Failure of two feed additives (shell-developer and ethacal) to improve eggshell quality

Two feed additives were tested for their ability to improve eggshell quality. One was Shell-Developer, containing approximately 60% NaHCO3, and the other was Ethacal, a sodium aluminosilicate. Both feed additives were fed to three commercial strains of hens. The first trial began in early summer and lasted 28 days, the hens having been in production for 56 wk at the start of the trial. Ethacal was fed at a rate of .75% of the diet. Shell-Developer was fed at a rate of 1.25% of the diet for 7 days, .625% for the next 7 days, and .3125% for the last 14 days. The second trial ran for 56 days in autumn utilizing the same hens after a forced rest and approximately 2 mo of production. The addition of Shell-Developer had no positive effects at any time on any of the characteristics measured. Ethacal had a negative effect on the rate of egg production and egg weight during the last 28 days of Trial 2. Ethacal also decreased feed consumption in three of the five data collection periods tested. In Trial 2 Ethacal significantly improved egg specific gravity and also improved the percentage of eggs with a specific gravity of at least 1.08. The negative effect of Ethacal on egg production and egg weight is postulated to be due to its negative effect on phosphorus nutrition