부산대학교 도서관

Microbiological assays were conducted to determine the level of total folate in poultry feed ingredients using Lactobacillus casei(ATCC 7469). Folic acid contents of fifty seven samples of poultry feedstuffs pretreated before assay with three enzymes (conjugase, amylase, a mixture of protease(Pronase^®)) were corn(N=14), 23.09±1.l8(㎍/100g ± SD); fish meal(N=7), 23.05±1.27; Milo(N=4), 29.34±0.55; bakery meal(N=5), 25.80±6.93; meat and bone meal(N=4), 56.76±4.97; wheat middlings(N=5), 85.14±2.56; soybean meal(N=18), 193.97±3.98. Predigestion with conjugase, α-amylase and Pronase^® liberated folic acid and increased values by 21.3% compared to conjugase predigestion alone(P＜0.05). Another five experiments were conducted to evaluated the effect of dietary supplemental folic acid(FA) in starting broiler chicks diets. In the first two experiments, basal diets based on corn and soybean meal contained 0.6 ㎎/㎏ folic acid but no supplemental methionine or choline. Chicks showed curvilinear responses to folic acid supplementation with maximum growth and feed efficiencies from 1.45 ㎎/㎏ diet. The liver folic acid response was also curvilinear but reached a plateau at 1.70 ㎎/㎏ FA diet. The basal diet for 3 additional experiments contained soybean meal that had been washed with methanol to remove most of the choline. The diet contained only 754 ㎎/㎏ choline. Chicks exhibited a larger growth response to folic acid at low choline levels as evidenced by a significant FAX choline interaction. Folic acid supplementation increased but then decreased valgus leg deformity. Choline supplementation also decreased the incidences of valgus and varus leg deformities and decreased bone ash and increased the incidence of tibial dyschondroplasia. It is concluded that chicks fed practical ingredient based diets require 1.45 ㎎/㎏ FA diet with low levels of choline, but only 1.25 ㎎/㎏ FA when choline is offered near the NRC recommended level of 1300 ㎎/㎏. At the last time, two experiments 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, 2.34) and four levels of dietary methionine(0.45, 0.53, 0.61, 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 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 ㎎/㎏, 0.89% in first experiment and 1.47 ㎎/㎏, 0.91% in second experiment, respectively. There were interactions between dietary folic acid and methionine on weight gain in both experiments. Chicks fed 2.34 ㎎/㎏ folic acid containing diet tended to have depressed growth, as previous experiments. There was a significant linear feed conversion response to folic acid in the first experiment, and significant quadratic feed conversion response to methionine in the second experiment. 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 was increased with increasing supplemental methionine, but there were no significant differences detected at P＜0.05.