Effect of serum magnesium and feed intake on serum growth hormone concentrations

Concentration of serum growth hormone was increased and feed intake was reduced in lactating dairy cows fed an 84% concentrate diet supplemented with either 100.8 g MgO or 121.2 g of Mg(OH)2. Analysis of serum growth hormone, feed intake, and serum Mg showed an interaction of serum Mg and feed intake, which suggests low concentrations of serum Mg lessen the increase of concentration of serum growth hormone caused by reduced feed intake. Also, compared with control, treatments with Mg supplementation and reduced feed intake increased growth hormone concentration 12 d into the subsequent treatment.