Evaluation of the Dietary Vitamin D₃ Requirement of Modern Broiler Chickens and Partial Replacement of Vitamin D₃ With 25 Hydroxycholecalciferol
Abstract
The goal of this dissertation was to explore the response of broiler chickens to dietary D₃
(vitamin D₃) and 25-OH-D₃ (25-hydroxycholecalciferol) as well as to establish a protocol that
precisely estimated the D₃ requirement of modern meat-type chickens through an oral gavage
bioassay. For this purpose, three research projects were conducted. For the first and second
experiments, broiler chickens were fed a diet devoid of D₃ for 21 d. The first 9 d of the study
served to deplete the maternal stores of D₃. On d-10 of the study, a crystalline source of D₃ was
diluted in corn oil to prepare graded levels of D₃ that were directly gavaged into the crop of birds
for 11 d. Broken-line regression was employed to estimate the requirement of D₃ for maximum
bone mineralization. The first experiment fed a mash corn-soy diet with reduced calcium and
non-phytate phosphorus. The second experiment fed a corn-soy diet as well but as crumbles, and
all nutrients met or exceeded industry-type nutritional requirements. The D₃ requirement of
starter broilers was estimated in experiment-1 to be close to the 500 IU/kg of feed and in
experiment-2 to be around 200 IU/kg of feed for maximum bone mineralization. I concluded that
nutrient restrictions increased the D₃ requirement with respect the NRC (1994), and that maternal
D₃ stores in the yolk highly influenced the growth performance and bone mineralization response
of broiler chickens to dietary D₃. Using industry-type nutritionally adequate diets, the dietary D₃
requirement appears to be in agreement with the NRC (1994).
In the third experiment, broiler chickens were subjected to a coccidiosis vaccine
challenge and fed dietary concentrations of D₃ or a partial replacement of D₃ with 25-OH-D₃.
Results suggested that the combination of both D₃ and 25-OH-D₃ was more effective than D₃
alone in promoting bone mineralization and enhancing vitamin D status as measured by total
plasma 25-OH-D₃ in young (21 d-old) broiler chickens. Additionally, the supplementation of
high dietary levels of D₃, independently of the source, above NRC (1994) recommendations,
yielded better performance, bone mineralization and total plasma 25-OH-D₃ in starter broiler
chickens.
Citation
Leyva Jimenez, Hector Enrique (2018). Evaluation of the Dietary Vitamin D₃ Requirement of Modern Broiler Chickens and Partial Replacement of Vitamin D₃ With 25 Hydroxycholecalciferol. Doctoral dissertation, Texas A & M University. Available electronically from https : / /hdl .handle .net /1969 .1 /174408.