Magnesium tolerance of the growing and laying chicken

The effects of various levels of magnesium in growing and laying rations on growth and laying performance were studied. Levels of magnesium in the growing and laying rations were 0.36, 0.59, 1.06 and 1.83 per cent and 0.48, 0.70, 1.20 and 1.96 per cent respectively.

Only the growing ration containing 1.83 per cent magnesium significantly reduced growth, percentage bone ash and food utilisation during the growing phase (9–20 weeks). In the laying phase (20–40 weeks) significantly greater gains in body weight and percentage bone ash were produced by the birds which had received the growing ration containing 1.83 per cent magnesium.

The magnesium content of the growing rations had no effect on rate of lay, egg weight or egg shell thickness.

Hens fed the laying ration containing 1.96 per cent magnesium gained less body weight, laid fewer and lighter eggs and utilised their food less efficiently than those fed other levels of magnesium.

Egg production and food required per dozen eggs were poorer with the ration containing 1.20 per cent magnesium, but were not statistically different from the rations containing 0.48 or 0.70 per cent magnesium.

Eggs with thinner shells were produced by hens fed the 1.96 per cent magnesium ration at 34 weeks of age than were produced by those fed the 0.48 or 0.70 per cent magnesium rations.