Effects of 25‐hydroxycholecalciferol with two D3 vitamin levels on production and immunity parameters in broiler chickens
The current National Research Council (NRC)‐recommended (1994) level of vitamin D3 supplementation is 200 IU/kg; however, this value is intended only to avoid vitamin deficiency and is much lower than the level used to increase production (5,000 IU/kg) in the poultry industry. Using 25(OH)D3 is associated with a number of advantages compared using to vitamin D3 and its other metabolites. For example, 25(OH)D3 exhibits better intestinal absorption because its polar nature allows absorption to occur by passive diffusion; in contrast, the absorption of vitamin D3 requires micelle formation (Calabotta, 1997). Furthermore, once it is in the bloodstream, 25(OH)D3 has a higher affinity for its carrier protein and a longer half‐life. Thus, the serum level of 25(OH)D3 is an excellent indicator of vitamin D3 status or availability (Soares, Kerr, & Gray, 1995). Given these factors, the present study seeks to evaluate the effects of dietary 25(OH)D3 supplementation on the growth and immunity of broilers.