Maternal dietary magnesium effects on lactation success and on milk yield and composition in the rat.

Maternal dietary magnesium (Mg) intake during lactation is known to affect the growth and development of the newborn. We fed three groups of lactating rats diets containing 125, 500 and 900 mg Mg/kg, and observed pup growth, milk yield, and milk Mg, calcium, protein, fat, lactose and energy concentrations on maternal dietary Mg; milk calcium decreased. Other milk constituents and yield did not appear to be directly affected, although deficient dams ate less food which did depress milk yield. Deficient dams also developed swollen and distended teats when milked. We conclude that less than a normally recommended amount of Mg in the maternal diet depresses pup growth, while more than a normal amount accelerates it. No clear connection was identified between the growth response and any milk constituent.