The optimum pH of phytase originated from Aspergillus niger is approximately 5.5. In the present study, we tried to modify the intraluminal pH by dietary acidic amino acid to maximize phytase activity. Single Comb White Leghorn male chicks at 7 days of age were fed the experimental diets for 10 days. The experiment was 2×2×2 factorial arrangement of treatments with two dietary amino acid sources (L-glutamine or L-glutamic acid at 50g/kg diet), two levels of dietary phytase (0 or 1,000U/kg diet) and two levels of dietary available P supplementation (0 or 6g/kg diet). The glutamic acid supplementation significantly reduced pH in the crop (5.4±0.2; n=7) compared with the glutamine supplementation (6.0±0.1; n=7). There was a significant interaction between dietary amino acid source and phytase level on bone ash response in the thigh. Dietary phytase significantly increased bone ash content in chicks fed diets containing glutamic acid but not in the glutamine group. These results suggest that the modification of pH in the crop could activate phytase in chickens.

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In order to develop the technique for in vitro culture of chicken primordial germ cells obtained from circulating embryonic blood vessels (cPGCs), participation of feeder cells and some of growth factors was examined. In this experiment, Dulbecco's MEM (DMEM) mixed with Ham's F12 was used in combination with some kind of cell growth factors such as chicken stem cells factor (SCF), human leukemia inhibitory factor (LIF), human basic fibroblast growth factor (bFGF) and chicken insulin-like growth factor (IGF-1). In the present study, chicken embryos incubated for 5, 6 and 7 days were subjected to the isolation of stroma cells from germinal ridges. These stroma cells isolated from germinal ridge which were used as feeder cells, were divided into two parts, left side stroma cells (L-GRSCs) and right ones (R-GRSCs). The cPGCs were obtained by the filtration method from blood samples aspirated from extra-embryonic veins. The short-term (6 days) culture of cPGCs with L-GRSCs derived from 5 days embryos showed slightly increased proliferation of the cells, by around 1.7-2.3 times. Contrariwise, the co-culture of cPGCs with R-GRSCs did not bring about any increase of PGCs number compared with the case of L-GRSCs. On the one hand, the co-culture with both L- and R-GRSCs derived from 6 and 7 day embryos, resulting in the disappearance of the cells after 7 days of culture. In case of the long-term (30 days) culture with L- and R-GRSCs, the number of PGCs significantly (P<0.05) increased, showing 70 to 100 times increment. In these cases, no significant difference was observed between L- and R-GRSCs or among growth factors added. In addition to this, the PGCs cultured for 30 days formed a kind of cell clumps surrounded by the co-cultured GRSCs. The results obtained in this experiment suggest the possibility of proliferation of the PGCs outside the body by co-culturing with germinal ridge stroma cells derived from the 5 day embryos.

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To estimate the value of metabolizable energy (ME) of soybean curd residue (SCR) (experiment 1), a semi-purified diet was substituted by SCR at 0 (CP; 18.4%, ME; 3.39kcal/g, Gross energy (GE); 4.16kcal/g), 10 (CP; 21.0%, GE; 4.35kcal/g) and 20% (CP; 23.9%, GE; 4.48kcal/g) levels. Chromic oxide was mixed with each SCR diet at a 0.3% level to measure digestibility. A total of 4 Single Comb White Leghorn cockerels of each group were given water and each diet ad libitum for 6 days preliminary adaptation period, then feces from each bird were collected 2 times a day for 4 days. According to the glucose substitution method, ME values of SCR was estimated from the difference between ME of SCR containing diet and ME of reference diet. From this method, ME of SCR was determined as 2.70kcal/g DM.
To investigate the effects of dietary SCR on feed intake and body weight gain in broiler chicks (experiment 2), all the diets were formulated to contain same amount of nitrogen (CP; 21.0%) and energy (ME; 3.00kcal/g). SCR was included at 0, 5, 10 and 15% levels in mash and pellet forms. Five broiler chicks were given each experimental diet and water ad libitum from 7 to 28-d-old. Five trials with same protocol were carried out using a total of 200 birds. In mash diets, the feed intake showed a tendency to decrease, but the body weight gain tended to increase with increasing the SCR levels, resulting in improved feed conversion ratio. However, in pellet diets, both feed intake and body weight tended to decrease due to inclusion of SCR, resulting in the impairment of feed conversion ratio. Although feed intakes were higher in each pellet diet than those of mash diets, the body weight gain did not show a definite increase. These results suggest that SCR could be incorporated into broiler chick diets up to 15% in mash form.

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Immunoglobulin Y (IgY) is transferred passively from maternal circulation to the yolk. The aim of this study was to determine whether the concentration of yolk IgY is affected by forced molting in hens. Molting was induced in laying hens of 515-days-old with 3-4 eggs in a sequence by the withdrawal of feed. Yolk samples were collected before the feed withdrawal (premolt), and 4 and 10 days after relaying (postmolt). Serum samples were collected before and 2 days after feed withdrawal, 3 days after cessation of laying, 4 and 10 days after relaying. The concentrations of IgY in the yolk and serum were determined by ELISA. IgY concentration in the yolk was significantly greater in postmolt hens than that of premolt hens. Although IgY concentration was slightly decreased in the yolk 10 days after relaying compared with 4 days after relaying, it was still significantly greater than that of premolt hens. Serum IgY concentration increased significantly during molting and remained higher in hens until 4 days after relaying. In the hens 10 days after relaying, serum IgY concentration decreased significantly and returned to almost a same level as that of premolt hens. These results indicate that IgY concentration in egg yolk is increased during early phase of postmolt.

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Avian primordial germ cells (PGCs) show a unique migration pathway during early development. As soon as the blood vessels have formed, PGCs enter the circulatory system, and migrate to the gonadal primordium. We measured the concentration and the size of PGCs and erythrocytes from the wild-type plumage and the sex-linked brown strains of Japanese quail embryos when PGCs are in circulation at Hamburger and Hamiltons stages 13-19. PGCs were high in concentration and large in size at stage 13, and it showed a significant decrease as the function of embryonic development. Erythrocytes showed a low concentration at stage 13 and a significant increase as the function of embryonic development but the size was constant during stages 13-19. No strain difference was observed in these characters between the two strains of quail embryos.

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An experiment was conducted to determine if dietary Stevia (Stevia rebaudiana) extract prevents gizzard erosion and ulceration of chicks induced by dietary histamine. Day old broiler chicks were fed on a basal diet, a diet with 0.4% histamine or a diet containing 0.2% Stevia extract (on dry matter basis) +0.4% histamine for 14 days. Dietary histamine reduced growth and caused occurrence of gizzard erosion and ulceration as previously reported. Feeding of Stevia extract containing diet partly prevented retardation of growth and occurrence of gizzard erosion and ulceration caused by histamine. The result shows that the Stevia extract contains active substance(s) that attenuates histaminic action.

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