Understanding NDF Digestibility Portage County Forage Council Annual
Understanding NDF Digestibility Portage County Forage Council Annual Meeting February 7, 2002 Craig Saxe UW-Extension, Juneau Co. 211 Hickory Street Mauston WI 53948 (608) 847 -9329 E-mail: craig. saxe@ces. uwex. edu
How Good is My Hay, Haylage, or Corn Silage?
Forage Quality Terms: • NDF - total fiber, effective fiber • ADF - quick method of estimating digestibility of the fiber • RFV - calculated from ADF & NDF • TDN - total energy content calculated using ADF
TDN vs ADF TDNm (Van Soest) TDNm (In Vitro) 80 TDNm, % 75 70 65 TDN (88. 9 -. 79 ADF) 60 55 50 45 40 20 25 30 35 ADF, % 40 45 50
Measuring Forage Quality • NRC Summative Energy Model TDN=ECP + EFA + ENDF + ENFC – 7 • NDF digestibility can now be measured on a quick and routine basis
A New Test, So What? • More accurately balanced ration • More predictable animal response • Better decision-making tool when buying or selling a forage
Ranges of NDF Digestibility for Common Forages Legume Silage/Hay Grass Silage/Hay Corn Silage NDF Digestibility, % of NDF * based on a 48 h in vitro true dry matter digestibility assay. 75 Excellent 70 65 Good 60 55 Average 50 45 40 Fair 35 30 25 20 Poor
Which would you prefer? Example A: Lot # 1 CP 17 ADF 35 NDF 50 TDN NEL 61. 25 0. 63 Lot # 2 17 35 50 61. 25 0. 63 Example B: Lot # 1 CP 17 NDF 50 NDFd TDN 60% 57. 8 NEL 0. 59 Lot # 2 17 50 40% 0. 51 50. 3 7. 5
Implications: • ADF is eliminated • Grasses are not unfairly penalized • Variance of forage quality is increased • Mature forages = very low energy contents • Better linkage between forage quality and cow response
Closing Thoughts: • Commercially Available (Marshfield + Others) • Different Labs = Different Reference Ranges • Total NDF content is still a dominant factor
- Slides: 12