Scientifically Speaking …
By Matthew Wedzerai
CAROTENOID-ENRICHED CORN IMPROVES EGG QUALITY
The replacement of synthetic carotenoids and extracts with biofortified cereals improves egg quality and health of chickens while reducing the costs of poultry feed.
Since chickens cannot synthesize carotenoids, they have to get them through the feed. Natural pigments such as marigold flower rich in lutein and zeaxanthin, paprika rich in capsanthin, and canthaxanthin, or synthetic pigments such as β-apo-8’-carotenal have to be added to poultry feed to meet consumer demands and health benefits, but this results in an increase in production costs. As an alternative to carotenoid additives, carotenoid-enriched
feedstuffs can be developed by engineering the carotenoid biosynthesis pathway. Carotenoids are antioxidants that protect cells against oxidative
stress and improve the performance of the immune system. However, some of these carotenoids are also vitamins with essential biological functions. Carotenoids in poultry feed are used to achieve the characteristic yellow-orange colour of egg yolks and skin. The results of two studies described in this article (Moreno et al.,
2019 and Nogareda et al., 2016) review the benefits of carotenoid- enhanced corn on egg quality and health status of chickens against coccidiosis.
Consumer preference Several surveys confirm that yolk colour is the first parameter of yolk quality and that it generally ranks third amongst egg quality parameters, after freshness and eggshell quality. Consumers seem to attach more importance to this internal quality parameter than size of the egg or eggshell colour. Yolk colour is a primary yolk quality parameter because it has an immediate visual impact on consumers, who are known to prefer darker colour yolks (Englmaierová et al., 2014; Lemahieu et al., 2014).
Study 1 Two diets were formulated with genetically engineered maize lines (Ph3 and BKT, with enhanced levels of carotenoids and ketocarotenoids, respectively). Two additional diets were formulated with the near isogenic white South African inbred maize (M37W) and standard commercial yellow maize (SC). The four different experimental diets were designated as follows:
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(a) Ph3 - supplemented with genetically engineered maize enriched in carotenoids. (b) BKT - supplemented with genetically engineered maize enriched in ketocarotenoids. (c) M37W - supplemented with wild-type M37W white maize; and (d) SC - supplemented with standard commercial yellow maize.
Egg yolk colour Hens fed on diets based on the Ph3 and BKT lines produced egg yolks with higher DSM colour index scores and had abundant carotenoids than white maize (M37W) and standard yellow maize diets (SC).
Egg production There were no significant differences for egg production indicators among treatments, however, hens fed on the SC and BKT diets laid significantly heavier eggs (67.5 g and 66.3 g, respectively) than M37W (65.7 g) and Ph3 groups (62.6 g). The egg production (hen- day %) was higher for the Ph3 and BKT diets (83.1% and 84.4%, respectively) than the white maize and yellow maize (79.4% and 82.5%, respectively).
Total carotenoids Visual yolk colour is not always a good indicator of total carotenoid levels in the yolk due to the differences in pigment range and intensity contributed by different carotenoid molecules (Karadas et al., 2006). High-performance liquid chromatography (HPLC) analysis showed that the yolks from the Ph3 treatment group accumulated more than double the carotenoid content of yolks from the BKT treatment group (57.5 and 26.2 μg/g feed, respectively) despite the lower DSM colour score, mainly reflecting the abundance of red-pigmented astaxanthin in the BKT yolks. The white maize (M37W) and the yellow commercial maize (SC) had low total carotenoids content of 1.81 and 11.5 μg/g feed, respectively. The Ph3 maize line increased the content of α-carotene,
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