FACTORS AFFECTING
FORAGE QUALITY
pp. 232 - 246
FORAGES OR ROUGHAGES
• General characteristics
– Higher fiber concentration than energy and protein
supplements
– Lower energy concentration than energy or protein
supplements
– Lower protein concentration than protein supplements
• May have higher or lower protein concentration than energy
supplements
• A high proportion of the protein in most forages is highly
degraded in the rumen
– Calcium concentration greater than energy and plant
protein supplements
– Concentrations of phosphorus and other minerals is
highly variable
– Concentrations of fat soluble vitamins high in fresh
forages, but low after storage
WHAT DEFINES FORAGE
QUALITY?
FACTORS DETERMINING FORAGE
QUALITY
•
•
•
•
Forage species
Maturity
Soil fertility
Harvest method and quality of storage
– Leaf-to-stem ratio
– Nutrient preservation
Total forage mass, lb/acre
MAJOR CLASSES OF FORAGE SPECIES
3000
2000
1000
0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Months
Cool season grass
Legumes
Warm season grass
Stockpiled gr-leg (Hay equiv.)
Corn stalks (Hay equiv.)
NUTRITIONAL VALUE OF LEGUMES, COOL SEASON
GRASSES, AND WARM SEASON GRASSES AT
COMPARABLE MATURITIES
DM basis
CP,
%
NDF,
%
ADF,
%
ADL,
%
TDN,
%
NEm
Mcal/
kg
NEg
Mcal/
kg
Ca,
%
P,
%
Cool season grasses
Immature
18
50
31
4
63
1.48
0.89
.72
.34
Mid-maturity
13
58
37
4
60
1.33
0.75
.66
.29
Mature
11
69
42
6
56
1.18
0.62
.47
.26
Immature
23
36
29
6
62
1.49
0.90
1.56
.31
Mid-maturity
21
43
33
6
59
1.38
0.80
1.37
.30
Mature
18
51
40
7
55
1.21
0.65
1.22
.28
Legumes
Warm season grasses
Immature
14
-
-
-
64
1.45
0.87
.63
.20
Mature
6
-
-
-
51
1.08
0.58
.40
.12
COOL SEASON GRASSES
• Most common grasses in the Midwest
– Kentucky bluegrass
– Orchardgrass
– Perennial ryegrass
- Tall fescue -Smooth bromegrass
- Reed canarygrass - Timothy
• Growth
– 66% of production occurs before early-June
– Very low productivity in mid-summer
– Some late season growth
• Yields
– Species effects
Tall fescue
Reed
>Smooth bromegrass>Timothy>>Kentucky
canarygrass
Orchardgrass
bluegrass
– Very sensitive to soil fertility
• N, P, and K
• When is it needed???????
USES OF COOL SEASON GRASSES
Grazing
Harvest
Kentucky
bluegrass
Excellent
Poor
Smooth
bromegrass
Excellent
Excellent
Orchardgrass
Excellent
Excellent
Better mid-summer growth
than other CSG
Tall fescue
Good
Good
Better fall growth than other
CSG
Reed
canarygrass
Good
Good
Grows well in wet
environments
Fair
Excellent
Preferred for horse hay
Good
Excellent
Higher quality, but poorer
persistence than other CSG
Timothy
Perennial
ryegrass
Comments
NUTRITIONAL QUALITIES OF COOL SEASON
GRASSES
• General
Compared to:
Legume forages
@ comparable
maturity
Grains
Plant protein
supplements
CP
Lower
Greater/Lower
Lower
NDF
Greater
Greater
Greater
ADF
Greater
Greater
Greater
TDN/NE
Lower
Lower
Lower
Ca
Lower
Greater
Comparable
Comparable
Comparable
Lower
P
• Effects of fertility
• N, P, K, Mg, and many trace minerals will affect their
concentration in cool season grasses
ANTI-QUALITY COMPONENTS IN COOL
SEASON GRASSES
• Endophyte fungus
– Found in
• Tall fescue
• Perennial ryegrass
– Produces toxic alkaloids
• Classes
– Lysergic acid amides
– Ergopeptines
» Ergovaline
• Location
– Primarily in the seed
– Also in stem and leaf
• Transfer to a pasture
– Via the seed
– Effects of fescue toxicosis
• Physiological effects
– Vasoconstriction
– High core body temperatures
– Low heart rate
– Low prolactin
– Suppression of immune system
• Results on animal
– Hoof loss
– Low forage intake and weight gains during summer
– Retention of winter hair coat
– Standing in water sources
– Low milk production
– Reproductive problems
» Low pregnancy rate
» Dystocia
» Retained placenta
– Management to prevent fescue toxicosis
•
•
•
•
•
Prevent excessive maturity of forage
Limit application of N-fertilizer
Plant or interseed legume forages in tall fescue pastures
Rotate animals to non-fescue pastures
Plant endophyte-free varieties of tall fescue
– Poor persistence
• Plant tall fescue varieties containing beneficial
endophyte
• Treatment of cattle with Ivermectin???
