Background: Several studies indicated that dietary organic selenium (Se) usually absorbed better than an inorganic source, with high retention and bioavailability. Dietary Se as an antioxidant element affects the immune system and hematological status in animals. Therefore, the aim of this study was to evaluate the effect of dietary supplementation of bacterial selenium as an organic source on hematology, immunity response, selenium retention, and gut morphology in broiler chickens. Results: The present results revealed that supplementation of inorganic Se was associated with the lowest level of RBC, HB, and PCV with signi cant difference than ADS18-Se. In the starter stage, both T2 and T5 were associated with the signi cantly highest IgG level compared to the basal diet, while all supplemented groups showed higher IgM levels compared to the control group. In the nisher phase, all Se supplemented groups showed signi cant (P 0.05) increases in IgG, IgA, and IgM levels compared to T1. Birds fed bacterial-Se showed high intestinal villus height and better Se retention more than sodium selenite. The organic selenium of ADS18 had a superior action in improving Se retention compared to ADS1 and ADS2 bacterial Se. Conclusion: Bacterial organic Se had a bene cial effect on the villus height of small intestine led to high Se absorption and retention. Thus, it caused a better effect of Se on hematological parameters and immunity response.

The effect of cholecalciferol (D 3 ) and 25-hydroxycholecalciferol (25-OHD 3 ) as isolated or associated sources of vitamin D (100%-0%, 75%-25%, 50%-50%, 25%-75%, 0%-100%) on the productive performance, egg quality, and bone characteristics was evaluated in white egg-laying hens fed two levels of calcium (Ca) and phosphorus (P) in the basal diet (BD) (BD1 = 0.38% Ca -0.36% available P and BD2 = 3.2% Ca -0.30% available P). Nine hundred and sixty Dekalb White hens (24 weeks old) were distributed into 80 cages, under a completely randomized factorial design for 16 weeks. The use of associated sources of vitamin D reduced the feed intake and feed conversion ratio, as well as BD1, which also increased the egg production and egg mass. The association of vitamin D sources with up to 50% 25-OHD 3 increased the eggshell percentage. There was interaction (p<0.05) between the sources of vitamin D and the concentrations of Ca and available P, sources with at least 50% 25-OHD 3 increased ash percentage and bone radiographic densitometry (BRD) with BD1; in BD2 the use of 25-OHD 3 as isolated vitamin D source increased BRD. The association of D 3 and 25-OHD 3 improved the productive performance, increased the percentage of eggshell and had different positive effects on the bone characteristics that depend on the concentrations of Ca and available P in the balanced feed of white egg-laying hens.Index terms: Vitamin sources, productive performance, eggshell quality, bone characteristics. RESUMOO objetivo desta pesquisa foi avaliar o efeito da suplementação de colecalciferol (D 3 ) e 25 hidroxicolecalciferol (25-OHD 3 ) como fontes isoladas ou associadas (100%-0%; 75%-25%; 50%-50%; 25%-75%; 0%-100%) de vitamina D sobre o desempenho, a qualidade de casca e as características ósseas, em galinhas poedeiras de ovos brancos de 24 semanas de idade alimentadas com duas concentrações de cálcio (Ca) e fósforo disponível (Pdisp) na dieta basal (DB) (DB1 = 0,38% Ca -0,36% Pdisp e DB2= 3,2% Ca -0,30 % Pdisp), durante um período experimental de 16 semanas. Foram utilizadas 960 galinhas Dekalb White em delineamento inteiramente casualizado, com oito repetições e doze aves por unidade experimental. Os tratamentos foram constituídos de um fatorial (5x2), associações de vitamina D e concentrações de Ca e Pdisp. As fontes de vitamina D associadase a maior concentração de Ca e Pdisp diminuíram o consumo de ração e a conversão alimentar. Além disso, a maior concentração de Ca e Pdisp incrementou a produção e massa de ovo. A suplementação a partir de 50% de 25-OHD 3 entre as associações de vitamina D aumentou a porcentagem de casca do ovo. Houve interação entre as fontes de vitamina D e as concentrações de Ca e Pdisp. As fontes de vitamina D na DB1 com pelo menos 50% de 25-OHD 3 incrementaram a porcentagem de cinzas e a densitometria óssea radiográfica (BRD). A suplementação de 25-OHD 3 na DB2 como fonte isolada de vitamina D aumentou a BRD.Termos para indexação: Fontes de vitamina, desempenho produtivo, qualidade de casca, caraterísticas ós...