Better Understanding Forage Fiber and Digestibility TTNDFD: A new (and better) tool to evaluate forages and monitor dairy rations Dr. David Combs Dept. of Dairy Science University of Wisconsin-Madison
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 => 1.5-2.5 L milk /day Fiber digestibility => 2.5-3 L milk /day
Assessing fiber digestion is not easy Poor digestion < 40% Excellent digestion > 50% A 2-3 unit change in fiber digestibility corresponds to a 0.5 liter change in milk yield.
TTNDFD Total Tract NDF Digestibility Licensed procedure through the University of WI >15 years of research, > $500,000 invested in development A more appropriate measure of forage digestibility in dairy cattle NDFD30 or undf How is TTNDFD determined? How to use TTNDFD information
Energy from forage is affected by: Plant characteristics The amount of fiber (NDF) The digestibility of fiber (NDFD) Potentially digestible fiber (pdndf) Rate of fiber digestion (kd) Animal and diet Intake affects rate of fiber passage (kp) Hindgut digestion of fiber is significant
TTNDFD combines feed and cow factors to measure energy from fiber Feed fiber Potentially digestible NDF Rate of fiber digestion Fiber digestion Rate of passage TTNDFD A 2-3 unit change in ration TTNDFD corresponds to a 0.5 l change in milk yield.
How is TTNDFD determined? Forage sample Rate of fiber digestion (kd) Potentially digestible NDF (pdndf) Rumen and hindgut digestion Standardized iv NDFD (24, 30, 48h) and indf Rate of fiber passage, (kp) PD NDF * kd/(kd +kp) TTNDFD (total tract NDF Digestibility)
Think of TTNDFD as how far you can travel on a tank of gas: How far you go depends on: The size of the tank (pdndf) AND The kilometers traveled per liter (kd) HOW much milk your forage will make depends on the amount of potentially digestible fiber AND the rate of fiber digestion!
Feed Analysis Lab Report TTNDFD is a prediction of NDF digestibility for a feed (or diet) in a 630 kg cow consuming 24 kg DM of a 28-30% NDF diet. TTNDFD 47.98 42.34
Typical NDF and TTNDFD values of forages 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%
Comparing Corn Silages from USA and Brazil Item USA* Brazil** NDF 42.7 47.8 TTNDFD 40.3 33.8 Starch 31 24.6 Starch digestibility 92? Crude Protein 7.8 7.8 *Rock River Labs 4 year average ** 3rlabs average 220 samples
Fiber digestion parameters of 106 samples total forages from Brazil (Lopes et al. 2013) N = 22 N = 30 N = 04 Palisade grass (Brachiaria brizantha) N = 31 Elephant grass (Pennisetum purpureum) N = 06 Star grass (Cynodon nlemfuensis) N = 13 Guinea grass (Panicum maximum) Mulato grass (Brachiaria hibrida) Bermuda grass (Cynodon dactylon)
NDF and TTNDFD of high quality grasses from Brazil Forage Specie n CP NDF TTNDFD DOM Palisade Grass Brachiaria brizantha 22 14.0 60.9 48.1 55.6 Mulato Grass Brachiaria hibrida 6 15.7 59.8 48.2 55.3 Bermuda Grass Cynodon dactylon 13 20.3 62.8 53.3 60.3 Star Grass Cynodon nlemfuensis 5 20.6 61.6 48.5 56.8 Guinea Grass Panicum maximum 31 17.3 62.5 47.8 54.5 Elephant Grass Pennisetum purpureum 30 18.3 60.4 53.0 58.4 Alfalfa Medicago sativa 946 18.0 46.0 46.5 71.0 Corn Silage Zea mays 993 6.8 44.9 40.3 68.8 Lopes, et al., 2013
