Animal diets have developed over the years to provide optimised nutrition, and this includes an increased focus on nutrients such as vitamins and minerals. A good example is vitamin D, mainly known for its involvement in calcium metabolism and bone strength.
However, there is more to vitamin D than this. Apart from its proven antimicrobial and anti-inflammatory activities, the vitamin has a role as an essential immunological mediator. Vitamin D (sub) deficiencies are also associated with increased mortality and immunological responses, highlighting the broad importance of the vitamin itself. This has led to more recent research focusing on the use of different vitamin D metabolites to improve immunity under stress, underlining the importance of proper vitamin D supplementation in poultry.
25-OH vitamin D3 put to the test
One of these trials evaluated the use of 25-OH vitamin D3 in animals under a highly infectious bronchitis virus (IBV) challenge. The economic importance of this virus speaks for itself, while a 25-OH metabolite was chosen for the trial as it is one of the most effective metabolites for animal supplementation.
The trial aimed to evaluate the hypothesis that dietary supplementation of 25-OH vitamin D3 could reduce the impact of the virus through decreased shedding of the virus itself as well as improving the immunocompetence of birds under these conditions.
To do so, 1,000 one-day-old Ross 308 broilers were evaluated for 35 days in a trial conducted in Egypt. The birds were vaccinated at hatch for infectious bursal disease (IBD) and received two different live attenuated IBV vaccines on day 4 and day 18. Birds were divided at random into four groups (10 replicates per group, 25 birds per replicate) and reared under commercial conditions. These four groups included a control (basal diet, standard vit D3 at 5,000 IU/kg feed) and three 25-OH vitamin D3 supplementation groups as follows:
- Bio D® 100: control diet + 100 g Bio D®/ton of feed (total of 5,558 IU vit D3/kg feed)
- Bio D® 300: control diet + 300 g Bio D®/ton of feed (total of 6,673 IU vit D3/kg feed)
- Bio D® 500: control diet + 500 g Bio D®/ton of feed (total of 7.784 IU vit D3/kg feed)
Bio D is a source of 25-OH vitamin D3, a metabolite of vitamin D3, produced via microbial fermentation. This specific production process sets it apart from other 25-OH vitamin D3 options on the market as it results in unique product characteristics. A formulation containing 69.7 mg 25-OH vit D3/kg product was used in the current trial, known as Bio D 500.
Mortalities were recorded daily during the challenge, as well as body weight and feed intake. Virus shedding was analysed by qRT-PCR of tracheal swabs on days 3, 5 and 7 post-challenge. At the end of the experiment on day 35, blood samples were collected from the wing vein of 10 randomly selected chickens from each group to further analyse blood and immunity parameters. Cell-mediated immunity gene expression was evaluated via cytokines gene expressions (interferon-ү and interleukin-10). Finally, the European production efficiency factor (EPEF) was calculated at the end of the trial.
Results
There was a clear and positive dose-response relationship between survival, recovery and immunity on one hand, and Bio D inclusion on the other hand. The results of the trial are presented in two Technical Bulletins (TBs). Click the links below to open and download the TBs:
Mortality and recovery
Immunity
Consequently, treatments with Bio D noted higher EPEF values. An EPEF value of 403 was calculated in the control group, whereas values of 420, 432 and 439 were calculated with the increasing Bio D concentrations.
Conclusion
Vitamin D has a wide metabolic impact and plays an important role in immunity. Supplementing an effective metabolite of the vitamin in the form of Bio D, containing 25-hydroxy vitamin D3 produced via fermentation, brings clear benefits during immunity challenges. These results underline the importance of proper and continuous vitamin D supplementation during production.
