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 proteinin 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 NUTRITIONAL VALUE OF LEGUMES, COOL SEASON GRASSES, AND WARM SEASON GRASSES AT COMPARABLE MATURITIES
DM basis CP, % NDF, % ADF, % ADL, % TDN, % NEmMcal/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 60 1.33 0.75 .66 .29 Mature 11 69 42 6 56 1.18 0.62 .47 .26 Legumes 23 36 29 62 1.49 0.90 1.56 .31 21 43 33 59 1.38 0.80 1.37 .30 51 40 7 55 1.21 0.65 1.22 .28 Warm season grasses 14 - 64 1.45 0.87 .63 .20 1.08 0.58 .40 .12 COOL SEASON GRASSES Most common grasses in the Midwest Growth Yields
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 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 Comments Kentucky bluegrass Excellent Poor Smooth bromegrass Orchardgrass Better mid-summer growth than other CSG Tall fescue Good Better fall growth than other CSG Reed canarygrass Grows well in wet environments Timothy Fair Preferred for horse hay Perennial ryegrass Higher quality, but poorer persistence than other CSG NUTRITIONAL QUALITIES OF COOL SEASON GRASSES
General Compared to: Legume comparable maturity Grains Plant protein supplements CP Lower Greater/Lower NDF Greater ADF TDN/NE Ca Comparable 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 Growth Yields Fertility needs Persistence
AlfalfaRed cloverWhite cloverBirdsfoot trefoil Sweet cloverBerseem cloverSweet clover Growth 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 Alfalfa Good
Excellent Perennial, sensitive to wet conditions Red clover Biennial, sensitive to drought, easy to interseed Birdsfoot trefoil Perennial, but responds to management that allows reseeding Ladino & White clover Poor Perennial, less sensitive to close grazing than other legumes Sweet clover Fair Biennial, less sensitive to soil conditions than other legumes Kura clover Perennial, very persistent Berseem clover Annual NUTRITIONAL QUALITIES OF LEGUMES
General Compared to: Cool season comparable maturity Grains Plant protein supplements CP Greater Lower NDF ADF TDN/NE Ca P Comparable Effects of fertility K fertility will affect itsconcentration 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 Coumarin Tannins
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 Growth Yields Persistence
Perennial SwitchgrassBig bluestemEastern gamagrass Annual SudangrassSorghum x SudangrassCorn 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 Perennial Big bluestem Good Eastern gamagrass Sorghum x Sudangrass Poor (Hay) Fair (Silage) Annual Sudangrass Whole plant corn Excellent Excellent (Silage) Corn stalks Fair (Baled) Good Silage NUTRITIONAL QUALITIES OF WARM SEASON GRASSES
Compared to: Cool season comparable maturity Grains Plant protein supplements CP Lower NDF Greater (Lower for whole plant corn) ADF TDN/NE (Greater for whole plant corn) Ca Comparable P NUTRITIONAL CONCERNS WITH WARM SEASON GRASSES
Nutritional quality of perennial WSG 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 ppmLimit to 50% of diet for stress animals 6000 9000 ppmPotentially toxic to cattle; Do not feed as only component of diet >9000 ppmDangerous 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 Annual Pasture Options ANNUAL FORAGES Species
Useful as cover crops following row crop harvest 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 A perennial broadleaf from sunflower family Drought resistant
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 NDF, % DM Alf Alf ADL, % DM SB I M Maturity I M Maturity Alf CP, %DM Digestible DM, %DM Alf SB SB I M Maturity I M Maturity CHANGES IN PLANT STRUCTURE WITH MATURITY
Immature Mature Secondary cell wall (Cellulose) Cell Contents L CC LL L LL L Primary cell wall (Hemicellulose) 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 Calcium hydroxide ??? Effects Increase digestibility 10% Increase intake 20% Only effective on grass lignins Economics Profitable at high feed prices A potential replacement for corn in ruminant diets? Brown mid-rib varieties
Corn and Sorghum Genetically engineered to have lower lignin content Increases digestibility and intake of forage Reduce stem strength