AIA was used to estimate the digestibility of nutrients (Van Keulen and Young, 1977). Milk sampleswere composited daily, according to yield, for both the a.m. and p.m. milking, preserved with 2-bromo-2 nitropropane-1, 3-dial, and stored at 4 °C until analysis for fat, protein, lactose, total solids, and solids-not-fat content by infrared methods using Milko-Scan 33 (Foss Electric, Hillerod, Demark).