factors affecting forage quality pp. 232 - 246. forages or roughages general characteristics...
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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
MAJOR CLASSES OF FORAGE SPECIES
Months
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
To
tal
fora
ge
ma
ss
, lb
/ac
re
0
1000
2000
3000
Cool season grassLegumesWarm season grassStockpiled gr-leg (Hay equiv.)Corn stalks (Hay equiv.)
NUTRITIONAL VALUE OF LEGUMES, COOL SEASON GRASSES, AND WARM SEASON GRASSES AT
COMPARABLE MATURITIESDM basis
CP, %
NDF, %
ADF, %
ADL, %
TDN, %
NEmMcal/
kg
NEgMcal/
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
Legumes
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
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 - Tall fescue -Smooth bromegrass– Orchardgrass - Reed canarygrass - Timothy– Perennial ryegrass
• Growth– 66% of production occurs before early-June– Very low productivity in mid-summer– Some late season growth
• Yields– Species effects Tall fescueReed >Smooth bromegrass>Timothy>>Kentuckycanarygrass Orchardgrass bluegrass– Very sensitive to soil fertility
• N, P, and K• When is it needed???????
USES OF COOL SEASON GRASSES
Grazing Harvest Comments
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
Timothy Fair Excellent Preferred for horse hay
Perennial ryegrass
Good Excellent Higher quality, but poorer persistence than other CSG
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
P Comparable Comparable Lower
• 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 Birdsfoot trefoil Sweet
clover Berseem clover Sweet clover• Growth
– Greatest in spring, but more uniform over the season than grasses
• YieldsAlfalfa > 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
Alfalfa 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
Kura clover Excellent Good Perennial, very persistent
Berseem clover Fair Good Annual
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
P Comparable Comparable Lower
• 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 Corn• 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
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
CP Lower Lower Lower
NDF Greater(Lower for whole plant
corn)
Greater Greater
ADF Greater(Lower for whole plant
corn)
Greater Greater
TDN/NE Lower (Greater for whole plant
corn)
Lower Lower
Ca Comparable Lower Lower
P Lower Lower Lower
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 Safe• 3000 - 6000 ppm Limit to 50% of diet for stress animals• 6000 – 9000 ppm Potentially toxic to cattle; Do not feed
as only component of diet• >9000 ppm Dangerous to cattle
– Management• 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
AnnualPasture Options
Species Digestible OM, %
Crude protein, %
Grasses (Grazed, hay or silage): Annual ryegrass 70 20 Cereal rye 68 22 Brown midrib sorghum or sorghum x sudan
68 12
Wheat 66 9 Triticale 65 9 Oat 65 9 Legumes (Grazed, hay or silage): Berseem clover 60 17 Brassicas (Grazed): Turnips 71 21
ANNUAL FORAGESSpecies
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
I MMaturity
I MMaturity
I MMaturity
I MMaturity
ND
F, %
DM
35
40
45
50
55
60
65
SB
Alf
AD
L, %
DM
5
10
15
CP,
%D
M5
1
0
15
2
0
SB
AlfD
iges
tib
le D
M, %
DM
45
50
55
60
65
70
SB
Alf
SB
Alf
CHANGES IN PLANT STRUCTURE WITH MATURITY
Immature Mature
CellContents
Primary cell wall(Hemicellulose)
L L L L L L
LL
LL
Secondary cell wall(Cellulose)
CC
Middle lamella(Lignin)
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
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