Effect of Some Dietary Synthetic and Natural Chelating Agents on the Zinc-deficiency Syndrome in the Chick

Abstract

The objective of these studies was to assess the effects of some synthetic and natural zinc-binding agents on the zinc-deficiency syndrome in chicks fed diets containing isolated soybean protein. Synthetic chelating agents EDDA (zinc stability constant 11.10), HEDTA (14.50), EDTA (16.50), and DTPA (18.14), at 1.8 mmoles/kg diet, and natural chelating agent cysteine (18.20) at 0.5% of the diet, alleviated all zinc-deficiency symptoms, which included poor growth, poor feathering, low length-to-width ratios of femurs, low zinc content of tibias and leg abnormalities. HEIDA (8.57) slightly improved the growth, feather score and leg score. Supplemental histidine (12.88) at 0.5% of the diet alleviated the bone disorder; however, it did not improve growth or increase the zinc content of bone. CDTA (18.67) substantially depressed growth of zinc-deficient chicks, but the effect was not statistically significant. Synthetic chelating agents DHEG (5.36), IDA (7.02) and EBONTA (11.00), and natural chelating agents xanthurenic acid, kynurenic acid and anthranilic acid (20.93), at 1.8 mmoles/kg diet, and glutamic acid (9.46), cystine and tryptophan (9.30) at 0.5% of the diet had no effect on the zinc-deficiency syndrome. All chelating agents with stability constants for zinc between 11.10 and 18.20, except histidine, overcame all zinc-deficiency symptoms, whereas histidine alleviated only bone and, to some extent, feather defects.