Pure-line dwarfs kept in individual cages and reproduced by artificial insemination exhibited fertility and hatchability comparable to those obtained with normal size females.In our genetic selection for hen-housed egg production on the basis of individual and family performance results were for a time disappointing. This apparently occurred because polygenes for hypothyroidism were segregating as a result of the inbreeding that accompanied our selection. .Age at first egg increased to 32 . 5 weeks but it has gradually decreased to 24 . 3 weeks in the current generation, which is still i.! weeks later than in our OSU Production Line.Hen-housed egg production was also disappointing in a number of years but it began to show improvement in the last three generations. It is now 8 3 . 4 per cent as high as that observed in the Production Line at 40 weeks of age. Egg size has gradually increased. Body weight has not changed (') Technical Paper no. 30 8 2 , Oregon Agricultural Experiment Station.

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Two experiments were conducted with Hubbard broiler chicks on the metabolism of high levels of dietary zinc. In the first experiment, chicks were fed a basal diet or the basal diet plus 500, 1,000, 2,000 or 4,000 ppm zinc, and in the second experiment chicks were fed the basal diet or the basal diet plus 1,000, 2,000, 4,000, 8,000 or 16,000 ppm zinc, using zinc acetate. Zinc was found to be associated with 4 peaks when the cytosols from tissues (liver, kidney, pancreas and intestinal mucosa) were eluted through columns of G-75 Sephadex. Although the zinc content of all four peaks increased with increased zinc content of the diet, the greatest elevation occurred in metallothionein (MT). This protein was purified from all four tissues (liver, kidney, pancreas and intestinal mucosa) and the amino acid analysis revealed the presence of about 30% cysteine. Zinc accumulated to the greatest extent (microgram in MT/g tissue) in MT of the pancreas. The zinc in MT disappeared very rapidly when chicks which had been fed a diet containing high levels of zinc were fed a low zinc diet, indicating the extreme lability of this metal in this protein. The results suggest the involvement of MT in zinc homeostasis.

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