Increasing vitamin D content of eggs

Nutritionists and agricultural scientists at Germany’s Martin Luther University Halle-Wittenberg (MLU) say the findings, published in the journal Poultry Science, can be put into practice in henhouses immediately.

Many people suffer from vitamin D deficiency, which as well as causing brittle bones can lead to an increased risk of respiratory diseases. During the summer, people are able to cover about 90% of their daily requirements themselves since it forms naturally in the skin through exposure to sunlight. The remainder is ideally consumed through food, such as eggs or oily fish.

However, the lack of sunshine during the winter and lifestyle choices prevent people from getting enough vitamin D throughout the year, and this led researchers to look to increase the amount of the vitamin in food.

MLU nutritionist Dr Julia Kuhn said: “The idea was to stimulate the natural vitamin D production of chickens. Using UV lamps on the hen houses would increase the vitamin D content of the eggs.”

In earlier studies, the researchers were able to prove the fundamental success of their approach when they illuminated the legs of the chickens with UV light but the experiments were always conducted under ideal conditions with one bird receiving one light.

The new study aimed to test the practical feasibility of the method and was conducted on two holdings with comparisons made between two different chicken breeds (Lohmann Selected Leghorn hens and Lohmann Brown hens), assorted lamps and different durations of light exposure per day.

The researchers not only continuously analysed the vitamin D content of the newly laid eggs during the trial period – they also investigated the impact the additional light had on the birds.

Professor Eberhard von Borell, an expert in animal husbandry at MLU, explained: “Humans cannot see UV light, but chickens can. Therefore, light regimes are a critical aspect in chicken husbandry because light influences behaviour and laying activity.”

His working groups analysed the behaviour of the animals using video recordings, and researchers also inspected the chickens’ plumage for injuries but other members in order to assess their potential for activity and aggression.

Results

The results showed that after only three weeks of UV light exposure for six hours per day, the vitamin D content of the eggs increased by 3.7-fold in eggs from the Lohmann Selected Leghorn hens and 4.2-fold in the Lohmann Brown hens. This value did not rise any further in the following weeks.

The additional UV light did not cause any problems for the hens – they neither avoided the area around the lamps, nor did they act differently.

As a results, researchers conclude that their method also works under practical conditions and this could represent an important step forward towards supplying the population with vitamin D.

• The study, “Feasibility of artificial light regimes to increases the vitamin D content in indoor-laid eggs,” was supported by the Competence Cluster for Nutrition and Cardiovascular Health, and funded by the Federal Ministry of Education and Research. It was published in Poultry Science.