Inbred Japanese quail were used to study the effect of γ-ray irradiation on the fitness of the birds. The dose of 150R (5R/min.), non-detrimental to reproductive organs, was administered to the female. Irradiated females were mated to non-irradiated full-sib males on the subsequent day.
The traits investigated for 28 days starting from 4 days after irradiation were as follow: hen-day egg production, percentage of hatching eggs, fertility, hatchability, viability to 4 weeks. Also fitness index, i.e., product of these five traits by multiplication, was examined.
1) The application of γ-rays on inbred females (F _??_ 42)improved fertility substantially and thus increased the fitness index.
2) The effect of irradiation on the fitness in the inbred line was different among families. Especially, there was a tendency of increase in the effect of irradiation on the families which showed severe inbreeding depression.
3) It is suggested that the fitness may be increased by heterozygosity due to γ-rayinduced polygenic mutations.

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Experiments were undertaken to investigate the effect of dietary calcium sources on the quality of egg shell in summer.
140 cross-bred White Leghorn laying hens were housed from middle of June to first of October and fed corn-soy type diets with different calcium sources, such as oyster shell, fossil shell, calcium lactate and calcium carbonate and with 2 calcium levels, 2.75 and 3.5% Ca (as calcium additives, 0.69% Ca is dicalcium phosphate and the others are calcium carbonate and different calcium sources), respectively. Oyster shell and fossil shell diets contained 2.75% Ca, and 0.5% was administered by the corresponding calcium sources. Calcium lactate diet contained also 2.75% Ca and 0.15% was administered by calcium lactate. These calcium sources were added at the expense of calcium carbonate. Calcium carbonate diets contained 2.75% and 3.5% Ca.
Fossil shell diet showed the highest values in shell thickness, egg shell strength, egg weight and plasma calcium concentration. Egg shell strength (P<0.1) and plasma calcium concentration (P<0.05) of fossil shell diet are significantly higher than other diets.
Shell thickness and egg weight decreased in the hottest August and increased in October, however, egg shell strength was the weakest in the first September and improved quickly in October.
There was no influence in egg production, feed consumption, feed convertion and body weight by dietary calcium sources and levels, except that calcium lactate diet showed rather lower egg production rate.

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Experiments were conducted to determine the effect of chlorella on the performance of laying hens, and the following results were obtained.
1. A diet containing 20% chlorella was compared with a 20% soybean meal diet, and it was observed that the chlorella diet reduced feed consumption, and consequently egg production tended to be decreased.
2. Feed consumption was reduced even when 5, 10 and 15% of soybean meal of a corn-soya type laying ration was replaced by the same levels of chlorella. Egg production also tended to be decreased, whereas no difference was found among the chlorella diets. It was concluded from these results that such a lowering effect on egg production of chlorella may not be due to the nutritive defect but to the reduction of feed consumption.

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High nutritive value of rice oil alkaline foots, a byproduct of the refining of food oil, was reported in the previous paper, but high moisture content and high viscosity of the foots made it rather difficult to use foots as a feed ingredient for poultry. To overcome these difficulties, a mixture of the foots and rice oil (4:6) was prepared, which contained 12.9% of moisture, 2.7% of crude ash, 0.5% of crude protein and 7.87kcal/g of gross energy.
Available energy of the sample was estimated by feeding the experimental diets containing 0, 4, or 8% of soybean oil or 4 or 8% of the sample to total 225 7-day-old chicks of egg-type male chicks and meat-type chicks of both sexes for 6 days, and to total 180 13-day-old egg-type male chicks for 21 days, and by feeding the experimental diets containing 0, 3.8 or 7.6% of soybean oil or 4 or 8% of the sample to total 200 oneday-old meat-type chicks of both sexes for 6 weeks.
Three estimates of available energy based on body weight gain per 100g feed taken by 5-point slope ratio assay in 3 experiments were quite agreeable within experimental error, regardless of the difference in age, breed and sex of the chicks as well as in length of experimental period. The findings again suggest that experimental period of 6 days is satisfactory for bioassay of available energy by chicks.
Average of 3 estimates of available energy of the sample was 7.3kcal/g, which corresponded to 93% of gross energy in the sample. High availability of energy in alkaline foots was re-confirmed again.

