Managing pastures properly #2 - Some Pasture Basics

pastureWhat is a pasture?
  • Pasture is a living community - intertwining plants of grass, clovers, herbs, weeds and bare ground. However, pasture plants are different from many plants - they can regrow rapidly after grazing and cutting.
  • A pasture is also a “miniature forest” containing insects, slugs, bacteria and fungi that feed on living plants and dead matter, including animal droppings.
  • The proportions of these plants vary greatly, over a paddock and over the seasons, and can be altered by grazing management.
  • Check this out by making a frame 500mm x 500mm with wire or thin timber. Throw it down at various places in a paddock and note the plants inside the frame area.
  • You will be surprised by the feed variety you offer your stock, and how the grass, clover and weed proportions vary.
  • Feeding your stock on pasture is so different to feeding livestock on grain or concentrate feed from a bag. This varies very little in nutrient value over time, but pasture offers variety - breakfast, lunch and dinner for your animals - and they prefer it that way, just like you.
  • Grazed pasture is also the cheapest feed. Silage and haymaking cost money and time, and grain or concentrates are by far the most costly feeds for livestock. And feed is about three-quarters of costs in livestock production - so the cheaper the feed, the better the profit margin (so long as it’s good quality feed).
Pasture varies year-round
  • To appreciate pasture variety, try to understand how pasture plants grow.
  • They start off as small seedlings and rapidly begin to spread by branching.
  • Grasses develop branches we call tillers - leafy shoots growing from buds near the plant base.
  • Encouraging tillering is vital to keep getting top quality feed, because grass is most nutritious to stock when it is in this leafy growth stage.
  • The best way to encourage tillering is by regular, controlled defoliation by grazing or cutting for silage or hay. Note - this in not complete defoliation. You should always leave stubble to enable the plants to recover.
  • White clover and lotus, another valuable nitrogen-fixing legume, spreads by developing creeping stems. These can root at the nodes (joints) and break into new plants.
  • Once established, pasture plants remain leafy until warmer temperatures and longer days induce them to flower.
  • Seed heads appear and the plant’s nutritive value decreases (helping to protect them from grazing so that they can reproduce by seeding).
  • Once seeds are produced, annual plants die off and perennials resume vegetative growth until the next year.
  • So remember that the pasture feeding value varies from day to day over the year, but is always best when the plants are leafiest.
Livestock need feed variety too - grow them a menu!
  • The needs of your stock vary over the seasons.
  • At one time stock will need high quality feed nutrients for growth, bearing their young and for lactation.
  • They can withstand lower quality feed when dry (not lactating), mature and when putting on excessive fat.
  • Most importantly, they need feed variety to maintain good health and condition.
  • International markets are also demanding primary produce from animals raised under stress-free and sustainable conditions.
The food factory in plants - the leaves
  • The leaves are the plant’s food factories - the greater the leaf area, the more food is produced.
  • Plants build up their food reserves using photosynthesis, a process that needs plenty of light and chlorophyll, the green pigment that absorbs light.
  • Plants rely on photosynthesis to take in carbon dioxide and give out oxygen during daylight. The end product is carbohydrate production.
  • Pasture plants then use these food reserves in respiration, when they take in oxygen and emit carbon dioxide. Sunlight is not essential for respiration, so it continues all the time.
  • These building and breakdown processes control the nutrient value of pastures. It’s changing all the time.
  • When farm animals graze plants too low, it takes longer for leaves to regrow and resume efficient food production.
  • Animals grazing too low can also consume ryegrass endophyte toxins (those causing ryegrass staggers), which are most concentrated in leaf bases, and fungal spores in deal pasture litter, which causes facial eczema.
Food storage in plants
  • Plants store food reserves in roots, stems and leaves.
  • Roots are major food stores, so the balance between roots and shoots is very important. They are also essential for absorbing water, and some pasture plants develop deep root systems and are more drought-tolerant than those shallow-rooted plants.
  • Many leaves are needed to feed the roots, and good root reserves encourage better leaf growth.
  • Pasture plants can be weakened, or even killed, very quickly by excessive grazing or cutting, as the root reserves become exhausted.
  • Plants need time to recover. Ryegrass and clover are popular pasture plants because recover quickly after grazing, but lotus needs more time for recovery, so needs a longer break between grazings.
  • To build up good food reserves, allow the plant time to photosynthesise and grow its leaves. Spelling a pasture between grazings is an essential part of pasture management - just like time management is essential for people in business!
Feed value varies as plants grow
  • Protein levels are highest in young pasture kept in regular tillering, and especially in pastures with good clover content evident.
  • As plants mature, their DRY MATTER (DM) content rises, but their feed quality declines.
  • DM is what’s left of a plant or feed after water has been removed using a stove oven or microwave oven.
  • Spring pasture is around 20% DM and pasture at the hay is around 80% DM.
  • But the DM feed value (energy and protein) is the crucial factor.
  • These days we talk about a feed’s ME - metabolisable energy. It is a measure of feed quality. Highly nutritious feeds have an ME 0f around 12, and poor quality feeds are around 6-7.
  • Protein levels fall rapidly as plants change from their leafy stage to flowering, and fibre levels increase rapidly.
  • Silage is cut when the pasture is still leafy, so is lower in fibre, but hay is high in fibre.
  • For high quality grazing, try to maintain pasture plants at the nutritious vegetative stage - when leaf content is high and fibrous seed head content is low.
Stock won’t eat everything on offer
  • Just like us, farm animals have well-developed taste and smell.
  • They don’t like to eat pasture contaminated by dung and urine, particularly their own.
  • They’ll only eat pasture around dung and urine patches after about 4-6 weeks in normal circumstances (when they’re not forced to).
  • Some farmers like to chain harrow the paddock as soon as stock are removed to spread the dung patches. This may a good idea if you have time, but other farmers say this only spreads the smell over a wider area, and it’s better to leave dung alone.
  • Some animals, especially sheep and horses, are more selective grazers than others. They usually graze the most palatable plants (especially clover) before other species, and eat the most palatable, leafy plants parts first.
  • However, they also like fibre at times, and this is a natural desire of ruminants (cattle, sheep, goats), and horses, llamas and alpacas, which have a slightly different digestive system.
  • All these animals can digest cellulose, which is a major carbohydrate in plants that humans cannot digest. Plants also have a fibrous carbohydrate called lignin, which is too tough for even farm livestock to digest. So they pass it through their systems.
Livestock have different preferences
  • Cattle prefer long pasture as they use their tongues to sweep grass into their mouths. The ideal is 2300-2500kg DM/ha, which is about 110-150mm high. They cannot graze too closely - below about 800-1000 kg DM/ha or about 50mm high.
  • Sheep will, however, graze much closer - down to 500-600kg DM/ha or 25mm high.
  • Deer prefer broad-leaved plants (clovers, chicory) to grasses, and leave high-endophyte ryegrass if they can.
  • Horses are patchy grazers, and prefer prairie grass to high-endophyte ryegrass.
  • Goats tend to be browsers, preferring more fibrous feed and tending to leave lush clover.
Pasture plants are different too
  • Grasses, such as ryegrass and cocksfoot, are bulky food and are high in fibre when flowering.
  • Legumes, like clovers and lotus, have three times the protein content of grasses.
  • Grazing herbs, such as chicory and plantain, offer essential minerals and even medicinal properties.
  • Trees and shrubs can offer shade and feed in hot, dry summers and pinch periods.
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