Abstract

Levels and forms of vitamin D in broilers diets

This study aimed to evaluate the concentration effects of two vitamin D isoforms, cholecalciferol (D3) and 25-hydroxycholecalciferol (25-OHD3) in broilers diets on performance, bone and physiological features of these birds. Of a total of 1920 one-day-old male chicks Cobb-500 were used from commercial hatchery, reared under bed creation systems. The animals were distributed in six treatments and eight replicates with 40 birds per treatment in a completely randomized design. The following vitamin D supplementation levels were applied: 70 and 87.5 μg/kg feed in initial phase; 56 and 70 μg/kg feed during the growth phase, and 35 and 47.35 μg/kg of feed in final phase of creation, obtained from two forms (D3 and 25-OHD3). The treatments consisted of supplementation of two levels from each isolated source and their associations (60% D3 + 40% 25-OHD3) according to the study phases. In the metabolism assay, 480 birds (14 and 35 days of age) were separated to be used for evaluation of calcium (Ca) and phosphorus (P) retention and excretion during the periods of 19 to 21 days and 40 to 42 days of age. The diets were based on corn and soybean meal, with supplementation of phytase (500 FTU/kg). The performance, bone characteristics, plasma levels, bone radiographic density, carcass yield, and P and Ca retention were evaluated. In the initial creation phase, we observed an increased P excretion by broilers fed diets supplemented with vitamin D3 (P 3 (P 3 (P 3 at 87.5 μg/kg resulted in higher plasma levels of Ca in relation to the same supplemented source with 70 μg/kg at 21 days of age (P 3 presented the lowest values of consumption and retention of Ca and P (P 3 and 25-OHD3) reduced the excretion values of Ca and P (p 3 and the association had better feed conversion ratio and higher bone ash content (P 3 + 25-OHD3 combined supplementation increased tibial density of broilers in relation to supplementation of only vitamin D3 (P 3 in the feed supplemented with vitamin D3 improve the feed conversion, increase the Ca plasma levels, and also increases bone density, providing higher retention coefficients of Ca and P and lower P excretion, regardless of the development phase of these birds.

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