Validating the TTNDFD model
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
Validating the TTNDFD approach at UW-Madison Can we optimize fiber use in dairy diets with TTNDFD? Grass feeding studies (Verbeten, 2012 UW-Madison) BMR vs conventional corn silage (Lopes et al, 2013a UW-Madison) Alfalfa vs corn silage utilization (Lopes et al, 2013b UW-Madison)
Cool Season Grass in TMR s Temperate Grasses: Are higher in NDF than alfalfa or corn silage Have higher TTNDFD than alfalfa or corn silage What s the potential of grass fiber for high NFC, low fiber diets (ie high corn silage rations)
What happens if we add grass fiber (high TTNDFD) or wheat straw fiber (low TTNDFD) to a diet with high quality alfalfa and corn silage? Control Tall Fescue Meadow Fescue Straw -----------------------% of Diet DM------------------------ Corn silage 26 17 17 20 Alfalfa silage 26 17 17 20 Bariane Tall Fescue* 17 Pradel Meadow Fescue* 17 Wheat Straw 8 High Moisture Corn 26 25 26 24 Protein/minerals 22 24 23 28 100 100 100 100 (Verbeten et al., 2012)
Trial 1 results: Adding grass or wheat straw to TMR with high quality corn silage and alfalfa Control Tall Fescue Meadow Fescue Straw Diet NDF 24 27 27 28 in Vivo NDFD 25 41 41 29 3.5 % FCM, L 41 42 43 42 Milk Fat, % 2.9 a 3.4 b 3.4 b 3.2 ab DMI, kg 26 ab 25 a 27 b 26 ab (Verbeten et al., 2012) Adding more digestible fiber from grass increased ration fiber digestibility and increased fat test
Trial 2: Using TTNDFD to Evaluate BMR and Conventional Corn Silage
Total Tract NDFD Prediction, % of NDF TTNDFD: BMR vs Conventional Corn Silage 65 60 55 50 45 40 35 30 25 20 20 30 40 50 60 70 Corn Silage NDF, % of DM Late 2012 BMR Late 2012 Conventional
Feeding TMR with low fiber digestibility corn silage (36 TTNDFD) vs high fiber digestibility corn silage (45 TTNDFD) Low Fiber Digestibility Corn Silage TMR High Fiber Digestibility Corn Silage TMR SE 4% FCM, L/d 34.3 35.0 1.0 Observed rumen NDFD, % of NDF 40.5 41.5 2.5 Predicted rumen NDFD, % of NDF* 38.4 b 42.8 a 0.9 * In vitro NDFD assay predicted rumen fiber digestibility at ad lib intake Lopes et al, 2013
Trial 3: Using TTNDFD to Evaluate Fiber Digestion in Alfalfa and Corn Silage Diets
Can the in vitro TTNDFD test detect a difference in fiber digestibility as ratios of corn silage (36% TTNDFD) and alfalfa(42% TTNDFD) change in the ration? Corn silage:alfalfa ratio 100CS 0AS 67CS 33AS 33CS 67AS 0CS 100AS DMI, kg/d 25.2 ab 25.3 a 24.3 b 21.9 c 0.8 4% FCM, l/d 36.3 35.4 35.2 36.0 0.9 SE Observed TTNDFD, in vivo 38.3 a 40.9 ab 39.4 ab 43.8 a 1.9 Predicted TTNDFD, in vitro* 38 41 41 45 2.1 Lopes et al, 2013 *In vitro TTNDFD analysis of feeds matched the observed (in vivo) NDF digestibility values
How to use TTNDFD
Lb milk Troubleshooting with TTNDFD 80 78 Switched from 2009 to 2010 Corn Silage WHAT HAPPENED? 76 74 72 70 68 Item 2009 2010 NDF 43% 37% NDFD30 62% 61% TTNDFD 48% 32%
2011, 2012 and 2013 Corn Silage Quality, Midwest & East NDF TTNDFD 47.3 46.0 46.5 44.1 43.7 39.8 2011 2012 2013 On average, 2013 crop corn silage is nearly 8 units lower in fiber digestibility (TTNDFD) last year s corn silage Adapted from Goeser, 2013 Hoard s Dairyman, Nov. Issue.
