Observations on several factors influencing the incidence of tibial dyschondroplasia in broiler chickens.

The effects of age vs. diet, potassium level, tetramethylthiuram disulfide (thiuram), and ionophores in the diet on the development of tibial dyschondroplasia in broilers was investigated. Changing broiler chicks from a diet that induced tibial dyschondroplasia to one that reduced the disease or vice versa caused a change in the incidence in the direction of the last-fed diet; however, in most cases the chicks did not develop as low or high an incidence of tibial dyschondroplasia as the birds fed the reducing or inducing diet, respectively, for the entire experimental period. Potassium supplementation of a corn-soybean meal diet that contained .88% potassium had no effect on the incidence of tibial dyschondroplasia. However, supplementation of a low potassium (.3%) corn-corn gluten meal-animal protein diet with potassium increased the incidence of tibial dyschondroplasia. The addition of thiuram to the diet caused an increase in tibial dyschondroplasia. When thiuram was added to the tibial dyschondroplasia-inducing diet, it also caused a decrease in bone ash and in the total and ultrafilterable plasma calcium. A significant negative correlation was obtained between incidence and score of tibial dyschondroplasia and bone ash of the ends and middles of the tibia when thiuram was fed. No consistent effects of the ionophores monensin and lasalocid on the development of tibial dyschondroplasia in broilers was noted in three experiments, although significant effects of the ionophores on the incidence or score of the disease was observed in two experiments.