferably from the genus Rhodospirillum , in particular A. rubrum , based on the total weight of the feed, results in production of poultry eggs with yolks of naturally decreased cholesterol levels and optionally also an improved colour.

The family Rhodospirillaceae contains many genera including the genus Phaeospirillum , which includes two species Phaeospirillum fulvum and Phaeospirillum molischianum , and the genus Rhodospirillum. In the context of the invention, the genus Rhodospirillum within this family is preferred. The genus Rhodospirillum contains 3 species Rhodospirillum rubrum (Imhoff and Truper, 1992), Rhodospirillumcentenum and Rhodospirillumphotometricum. There are also four bacteria, which have not officially been recognised as species in the Rhodospirillum genus, which are Rhodospirillumsalexigens , Rhodospirillum salimarum , Rhodospirillum sodomense, and Rhodospirillum tenue. Due to their close-relatedness as well as their genetic, physiological, and molecular-content similarity, it is anticipated and highly plausible that bacterial biomass obtained from all of these officially recognised and non-recognised species, especially those in the Rhodospirillum genus, will all have the same effects on poultry egg yolks as observed following poultry feed supplementation with R. rubrum biomass.

Consequently, in a first aspect, the invention relates to a poultry feed comprising at least 0.05 wt% and less than 2 wt% of biomass from bacteria in the Rhodospirillaceae family, preferably from the genus Rhodospirillum , more preferably R. rubrum , based on the total weight of the feed.

In an embodiment, the poultry feed is provided comprising less than 1.5 wt%, less than 1.4 wt%, less than 1.25 wt%, less than 1 wt% or less than 0.75 wt% of the biomass based on the total weight of the feed.

In a further embodiment, the poultry feed is provided comprising at least 0.1 wt%, at least 0.25 wt%, possibly about 0.5 wt% of the biomass based on the total weight of the feed.

In another embodiment, the poultry feed comprises at least 0.05 wt% and less than 1.5 wt% biomass based on the total weight of the feed, preferably at least 0.05 wt% and up to 1.4 wt%, more preferably 0.1 wt% up to 1 wt%, even more preferably 0.25 wt% up to 0.75 wt%, most preferably about 0.5 wt%.

The inventors surprisingly found that by using the disclosed ranges of R. rubrum biomass in a poultry feed both a reduced cholesterol level and a more intense darker egg yolk colour were observed in the eggs harvested from poultry animals being fed with said feed. The cholesterol reducing effect of the R rubrum biomass was, however, unexpectedly lost when the R. rubrum biomass content exceeded 2 wt%. In anaerobic conditions, bacteria in the Rhodospirillaceae family, including R. rubrum , synthesize bacteriochlorophylls and/or carotenoids through photosynthesis. It is hypothesized that these compounds may contribute to the effect on the egg yolk colour when biomass from these bacteria is used in a poultry feed. Consequently, in an embodiment, the biomass comprises bacteriochlorophylls and/or carotenoids as synthesized by the bacteria.

Despite its ability to synthesize carotenoids, it has been found that R. rubrum , and related bacteria species from the Rhodospirilliceae family, do not synthesize the carotenoid canthaxanthin. Therefore, the harmful effects of this colouring agent will not be present when using biomass from these bacteria to improve the colour of a poultry egg yolk.

In an embodiment, the biomass comprises alive whole cells, dead or inactivated whole, or substantially whole, cells, cell fragments and/or cell membrane fragments. Additionally, the biomass may also be dried, preferably freeze-dried and/or oven-dried. Hence, in another embodiment, a poultry feed is provided, wherein the biomass comprises dried, preferably freeze-dried and/or oven-dried bacteria from the Rhodosprilliceae family, in particular from the genus Rhodospirillum, preferably A. rubrum.

It was discovered by the inventors that biomass is very robust in its effectiveness. It seems that the biomass can be processed in various different ways while retaining its advantageous effects in a poultry egg yolk.

Depending on the specific type of poultry feed in which the biomass is used it may be preferable to have the biomass provided in powder, paste or suspension form. The inventors found that the effects were observed regardless of what form of biomass was used in the feed. Therefore, in an embodiment, the biomass is provided as a powder, paste or suspension.

In another embodiment, the poultry fed with the feed are chickens, preferably laying hens. Hence, in an embodiment the feed is chicken feed.

The breed Arbor Acres is one of the most common chicken breeds used in the poultry industry today. The poultry feed according to the invention was tested on this breed of chicken and found to be effective in reducing the cholesterol content and improving the egg yolk colour of eggs laid by these chickens.

