Dr. Dan Undersander Professor of Agronomy University of Wisconsin

Transcription

1 Dr. Dan Undersander Professor of Agronomy University of Wisconsin

2 Hybrid South Central South Hybrid 1 Milk/t Milk/a NDFD Starch Hybrid 2 Milk/t Milk/a NDFD Starch 31 29

3 % Dry matter Dry matter of alfalfa haylage, Prairie du Sac /09/03 06/28/03 08/17/03 10/06/03 11/25/03 01/14/04 Sample Date

4 % NDF NDF of alfalfa haylage, Prairie du Sac /09/03 06/28/03 08/17/03 10/06/03 11/25/03 01/14/04 Sample Date

5 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

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

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

8 Midwest TDN % = (.70 x ADF) NEL (Mcal/lb) = (TDN X.01114) New York DHIA TDN % = (53.1 x NEL) ENE (Mcal/lb) = NEL x NEL (Mcal/lb) = (0.008 x ADF) Penn State TDN % = 31.4 (53.1 x NEL) ENE (Mcal/lb = NEL x NEL (Mcal/lb = (00344 x ADF

9 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

10 Digestibility, % DM R² = 0, Acid Detergent Fiber Source: Worlds Forage Superbowl

11 In Vitro Digestibility, % DM y = 1.19x R² = NDF, % DM Source: Worlds Forage Superbowl 2014

12 In Vitro Digestibility, % DM y = 1.21x R² = NDFD, % of NDF Source: Worlds Forage Superbowl 2014

13 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) NDF degradability using 30 or 48h in vitro assay or

14 Fermentation time (hours) NDFD (% of NDF) Standard Deviation a Data from Dave Combs, Error between runs, i.e. one week to next

15 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)

16 Alfalfa/mixed stands Constituent Mean R 2 Crude Protein ADF andf IVDMD 30 hr IVDMD 48 hr Ash Lignin

17 Corn Silage Constituent Mean R 2 Crude Protein ADF andf IVTD 30 hr IVTD 48 hr Ash Starch Lignin to 95 % of North American Forage Analysis are run by NIR

18 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

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

20 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

21 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.

22 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%

23 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 % 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 % of NDF St. Dev. 8.8

24 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

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

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

27 High Fiber Digestibility Means More Value NDF TTNDFD NEl Value/ton* Green Spirit Italian Ryegrass Hay $17/ton Low Fiber Cool Season Grass *Feedval12

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

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

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32 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