– A dewormer
• Treatment of pregnant mares with Domperidone
– Blocks receptors for dopamine
• Tryptamine alkaloids
– Common in native reed canarygrass varieties
– Physiology
• Serotonin receptor agonists
• Can cause staggers or sudden death
– Common effects on animal
• Reduced feed intake and growth
– Management
• Plant low alkaloid varieties of reed canarygrass
• Rotate animals for paddocks that do not contain reed
canarygrass
• Cobalt supplementation
LEGUMES
• Species
– Alfalfa Red clover
White clover
Sweet clover
Berseem clover
• Growth
Birdsfoot trefoil
Sweet clover
– Greatest in spring, but more uniform over the season than
grasses
• Yields
Alfalfa > Red clover > Birdsfoot trefoil >> White clover
Sweet clover
• Fertility needs
– N fertilization is not required
• May reduce legume persistence in grass-legume pasture
– Sensitive to pH, P, and K
• Persistence
– Very sensitive to management
• Most species require some type of rest period to allow
nutrient storage in roots and crown and/or reseeding
• Competition with cool season grasses
• Sensitive to most herbicides
USES OF LEGUMES
Species
Grazing
Harvest
Comments
Good
Excellent
Perennial, sensitive to wet
conditions
Red clover
Excellent
Good
Biennial, sensitive to
drought, easy to interseed
Birdsfoot trefoil
Excellent
Good
Perennial, but responds to
management that allows
reseeding
Ladino & White
clover
Good
Poor
Perennial, less sensitive to
close grazing than other
legumes
Sweet clover
Poor
Fair
Biennial, less sensitive to
soil conditions than other
legumes
Excellent
Good
Perennial, very persistent
Fair
Good
Annual
Alfalfa
Kura clover
Berseem clover
NUTRITIONAL QUALITIES OF LEGUMES
• General
Compared to:
Cool season
grasses @
comparable
maturity
Grains
Plant protein
supplements
CP
Greater
Greater
Lower
NDF
Lower
Greater
Greater
ADF
Lower
Greater
Greater
TDN/NE
Greater
Lower
Lower
Ca
Greater
Greater
Greater
Comparable
Comparable
Lower
P
• Effects of fertility
• K fertility will affect its concentration in legumes
NUTRITIONAL CONCERNS WITH LEGUME
FORAGES
• Bloat
– Inability of ruminants to release fermentation
gases
– Occurs in ruminants consuming fresh, immature
legumes like alfalfa, white clover, red clover, and
kura clover
– Caused by a high concentration of soluble protein
in these legumes
• Results in the formation of foam in the rumen
• Inhibits eructation
• Can result in death
– Bloat prevention
•
•
•
•
•
•
•
•
Plant mixtures of grasses and legumes
Utilize non-bloating legumes
Allow legumes to mature before grazing
Feed animals some dry hay before placing animal on
pastures
Avoid moving animals into a pasture or paddock
containing a high concentrations of legumes early in the
morning
Limit the daily forage allowance to the cattle
Have water available in each paddock of a rotationally
grazed pasture
Make poloxalene available to animals grazing legumes
– Sold as ‘Bloatguard’
– Available in blocks or supplements
– Intake can be variable
• Phytoestrogens
– Present in alfalfa, red clover, and ladino clover
– Have affected reproduction and mammary
development in sheep
• Coumarin
– Present in sweet clover
– Converted to dicoumarol in moldy sweet clover
• Results in hemorrhaging in animals consuming the hay
• Tannins
– Present in birdsfoot trefoil
– Reduce protein degradation in the rumen and feed
intake
WARM SEASON GRASSES
• Warm season grasses
– Perennial
• Switchgrass
Big bluestem
Eastern gamagrass
– Annual
• Sudangrass Sorghum x Sudangrass
• Growth
– 70% of production occurs in June and July
• Yields
– Very productive
– Very sensitive to soil fertility
• N, P, and K
• Persistence
– Require rest
– Competition with cool season grasses
– Very sensitive to early harvest or grazing
Corn
USES OF WARM SEASON GRASSES
Species
Grazing
Harvest
Comments
Switchgrass
Fair
Fair
Perennial
Big bluestem
Good
Fair
Perennial
Eastern
gamagrass
Good
Fair
Perennial
Sorghum x
Sudangrass
Good
Poor (Hay)
Fair (Silage)
Annual
Sudangrass
Good
Poor (Hay)
Fair (Silage)
Annual
Whole plant corn
Excellent
Excellent (Silage)
Annual
