Week 4

Roughages

Classes of Forage - Grasses

Text Transcript

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• Forage classes
• Classes: grasses, legumes, forbes, and browse
• Primary grown forages
• Grasses and legumes
• Natural habitats
• Combination of four classes
• Forbes
• Primarily broadleaf, nonwoody plants
• Browse
• Woodier plants; herbaceous and softer component consumed
• Classifications of forage
• Annuals
• Survive one year or less
• Biennials
• Survive two years
• Perennials
• Survive at least three years
• Additional references
• Cited in text
• Electronic resources
  • http://forages.oregonstate.edu/main.cfm?PageID=8
  • http://www.forages.psu.edu/
  • http://www.agry.purdue.edu/ext/forages/index.html
  • http://www.oznet.ksu.edu/pr_forage/
• Grasses
• Gramineae family
• Feedstuff
• Additional agronomic properties
• Reduce soil N, contribute organic matter, improve soil texture, increase water holding capacity, and decrease erosion
• Figure 8.2 – Basic structure of grass plant



• Nutritional value as compared to legumes
• Lower in CP, digestible energy, Ca, and Mg
• Grow in range of conditions and perform range of functions
• Selection of grasses
• Climatic conditions
• Amount and timing of moisture, solar energy, heat
• Soil conditions
• Composition, fertility, and pH
• Soil test
• Critical nutrients for grasses
• N, P, K, Ca, Mg, S, and microminerals
• Nitrogen critical
• Limiting N will restrict nutritional value and yield
• Fulfill nutrient and dry-matter requirements for specific animals
• Nutritional value and yield varies
• By species and maturity at harvest
• Timing of availability
• Forage system may include grass and/or legume species
• Appropriate management required to maintain forage system
• Examples of management decisions for maintenance: selection, application rate, and timing of fertilizer and irrigation, method and timing of harvest, and management of species
• Classification
• Dependent on classification scheme
• Options include: cool-season, warm-season, temperate, tropical, or combination
• Temperate
• Only cool-season grasses or both cool- and warm-season grasses
• In this course, cool-season, warm-season, or tropical grasses
• Cool-season grasses
• Grow best in cool, moist climates
• Most productive in spring and fall
• Figure 8.3 – Growth patterns of grasses



• Generally, winter hardy
• Drought tolerance varies
• C3 grasses
• Examples: brome grasses, Kentucky bluegrass, tall fescue, orchardgrass, perennial ryegrass, reed canarygrass, and timothy  
• Information on specific cool-season grasses refer to links above
• Warm-season grasses
• Grow best in summer
• Tolerant to high temperatures and drought
• Generally, not winter hardy
• Higher yields and poorer-quality forage compared to cool-season grasses
• C3 and C4
• Examples: bahiagrass, bermudagrass, bluestems, Indiangrass, carpetgrass, johnsongrass, and switchgrass
• Information on specific warm-season grasses refer to links above
• Forage cereals also forage grasses
• Pasture, silage, and hay
• Corn
• Silage
• Field residues
• Figure 8.4 -  Cattle grazing corn field residues



• Oats
• Sorghum
• Presence of antinutritional cyanogenic glycosides
• Wheat
• Potential issues are bloat, grass tetany, and nitrate poisoning
• Primary issues for consideration for grasses
• Nitrate toxicity or nitrate poisoning
• Consumption of excessive levels of nitrate
• Primarily cattle, also may affect sheep and horses
• Etiology
• Microbes convert nitrate to nitrite
• Nitrite absorbed
• In bloodstream, nitrite combines with hemoglobin to form methemoglobin
• Methemoglobin does not transport oxygen
• Figure 8.5 – Pathways of nitrate in the ruminant



• Signs
• Respiratory distress, bluish mucous membranes, convulsions, and death
• Amount for toxicity varies
• Prevention
• Avoid excess nitrate in forages
• Consider fertilization rate and growing conditions
• Analyze questionable forages
• Ensiling of questionable forages
• Provide adequate energy
• Treatment
• Administration of methylene blue
• Grass tetany, grass staggers, or hypomagnesemia
• Complex disorder
• Caused by low blood Mg levels
• Generally, in ruminants consuming lush grass forages
• Immature forages have low Mg
• Additional factors contributing to grass tetany include high K, high N, and low Ca
• Signs
• Nervousness, incoordination, convulsions, and death
• Urine sample accurate guide for Mg
• Treatment
• Administration of Mg and/or Ca
• Prevention
• Provide supplemental Mg
• Feeding of Mg, feedstuff high in Mg, or administration of Mg to plant
• Planting legumes with grass forages
  • Legumes higher in Mg
• Monitor Ca, N, and K in diet
• Endophyte toxicity
• Ruminants and horses
• Tall fescue and ryegrass
• Associated with turf versus forage varieties
• Endophyte
• Fungus
• Produce toxins detrimental to animals
• Lab analysis required for ID
• Signs in tall fescue
• Hyperthermia, decrease in production, reproductive problems, and tissue death
• Signs in ryegrass
• Poor muscle control
• Prevention
• Feed low-endophyte or endophyte-free grass forages