R. A. Zinn University of California, Davis

Transcription

1 Fecal starch how can this tool helps to improve feedlot performance R. A. Zinn University of California, Davis

2 Advantage of Flaked vs Dry processed corn Performance and net energy advantage (%) of steam flaked corn grain over dry corn grain Control Item corn ADG, % DMI, % ADG/DMI Authors Matushima and Montgomery (1967) Ground Lee et al. (1982) Trial 1 Whole Lee et al. (1982) Trial 2 Whole Ramirez et al. (1985) Whole Zinn (1987) dry rolled Barajas and Zinn (1998) Urea dry rolled Barajas and Zinn (1998) Cottonseed dry rolled Ward et al. (2000) dry rolled Trials average

3 Estimated NE value of steam-flaked corn using Replacement technique Performance and net energy advantage (%) of steam flaked corn grain over dry corn grain Improvement Control SFC, Mcal/kg over DRC, % Item corn NEm NEg NEm NEg Authors Matushima and Montgomery (1967) Ground Lee et al. (1982) Trial 1 Whole Lee et al. (1982) Trial 2 Whole Ramirez et al. (1985) Whole Zinn (1987) dry rolled Barajas and Zinn (1998) Urea dry rolled Barajas and Zinn (1998) Cottonseed dry rolled Ward et al. (2000) dry rolled Trials average

4 Estimated NE value of steam-flaked corn using Substitution technique Literature summary of energy values of dry rolled and steam flaked corn grain from Owens et al. (1997) ME NE, Mcal/kg Item Trials Mcal/kg Std Dev Maint. Gain Corn form Dry rolle d Steam flaked Advantage, %

5 Improvement in NE of corn due to flaking Replacement technique (direct comparison) Improvement in NE, % Maintenance 14% Gain 19% Substitution technique (indirect comparison) Improvement in NE, % Maintenance 14% Gain 17% Observed increase in NE agree closely with expected increases based on measures of digestion

6 How does steam flaking bring about this dramatic improvement in the feeding value of corn?

7 Generally recognized that steam flaking corn increases starch digestion (Zinn et al., 1995) Digestion, % DRC SFC %D Starch

8 Steam flaking increases digestion of nonstarch OM to the same extent that it increase starch digestion (Zinn et al., 1995) DRC SFC %D Digestion, % Starch OM

9 The objective of steam flaking is to optimize feeding value The primary factor limiting digestion is the availability of starch to the enzymatic process. This limitation is not solely a function of starch solubility Raw corn starch has very low solubility (3%) but very high ruminal digestibility (>90%) Disruption of the protein matrix capsulating the starch granule is a key limiting factor

10 CORN COMPOSITION

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14 We flake corn to bring about completeness of starch digestion, and that effect occurs in the small intestine. Flaking technique will alter site of digestion However, most importantly, flaking can bring about completeness of digestion. 99 vs 90% starch digestion This difference in completeness of digestion does not occur in the rumen. It occurs in the small intestine. Completeness of starch digestion is associated with increased intestinal protein digestion

15 Influence of flaking on postruminal protein and starch digestion Post ruminal digestion, % entering SI DRC SFC %D Zinn, 1990 Protein Starch Zinn et al., 1995 Protein Starch Barrajas and Zinn, 1998 Protein Starch Zinn et al., 1998 Protein Starch Average Protein Starch

16 Disruption of the protein matrix surrounding the starch granule A function of: moisture uptake by the starch granule degree of shear (flake thickness) Disruption of the matrix will also increase starch solubility

17 Steam flaker component illustration Figure 4. Steam flaker component illustration. FACTORS IN FLAKE QUALITY 1. Steam chest temperature 2. Steaming time 3. Moisture uptake 4. Grain distribution across rolls 5. Roll corrugation 6. Ram pressure 7. Roll gap

18 ROLL CORRUGATION facilitates drawing grain through the rolls

19 The process of steam flaking is intended to: 1 Induce moisture uptake or swelling of starch granules 2 Application of shear to swollen granules to disrupt the protein matrix Influence of steaming vs steaming and flaking on enzymatic starch reactivity (Osman et al., 1970) Sorghum grain Untreated Steam, not flaked Starch reactivity, % Steam-flaked Course Medium Thin

20 Assessing quality of flaked corn Common measures include: Flake density Flake thickness Enzymatic starch reactivity Fecal starch

21 FLAKE DENSITY COMPARISON

22 Total starch digestion, % TSD = * Flake density, r 2 = Flake density, kg/l

23 Flake density and flake thickness are closely associated FD, kg/l = (0.175 FT)

24 Flake density vs starch reactivity (Zinn, 1990) Equation Amyloglucosidase reactivity = (FD kg/l) Porcine pancreatin reactivity = (FD kg/l) R

25 Fecal starch, a more reliable tool for assessing adequacy of corn processing.

26 Relationship between fecal starch and starch digestion in cattle a. Steam flaked Dry rolled Whole shell Fecal Starch,% 2.4 (1.2) b 16.6 (5.1) 22.6 (1.3) Starch digestion, % Ruminal 84.5 (4.8) 66.9 (8.8) 65.9 (3.0) Total 99.0 (0.7) 90.5(3.0) 80.3 (3.9) a 64 trials summary b Values in parenthesis are standard deviations

27 Starch Starch digestion, digestion, % % 32-trial summary/ 637 individual data points Relationship between fecal starch percentage (FS) and total tract starch digestion [starch digestion, % = FS FS 2, R 2 = 0.96] Fecal starch, 25 % Fecal starch, %

28 For steam-flaked corn or sorghum based diets, prediction of starch digestion is improved by including measure of fecal N in the analysis When starch digestion is 5% Estimate is improved by including Fecal N Predicted starch digestion, % of intake = 100 {1 [( FN FN 2 ) FS/DS]} where FN, FS, and DS are the percentages of DM represented by fecal N, fecal starch, and dietary starch, respectively [observed starch digestion, % = (SE = ) predicted starch digestion, r2 = 0.94]. Zinn et al., 2007

29 Change in grain NEm, Mcal/kg Relationship between change in total tract starch digestion (CSD, %) and change in grain (corn, wheat, sorghum) NEm: change in grain NEm, Mcal/kg = CSD, % (r2 = 0.97) Corn Sorghum Wheat Change in starch digestion, percentage unit

30 Where corn is the principle source of dietary starch: corn NEm = FS FS 2 corn NEg = NEm Example: FS = 3 vs 8% 3% FS, corn NEm = 2.40 Mcal/kg 8% FS, corn NEm = 2.31 Mcal/kg

31 Where dietary starch (DS) is less than 50%, fecal starch requires adjustment: Adjusted Fecal Starch = FS*50/DS Example: FS = 3%, DS = 20% (from corn grain) Adjusted FS = 7.5% Starch digestion = 96.1% Starch digestion, % = FS FS 2 Corn NEm = 2.32 Mcal/kg NEm = FS FS 2

32 Where corn is the principle source of dietary starch: For each percentage unit increase in fecal starch above 3%: Feeding value of flaked corn decreases by 0.8 to 1.0%!

33 Conclusions Steam flaking increases the NEm and NEg values of corn by 14 and 18.5%, respectively Actual value will depend on quality of the flake

34 The value of steam flaking grain is enhanced when: Corn is flaked properly Density =.31 to.36 kg/l 24 to 28 lbs/bushel 01.8 to 2.0 mm flake thickness

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