Re-evaluation of sodium requirement of commercial laying hen

Two experiments were conducted with 36-wk old Hy-Line(R) W36 hens to determ ine their Na requirement. A corn-soybean basal diet was used which containe d 0.056% Na. Hens were maintained in individual cages and fed diets contain ing Na levels of 0.056, 0.078, 0.100, 0.122, 0.144, 0.166, 0.188 and 0.210% in Experiment 1. The levels of 0.188 and 0.21% Na were not fed in Experime nt 2. Supplemental Na was provided by NaCl. The city water contained 9 ppm Na. The first 2 wk were considered as a depletion period with Wk 3-8 used t o measure treatment effects in Experiments 1 and 2, respectively. Reducing the daily Na intake below 114 and 110 mg/hen in Experiment 1 and 2, respect ively, resulted in a significant decrease in egg production beginning the s econd wk. As the level of Na decreased, egg weight, feed intake, hatchabili ty and body weight gain decreased. Broken line regression of Na intake on e gg content and egg production indicated a daily Na requirement of 113 and 1 02 mg/hen per d, respectively. In Experiment 2 the requirement for egg prod uction was 99 mg/hen per d.