Calcium and Phosphorus Content of Strong and Weak Chicks from Hens with and without Calcium Carbonate in Their Diet1

It has been estimated that under ordinary conditions from 5 to 10 per cent of all chicks hatched are weaklings that cannot be raised successfully to maturity and for this reason are destroyed by the intelligent poultryman. The cause of this condition has been attributed, 1, to a tendency of hens which have been laying heavily during the winter to lay eggs having weak germs the subsequent spring; 2, to improper care of the breeding stock, such as improper housing, feeding and sanitary conditions, which undoubtedly have a weakening effect on t.he chicks; and 3, to improper conditions during incubation. In an effort to throw more light on this complicated subject an experiment was planned to study from a chemical standpoint, the conditions resulting from the feeding of a grain-buttermilk ration, with and without a calcium carbonate supplement, to laying hens. The authors have shown (1924) that when a calcium carbonate supplement such as oystershell or limestone is added to a grain-buttermilk ration for laying hens, the tot.al number of eggs is greatly increased and the contents or edible portion of the eggs and the shells weigh distinctly more than those from similar hens having been fed the same ration without the calcium carbonate supplement, and that under the same conditions (1925a) both the yolks and whites are increased in size, when the calcium carbonate supplement is added. They have shown further (192513) that the hatchability of eggs is markedly diminished by withholding the calcium carbonate supplement from the laying hens. Cross (1912) has stated that “the weak chick is equally as rich in phosphorus as the strong chick. The chicks are designated weak and strong according to their ancestry. There is, of course, a possibility of the offspring of weak parents being strong and vice versa, so conclusive proof is not here shown,” and finally concludes in the summary that “the weak chick is equally as rich in phosphorus as the strong chick.”