Dr. Dan Undersander Professor of Agronomy University of Wisconsin

Dr. Dan Undersander Professor of Agronomy University of Wisconsin

Hybrid South Central South Hybrid 1 Milk/t 3180 3340 Milk/a 35400 37100 NDFD 62 63 Starch 28 33 Hybrid 2 Milk/t 3250 3040 Milk/a 36000 35900 NDFD 62 60 Starch 31 29

% Dry matter Dry matter of alfalfa haylage, Prairie du Sac 60 55 50 45 40 35 30 25 20 05/09/03 06/28/03 08/17/03 10/06/03 11/25/03 01/14/04 Sample Date

% NDF NDF of alfalfa haylage, Prairie du Sac 40 35 30 25 20 15 05/09/03 06/28/03 08/17/03 10/06/03 11/25/03 01/14/04 Sample Date

Best indicator of animal performance is a feeding trial Second best indicator is in situ or in vitro digestion Does not account for rumen retention time/rate of passage Chemical analyses are estimates of digestion

Empirical equations Summative equations In Vitro/in situ Digestion Total Tract Digestibility

University of Wisconsin Grasses and Legumes TDN% = DDM TDN = 88.9 -(.779*ADF) NEl (Mcal/lb) = (TDN *.01114) -.054 New York DHIA Legumes NEl (Mcal/lb) = 1.044 - (.0123* ADF) Grasses NEl (Mcal/lb) = 1.085 - (.0150* ADF) Penn State Legumes NEl (Mcal/lb) = 1.044 - (.0119* ADF) Grasses NEl (Mcal/lb) = 1.085 - (.0124* ADF)

Midwest TDN % = 87.84 (.70 x ADF) NEL (Mcal/lb) = (TDN X.01114) 0.054 New York DHIA TDN % = 31.4 + (53.1 x NEL) ENE (Mcal/lb) = NEL x 0.826 NEL (Mcal/lb) = 0.94- (0.008 x ADF) Penn State TDN % = 31.4 (53.1 x NEL) ENE (Mcal/lb = NEL x 0.826 NEL (Mcal/lb = 0.7936 (00344 x ADF

Regression of digestibility to a chemical component (ADF, NDF or CP) Easy to measure Population dependent r or r 2 indicate how well a population of data fits an equation, not how well a single observation fits the model Poor sensitivity

Digestibility, % DM 80 75 70 65 60 55 50 45 R² = 0,5458 25 30 35 40 45 50 Acid Detergent Fiber Source: Worlds Forage Superbowl

In Vitro Digestibility, % DM 80 75 70 65 60 55 50 45 40 y = 1.19x + 18.87 R² = 0.20 30 32 34 36 38 40 NDF, % DM Source: Worlds Forage Superbowl 2014

In Vitro Digestibility, % DM 80 75 70 65 60 55 50 45 40 y = 1.21x - 12.84 R² = 0.54 50 55 60 65 70 NDFD, % of NDF Source: Worlds Forage Superbowl 2014

Uniform feed fractions have predictable digestion coefficients TDN 1-X =tdcp + (tdfa x 2.25) + tdndf + tdnfc -7 An estimate of NDF digestibility at maintenance intake:.75 x (NDFn - Lignin) x [1 -(Lignin/NDFn) 0.667 NDF degradability using 30 or 48h in vitro assay or

Fermentation time (hours) NDFD (% of NDF) Standard Deviation 24 45.3 52.5 30 46.1 20.2 48 56.5 7.6 a Data from Dave Combs, 2004. Error between runs, i.e. one week to next

Reasons why NDFD 30 or NDFD 48 values are poor predictors of fiber digestibility: 1. Single time point values do not differentiate between indigestible and undigested potentially digestible fiber. 2. Single time point in vitro values to not necessarily reflect rate of fiber digestion. To evaluate forage fiber utilization you need to know pdndf, kd and kp! Fiber digestibility = pdndf x kd (kd + kp)

Alfalfa/mixed stands Constituent Mean R 2 Crude Protein 17.5 0.95 ADF 37.7 0.90 andf 47.2 0.96 IVDMD 30 hr 69.2 0.89 IVDMD 48 hr 78.6 0.84 Ash 10.0 0.90 Lignin 7.6 0.81

Corn Silage Constituent Mean R 2 Crude Protein 9.1 0.87 ADF 27.2 0.92 andf 45.6 0.93 IVTD 30 hr 78.2 0.92 IVTD 48 hr 81.9 0.82 Ash 4.7 0.73 Starch 21.7 0.97 Lignin 3.5 0.63 90 to 95 % of North American Forage Analysis are run by NIR

Carbohydrate Digestibility Affects Health & Production Properly balancing NFC and NDF is critical for health and production in high producing dairy cows. Variations in fiber digestibility affect production more than variations in starch digestibility Starch digestibility => 1½ to 2¼ l/day Fiber digestibility => 3+ l/day

Poor digestion < 40% Excellent digestion > 50% A 2 to 3 unit change in fiber digestibility corresponds to ½ l change in milk yield.

TTNDFD is a more complete analysis of fiber quality indf the proportion of undigestible fiber Kd the rate of fiber digestion Kp the rate of passage Unless you account for all three you don t really know how good your forage is

Feed and cow factors are combined to true fiber digestion Fiber digestion Rate of passage TTNDFD Feed fiber Potentially digestible NDF Rate of fiber digestion A 2-3 unit change in ration TTNDFD corresponds to 1 pound change in milk yield.

NDF TTNDFD Average Good Alfalfa < 40% 42% > 48% Corn Silage < 40% 42% > 48% Temperate Grasses < 45% 44% > 50% Dairy quality alfalfa and corn silages will be < 40% NDF with a TTNDFD value of at least 42%

What do the real experts say? Legume/grass feeding trials Mean 47.3 % of NDF (20 trials, 64 observations Median 47.5 % of NDF In vivo NDF diet digestibility) Range 31.1-66.2 % of NDF St. Dev 8.1 Cows report that TTNDF digestibility of legume/grasses are higher than TTNDF digestibility of corn silage. Corn Silage/Sorghum feeding trials Mean 40.2 % of NDF (25 trials, 81 observations, Median 41.1 % of NDF In Vivo NDF diet digestibility) Range 20.1-58.8 % of NDF St. Dev. 8.8

Feed Analysis Lab Report TTNDFD is a prediction of NDF digestibility for a feed (or diet) in 1400 lb cow consuming 53 lb DM of a 28-30% NDF diet. TTNDFD 47.98 42.34

Total wet rumen content = 10546 kg Total wet rumen content = 23,435 lbs

Feed Analysis Lab Report andf 39.7 % Low NDF corn silage (good) TTNDFD 37.1 BUT- Lower than average fiber digestibility (bad)

High Fiber Digestibility Means More Value NDF TTNDFD NEl Value/ton* Green Spirit Italian Ryegrass Hay 50 59 0.78 + $17/ton Low Fiber Cool Season Grass 50 48 0.71 *Feedval12 http://dairymgt.info/tools/feedval_12/index.php

Lb milk Troubleshooting with TTNDFD 80 78 Switched from 2009 to 2010 Corn Silage WHAT HAPPENED? 76 74 72 Item 2009 2010 NDF 43% 37% NDFD30 62% 61% TTNDFD 48% 32% 70 68

Remember 42% TTNDFD Corn silage and haylage average! Grasses = 44% TTNDFD Goal = 48+%

Fiber and starch, by themselves, are not good estimates of quality Digestibility of each component must be estimated Total Tract NDF digestibility (TTNDFD) additionally incorporates indf, the rate of fiber digestion and the rate of passage to give a more complete picture of forage quality