The use of fly ash in diets of cage and floor broilers

Three experiments were conducted to compare limestone to fly fly ash from a coal-fired generator station as a calcium source for broilers. In Experiment 1, 5 male and 5 female broiler chicks were placed in each of 32 cages. Sixteen cages of birds were fed a ration with limestone supplying 30% of the total calcium and 16 cages were fed a ration with 30% of the total calcium supplied by fly ash. The total calcium and phosphorus levels of the rations were 1.0% and .5% respectively. In this experiment no significant difference (P < .05) was found for 8-week body weight between diets where the added calcium was from limestone or fly ash. In Experiment 2 a group of 40 male and 40 female cage reared broilers and 40 male and 40 female floor reared broilers were fed a basal diet of limestone providing 33% of the total calcium. Three diets with increasing fly ash levels were fed to three cage groups of 40 male and 40 female broilers providing 33, 46, and 45% of the total calcium of .9, 1.1, and 1.8%, respectively. Broilers fed the highest fly ash level weighed significantly less (P < .05) at 8 weeks than the caged controls but did not differ from the other treatments. Bone breaking strength as measured by the Allo Kramer Shear Press was similar between the basal and low level fly ash group and increased with higher fly fly ash levels. Humerus and radius bone strength were greatest in floor broilers when compared with cage broilers. Tibia ash content of the floor-reared broilers and higher fly ash level of caged broilers were similar and greater than that of the basal cage group. Humerus and radius ash content were higher for the higher calcium groups. In Experiment 3 four groups of 40 male broilers in cages were fed limestone diets with graded levels of limestone for the calcium source. Another four groups of 40 caged male broilers were fed fly ash diets with equivalent graded levels of fly ash for the calcium source. Both limestone and fly ash diets provided .17, .34, .51, and .68% calcium of a total calcium content of .28, .45, .62 and .79%, respectively. The four limestone groups exhibited a definite linear improvement in both 3-week body weight and bone weight (tibia and femur combined) as the dietary calcium level was upgraded. The two low fly ash groups were similar in body and bone weight to their counterpart limestone groups, but further increases in the fly ash component did not improve body or bone weight. Bone ash values for both limestone and fly ash groups showed a similar improvement with each calcium increase, except the high value for the second level of fly ash.