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Available energy of 2 samples of n-paraffin, Sample 1 mainly composed of n-paraffin of carbon chain length of 11 to 13, and the other Sample 2 mainly composed of n-paraffin of 14 to 16 carbon, were determined by 7-point slope ratio bioassay procedure feeding experimental diets to total 100 male and 100 female meat-type 7-day-old chicds for 6 days. Since 92% of Sample 1 and 17% of Sample 2 in the diets were found lost by evaporation during the experimental period, available energy was estimated with and without correction for the loss. The loss of the samples in the diet was confirmed by weighing the diets daily using a balance measurable to 0.01g.
Available energy of Sample 1 corrected for loss by evaporation was estimated to be 2.5kcal/g, corresponding to 22% of gross energy of Sample 1. However, it was discussed that the figure will be higher than the true value. Available energy of Sample 2 was negligible. With thess findings together with the finding of larger loss by evaporation of n-paraffin with shorter carbon chain length, possibility of using n-paraffin as energy source for poultry will be low from economical view point.
Though nitrogen-corrected metabolizable energy of the samples was determined in this experiment, the data are unreliable since loss of the sample by evaporation took place from both diet and excreta.

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Oxytetracycline (abbreviated OTC) was fed to laying hens for 7 days at the dietary levels of 0, 20, 500, 1, 000, 2, 000 and 4, 000ppm, and OTC content in egg white and yolk laid on the 7th day was analyzed microbiologically. To the hens fed 4, 000ppm of OTC, OTC-free basal diet was fed for another 7 days and all of the eggs laid during 14 days of experimental period were analyzed for OTC content.
No OTC was detected in the eggs laid by the hens fed 20ppm of dietary OTC, which is allowed for growth promoting purpose.
Feeding the diets containing OTC at the level higher than 500ppm for 7 days, content of OTC in the eggs increased in proportion to the dietary OTC level. Average OTC content in whole eggs laid by the hens fed 4, 000ppm of OTC increased linearly after the start of OTC feeding, and decreased exponentially after the withdrawal of dietary OTC.
The similar equation was induced to describe the behaviour of OTC to the equation for spiramycin (SP). From the equation, it is suggested that about 10 times more dietary SP is transferred into eggs than dietary OTC, and that no OTC will be detected even on the 7th day, if dietary OTC level is less than 247ppm.
Biological half life of OTC in whole egg was 1.1 days with 95% confidence interval from 1.6 to 0.8 days, which is shorter than 2.4 days for SP, and similar to 1.3 days for tylosin.

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A diet containing extremely high level of 8, 000ppm of chlortetracycline (abbreviated CTC) was fed to 35 laying hens for 7 days, and thereafter, the hens were fed the basal diet free from CTC for another 7 days. Five hens each were sacrificed on 0, 1, 2, 3 and 5 days after the termination of CTC feeding to analyze CTC content in the liver micro-biologically. Among the rest of the hens, 5 hens, who laid more eggs continuously for 14 days than the others, were selected and CTC content of all of the eggs laid by them were analyzed.
Content of CTC in egg white and whole egg increased rapidly after feeding CTC and reached plateau on the 2nd and 4th day, respectively. After the withdrawal of dietary CTC, the content of CTC in whole egg, egg white and the liver decreased exponentially.
Combining the data, an equation was induced to describe the behaviour of dietary CTC at 8, 000ppm, which resembles that of tylosin.
Biological half life of CTC in whole egg was calculated to be 1.6 days with 95% confidence interval from 1.7 to 1.5 days, and that in the liver to be 0.5 days from 0.6 to 0.4 days.

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