Another aspect of the invention relates to a method for producing a poultry feed according to the invention comprising the steps of: a. growing or culturing bacteria from the Rhodospilliceae family, preferably from the genus Rhodospirillum, more preferably A. rubrum ; b. collecting biomass from said bacteria and optionally inactivating, drying and/or grinding the biomass; c. providing conventional poultry feed; and d. mixing the conventional poultry feed with the obtained biomass to obtain a feed with the desired weight percentage of biomass based on the total weight of the feed.

As was mentioned here above, the inventors found that adding the biomass from bacteria in the Rhodospirillaceae family, in particular A. rubrum , in a weight percentage of least 0.05 wt% and less than 2 wt%, or up to 1.5 wt%, based on the total weight of the feed resulted in at least a lower cholesterol level and advantageously also a darker colour in the egg yolks of the poultry eggs obtained from the method.

In line with the above, good results were also observed for between 0.05 wt% and 1.4 wt%, more preferably 0.1 wt% up to 1 wt%, even more preferably 0.25 wt% up to 0.75 wt%, most preferably about 0.5 wt%.

A further aspect of the invention concerns a method for obtaining a poultry egg with a reduced cholesterol content in the egg yolk comprising the steps of: a. feeding a poultry animal with the poultry feed according to the invention for a period of at least 3 weeks, preferably at least 6 weeks, more preferably at least 7 weeks; and b. harvesting the poultry egg from the poultry animal.

The inventors surprisingly found that already after only 3 weeks of feeding a poultry animal with the feed according to the invention resulted in a significant decrease in the cholesterol level in the egg yolk. This effect continued to be observed after 7 weeks of the poultry animal being fed with the feed, which indicates that long-term feeding with the feed according to the invention will result in the production of poultry eggs with a reduced cholesterol level in the egg yolk.

Since chickens are one of the most popular species of poultry animal, it is envisioned that the method according to the invention can be applied to chickens, for example to the chicken breed Arbor Acres.

Furthermore, the invention also relates to a poultry egg obtainable from, or obtained by, the method according to the invention, wherein the egg yolk optionally has an improved colour.

The poultry eggs obtained from, or obtainable by, the method according to the invention can be distinguished from poultry eggs, from the same poultry species, subspecies, breed and/or race, which are not obtained from, or obtainable by, the method according to the invention by comparing the respective cholesterol levels as well as, optionally, the colour of the egg yolks. In poultry eggs obtained from, or obtainable by, the method according to the invention a lower cholesterol level will be observed in the egg yolk. Possibly, a darker, more intense orange colour in the egg yolk is observed as well. For example, after 7 weeks of feeding a poultry animal with the feed according to the invention, the inventors found that the egg yolk had an improved colour. The observed eggs were found to have a darker and more intense orange yolk when compared to the eggs harvested from the same species, subspecies, breed and/or race of poultry animal which had been fed a conventional feed without the biomass for 7 weeks.

Since R. rubrum , and related bacteria species from the Rhodospirilliceae family, do not contain canthaxanthin, the improved colour of the poultry egg yolk will not be associated with any of the detrimental effects caused by the use of canthaxanthin. Therefore, using the natural colourants as synthesized by these bacteria, and thus present in the biomass, as a colouring agent presents a safer option than canthaxanthin.

In an embodiment, the poultry egg is a chicken egg, preferably from a laying hen of the breed Arbor Acres.

Another aspect of the invention relates to the use of bacteria from the Rhodospirilliceae family, in particular from the genus Rhodospirillum , preferably R. rubrum or biomass thereof for preparing a poultry feed according to the invention.

As mentioned here above, it was found that R. rubrum is very robust in its ability to produce the observed effects of lowering the cholesterol level and, above certain concentrations, improving the colour of the egg yolk when it is used in a poultry feed. Therefore, it is hypothesized that any form of bacteria from the Rhodospirilliceae family or biomass thereof, in particular from the genus Rhodospirillum , preferably R. rubrum or R rubrum biomass, may be suitable for use in the poultry feed according to the invention.

The bacteria or biomass may be alive whole cells, dead or inactivated whole, or substantially whole, cells, cell fragments and/or cell membrane fragments. The bacteria or biomass may also be dried, such as freeze-dried or oven-dried. Furthermore, it can also be processed further into a powder, paste or suspension.

A further aspect of the invention concerns the use of the poultry feed according to the invention for the production of poultry eggs, from a particular species, subspecies, breed or race of poultry animal, with a decreased cholesterol level in the egg yolk when compared to an egg yolk of a poultry egg, from the same species, subspecies, breed or race of poultry animal, not being fed with the poultry feed according to the invention, or in other words a poultry feed with contents similar to the poultry feed according to the invention, but lacking the biomass from bacteria in the Rhodospirillaceae family, in particular A. rubrum.

