Dairy Pipeline: December 2004 and January 2005
Charles C. Stallings
Extension Dairy Scientist,
Nutrition and Forage Quality
Virginia Cooperative Extension faculty have been conducting corn silage variety testing for several years and since 2002 have been comparing results expressed as potential milk production expressed per ton of silage or per acre (MILK2000). Use of this index in comparing silage varieties is similar to comparing bulls using bull proofs. It is possible to rank varieties with MILK2000 taking into consideration both silage yield and quality. Milk2000 was developed by Undersander, Schwab and Shaver of the University of Wisconsin. In order to make the needed calculations it is necessary to know the silage dry matter, crude protein, neutral detergent fiber (NDF), NDF 48 hour digestibility, starch, NDF crude protein, ash, either extract, and dry matter yield. NDF crude protein, ash, and ether extract can be estimated by using book values such as the Dairy 2001 NRC if actual lab results are not available. Corn silage has relative little of these fractions anyway. The basic premise of this method is net energy of lactation is calculated for corn silage by projecting the digestibility of crude protein, fat, NDF, and non fiber carbohydrate. Non fiber carbohydrate includes the starch plus non starch carbohydrates. Starch digestibility is calculated by an equation using the dry matter % and considers kernel processing. Kernel processing increases the starch digestibility. Corn silage dry matter intake can be projected by knowing body weight, NDF of silage, and NDF digestibility. Fat corrected milk can be projected by knowing the net energy of the silage as calculated above, body weight, and % of the diet as silage. Dividing fat corrected milk potentially produced by corn silage dry matter intake will provide milk produced per ton of corn silage dry matter. According to Tom Stanley, Extension Agent in Augusta County, "Milk2000 can be a useful tool in making corn silage hybrid selection decisions. The Milk2000 score should be used along with other quality and agronomic characteristics such as relative maturity, disease resistance, standability, etc. in making a selection decision." If you would like to do some actual calculations go to the following web site for a spreadsheet that will do the actual calculation for you: http://www.uwex.edu/ces/forage/articles.htm#milk2000 or contact your local Cooperative Extension office for more information on results of this years variety testing.