Metabolic effect of iodine addition in laying hens

Veterinarni Medicina 43, 1998, 207-212

The objective of this study was to reveal potential production and metabolic risks in laying hens with targeted production of consumer eggs with high iodine content. A trial lasted 74 days and was conducted in four groups of hens (n = 11) of laying type Hisex Brown. All groups of hens had a free choice of complete feed mixture for laying hens - N-1. These iodine additions per 1 kg of feed mixture were applied to experimental groups: 3.5 mg to group B, 1.3 and 10.0 mg to group C, 7.0 and 15.0 mg to group D. Hen weight (Tab. I), and feed and water intake (Tab. II) were determined during the trial. Iodine content in yolk (Tab. III) was determined colorimetrically after alkaline digestion. These methodical principles were used to determine blood parameters: hemoglobin content in blood as hemoglobin cyanide(Fig. 1), leukocyte counts in blood - microscopically in Burker chamber (Fig. 2), plasma cholesterol - reaction with acetic anhydride (Fig. 4), total protein biuret reaction (Fig. 3), protein fractions - electrophoresis on cellulose acetate foils (Tab. IV), triiodothyronine - RIA (Tab. IV). Iodine supplements significantly (P < 0.01) stimulated an increase in iodine concentration in yolk, ranging from 2 303 +/- 691 in control group A to 23 592 +/- 9 436 mu g/kg of fresh matter after an addition of 15 mg I/kg of feed. Significantly higher feed consumption (P < 0.01) in groups C and D receiving the highest additions of iodine was accompanied by a significant decrease in water intake (P < 0.01). Iodine load was followed by a significant decrease in hemoglobin content (P < 0.01) only at the intake of 15 mg I per kg of feed. The character of changes in leukocyte counts and protein content in blood plasma in experimental groups did not differ very much from the control group under iodine load. A significant increase in gammaglobulin content (P < 0.01) was observed after additions of more than 7 mg I per kg of feed. Plasma cholesterol content increased significantly (P < 0.01) only after an addition of 15 mg I per kg of feed. Triiodothyronine content in blood plasma was increasing after additive iodine intake while the difference from control group was significant (P < 0.01) after additions of more than 7 mg I per kg of feed. A significant decrease in hemoglobin content and an increase in cholesterol content in blood plasma following an addition of 15 mg of iodine, accompanied by higher of gamma-globulin and triiodothyronine concentrations after the additive intake of 7-15 mg iodine per kg of feed, suggest a metabolic action of iodine that should be studied in greater detail with respect to production of iodine-enriched eggs

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