Week 4

Roughages

Classes of Forage: Legumes

Text Transcript

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• Leguminosae family
• Examples: alfalfa and clovers
• Nitrogen fixation
• Process
• Rhizobia microorganisms in nodules associated with root system convert atmospheric nitrogen as N2 to NH3
• Ammonia fulfills nitrogen requirement of legume
• Do not require application of nitrogen
• Symbiotic relationship
• Figure 8.6 – Root nodules



• Nutritional value of legumes
• Compared to grasses, higher in CP, DE, Ca, and Mg
• Planting of legumes and grasses in one system
• Improve nutritional value
• Increase productivity
• Species adapted to range of environmental conditions
• To learn more about legume species
• http://www.agry.purdue.edu/ext/forages/publications/ay211.htm
• Alfalfa
• Introduction
• In world and in U.S., most popular forage legume
• Figure 8.7 – Alfalfa field



• Figure 8.8 – Alfalfa plant



• In U.S., 1999, greater than 84.3 million tons of alfalfa hay produced
• Growing conditions
• Varieties developed to grow in variety of climatic and soil conditions, given adequate water
• Prefers well-drained, fertile, slightly alkaline, deep, loam soils
• Productive
• Feeding livestock
• Hay, silage, pasture, and dehydrated meal
• All domestic species
• Especially important for ruminants with high nutrient requirements
• Feeding value
• Nutritional value
• Source of fibrous carbohydrates, protein, energy, minerals (i.e. Ca, P, Mg), and vitamins
• Palatable
• Time of harvest
• Influence quality, yield, and longevity
• Figure 8.9 – General relationship between quality and yield for forage grasses and legumes



• As alfalfa matures
• Quality decreases
• Change in plant components
• Greater proportion of plant is stems and lesser proportion is leaves
• Compared to stems, leaves are higher in protein, lower in fiber, and higher in digestibility
• Yield increases
• Earlier harvested relatively higher CP, lower structural CHO, higher digestibility and lower yield
• Table 7-3 on page 121 in text – Effect of stage of maturity on digestibility of alfalfa
• Crop or stand longevity
• Depletion of CHO reserves in root will decrease longevity
• Earlier harvest
• Overgrazing
• Varieties developed to reduce detrimental effect from early harvest
• Cutting frequency
• Table 7-4 on page 122 of text – Effect of different alfalfa cutting frequencies on yield, quality, weeds, and longevity
• Additional forage legumes
• For additional information
  • http://www.agry.purdue.edu/ext/forages/ForageID/forageid.htm
  • http://forages.oregonstate.edu/main.cfm?PageID=33
• Clovers
• Red clover
• Compared to alfalfa
• Similar nutritional value
• Less productive
• Fresh or preserved forage
• White clover
• Pasture forage
• Resistant to grazing
• Complements nutritional composition of grasses
• Alsike
• Sweetclover
• Subterranean or sub clover
• Annual
• Crimson
• Annual
• Additional temperate forage legumes
• Trefoils
• Birdsfoot trefoil
• Compared to alfalfa
• More tolerant of infertile, poor-draining, acidic soils
• Lower productivity and quality
• Moderate to high in tannins
• At moderate levels
• Increase proportion of rumen by-pass protein
• Reduce incidence of bloat
• Lespedezas
• Southeastern region
• Nutritional value of annuals greater than perennials
• Vetch
• Multiple species
• Bloat
  • Primary potential issue
  • Nutritional disorder
  • Excess accumulation of gases in tract
  • Distention of reticulorumen
  • Etiology
    • High content of readily available carbohydrates in legumes
      • Fermentation produces gases
    • High content of soluble proteins in legumes
      • Associated with production of stable foam
    • Stable foam prohibits eructation of gases
    • Accumulation
    • If not treated, may lead to death
  • Treatment
    • Release of gases and use of antifoaming agent
  • Prevention
    • Feed legumes as hay versus fresh
    • Use of low-bloat varieties
    • Prevention of initial overconsumption
    • Use of antifoaming agent
  • Incidence varies by legume
• Additional antinutritional components
• Coumarin
• Clovers; especially sweetclover
• Tannins
• Lespedezas and trefoils
• Alkaloids
• Lupines
• Saponins
• Alfalfa
• Phytoestrogens
• Number of legumes; especially sub clover
• Varieties and prevention techniques to reduce impacts