Protein Supplementation Assists in Dry Feed Utilisation

At the start of summer, good quality dry standing paddock feed and stubble is available. Feed value generally starts to decline by mid-summer, especially if large amounts of rain have been experienced and by the end of summer very poor dry feed is often all that remains or what was available has already been utilised. For many producers supplementary feeding of sheep needs to start occurring in the middle of summer, before body condition starts to deteriorate. Dry pastures and straw can be useful feeds when utilised in conjunction with supplements.

As a general rule, the most limiting factor is not mineral content of dry feed that reduces the value of the feed source but sufficient levels of protein and energy. In addition to this, the high fibre (NDF) content of the feed restricts the amount a sheep is able to physically consume. To make the most of dry paddock feed, supplying additional protein can increase rumen function and therefore utilisation of dry paddock feed and stubbles.

The sheep requires both microbial protein and bypass protein to meet its protein requirements and this determines the efficiency in which a sheep can use utilise poor quality feed. The cellulose component of dry feed is digested by rumen microbes to provide energy to the animal. When protein supply from the feed is low, microbe activity is reduced and results in decreased digestion and utilisation of dry feed.

There are three sources of protein including:

  • Non-protein nitrogen sources such as urea and sulphate of ammonia dissolve quickly in the rumen and any surplus nitrogen is wastefully excreted. To be effective, the non-protein supplements must be fed little and often and an energy source must be fed to enable the stock to utilise the nitrogen. Molasses or cereal grains are commonly used. Sheep must be introduced carefully to non-protein nitrogen sources. Urea in particular needs to be incorporated into a ration as urea poisoning kills stock quickly.
      • Protein meals, such as cottonseed meal or canola meal, release their protein differently, allowing sheep to use the protein efficiently over a longer period. Twice-weekly feeding is as effective as daily feeding. These meals also have a reasonable energy value.
  • High-protein grains (e.g. lupins, peas, beans) are more degradable, with a higher protein release rate, and should be fed every second or third day. Lupins are relatively safe but it is advisable when feeding peas and beans that they are carefully introduced to avoid acidosis issues. Legume grains also have the advantage of good available energy.
  • Lick blocks are a convenient supplement to dry feed but are often moderately successful when compared to supplementation with a protein meal or legume grain.

    Supplementary feeding should start before sheep lose weight to below optimal condition score. Allowing sheep to lose too much weight and then needing to gain weight comes at a higher energy cost. Losses in wool strength and fertility may also occur if sheep are allowed to fall too far below optimal condition score.

    Prepared by Tiffany Bennett, Primary Industries and Regions SA.