Naturally, as it will be appreciated by those skilled in the art, the levels of cholesterol present in an egg yolk will ultimately depend on a multitude of factors, including the genetics of the egg-laying, female, poultry animal, usually belonging to the subspecies of domesticated fowls also commonly known as chickens ( Gallus gallus domesticus), the feed that the poultry animal receives, possibly the hen’s level of activity and/or its bodily constitution and/or age, etc.

Consequently, it is difficult to define numerical values for what should be considered a decreased cholesterol level, as this will be relative to the above-listed, and possibly more, underlying factors. However, as demonstrated by the experiments presented here below in the Examples, when laying hens of the same breed, age, housing conditions etc. and/or comparable generic background are fed with the same type of feed, wherein one hen received the feed supplemented with the disclosed herein advantageous amounts of biomass from bacteria from the Rhodospirilliceae family, in particular from the genus Rhodospirillum , and preferably R. rubrum , and the other hen receives the same feed type but not supplemented with the biomass, the laying hen receiving the feed supplemented with the biomass according to the invention will lay eggs having lower relative levels of cholesterol in the egg yolks when compared to the egg yolks from the eggs laid by the hen receiving the non-supplemented feed. The effect appears to be robust and reproducible, and interestingly and surprisingly, appears to disappear when the biomass reaches the amount of 2 wt% biomass based on the total weight of the feed.

As is further illustrated below by the Examples, the poultry eggs from the same species, subspecies, breed and/or race of poultry animal were found to be different when either the feed according to the invention was used or when a conventional feed, without biomass, was used.

The invention furthermore relates to the use of the poultry feed according to the invention for the production of poultry egg yolks with a visibly improved egg yolk colour.

As is further illustrated by the Examples below, the poultry eggs from the same species, subspecies, breed or race of poultry animal were found to have different egg yolk colours depending on whether the feed according to the invention was used.

In fact, even a small amount of only 0.05 wt% of R. rubrum biomass added to the poultry feed was already sufficient to result in a colour difference in the egg yolk when visually compared to the colour of the egg yolk of the same species, subspecies, breed and/or race of poultry animal being fed a conventional feed without the R rubrum biomass.

The inventors observed that the higher the content of R. rubrum biomass present in the feed, the darker and more intense orange the egg yolk colour would become. The biggest improvement in colour was seen at between 0.5 wt% and 2 wt% of R. rubrum biomass in the feed based on the total weight of the feed. The colour difference between 0.5 wt% and 2 wt% was much smaller than the colour difference between 0.05 wt% and 0.5 wt% of R. rubrum biomass, indicating that the effect is strongest at about 0.5 wt% of R. rubrum biomass in the feed based on the total weight of the feed.

It is to be noted that, analogous to the relative changes in cholesterol levels in egg yolks as discussed here above, the skilled person will understand that the base egg yolk colour will depend on the poultry animal’s genetics and the feed they receive. Therefore, it will be understood that the base egg yolk colour will influence the perceived improvement in colour of the egg yolk. Consequently, it is not practical to attribute numerical values of measurement methods to define the egg yolk colour improvement as achieved by the R. rubrum biomass supplemented poultry feed according to the invention. As can be expected, effects on naturally light yellow egg yolks may potentially already be visible at smaller amounts of R. rubrum biomass in the feed compared to the situation when no R. rubrum biomass was supplemented to the feed. Such differences may obviously remain unperceived, or less clearly perceived, in cases of naturally darker, more orange, egg yolks. The advantageous contribution is hence relative and heavily dependent on the underlying biological and/or environmental factors, but as the data presented herein show, it also is robust and reproducible.

Additionally, as explained here above, since canthaxanthin is not present in biomass from R. rubrum or other bacteria from the Rhodospirilliceae family, the harmful effects associated with the use of canthaxanthin as a colouring agent are not expected to be present when using these bacteria as a colouring agent instead. Therefore, using biomass from these bacteria, and in particular R rubrum , in poultry feed is a safer alternative for a colouring agent when compared to canthaxanthin for poultry egg yolks.

Another aspect of the invention concerns the use of the poultry egg obtainable from, or obtained by, the method according to the invention as a food product or as a food ingredient.

One of the disadvantages of the methods for lowering the cholesterol level in the egg yolk of a poultry egg as used in the prior art is that the egg is no longer intact when the process has been completed. Using the method according to the invention means that the egg will still be intact and can be used as a food product or food ingredient. Additionally, since the egg is still intact at the end of the method steps, it will be easier to store and transport.

The concept underlying the present disclosure has been described by reference to different embodiments as discussed above. It will be recognized that these embodiments are susceptible to various modifications and alternative forms well known to those of skilled in the art.