Corn stalks
Excellent
Fair (Baled)
Good Silage
Annual
NUTRITIONAL QUALITIES OF WARM SEASON
GRASSES
Compared to:
Cool season grasses @
comparable maturity
Grains
Plant protein
supplements
Lower
Lower
Lower
NDF
Greater
(Lower for whole plant
corn)
Greater
Greater
ADF
Greater
(Lower for whole plant
corn)
Greater
Greater
Lower
(Greater for whole plant
corn)
Lower
Lower
Comparable
Lower
Lower
Lower
Lower
Lower
CP
TDN/NE
Ca
P
NUTRITIONAL CONCERNS WITH WARM
SEASON GRASSES
• Nitrates
– Most common in drought-stricken corn and sorghum
• Highest concentrations in stalks
• Also present in some weeds
– Converted to nitrite in the rumen
• Inhibits oxygen transport by hemoglobin
– Levels (DM basis)
• < 3000 ppm
• 3000 - 6000 ppm
• 6000 – 9000 ppm
• >9000 ppm
– Management
Safe
Limit to 50% of diet for stress animals
Potentially toxic to cattle; Do not feed
as only component of diet
Dangerous to cattle
• Ensile crops
– Take measures to avoid exposure to nitrogen dioxide
• Dilute high nitrate feeds with other feeds
– Particularly grains
• Cyanogenic glycosides
– Present in new growth of sorghum x sudangrass
and sudangrass forages
• May be in spring growth or regrowth after harvest,
drought or frost
– Converted hydrocyanic acid (prussic acid)
• Inhibits oxygen uptake by the hemoglobin
– Management
• Avoid grazing until forage is a minimum of 18
inches tall
• Excessive corn intake
– May occur in cattle grazing standing corn or
grazing corn stalks fields with a large amount of
fallen ears
– May result in lactic acidosis or founder of the
grazing animals
– Management:
• Limit grain intake by controlling access
Annual
Pasture Options
ANNUAL FORAGES
Species
Species
Digestible
OM, %
Grasses (Grazed, hay or silage):
Annual ryegrass
70
Cereal rye
68
Brown midrib sorghum or
68
sorghum x sudan
Wheat
66
Triticale
65
Oat
65
Legumes (Grazed, hay or silage):
Berseem clover
60
Brassicas (Grazed):
Turnips
71
Crude
protein, %
20
22
12
9
9
9
17
21
LIMITATIONS OF ANNUAL FORAGES
• May have limited production
– Drought
– Length of growing season before frost
– Shading in standing row crop
• Weather losses of nutrients
– Problem with brassicas and berseem clover
• Winter varieties must be killed before
planting in the subsequent year
– Unless reseeding is desired (Annual rye)
• Limited spring use
– Soil compaction
– Late growth
• Health problems
– Bloat with brassicas and wheat
– Goitrogens in brassicas
Chicory
•
•
•
•
A perennial broadleaf from sunflower family
Drought resistant
Persistent for three to four years
Uses
– Good for grazing
– Poor for harvest
• Good nutritional value:
– 60 – 70% TDN
– 13 – 16% CP
MATURITY EFFECTS ON FORAGE QUALITY
• Increasing forage maturity
– Increases NDF
• Reduces feed intake
– Increases ADF and lignin
• Reduces digestibility
– Reduces CP and soluble carbohydrates
• Reduces digestiblity
EFFECTS OF MATURITY ON THE COMPOSITION OF FORAGES
SB
Alf
Alf
I
M
Maturity
Alf
SB
I
M
Maturity
Digestible DM, %DM
45 50 55 60 65 70
SB
I
M
Maturity
Alf
SB
I
M
Maturity
CHANGES IN PLANT STRUCTURE WITH
MATURITY
Immature
Mature
Secondary cell wall
(Cellulose)
Cell
Contents
CC
L L L
L
L
L
L
L
L
Primary cell wall
(Hemicellulose)
Middle lamella
(Lignin)
L
LIGNIN
• A complex polymer of phenylpropane units
• Binds to hemicellulose in cell wall
– Needed to provide strength to plant
• Increases with maturity
• Reduces the digestibility of plant cell walls
• Bonds to carbohydrates differ between forage
species
– Legumes
• Ether linkages
• Tough
– Grasses
• Ester linkages
• Degraded by alkali treatment
STRATEGIES TO MANAGE LIGNIN BEYOND
CONTROLLING MATURITY
• Alkali treatments
– Mature grass, straw, corn stalks
– Treatments
• 3% anhydrous ammonia
• 4% sodium hydroxide
• 5% calcium oxide
– Effects
• Increase digestibility 10%
• Increase intake 20%
• Only effective on grass lignins
– Economics
• Profitable at high feed prices
• Brown mid-rib varieties
– Corn and Sorghum
– Genetically engineered to have lower lignin
content
– Increases digestibility and intake of forage
– Reduce stem strength