Effect of Bird-Resistant Sorghums and Tannic Acid on Yolk Mottling

In two experiments commercial egg-type hens were fed a corn-soy diet to which up to 4.00 percent tannic acid was added. Additional diets used bird-resistant and non-bird-resistant sorghum grains to replace 60 percent of the yellow corn. The sorghum grains comprised 40 percent of the diet and their tannin content ranged from 0.75 percent for the non-bird-resistant variety to 2.44 percent for one of the bird-resistant varieties harvested in the dough stage. Yolk mottling was significantly increased only when the hens were fed tannic acid as 2.00 and 4.00 percent of the diet. These yolks also exhibited a greenish tint. This study shows that bird-resistant sorghum grain can replace 60 percent of the yellow corn of laying hen diets without affecting yolk mottling scores and that a 100 percent substitution of a mature stage bird-resistant variety would not be likely to have any deleterious effect on yolk mottling or discoloration.