Cereal Chaff (Graminae Species)

Winter cereal crops of oats and wheat are grown in most states for chaffing, with limited amounts available as hay in sheaves, or as small and large bales. In some cases, cereal craps that have been stressed and stunted in growth by poor seasonal conditions before they come to head are cut, baled and then chopped into chaff. Chaff in Australia refers to chopped hay, but in overseas countries, the term "chaff is used as a term for hills, awns and fibre waste as grain is harvested and threshed.
As cereal hay is often not well utilized and can be variable in quality, chopping it, into small segments as chaff helps to improve acceptance and reduce selectivity when it is mixed into a feed.

Mixing amounts of no more than 2: 1 in volume of cereal chaff with grain or "sweet" feeds helps dilute the concentrate portion of the ration, slowing intake and increasing the time taken to consume the meal thus reducing the risk of grain overload into the large intestine.
Rough cut chaff decreases the rate of consumption and speed of passage of the fibrous mass through the digestive tract as compared to finely cut cereal chaff and thus by being consumed less quickly may possibly lead to less risk of impaction colic.

Cereal chaff is widely used as bulking roughage feed when mixed into the grain based diets of racing and working horses.

Major Advantages

• Mixing limited amounts of no more than 2:1 in volume of cereal chaff with grain helps dilute the concentrate portion of the ration, slowing intake and increasing the time taken to consume the meal, thus reducing the risk of grain overload into the large intestine.
• Good Duality cereal chaff reduces the selectivity of horses, especially "picky" eaters,: and minimizes wastage of the roughage as compared to equal quality cereal hay.

Major Disadvantages

• Cereal- chaff can vary considerably in plant maturity, stem to leaf ratio, amount
  of dust, grain content and digestibility depending on the time and conditions of harvest.
• Large intakes of dry, finely chopped cereal chaff in a hungry horse can lead to choke and may compact in the large intestine.
• Cereal chaff can be dusty and blow away easily from paddock feeders situated in windy or exposed areas, if it is not dampened when mixed into the feed.
• Feeding an excess bulk of finely chopped chaff with grain can reduce the
  chewing efficiency and shield the action of enzymes that digest the grain
  starch .in the small intestine. This will decrease the digestibility of the grain,
  with more being overloaded into the hindgut to ferment or pass out in the
  droppings.

Quality and Selection of Cereal Hay and Chaff
Making hay of chaff from cereal grain crops before the heads are fully formed results in a higher fermentable cellulose content, more nutrients in the retained leaves and a "softer" chaff; Chaff made from mature cereals with a high stem to leaf ratio, with full seed heads, contains more indigestible lignin and a lower crude protein as well as other digestible nutrients. Leafy parts contain twice the protein and 40% more digestible energy on a weight basis than the stems.

Research has shown that the stage of cutting of cereal plants greatly influences the yield of the crop as a fodder. Cutting the crop early reduces the total yield to about 55-
60% (mid stage growth) and 65%-70% (prior to full flowering) compared to 100% of the potential yield and return on the crop cut as hay is highest when the plants are mature with heavy seed heads, hay cut at the mid bloom stage, with 7-9% crude
Protein content and lower indigestible lignin fibre content is more suitable for horses.

Mature cereal crops contain from 4-6% crude protein and, although the crop may contain seed heads that boost the energy content of the hay, the overall nutritional value and utilization by horses is reduced as a crop reached maturity.
Chaffing hay Increases the rate of consumption and speed of passage of the fibrous mass through the digestive tract. Overseas studies suggest that finely cut cereal chaff, especially when moistened with molasses, may be consumed too quickly, without being mixed with sufficient saliva as it is being chewed, leading to a risk of impaction colic.

Cereal hay and chaff can be evaluated by the following criteria:

• Leaf to stem ratio
  A higher leaf to stem ratio indicates a greater content of fermentable cellulose to indigestible lignin, especially in mature stands.
• Colour of the leaf content
  A green leaf does not always indicate a high Vitamin A or other nutrient content. However, bleached leaves and stems may suggest that soluble nutrients and vitamins may have been leached out by weathering prior to harvesting.
• Presence of grain
  Although some£ grain may increase the energy and protein content, a high proportion of mature stems and a low leaf content in hay or chaff indicates a less nutritious sample.
• Length of chaff fragments
  Chaff containing larger bruised fragments of stem and leaf (variable length or long chop chaff) is less likely to compact in the large intestine as horses will normally chew and salivate more to prepare it for digestion.

Key Point

• Cereal hay cut as a variable length chaff is chewed more effectively and better prepared for digestion by the addition of copious amounts of saliva, thus avoiding the risk of impaction colic often associated with finely cut mature cereal chaff
• Good quality cereal roughage (hay and chaff) should have low dust content and contain no mouldy or clumped areas in the chaff. It should be free of weeds or other plant contaminants.

Nutrient Composition of Wheaten Chaff
(Average value as fed, 90% Dry Matter, unless otherwise stated)

Source: AFIC (1987), NRC (1989), Ensminger at al (1990), Lewis (1995), Frape (1997), Feedstuffs Annual (1997)