THE FOLIC-ACID REQUIREMENTS OF STARTING BROILER CHICKS FED DIETS BASED ON PRACTICAL INGREDIENTS .2. INTERRELATIONSHIPS WITH DIETARY METHIONINE

Two experiments were conducted to determine the effects of dietary sup plemental folic add and methionine on the performance of starting broi ler chicks for 18 d. Four levels of dietary folic acid (.24,.54, 1.14, and 2.34 mg/kg) and four levels of dietary methionine (.45,.53,.61, a nd .69%) were fed in a factorial design. There were three replicates o f eight chicks each per each treatment. The basal diet was based on co rn, isolated soybean protein, meat and bone meal, and fish meal. It co ntained adequate amounts of all nutrients except methionine and folic add. Increased growth was observed in chicks fed the basal diet supple mented with either folic acid or methionine. Total dietary folic acid and methionine plus cysteine requirements for maximum growth were esti mated to be 1.80 mg/kg and .85% in Experiment 1 and 1.47 mg/kg and .87 % in Experiment 2, respectively. There were interactions between dieta ry folic add and methionine on weight gain in both experiments. Chicks fed the diet containing 2.34 mg folic acid/kg tended to have depresse d growth, as in previous experiments. There was a significant Linear f eed conversion response to folic acid in Experiment 1 and to methionin e in Experiment 2. There were both Linear and quadratic liver folic ad d responses to dietary folic acid in both experiments. There was no in dication that dietary methionine had any effect on liver folic acid co ntent. No differences in bone ash, hemoglobin, hematocrit, or incidenc e of tibial dyschondroplasia were detected due to methionine or folic acid supplementation.