Adverse responses in egg shell quality in late-lay resulting from short-term use of saline drinking water in early- or mid-lay

Three experiments were carried out to determine the long-term responses in egg shell quality when hens were given saline drinking water for only a few weeks either at the start of lay or in mid-lay. Shell quality of eggs from hens given town water containing an additional 2 g sodium chloride (NaCl)/L as drinking water for periods of 5 or 6 weeks prior to 30 weeks of age or between 48 and 53 weeks of age was significantly poorer at the end of lay than shell quality of eggs from hens given town water throughout lay. Apart from these short periods of saline water supply the NaCl-treated hens received town water throughout lay. Shell defects were increased significantly after 55 weeks of age even when no apparent detrimental effects of saline drinking water on shell quality were observed during the period of saline water intake or when the incidence of shell defects returned to normal after the replacement of saline water with town water. The results indicate that the adverse effects of saline drinking water on egg shell quality is of long-term significance, being especially noticeable towards the end of lay.