Pigmenting eggs and broiler chickens
Carotenoids in nature
Birds and mammals are unable to synthesize carotenoids, and therefore rely upon food sources to obtain them. In the wild, birds do this by consuming seeds, insects and molluscs, so that the carotenoids are absorbed and deposited (depending on gender) in different organs. In male birds, carotenoids are deposited in the feathers, giving them the coloring that allows them to stand out and attract females (and predators). Only the healthiest males can display these bright colors, as carotenoids need to be ingested, absorbed and deposited. As a result, there needs to be mobility, intestinal integrity and also immune integrity in order for the birds not to have to use carotenoids as antioxidants or as sources of vitamin A1.
Females (according to the species), on the other hand, need to keep a low profile to avoid attracting predators. As such, they deposit all carotenoids in the fat and in particular in the ovaries, where they are converted into a source of antioxidants, enabling the future embryo to avoid the oxidative stress associated with the transformation from fertilized egg to chick2.
Use of carotenoids in poultry farming
The use of carotenoids for modifying bird parameters began with a non-domestic species. In the mid-20th century, flamingos kept in captivity were not reproducing effectively and or preserving the pink color that was so characteristic of their cousins in the wild. Biologists from Basel Zoo collaborated with scientists from Hoffmann-La Roche and discovered the diet of animals in captivity was lacking the carotenoids necessary for reproduction, so they set themselves the task of supplementing canthaxanthin in specimens. As a result, this became the first group of flamingos in the world to breed in captivity and retain the color that characterizes their cousins in the wild3.
On the other side of the Atlantic, the emerging Mexican poultry business was facing consumer rejection. As poultry farming became industrialized, the change from yellow corn to sorghum caused eggs and chickens to lose their distinctive pigmentation, leading consumers to reject the new farm-reared chickens and egg yolks with their inferior shade. A group of Mexican scientists led by Dr. Sergio Brambila from the National Institute of Livestock Research (INIP, now known as INIFAP) was tasked with solving the problem. Using alfalfa was one possibility, but it was expensive and impractical.
Dr. Brambila and the chemist Carmen Mendoza found that Aztec marigold, a rich source of the carotenoids lutein and zeaxanthin, provided a cheap and readily available alternative for adding pigment to chicken and egg yolk4,5. This sparked the beginning of the multi-million dollar marigold flower industry, today the primary source of lutein for animal and human consumption.
Carotenoids perform a number of important metabolic roles; acting as visual communicators through mimicry and coloration, vitamin A precursors, immune modulators and antioxidants. The carotenoid structure can determine its function. Those with nine or more conjugated double bonds possess superior antioxidant properties. It has been proven that eggs containing canthaxanthin possess superior antioxidant capacity than those without6. In addition, chicks from hens fed with canthaxanthin have macrophages with a superior bactericidal capacity and therefore improved immune function7.
Egg yolk pigmentation
Preferences for a certain yolk color are highly variable depending on the given culture and country. Some market research studies conducted over the last decade indicate that in several cultures there is a preference for dark orange-colored yolks as a reflection of the product's internal quality. In the studies mentioned, yolks with a dark orange shade (DSM Yolk Fan score > 13) are preferred in up to 60% of cases in various countries across Europe, America and Asia. The consumer associates the yolk's intense color with an egg that is fresh and rich in nutrients. What is certain is that a pigmented egg will always come from a healthy hen8, as compromised nutrient absorption results in a loss of pigmentation in hens and broiler chickens9.
Another important factor in some markets is the use of carotenoids to differentiate between eggs from certain brands or with certain nutritional properties. In a recent study in Beijing, it was discovered that for every unit of increase in YolkFan™, the price rose by 0.18 RMB (approx. $0.025) per egg. In other countries and markets, it is also common to increase pigmentation for products enriched with omega 3 or free from antibiotics. In India, the yolk color is displayed on the egg brand's external packaging.
The most commonly used carotenoids for egg pigmentation are canthaxanthin and paprika extracts for the red base, while apo-ester and lutein/zeaxanthin (marigold, or targets) are used for the yellow base. Corn and its co-products (gluten, DDGS) are recognized as a good source of carotenoids (particularly lutein/zeaxanthin).
The recommendations are clearly established and guide a process that can be followed without any major obstacles, providing that:
- The exact carotenoid content of various sources is known.
- The formulation is determined and adjusted to consider losses during the process. The important value is what the bird has in its feed trough.
- An optimal mixing process is maintained. It is preferable to incorporate pigments in the premix.
- Animals are kept free of health problems.
These are essential to ensure eggs command the highest value and maintain brand reputation and quality standards. The source of carotenoids must be stable, consistent and demonstrate good bioavailability.
In very specific markets, chicken skin color is very important and considered a symbol of quality, freshness and nutritional value. In markets such as Mexico, Spain, France, Italy and China, chickens are sold with skin color variations ranging from yellow to golden orange. In broiler chickens, carotenoids are primarily deposited in the feet, skin and subcutaneous fat. Slaughter and plucking conditions are also very important. The carotenoids used for skin pigmentation are canthaxanthin for the red base, and apo-ester and lutein/zeaxanthin for the yellow base. Pigmentation recommendations are very varied and depend on regional and market requirements. However, the common denominator in consumer demand is color homogeneity.
In Europe, a system based on a fan10 is used which serves as a standard for setting targets and evaluating them, as well as a formulation program that considers the carotenoid sources available in order to achieve various pigmentation targets. The program is perfectly adapted to European and Asian conditions of medium pigmentation and is a well established method.
In order to be able to pigment chickens successfully, all the above mentioned precautions mentioned for eggs must be followed, in addition to the following specific guidelines for chickens:
- The scalding temperature must be kept below (but close to) 54°C.
- Pigment carotenoids must be present in the feed for at least three weeks prior to slaughter.
- In the summer, consumption must be monitored and adjustments made to the formulation so that pigmentation is not affected. In some conditions, carotenoids can be used in the drinking water in order to fortify it.
Measuring color it is always a case of evaluating something subjective which depends on reflected light, the color of the surroundings, the light present and the observer's eye. However, procedures have been refined over the course of the last and current century, and will continue to be refined over time.
The DSM Yolk Fan™ is the reference standard for setting egg pigmentation targets. It is easy to use, effective and economical. Even though there may be variations between observers, it also provides a universal language for talking about color. This tool is also used in several markets to measure foot pigmentation.
In order to get the maximum value for your eggs and boost the consumer experience, use safe and reliable carotenoids in the feed.
1 Chew, B. 2010. Proceeding 31st Western nutrition Conference. Saskatoon, Sask.
2 Blount, J.D., et al., 2000. Trend. Evol. & Ecol. 15:49
3 Thommen, H. y Wackernagel, H. 1963. Biochemica Biophysica acta. 69:387
4 Brambila et al., 1963. Poult. Sci. 42:294
5 Cuca, M. et al. 1963. Tec.Pec.Mex. 1:39
6 Zhang, et al.2011. 90:1516.
7 Johnson, et al., 2011. The Effect of Canthaxanthin and Hen Age on Chick Innate Immunity. Abstract. PSA meeting. St. Louis, Mo.
8 Fernandez, S. 2010. Western Nutrition Conference. Saskatoon, Canada. September.
9 Tyczkowski, et al. 1991. Poult. Sci. 70:2275
10 Hamelin, C. and Hernandez, J.M. 2010. XIIIth European Poultry Conference, Tours, 23-27 August