Abstract
In Experiment 1, microbial assays were conducted on 57 feed ingredient samples to determine the content of total folic acid using Lactobacillus casei(ATCC 7469). Folic acid contents of feed samples pretreated with conjugase, ${\alpha}$-amylase, and a mixture of protease(Pronase)were corn, 09${\pm}$1.18($\pi$g${\pm}$SD); fish meal, 23.05${\pm}$1.27; milo, 29.34${\pm}$0.55; bakery meal, 25.80${\pm}$6.93; meat and bone meal, 56.76${\pm}$4.97; wheat middlings, 85.14${\pm}$2.56; and soybean meal, 193.97${\pm}$3.98. Experiments 2 and 3 were conducted to determine the effects of dietary supplemental folic acid and methionine on the performance of starting broiler chicks for 18 days. Four levels of dietary folic acid(0.24. 0.54,1.14 and 2.34mg/kg) and four levels of dietary methionine(0.45, 0.53,0.61, and 0.69%) were fed in a factorial design. The basal diet was based on corn, isolated soybean protein, meat and bone meal, and fish meal. It contained adequate amounts of all nutrients except methionine and folic acid in both experiments. Increased growth rate was observed in chicks fed the basal diet supplemented with either folic acid or methionine. Total dietary folic acid and methionine plus cysteine requirements for optimum growth were estimated to be 1.80 mg/kg and 0.89% in Experiment 2, and 1.47 mg/kg and 0.91% in Experiment 3, respectively. There were interactions between dietary folic acid and methionine on weight gain in both experiments. Chicks fed diets containing 2.34 mg folic acid /kg tended to display slow growth rate in both experiments. There was a significant linear feed conversion response to folic acid in Experiment 2, and a significant quadratic feed conversion resuonse to methionine in Experiment 3. There were both linear and quadratic liver folic acid responses to dietary folic acid in both experiments. There was no indication that dietary methionine had any effect on liver folic acid content. The incidence of tibial dyschondroplasia increased with increasing supplemental methionine, but were no significant differences detected at 5% level.
