The effects of ingestion of low levels (0.014 and 0.018 p.p.m.) of mercury over prolonged periods by male and female birds of one broiler strain and three White Leghorn strains were studied. The sources of mercury were herring meals manufacutured from fish caught off the Pacific and Atlantic coasts of Canada and containing 0.22 and 0.17 p.p.m. respectively of mercury.The difference in concentrations of mercury in the two meals was reflected in differences in tissue concentrations of mercury of the birds fed the respective meals. Genetic differences in tissue accumulation of mercury were evident both in tissues which accumulated higher concentrations of mercury (feather, claw, kidney) as well as in muscle which accumulated relatively little. There was no apparent relationship between the incidence of mortality and tissue accumulation of mercury. Egg production and egg quality were unaffected by the source of herring meal in the diet. Most of the mercury in the eggs was present in the albumen and the overall average concentrations of 47 and 40 p.p.b. in the albumen and 16 and 15 p.p.b. in the yolks of the eggs from the hens fed the respective meals reflected the difference in the mercury concentration in the meals. The concentration of mercury in the eggs did not increase with the length of time during which the herring meals were fed. Fertility and hatchability of eggs were not affected by the source of herring meal fed.
ABSTRACTTwo herring meals containing 0.17 and 0.22 p.p.m. of mercury respectively were fed to broilers at dietary levels of 5, 10 and 17.1%. The amounts of mercury present in the diet from this source thus varied from 0.0085 to 0.0376 p.p.m. Growth rate and mortality to eight weeks of age were unaffected by the level or source of herring meal in the diet. The amount of mercury ingested by the birds fed any of the diets resulted in negligible effects on the concentration of mercury present in breast or leg muscle. There was, however, significant accumulation of mercury in liver, kidney, claw and feather tissue, which reflected the dietary concentration of mercury. The amount present in the feathers was high as 0.845 p.p.m. This amount may be sufficiently high to warrant concern when feathers are processed into meal.
White Leghorn pullets of two strains were fed soybean or rapeseed meal during either or both the growing period and laying period in two separate experiments. Rapeseed meal may be fed to growing pullets at levels up to 17% of the diet without adversely affecting the subsequent rate of egg production or egg size. Birds fed laying diets containing 19% of rapeseed meal produced a greater egg mass per hen-day and gained more weight during the laying period when the growing diet contained rapeseed meal instead of soybean meal. Birds shifted at sexual maturity from soybean to rapeseed meal as dietary protein supplement undergo metabolic adjustment which retards the attainment of maximum rate of production and induces cannibalism. Both rate of production and egg size were lower when rapeseed meal constituted 19% of the laying diet in replacement of soybean meal as protein supplement. Mortality, exclusive of that resulting from cannibalism, was 4.1% and 4.6% respectively in the two experiments. Death from liver haemorrhage occurred only in birds of one strain which were fed rapeseed meal during the laying period and principally in birds which had been fed rapeseed meal during the growing period as well.
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