EFFECTS OF AD LIBITUM VERSUS RESTRICTED INTAKE OF CONCENTRATE AND STAGE OF LACTATION ON THE MINERAL CONTENT OF COW’S MILK

Abstract

Concentrates, one consisting primarily of oats and the other barley, were fed ad libitum to cows or at the rate of 1 kg per 3 kg of milk yield for an entire lactation. Calcium, potassium, magnesium and sodium content of the milk and milk yield were measured monthly. Potassium content and milk yield decreased and sodium content increased significantly (P < 0.05) with advancing stage of lactation. The calcium content of milk was significantly greater (P < 0.05) when the barley-based compared with the oat-based concentrate was fed. The sodium content of milk from cows fed concentrate ad libitum was significantly higher than from cows fed restricted amounts of concentrate. Ayrshire milk was significantly greater (P < 0.05) in magnesium concentration than Holstein milk.