The effects of withdrawal of vitamin and trace mineral supplements from layer diets on egg yield and trace mineral composition

1. This study was conducted as three trials. 2. In the first trial, zinc, manganese, copper and iron concentrations were determined in dietary raw materials collected from various regions of Turk ey. 3. In the second trial, 200 Hisex Brown laying hens, 30 weeks of age, were divided into two groups. The first group served as controls and were fed on a standard commercial layer diet. The second group were fed on a commercia l layer diet that was not supplemented with trace minerals and vitamins. Eg g production, egg weight, specific gravity, food consumption and food effic iency of the birds in each group were determined. In the unsupplemented gro up, egg production (0.75 vs 0.83) and food intake (114 vs 122 g) were lower than the those of the control group (P<0.05). Food efficiency was 2.42 (kg food/ kg gain) in the group consuming the unsupplemented diet and 2.36 in the controls. 4. In the third trial, as in Trial 2, Hisex Brown laying hens, 62 weeks of age were used. In the unsupplemented group, the mean egg weight was signifi cantly lower than that of controls (68.0 vs 69.6 g) (P<0.01). 5. At the end of the second and third trials, egg samples collected from ex perimental groups were hard boiled in water. The levels of zinc, manganese, copper and iron in the egg yolk were determined. The zinc level of the egg yolk from the control group of second trial was higher (23.5 mg/kg) than t hose of the unsupplemented group (13.6 mg/kg).