The effect of phenyl mercury on reproductive performance in laying hens.

The effect of phenyl mercury with and without selenium on the egg production of laying hens and on the fertility, hatchability and properties of eggs was studied. Mercury was administered via the feed at dosages of 5 ppm, 30 ppm, and 30 ppm Hg + 4 ppm Se, for 56 days. After two months, egg production decreased by 8.18% and 7.74% in hens fed 30 ppm Hg, and 30 ppm Hg + 4 ppm Se, respectively. Egg weight decreased in all experimental groups. In comparison to the controls, these results were highly significant (P < 0.01) in hens fed 30 ppm Hg and 30 ppm Hg + 4 ppm Se and significant (P < 0.05) between hens fed 5 ppm Hg and 30 ppm Hg. Fertility rate and hatchability were not affected. Mercury exposure did not affect egg shape, egg-white height, egg-shell hardness or yolk colour. Both egg-shell thickness and weight decreased in all experimental groups. In the group supplemented with selenium there was a nonsignificant improvement in egg production, hatchability and all qualitative properties of eggs in comparison with the group without selenium supplementation. Residual mercury levels in egg yolk greatly surpassed the level found in the egg white: the highest values were measured in the group fed 30 ppm Hg. The addition of selenium had a protective effect upon residual Hg deposits in the yolk, but not in the egg-white.

The effect of cadmium treatment on breeding hens and cocks and early viability of their chickens.

The effect of cadmium, with and without selenium, on breeding hens and cocks and their offspring up to 7 days of age was studied. In adult birds, the body weight, mortality rate, pathological changes and cadmium level were determined. In chicks, the mortality rate and level of cadmium were evaluated. Cadmium as cadmium chloride was orally administered to the hens at three dosages: 3 ppm, 20 ppm and 30 ppm + 4 ppm of selenium. Cadmium levels in the muscles, liver and kidneys of laying hens analysed after 60 days and those of chicks after 30 and 60 days of the experiment. Cd determinations were conducted by the method of electrothermic atomization, using an atomic absorption spectrophotometer. Body weight in laying hens was maintained at the control level, while in cocks it slightly increased in all experimental groups. In the adult birds, no mortality occurred while 0.25 - 1.11% mortality was observed in chicks. The results showed a variability in cadmium levels in hens, according to the dosage applied. These levels were high in the kidneys and liver, and lower in the muscles. A non-significant increase of cadmium level was found in the liver and kidneys of chicks after the first month of application. The addition of selenium resulted in a reduction of cadmium level in the liver and kidneys of laying hens but not in the muscles. Gross pathological and histological changes in the kidneys and liver were observed in groups fed 20 ppm and 30 ppm of cadmium.