Carotenoid-enriched transgenic corn delivers bioavailable carotenoids to poultry and protects them against coccidiosis

Abstract

Carotenoids are health-promoting organic molecules that act as antioxidants and essential nutrients. We show that chickens raised on a diet enriched with an engineered corn variety containing very high levels of four key carotenoids (β-carotene, lycopene, zeaxanthin and lutein) are healthy and accumulate more bioavailable carotenoids in peripheral tissues, muscle, skin and fat, and more retinol in the liver, than birds fed on standard corn diets (including commercial corn supplemented with colour additives). Birds were challenged with the protozoan parasite Eimeria tenella and those on the high-carotenoid diet grew normally, suffered only mild disease symptoms (diarrhoea, footpad dermatitis and digital ulcers) and had lower faecal oocyst counts than birds on the control diet. Our results demonstrate that carotenoid-rich corn maintains poultry health and increases the nutritional value of poultry products without the use of feed additives.

Keywords: Eimeria tenella; antioxidants; bioavailability; carotenoids; genetic engineering; poultry.

Figure 1

Morphological comparison of chickens fed on the control and high‐carotenoid corn diets. (a) Heads on day 35, showing carotenoid accumulation in tegument structures such as the beak, crest, eyelids and facial feathers in the high‐carotenoid diet group. (b) Dissected thighs showing carotenoid accumulation in the skin and cutaneous structures, in the high‐carotenoid diet group. (c) Cutaneous structures of the feet. (d) Fat surrounding the gizzard. (e) Serum samples. (f) Carotenoid accumulation in the cutaneous structures at the base of feathers in the high‐carotenoid diet group.

Figure 2

Carotenoid levels in broiler breast (upper chart) and thigh (lower chart) muscle presented as μg/g freeze‐dried tissue. Values are means ± SE for control and high‐carotenoid corn (n = 5). ***P < 0.001. Viol, violaxanthin; Lut, lutein; Zeax, zeaxanthin; β‐Cry, β‐cryptoxanthin; β‐Car, β‐carotene; epox, epoxides; ND, nondetectable.

Figure 3

Carotenoid levels in broiler liver. Values are means ± SE for the four diets (n = 3). *P < 0.05. Lut, lutein; Zeax, zeaxanthin; α‐Cry, α‐cryptoxanthin; β‐Cry, β‐cryptoxanthin; ND, nondetectable.

Figure 4

Commercial‐scale trial under farm conditions. Groups of animals were reared on the control and experimental diets. Each group comprised 24 animals (in randomized cages of 12 animals each) separated from the other animals with fences.

Figure 5

Footpad dermatitis and digital ulcer counts (Welfare Quality®, 2009) on the feet of birds in each treatment category on day 19 or 22 in terms of age. Treatment categories: (a) control diet nonchallenged, (b) control diet challenged with E. tenella, (c) high‐carotenoid diet nonchallenged and (d) high‐carotenoid diet challenged with E. tenella. The images show two representative dissected feet from each treatment group at the end of the experiment. Numbers indicate the quantitative values for footpad dermatitis and ulceration. Values are means ± SE (n = 14). Values in the same column with a letter in common do not differ significantly (**0.01 > P > 0.001 based on Duncan's test).