RESUMEN
This study was performed in Ross 308 chickens aged 1-21 days and aimed to evaluate whether the addition of 25-hydroxycholecalciferol (25(OH)D3 ) to broiler chicken diets affects their growth performance and immunity. A completely random 2 × 2 factorial arrangement was used with two levels of vitamin D3 and the absence or presence of 25(OH)D3 , corresponding to four treatments based on sorghum + soya bean diets: (i) 200 IU of vitamin D3 /kg of feed (Diet 1) (NRC, ), (ii) Diet 1 + 69 µg of 25(OH)D3 /kg of feed (Diet 2), (iii) 5,000 IU of vitamin D3 /kg of feed (Diet 3) and (iv) Diet 3 + 69 µg of 25(OH)D3 /kg of feed (Diet 4). Each treatment was conducted with six replicates of 10 chickens each. Water and feed was supplied ad libitum. The results showed significantly increased growth and tibia ash (p < .05) in the birds fed 5,000, IU of vitamin D3 /kg + 25(OH)D3 . Additionally, the cellular immune response increased significantly (p < .05) in both treatments with added 25(OH)D3. Based on the results obtained under the current test conditions, the addition of 25(OH)D3 at a rate of 69 µg/kg to diets containing vitamin D3 improved the cellular immune response and mineral deposition in the bones of broilers aged 1-21 days. Because these parameters are very important in modern poultry farming, these results indicate that supplementation with 25(OH)D3 should improve broiler production.