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Feed Value of Stubbles over summer

Key Points:

  • Greatest feed value is in the grain
  • Determine available feed through feed budgets
  • Use condition scoring to assess when to supplement feed
 

Stubbles are an effective feed for sheep over Summer and Autumn but it is important to remember that the greatest value lies in the grain and weeds in the paddock. Once any grain that is on the ground has been eaten, the feed value in the paddock is generally low, unless summer rains germinate new growth. Feed budgeting and condition scoring of sheep are useful tools in determining when supplementary feeding should be implemented.

The relative feed value of a feed source is a combination of Metabolisable Energy, Protein and other nutritional values. The digestibility of the feed is also the main factor in determining the amount of energy that is provided to livestock. At digestibilities of 55% or below, sheep will generally lose weight and condition.

Feed tests taken from a SheepConnect Focus Farm sites on the Eyre Peninsula demonstrated that the highest feed value from stubbles is in the grain. Tests also highlighted the large difference between the quality of the leaf and the stem. In this case it showed that barley leaf had a digestibility of 56% whereas the stem material was 30% digestible. Digestibility will continue to decline about 1% per week and this rate will increase with summer rain.

The barley stubble at the Poochera site had an average of 365kg of grain per ha on the ground ranging from 100kg to 600kg across the paddock. Once the grain is eaten the barley leaf would maintain dry stock. However once stock only have stem to eat they would begin to lose weight. Lambs will require greater than 100 kg/ha of grain on the ground to continue growing. Generally after six weeks, sheep grazing stubbles will no longer be able to gain weight and supplementary feeding should be implemented. Studies have shown that supplementing sheep grazing stubbles with lupins as low as 100g per head per day can maintain weights.

A feed budget should be calculated to determine available grain and dry matter. Feed budget calculations should be based on a dry sheep equivalent consuming 1.5kg of dry matter per day but this could be as high as 4kg per day taking into account wastage through trampling. At least 1 to 1.5 tonnes of dry matter should be retained for efficient ground surface cover.

A quick estimate of the amount of grain in a stubble can be gained by counting the number of seeds in a 0.1 m (squared) square (ie. the old cropcheck square or your Akubra hat). The number of grains that equate to 100 kg/ha are: 28 for wheat/oats; 25 for barley; 8 for lupins; 5 for field peas & chickpeas; 2 for faba beans.

Condition scoring is a useful tool to assess the body reserves of sheep and is best undertaken in a race when the animal is standing and relaxed. A sample of 50 sheep from a mob will provide a good indication of the overall condition of the mob and should be conducted regularly. You will not notice stock losing some weight (ie. 100g per day) but over two months this equates to nearly 1 condition score. It is easier & cheaper to maintain stock condition than try and put it back on later.

The feed value of stubbles generally reduces over summer, especially once any grain on the ground has been eaten. Stubbles should be grazed as soon as possible after harvest to take advantage of any fallen grain. Regular condition scoring of stock should be conducted to indicate a loss in condition and the need for supplementary feeding.

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