The study was conducted to survey the production of laying hens which have high genetical performance of productions, in the subtropical zone. It is considered that relatively high temperature and humidity throughout the year in the zone would depress the production of the hens. A large scale chicken farm in Okinawa Island has kept Shaver Star Cross 288. Their production records were analyzed and also management of the hens in the subtropical zone were discussed here.
Production records were obtained from approximately 750, 000 laying hens of 48 flocks (approximately 15, 600 per flock) which were kept in 10 years during 1979 to 1988 in the farm.
1) Mean production indicated that production of the hens in subtropical zone was not different from production of layers which were kept in a farm under superior management in the temperate zone.
2) Hatching season of the layers did not influence their productions. Production during 3 months of summer was lower than that in the other seasons. No adverse effect, however, was observed in total production during 181 to 599 days of age.
3) The hens in 8 flocks out of 11 which hatched in 1987 and 1988 recorded low egg production. It was suggested that low production of the hens of the flocks was due to genetical performance.
4) There were no special facilities to protect high temperature and humidity. Polyethylene ducts in a house supplied fresh air and plywood boad in an attic protected sun heat. The hens fed a commercial formulated feed ad libitum.
5) Analysis of production of the laying hens in the study indicates that the production of the hens having genetical high performance was not affected by climate of subtropical zone.

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Ultrastructures of the yolk sac, intestine and liver of chicks were examined to clarify the mechanism of yolk absorption before and after hatching, using an electron microscope.
In endodermal cells of the yolk sac, many phagocytotic arms and pinocytotic invaginations were seen along the apical surface. Yolk granules were present within the cytoplasm. Some of the granules consisted of relatively electron-lucent material, indicating partial digestion. These figures were observed frequently until just before hatching and occasionally after hatching. Lipid droplets and glycogen granules were also present in the cytoplasm. The lipid droplets slowly decreased in number after 15 days of incubation. The number of glycogen granules rapidly decreased just before hatching, but gradually increased thereafter. Numerous mitochondria and well-developed rough-surfaced endoplasmic reticulum could be seen in the basal cytoplasm just before hatching.
In epithelial cells of the jejunum, at 15 days of incubation, mitochondria, rough-surfaced endoplasmic reticulum and Golgi complex were poorly developed, and short microvilli were irregularly arranged on the cell surface. These structures showed marked development after 19 days of incubation.
In parenchymal cells of the liver, mitochondria and rough-surfaced endoplasmic reticulum were seen at 15 days of incubation. Changes in the number of glycogen granules and lipid droplets were essentially similar to those in endodermal cells.
These observations indicate that, during the early stages of incubation, yolk substances may be absorbed into endodermal cells of the yolk sac by endocytosis and then digested within the cell, and that the products of breakdown may be transported to the liver where they are actively metabolized. The development of microvilli and cytoplasmic organelles in intestinal epithelial cells would appear to be stimulated by yolk substances directly forced into the intestinal tract just before hatching.

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The localization of estrogen receptors (ERc) in the magnum and shell gland of the oviduct was examined immunohistochemically in immature and laying chickens with or without estrogen treatment.
In the magnum and shell gland of the oviduct in laying hens, nuclear immunoreac-tion showing ERc localization was observed in cells of the tubular gland of the lamina propria, but not in epithelial cells of the mucosa. Immunoreaction in estrogen-treated laying hens was strongly evident in the nuclei of cells of the tubular gland, comparing with that in non-treated layers.
In the magnum and shell gland of the oviduct in immature chickens, nuclear immunoreaction was apparent in epithelial cells of the mucosa and in cells of connective tissue of the lamina propria. After estrogen treatment, the tubular gland developed in the lamina propria of the magnum and shell gland of the oviduct. Nuclear immunoreaction was observed in cells of the tubular gland. However, no immunoreaction could be detected in the nuclei of epithelial cells.
These findings suggest that estrogen directly acts on the development of the oviduct in immature chickens, and on secretory functions of the tubular gland in laying chickens.

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Bactericidal efficacy of a disinfectant has been mainly estimated against bacteria in the broth cultured described as phenol coefficient or minimum inhibitory concentration. It is doubtful whether an efficacy against bacteria contaminating a material naturally correspond with that in broth cultured or not.
Experiments were conducted to compare the bactericidal efficacy of three kinds of disinfectant against bacteria in broth culture with that against contaminating chicken house naturally. Main chemical composition of the disinfectants used in the experiments were didecyl-dimethyl anmonium chloride (D), glutaraldehyde (G) and mixture of didecyl-dimethyl anmonium chloride and gultaraldehyde (DG).
Broth culture of Staphylococcus aureus, Escherichia coli and Salmonella typhimurium were used to estimate phenol coefficient and minimum inhibitory concentration. The D was recorded the higher value of phenol coefficient and the lower concentration of minimum inhibitory concentration than those of G or DG. On the contrary, when the disinfectant were sprayed in broiler house, higher degree of bacterial reduction was observed after spraying DG comparing with D and GA. Different evaluation of bactericidal efficacy was obtained by two estimations.
The results of the experiments suggest that bactericidal efficacy of disinfectant seems to evaluate the effect on bacteria both in broth and contaminated in nature.

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