The vitamin D3 requirement of broiler breeders

An experiment was conducted with 25- to 66-wk-old Ross broiler breeders in an environment excluding ultraviolet light to determine the cholecalciferol (D-3) requirements for hen day egg production; hatchability; body weight of the progeny at 1 d; embryo mortality during the early (1 to 10 d of incubation), middle (11 to 15 d of incubation), and late stages (16 to 21 d of incubation) of development; egg weight; specific gravity; and body ash of the progeny at 1 d of age. Five levels of vitamin D-3 (125, 250, 500, 1,000, and 2,000 IU/kg of diet) were fed to hens from 25 to 66 wk of age. One additional group was fed no supplemental D-3 until 36 wk of age and was then changed to 4,000 lU/kg of diet. Separate regression analyses were performed for wk 27 to 36 (peak original design) and for wk 37 to 66 (postpeak production modified design). The D-3 levels for the predicted maximum hen day egg production during peak and postpeak were 1,424 and 2,804 IU/kg, respectively. The D-3 levels for the predicted maximum hatchability were 1,390 IU/kg (peak) and 2,708 lU/kg (postpeak). The level of D-3 that resulted in the minimum early embryo mortality was 1,288 IU/kg at peak; however, no significant effect was observed at postpeak. The D-3 levels for minimum middle stage embryo mortality were 1,130 IU/kg (peak) and 2,568 IU/kg (postpeak) and for late stage embryo mortality were 1,393 IU/kg (peak) and 2,756 IU/kg (postpeak). The D-3 level for maximum egg weight was 1,182 IU/kg (peak) and for specific gravity was 1,337 IU/kg (peak) and >2,000 IU/kg (postpeak). The D-3 level for maximum body ash of progeny at d 1. was >2,000 IU/kg. Analysis of the data from the original design of the experiment (treatments providing 0, 125, 250, 500, 1,000, and 2,000 IU of vitamin D-3/kg for the 27- to 36-wk-old birds) indicates a requirement of approximately 1,400 IU of D-3/kg of feed for broiler breeder hens. When the data from the modified experiment (37 to 66 wk of age) include conversion of the treatment provided at 0 IU of D-3/kg to a treatment providing 4,000 IU d D3/kg, the requirement may be approximately 2,800 IU of D-3/kg.