Undersander et al. (1993) developed a method for estimating milk per ton of
forage dry matter (DM) as an index of forage quality. The milk per ton index is based
on energy content of the forage predicted from acid detergent fiber (ADF) content and
DM intake potential of the forage predicted from neutral detergent fiber (NDF) content.

The milk per ton index has now been modified to use new NRC recommendations
(National Research Council, 2001) for calculating energy (Schwab and Shaver,
2001), and an easy to use Excel 5.0 spreadsheet called Milk2000 has been developed.
MILK2000 uses forage analyses (crude protein, NDF, in vitro NDF digestibility, starch
(corn silage only), and non-fiber carbohydrate) to estimate energy content using a
modification of the NRC (2001) summative approach and DM intake from NDF
(Mertens, 1987) and in vitro NDF digestibility (Oba and Allen, 1999) to predict milk
production per ton of forage DM. In MILK2000, the intake of energy from forage for a
1350 lb. milking cow consuming a 30% NDF diet is calculated and the cow’s
maintenance energy requirement (proportioned according to the percentage of forage in
the diet) is then subtracted from energy intake to provide an estimate of the energy
available from forage for conversion to milk (NRC, 1989). Forage DM yield multiplied
times the milk produced per ton of forage DM provides an estimate of the milk produced
per acre and combines yield and quality into a single term.