The invention will be further illustrated by the Examples presented here below. These Examples are in no way meant to represent a limitation of the scope of the invention. EXAMPLES

The effect on cholesterol level and colour in the egg yolk by feeding chickens the poultry feed according to the invention was tested.

Materials and methods

24 laying hens, Arbor Acres, 35 weeks old housed in cages in 4 groups of 6 animals were fed with conventional chicken feed (De Heus Voeders B.V.) by Research Diet Services, Wijk bij Duurstede on a conventional feeding schedule.

The tests were performed at Experimental farm Feed Innovation Services, Culemborg, NL. Cholesterol analyses of egg yolks were performed at Nutrilab, Giessen, NL. Cholesterol analyses of chicken plasma were performed at Varidon, Elspeet.

Units used in the study to measure and report cholesterol content:

• In plasma of laying hens: mmol/1

• Calculation factor: mmol/1 = 0,02586 mg/dl

• In egg yolk: mg/ gram dry matter yolk

For the first group no R rubrum biomass was added to the feed (control group).

For the second group 0.05 wt% R. rubrum biomass based on the total weight of the feed was included in the feed (experimental group 1).

For the third group 0.5 wt% R. rubrum biomass based on the total weight of the feed was included in the feed (experimental group 2).

For the fourth group 2 wt% R. rubrum biomass based on the total weight of the feed was included in the feed (experimental group 3).

Cholesterol in egg yolk

Cholesterol levels in the egg yolk were measured before the start of feeding and after 3, 6 and 7 weeks of feeding.

The cholesterol measurements in mg/gram dry matter of the egg yolks in the four groups at the indicated time points is shown in Table 1 as well as Figures 1 and 2. Table 1. Cholesterol levels in egg yolk mg/gram dry yolk matter.

As can be seen from Table 1, and the calculations included in Figures 1 and 2, chickens fed with a feed containing 0.05 wt% R. rubrum biomass for 7 weeks had an average decrease in cholesterol level in the egg yolk of 18%, while chickens fed with the feed containing 0.5 wt% R. rubrum biomass had an average decrease of 11%.

In contrast there was no decrease observed in the control group and for the 2 wt% R. rubrum biomass an increase in cholesterol level was observed (first measurement value 25.8 mg cholesterol/gram dry yolk matter). Because this was highly unexpected, the experiment was repeated, confirming the result (second measurement value 25.1 mg cholesterol/gram dry yolk matter), which indicates that R. rubrum biomass amounting to 2 wt% or more may result in a relative increase in cholesterol levels, which is an undesirable effect. The inventors have not found an explanation for the resulting relative higher cholesterol values observed at 2 wt% R. rubrum biomass, and hypothesise compensation could at least partially explain this.

Consequently, the inventors conclude that adding R. rubrum biomass to poultry feed can decrease the cholesterol level in the resulting egg yolk, but this beneficial effect seems to be lost as soon as more than 2 wt% of R. rubrum biomass is added.

Cholesterol (total) in plasma

Additionally, the inventors observed that not only the cholesterol level in the egg yolks was decreased, but also the plasma cholesterol level in the chickens was deceased due to the feed. Results of blood plasma cholesterol levels in the chickens are illustrated in Table 2 and Figures 3-6. Table 2. Blood plasma cholesterol in chickens.

As can be seen from Table 2 and Figures 3-6, the addition of 0.05, 0.5 and 2 wt% R. rubrum biomass to the diet of the hens resulted in a statistically significant (p=0.05) decrease of the plasma cholesterol level after only 5 weeks of treatment. However, an obvious dose-response effect could not be established. Therefore, the decrease in cholesterol in the egg yolks could possibly be at least partially linked to the feed according to the invention since a decrease in total plasma cholesterol was also observed in the chickens. Colour measurement in the egg yolks

The colour of the egg yolks in the four groups was assessed using a BASF colour fan (Lucantin® yellow).

The colour observations were conducted as the inventors believed to have strong indications that the natural colouring agents present in R. rubrum biomass may be related with the cholesterol reducing property of the biomass.

The colour of the egg yolks was analysed after the 7 weeks of feeding the chickens with the different feeds as described here above. The inventors observed that with an increasing weight percentage of R. rubrum biomass the egg yolk became an increasingly more intense orange colour, which is considered an attractive colour for consumers as well as a sign that the chicken is healthy. The results of the colour measurements are shown below in Table 3 and Figure 7. Table 3. Colour measurements egg yolk.

As is clear from Table 3, the colour of the egg yolk increases in intensity once R. rubrum biomass is added to the feed resulting in a more appealing egg for consumers that is more likely to be purchased and enjoyed upon consumption.