EGG YOLK COLOR. Introduction

Transcription

1 EGG YOLK COLOR Introduction The hen incorporates various carotenoids in her skin and eggs as part of her normal physiology and does so consistently if it is available in the diet and absorption is not compromised. Carotenoids are molecules that radiate a range of yellow to red colour due to the nature of their chemical structure. Figure 1: Structure of C 30 ester Figure 2: Structure of Canthaxanthin Carotenoids are available everywhere in nature and are usually produced by plants and lower organisms. Most fish, avians and mamalians have lost the ability to make these molecules, but utilise it in their bodies for coloration or antioxidants. The structure of the molecule can be altered in the cells of animals to meet the needs of the animal.

2 Measurement Egg yolks are measured using the BASF Ovo colour fan. The fan consists of a range of blades coloured in fifteen possible outcomes of egg colour and numbered accordingly. The measurement should be done using a white background (a white dinner plate is the most practical), utilising diffused light (shaded sunlight). Holding the blades immediately above the yolk, compare the colour of the yolk with the fan colours, a corresponding blade and number can then be allocated to the egg. Remember that the yolk in the membrane usually appears about 1 2 blades paler than the yolk inside. Fig 3: The Ovo color fan Principles of egg colour perception and egg colouration The basic colour of the egg is yellow, which means that this is the colour that should be supplied in majority. The nature of how colour is perceived by the eye means the yellow pigments cannot produce an egg darker than a 7 8 on the BASF Ovo color

3 fan scale, independent whether large amounts of yellow pigment is supplied or not. To produce an egg with a darker (more orange hue), a source of red colour should be supplied in the diet. Different sources of carotenoids are digested, metabolised and deposited in different ways in the animal body, therefore different molecules will have different efficiencies in colouration, largely independent of the colour of the molecule itself. The following paragraphs explains why C 30 ester ($ apo 8 carotenoic acid ethyl ester) is the most efficient source of yellow colour and canthaxanthin is the most efficient source of red colour for commercial purposes (see table 1). Canthaxanthin C 30 ester Skin and organs of various birds and fish Occurs as a metabolic product of apocarotinal Cantharellus cinnabarius (chantterele) fungus Can be extracted from: grass, lucerne, citrus fruits, green vegetables. Various insects Some crustaceans skin pigmentation Table 1: The natural occurrence of C 30 ester and Cantaxanthin Common sources of yellow colour are lutein (tagetes/maize, 445 nm) and zeaxanthin (maize, 450 nm), the wavelength of C 30 ester is close to the wavelength of zeaxanthin, which means they both appear intensely yellow to orange as opposed to the relatively bland yellow colour of lutein. The deposition rate of lutein and zeaxanthin is % of the dietary levels and the depositon rate of C 30 ester is about 40 50%, this means that C 30 ester is gram for gram three times more efficient than zeaxthanthin and lutein i.t.o. pigmenting efficiency of eggs. Common sources of red (orange) colour are citranaxanthin (commercial, ~ 472 nm) and capsanthin/capsrubin (paprika, 475 nm) where the wavelength of canthaxanthin is about 468 nm. Again the deposition rate of canthaxanthin is superior to the other commercially available products: 1,5 times more efficient than citranaxanthin, and 2,5 to 2 times more efficient than capsanthin/capsrubin. BASF carotenoids Lucantin yellow and Lucanthin red contains 10 % of the carotenoids protected in a stabalised beadlet (see fig. ), with a specific particle size distribution to ensure a consistent distribution throughout the feed and ensuring a even supply of carotenoids to all the laying hens. Recommendations Supplement Y=Lucantin Yellow R=Lucantin Red Natural yellow Required