Feed Analysis Lab Report andf 39.7 % Low NDF corn silage (good) TTNDFD 37.1 BUT- Lower than average fiber digestibility (bad)
Feed Analysis Lab Report andf TTNDFD 42.6% 51.4 Which is the better Haylage? andf TTNDFD 42.2% 44.1
TTNDFD: The Take Home Message 1. Fiber digestibility has a big impact on milk yield. A 2-3 unit change in ration TTNDFD corresponds to a 0.5 liter change in milk yield. 2. The TTNDFD test was developed to predict fiber digestibility in high producing dairy cattle Can be used across forage types and byproduct feeds Can be used in ration balancing and evaluation
TTNDFD Guidelines Remember 42% TTNDFD Corn silage and haylage average! Grasses = 44% TTNDFD Goal = 48+%
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Total Tract NDF digestibility 60 30 h in vitro NDFD values are poorly correlated with TTNDFD 50 40 30 y = 0,0783x + 35,279 R² = 0,0088 20 10 1000 corn silage samples 20 40 60 80 100 In Vitro NDFD30
In vivo NDF digestion, % In vivo NDF digestion, % Stand-alone in vitro NDFD30 or indf values are poor predictors of in vivo fiber digestion In vivo NDF digestion vs In vitro NDFD30h In vivo NDF digestion vs indigestible NDF (240h in vitro or 288h in situ) 60 60 50 50 40 40 30 30 20 10 0 y = 0.043x + 42.8 R² = 0.005 0 20 40 60 20 10 0 y = -0.864x + 68.3 R² = 0.364 0 10 20 30 40 50 60 NDFD 30h in vitro, % Indigestible NDF, % of NDF Arndt C, Armentano LE, Hall MB. J. Dairy Sci. 2009;92 (E-Suppl. 1):94. Ferraretto L. F., A. C. Fonseca, C. J. Sniffen, A. Formigoni, and R. D. Shaver. 2014. Submitted to ADSA meeting 2014. Fredin SM, Bertics SJ, Shaver RD. 2013 J. Dairy Sci. 2013;96(E-Suppl. 1):149. Fredin SM, Ferraretto LF, Akins MS, Shaver RD. 2013 J. Dairy Sci. 2013;96(E-Suppl. 1):34. Lopes, F., D. E. Cook, R. W. Bender and D. K. Combs. 2013a. J. Dairy Sci. 96( E-Suppl 1): 523.. Lopes. F., D. E. Cook and R. W. Bender and D. K. Combs. 2013b.. J. Dairy Sci. 96( E-Suppl 1): 16.. Verbeten, W. D., D. K. Combs and D. J. Undersander. 2011. J. Dairy Sci. 94 (E-Suppl 1): 556.
In vivo NDF digestion, % TTNDFD combines in vitro rate of NDF digestion with indf to improve the prediction of in vivo fiber digestion 60 55 50 45 40 35 y = 1.03x R² = 0.660 30 25 25 30 35 40 45 50 55 60 TTNDFD in vitro, %
Fiber digestion is affected by plant and animal factors Rumen Fiber digestibility = pdndf x kd + hindgut fiber digestion (kd + kp) TTNDFD is an indexing tool that predicts how fiber will be utilized in a cow consuming 53 lbs of DMI/d of a typical dairy diet (28-30 % NDF)
In Vitro NDF Digestion: TTNDFD is different from NDFD 30 or NDFD 48
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)
Trial 2: Feeding TMR with Normal corn silage (36 TTNDFD) vs BMR corn silage (45 TTNDFD) Normal Corn Silage TMR BMR Corn Silage TMR SE DMI, lb/d 56.1 56.3 2.9 4% FCM, lb/d 75.5 77.0 2.4 Observed rumen NDFD, % of NDF 40.5 41.5 2.5 Predicted rumen NDFD, % of NDF* 38.4 b 42.8 a 0.9 * In vitro NDFD assay predicted rumen fiber digestibility at ad lib intake Lopes et al, 2013
In Vivo Fiber Digestion Kinetics High Starch High Starch Low Starch Low Starch HMC Dry Corn HMC Dry Corn SE Diet Starch, % 31.1 32.2 21 21.3 0.5 Diet NDF, % 23.1 24.2 30.1 30.5 0.2 Rumen digestion rate, %/h Pot. Dig. NDF 2.25 2.91 3.15 3.44 0.23 Rumen passage rate, %/h Pot. Dig. NDF 2.59 3.01 2.84 2.67 0.33 Total Tract Digestibility NDF 37.5 35.2 39.3 38.2 3 Oba and Allen 2003 Over 50 feeding studies (> 175 treatments) have been published that have measured kd, kp and pdndf in lactating cattle
Validation: Do in vitro TTNDFD model inputs and outputs match what was measured in the cow? Fiber digestibility = pdndf x kd + hindgut digestion (kd + kp) Method* P-value Predicted In vivo SEM Method Input pdndf, % of NDF 71.5 67.4 1.01 <0.01 pdndf kd, %/h 4.11 4.27 0.46 0.72 pdndf kp, %/h 2.67 2.79 0.35 0.56 Output Rumen digested NDF, kg 2.73 2.63 0.22 0.64 Hindgut digested NDF, kg 0.36 0.64 0.19 0.05 Total tract digested NDF, kg 3.09 3.27 0.22 0.42 Total tract NDF digestibility, % of NDF 46.4 49.5 2.07 0.13 *Predicted by the in vitro TTNDFD model, or measured in cattle by fill and flux method. Lopes et al., 2014. Effect of source of corn silage and level of dry matter intake on rumen digestion kinetics and total tract digestibility in dairy cows.