MODIFICATION OF FORAGE QUALITY POST-HARVEST

Transcription

1 MODIFICATION OF FORAGE QUALITY POST-HARVEST Gwinyai E. Chibisa, Ph.D.

2 Chemical Treatments: Hydrolytic Agents Hydrolytic agents = Alkali s e.g., NaOH, Ca(OH) 2, NH 3, urea Disrupt lignocellulosic structure i. Partially solubilize bonds between lignin, and cellulose and hemicellulose ii. Disrupt H-bonds in cellulose

3 Chemical Treatments: Hydrolytic Agents

4 Chemical Treatments: NaOH Used at 3 to 5% of DM Wet application = soak cereal straw in NaOH for 3 days and wash off residual chemical Leaching of nutrients during washing (10-15% DM loss) Disposal of residual NaOH

5 Chemical Treatments: NaOH Dry application = spray on forage Less effective than wet application

6 Chemical Treatments: NaOH Effect of NaOH Treatment on Fiber Content (%) of Bermuda grass NDF ADF Lignin Control NAOH trt. Utley et al., Can. J. Anim. Sci. 62:

7 Chemical Treatments: NaOH 60 Effect of NaOH Treatment on Nutrient Digestibility (%) Dry matter NDF ADF Control NAOH trt. Utley et al., Can. J. Anim. Sci. 62:

8 Chemical Treatments: NaOH Effect of NaOH treatment on Production Performance ADG, kg/d 0.69 Control NAOH trt. Feed:Gain Utley et al., Can. J. Anim. Sci. 62:

9 Chemical Treatments: NaOH Treatment issues i. Hazardous (caustic alkali) ii. iii. iv. Na accumulation in manure Expensive Wet application = leaching + disposal of residual NaOH

10 Chemical Treatments: Ca(OH) 2 Quicklime, burnt lime (CaO) used Add water and forms hydrated lime (Ca(OH) 2 ) CaO + H 2 O Ca(OH) 2 + Heat Handle with care when mixing! Quicklime dust causes severe irritation!

11 Chopping: 3 to 6 inches Chemical Treatments: Ca(OH) 2

12 Chemical Treatments: Ca(OH) Effect of CaO treatment on Nutrient Digestibility (%) of Corn Stover Dry matter Organic matter NDF Untreated Treated Shi et al., J Anim Physiol a Anim Nutr. DOI: /jpn.12381

13 Chemical Treatments: Ca(OH)2

14 Chemical Treatments: Ammoniation Most widely used method of alkali treatment in the US Not as effective as NaOH treatment But increase CP content Works better with poor quality forages/residues < 5% CP < 45 50% TDN

15 Chemical Treatments: Ammoniation (cont.) Application rate = 1.5 to 3% of DM (~60 lb/ton of dry forage)

16 Chemical Treatments: Ammoniation (cont.) Key reaction: Conversion of anhydrous NH 3 (liquid) to gas (several weeks) Gas can penetrates forage (but losses) Better reaction with; i. High moisture in forage ii. High ambient temperature

17 Chemical Treatments: Ammoniation (cont.) Effect of Ammoniation on Nutrient Composition & Digestibility (%) of Wheat Straw NDF content CP content NDF digestibility Untreated Treated Bals et al., Anim. Feed Sci. Technol. 155:

18 Chemical Treatments: Ammoniation (cont.) Increases intake and digestibility Can partially replace conventional hay with treated straw Up to 65% in late-gestation cows Up to 35% in cows nursing calves

19 Chemical Treatments: Ammoniation (cont.) Always consider ammoniation cost vs. hay price! Estimated cost to treat 1 ton of forage: $26-30 for anhydrous ammonia $5-9 for plastic Total = $31-39/ton If wheat straw = $45-50/ton, ammoniated straw = $76-89/ton

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24 Chemical Treatments: Urea Urea used as a source of NH 3 Urease Urea NH 3 + CO 2 Mixed with roughage in silo, pelleter, etc. Safer than handling anhydrous NH 3 Variable results Moisture content? Urease activity? Temperature?

25 Chemical Treatments: Oxidative Agents

26 Chemical Treatments: Alkaline Hydrogen Peroxide (AHP) Effect of AHP Treatment on Nutrient Composition (%) of Wheat Straw Lignin Cellulose Hemicellulose Untreated AHP Treated Chaudhry, Anim. Feed Sci. Technol. 74:

27 Chemical Treatments: Alkaline Hydrogen Peroxide (AHP) Effect of AHP Treatment on Nutrient Digestiility (%) of Wheat Straw NDF ADF Cellulose Untreated AHP Treated 85.4 Chaudhry, Anim. Feed Sci. Technol. 74:

28 Chemical Treatments: Peroxides Effective in improving digestibility, but; Higher cost than NaOH or NH 3 treatment Not as practical as NaOH of NH 3 treatment Some peroxides are pollutants (e.g., ozone)

29 Microbial/Enzymatic Treatments Advantages; i. Fewer chemicals ii. Lower energy inputs Disadvantages; i. Longer treatment time ii. Loss of substrate during incubation

30 Microbial Treatments: White-rot Fungi Effective in degrading lignocellulosic material But loss of carbohydrates (CHO); i. 1 st utilize soluble CHO before producing lignin-degrading enzymes ii. Degrade CHO from delignified cell wall

31 Enzymatic Treatments Use of various enzyme cocktails; i. Cellulases, ii. iii. Xylanases Ligninases, etc. Inconsistent results!! High cost

32 Summary