4 carotenoid level Ovocolor value 0 2 Y Y Y Y ADVIT Animal Nutrition 137 Terrace Road Sebenza, 1610 PO Box 8689 Edenglen, 1613 Tel: Fax: admin@advit.co.za Y Y Y R Y R Table 2: Recommended Lucanthin levels to achieve different Ovocolour values. This table assumes an intake of 115g of feed per hen per day. Factors affecting egg colour and problem solving Factors influencing egg yolk pigmentation 1. High levels of linoleic acid (such as from soya) in the feed improves the level of pigmentation achieved. 2. Highly unsaturated fats have no effect on egg colour, whereas saturated fats tend to increase egg yolk pigmentation. 3. Emulsifiers like lecithin can increase the absorption of carotenoids. 4. Large doses of vitamin E increases absorption of carotenoids and acts as a biological antioxidant in vivo. 5. In feed antioxidants protect feed fat and xantophylls. 6. High in feed peroxide levels (indication of rancidity) affects the in vivo and in vitro stability of carotenoids. 7. High dietary protein levels reduce egg colour and low levels increase it. Lysine levels do not affect colour, but low methionine levels causes lower

5 2/10/2015 :: ADVIT Animal Nutrition TRYPTOPHAN WHAT YOU NEED TO KNOW :: fan numbers. These effects can beesult in up to ½ a fan number. 8. Oversupply of calcium in the diet adversely affects egg yolk colouration do not oversupply calcium beyond necessary dietary levels. 9. With a mild level of aflatoxins contamination, the initial response is an increase in colour due to lower egg output. But in general mycotoxins in the feed reduces serum carotenoid levels and the deposition in the egg. 10. Though impractical in most commercial diets, levels of rice bran above 30 % will reduce egg colour by 1 fan value. 11. When compared with wheat based diets, barley based diets produce egg colour with about ½ fan value lower, with the same carotenoid content. 12. Due to absorption competition, high levels of vitamin A (above IU/kg) negatively affects egg colouration. 13. Colouration is dependant on the amount of carotenoids absorbed into the bloodsream, any factor influencing feed intake like high energy levels or high temperatures will reduce the pigmentation levels of eggs. 14. Metabolic disturbances reducing the secretion of bile acids reduce the absorption of fat soluble carotenoids. Mycotoxins in the feed prevent or reduce bile production, this is one of the major reasons. 15. Diseases that damage the mucosal layer of the digestive tract will reduce absorption. Diseases like Newcastle, salmonellosis, coccidioses or endoparasite infestation causes such damage. Hence the consumer might be right in judging a dark colour as a healthy egg? 16. Older hens absorb nutrients less efficiently and lay slightly lighter eggs than younger hens. 17. Hens laying high numbers of eggs relative to their feed intake will lay eggs with lighter yolks. 18. Flocks should receive sufficient pigment sources 2 to 3 weeks before they come into lay to ensure that they continue laying well pigmented eggs throughout peak. 19. Hot and/or humid feed storage conditions damage the carotenoid molecules and hence their ability to colour eggs. Problem solving process: 1. All eggs produced has poor egg colour: Check calculations r.e. carotenoid levels as well as actual feed carotenoid levels and feed intakes. 2. Assays and calculations are correct and still insufficient colour: Interaction between feed ingredients suspected like rice bran or high levels of saturated fats. 3. Some flocks report poor yolk colour, some flocks red colour: Suspect homogeneity of premix or premix volume (premix quantity too low). 4. Individual flocks report poor egg yolk pigmentation: Localised issue: poor feed storage (mycotoxins), flock age as well as a range of management issues. 5. Should the effect spread from one flock to the other, suspect a disease outbreak. 6. A mottled effect or red tint is indicative of too little yellow pigment in the diet. A poor homogeneity of premixes, or demixing/poorly mixed feed causes a similar effect. 7. REMEMBER that any response to changes in carotenoid level takes about 14 days to take full effect in yolk pigmentation. file:///g:/laptop%20d/limegreen%20backup/work/advit/mailers/2012/07%20september%202012/advit_mailer_may12.htm 5/5