The effect of changing the excreta moisture of caged laying hens on the excreta and microbial contamination of their egg shells.

1. An experiment that included 1440 caged laying hens in 24 experimental units was conducted to determine the effect of differences in excreta moisture on the proportion of dirty eggs and the microbial contamination of eggs that were ostensibly uncontaminated by excreta. Excreta moisture contents were changed by giving the hens diets that contained 4 different concentrations of sodium. 2. Diets containing 1.6, 5, 10 or 15 g/kg dietary sodium were fed ad libitum to 1140 laying hens for a 12-week feeding period. A sample of excreta was collected from each experimental unit each week and its moisture content determined. All eggs produced were classified as clean or dirty according to the European Community Egg Marketing Regulations. A sample of eggs were collected from each experimental unit on 4 separate occasions in the last 4 weeks of the feeding period and the total bacterial numbers on ostensibly clean egg shells were determined. 3. Increasing dietary sodium concentration gave linear (P<0.01) increases in excreta moisture. Each 100 g/kg increase in excreta moisture increased (P<0.001) dirty egg numbers by 0.52% of the total eggs produced. Increasing excreta moisture gave a linear increase (P<0.001) in the (log-transformed) numbers of microorganisms that contaminated ostensibly clean egg shells.