Animal diets have developed over the years, with an increased interest in nutrients such as vitamins and minerals. A good example is vitamin D, mainly known for its role in calcium metabolism and bone strength (Khan et al., 2021).
However, there is more to vitamin D than this. Vitamin D (sub-)deficiencies have been clearly associated with increased mortality and reduced immunological responses, highlighting the broad importance of the vitamin beyond skeletal integrity (Khan et al., 2021; Hashim et al., 2023). This has led to more recent research focusing on the use of different vitamin D metabolites to improve other parameters in poultry, including those relevant to broiler-breeders. Of these metabolites, 25-hydroxy vitamin D3 is of major interest as it:
- has a long half-life
- acts as the major reserve form of vitamin D within the body
- does not rely on the liver in the remainder of the metabolic vitamin D pathway (Sakkas et al., 2018)
Within the group of 25-OH D3 metabolites, the main difference comes down to the production process: either via a synthetic pathway or via fermentation. To evaluate the first commercially available 25-OH D3 from fermentation, Bio D® (Huvepharma) was put to the test in two broiler-breeder trials.
Both trials were performed at a commercial research centre in France with the treatments listed in Table 1. For the first trial, a total of 1080 female broiler breeders from the Hubbard D line were used. These were divided at random into three batches of 360 female broiler breeders each, divided over 45 replicates of 24 females each (4 hens/cage x 6 cages/replicate). The trial ran for 70 days, from week 52 to 62 of age. Egg quality and embryo mortality were evaluated at two different time points (57 and 62 weeks of age).
For the second trial, a total of 720 female broiler breeders from the Hubbard D line were used. These were divided at random into three batches of 240 female broiler breeders each, divided over 10 replicates of 24 females each. The trial ran for 105 days from week 48 to 62 of age. In this trial, hatching performance as well as day-old chick (DOC) and embryo mortality were evaluated.
In the first trial, inclusion of Bio D in the feed significantly improved mortality parameters in a dose-response fashion (Figure 1). Broiler breeders in the Bio D groups also showed an improved egg quality (Table 2).
In the second trial, supplementing Bio D significantly decreased embryo mortality both in terms of early mortality (<7 days) and totals, while DOC mortality improved numerically. Similarly, broiler-breeders in this group showed a significantly better hatching performance compared to the control (Table 3).
In both trials, the addition of 25-OH D3 had clear benefits related to the performance of broiler-breeders. The observed effects occurred in a dose-response manner in Trial 1 and were most pronounced in mortality-related parameters.
The current hypothesis to explain these results would be a maternal transfer of 25-OH D3 to the developing eggs, where the increased levels of vitamin D support the early development of the embryo. This transfer hypothesis is supported by the established use of dietary vitamin D to increase final vitamin D levels in eggs for human consumption, known as a "functional food". Regarding improved eggshell quality, the role of calcium in the formation of eggshell is well-established. As vitamin D is closely linked with calcium metabolism, improving the vitamin D status of the animal impacts its calcium metabolism as well.
The results underline the importance of adding an effective 25-OH D3 metabolite in broiler-breeder operations, even if animals are already supplemented with standard levels of regular vitamin D3. Thanks to its unique 25-OH D3 from fermentation, Bio D offers a great solution to do so.