The use of carotenoids in post-War poultry diets
After the World War II, the spread of intensive farming methods accelerated, and with it, egg production. Poultry feed was wheat-based in Europe. However, the main problem was the color of the yolks, which were not yellow enough for the taste of the European consumer The yolk color depends its carotenoid content, in terms of quantity and type; and this is highly influenced by the type of feed, as described by Hughes and Payne as far back as 1937. It was clear, then, that if the yolk color were to be intensified in a natural way, it would be necessary to include carotenoids in the feed of the laying hen. Roche consequently examined the possible use of nature-identical carotenoids, produced by industrial methods, as feed additives (Isler et al., 1956). By 1956, the German egg market was surprised at the appearance of the first yolks pigmented with synthetic carotenoids. The innovation was a success, giving consumers the opportunity to enjoy eggs with a vibrant shade of orange in the winter, just as they were in the summer, when hens have access to plenty of green vegetation (an excellent source of carotenoids). The addition of beta-carotene, canthaxanthin and, later, apo-ester became a fundamental element in successful egg production and marketing worldwide. (On a side note, the first ever synthetic canthaxanthin, produced by F. Hoffman-La Roche, was partially responsible for the first ever successful flamingo breeding event in captivity, which occurred at Basel Zoo in 1958.)
The development of the Yolk Color Fan
However, as with any other productive activity, it was necessary to measure the success pigmentation programs, and the only way to do this was by evaluating yolk color in an objective and consistent way across the value chain. This was quite a task, as described in 1970 by K. Streiff, an agronomist working for Roche, when he outlined the journey towards the first ever Yolk Color Fan. The ways available for measuring color at that time were either subjective and inconsistent (DIN-Tables, Heiman-Carver Rotor, or the Lovibond tintometer), cumbersome (the NEPA system), or else made use of light absorption of the yolk mass in a photometer. Neither of these methods were user-friendly for poultry producers, nor were they consistent and objective, so Roche’s Art Department of Roche commenced an initiative to collect eggs from all over the world (imagine coordinating that daunting task in the late 1950s!) and trying to reproduce the color of the various yolks in combinations of round, oval, square and elongated shapes of wood or plastic. The result was the first ever Yolk Color Fan, which was produced in 1956, with 12 egg-yolk shades, each on a separate blade. The color sheets were spray-dyed press-board lamellae of 3 cm x 16 cm. The paint was blended by hand, and the match was checked by mere visual comparison. This first fan was distributed in a limited fashion, but it played a critical role in establishing the basis of a standardized system for measuring yolk color from the farm to the consumer’s kitchen table (Steinegger and Zanetti, 1957). The situation changed when apo-ester became available for yolk pigmentation, since it was evident that a wider range of orange-yellow hues was available and therefore the 12-blade version of the fan was no longer enough.
From the Roche to the DSM Yolk Color Fan
The 1965 edition of the Yolk Color Fan contained 15 colors and was based on the “tristimulus values” of the standard C.I.E. system of 1931, as described in the classic paper by Vuilleumier in 1969. A “yolk color band” was constructed as the range of hues in to which all the desirable yolk colors known can be placed, from a very pale shade to the most intensive hue. This version of the fan grew in acceptance, and despite minor corrections in 1984 (involving better colorimetric and printing techniques) it is still regarded as the standard guide to egg yolk color around the globe, being published in various versions and languages (Figure 2). In 2003, Roche’s Vitamins & Fine Chemicals Division was acquired by DSM B.V. and renamed DSM Nutritional Products. From that years, production of the Roche Yolk Color Fan ceased that year, making way for production of the DSM Yolk Color Fan (Figure 3), the successor to this long tradition of tools for measuring yolk color. This edition of the fan helped to launch the concept of MaxiChick® , by measuring the color of the yolk of breeders in order to measure the deposition of canthaxanthin in the yolk with the subsequential influence on fertility, hatchability and chick vitality (Figure 4). This is also reflected in the color of the shanks.