Gwinyai E. Chibisa, Ph.D.

MODIFICATION OF FORAGE QUALITY POST-HARVEST

http://www.hayhorsefeeders.com/round-bale-feeders.html

Chemical Treatments: Hydrolytic Agents

Hydrolytic agents = Alkali’s e.g., NaOH,

Ca(OH)2, NH3, urea

Disrupt lignocellulosic structure

i. Partially solubilize bonds between lignin, and

cellulose and hemicellulose

ii. Disrupt H-bonds in cellulose

http://www.intechopen.com/books/cellulose-fundamental-aspects/structural-characteristics-and-thermal-properties-of-native-cellulose

Chemical Treatments: Hydrolytic Agents

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

Chemical Treatments: NaOH

Dry application = spray on forage

Less effective than wet application

Chemical Treatments: NaOH

73.7

35.9

5.6

67.4

32.6

4.88

0

10

20

30

40

50

60

70

80

NDF ADF Lignin

Effect of NaOH Treatment on Fiber Content (%) of Bermuda grass

Control NAOH trt.

Utley et al., 1982. Can. J. Anim. Sci. 62:499-505

Chemical Treatments: NaOH

48.8 49.4

43

55.8 55.4

46.8

0

10

20

30

40

50

60

Dry matter NDF ADF

Effect of NaOH Treatment on Nutrient Digestibility (%)

Control NAOH trt.

Utley et al., 1982. Can. J. Anim. Sci. 62:499-505

Chemical Treatments: NaOH

0.65

11.2

0.69

9.91

0

2

4

6

8

10

12

ADG, kg/d Feed:Gain

Effect of NaOH treatment on Production Performance

Control NAOH trt.

Utley et al., 1982. Can. J. Anim. Sci. 62:499-505

Chemical Treatments: NaOH

Treatment issues

i. Hazardous (caustic alkali)

ii. Na accumulation in manure

iii. Expensive

iv. Wet application = leaching + disposal of residual

NaOH

Chemical Treatments: Ca(OH)2

Quicklime, burnt lime (CaO) used

Add water and forms hydrated lime (Ca(OH)2)

CaO + H2O Ca(OH)2 + Heat

Handle with care when mixing!

“Quicklime dust” causes severe irritation!

Chemical Treatments: Ca(OH)2

Chopping: 3 to 6 inches

Chemical Treatments: Ca(OH)2

36.3 36.4 36.7

51.8 50.353.1

0

10

20

30

40

50

60

Dry matter Organic matter NDF

Effect of CaO treatment on Nutrient Digestibility (%) of Corn Stover

Untreated Treated

Shi et al., 2015. J Anim Physiol a Anim Nutr. DOI: 10.1111/jpn.12381

Chemical Treatments: Ca(OH)2

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

Chemical Treatments: Ammoniation(cont.)

Application rate = 1.5 to 3% of DM (~60

lb/ton of dry forage)

Chemical Treatments: Ammoniation(cont.)

Key reaction: Conversion of anhydrous NH3

(liquid) to gas (several weeks)

Gas can penetrates forage (but losses)

Better reaction with;

i. High moisture in forage

ii. High ambient temperature

Chemical Treatments: Ammoniation(cont.)

82.1

2.56

31.5

73.9

11.875

51.2

0

10

20

30

40

50

60

70

80

90

NDF content CP content NDF digestibility

Effect of Ammoniation on Nutrient Composition & Digestibility (%) of Wheat Straw

Untreated Treated

Bals et al., 2010. Anim. Feed Sci. Technol. 155:147-155

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

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

Chemical Treatments: Urea

Urea used as a source of NH3

Urea NH3 + CO2

Mixed with roughage in silo, pelleter, etc.

Safer than handling anhydrous NH3

Variable results

Moisture content? Urease activity? Temperature?

Urease

Chemical Treatments: Oxidative Agents

Chemical Treatments: Alkaline Hydrogen Peroxide (AHP)

10.4

45.1

25.9

11.5

56.2

2.3

0

10

20

30

40

50

60

Lignin Cellulose Hemicellulose

Effect of AHP Treatment on Nutrient Composition (%) of Wheat Straw

Untreated AHP Treated

Chaudhry, 1998. Anim. Feed Sci. Technol. 74:315-328.

Chemical Treatments: Alkaline Hydrogen Peroxide (AHP)

49.446.4

58.8

76.1

67

85.4

0

10

20

30

40

50

60

70

80

90

NDF ADF Cellulose

Effect of AHP Treatment on Nutrient Digestiility (%) of Wheat Straw

Untreated AHP Treated

Chaudhry, 1998. Anim. Feed Sci. Technol. 74:315-328.

Chemical Treatments: Peroxides

Effective in improving digestibility, but;

Higher cost than NaOH or NH3 treatment

Not as practical as NaOH of NH3 treatment

Some peroxides are pollutants (e.g., ozone)

Microbial/Enzymatic Treatments

Advantages;

i. Fewer chemicals

ii. Lower energy inputs

Disadvantages;

i. Longer treatment time

ii. Loss of substrate during incubation

Microbial Treatments: White-rot Fungi

Effective in degrading lignocellulosic material

But loss of carbohydrates (CHO);

i. 1st utilize soluble CHO

before producing

lignin-degrading enzymes

ii. Degrade CHO from

delignified cell wallhttp://www.mykoweb.com/articles/DeconstructingDecomposing.html

Enzymatic Treatments

Use of various enzyme cocktails;

i. Cellulases,

ii. Xylanases

iii. Ligninases, etc.

Inconsistent results!!

High cost

Summary