Tool 10.7 Standard reference weight calculator
Standard reference weight calculator
Standard reference weight is the liveweight of a fully grown, bare shorn, non-pregnant sheep in condition score three (CS3) with no gut fill (i.e. empty).
Determining the standard reference weight (SRW) of your flock provides a useful comparison across a range of animals of varying liveweights and condition scores to make decisions about meeting their nutritional requirements for maintenance or growth.
To calculate SRW, use scales to weigh a representative sample of your adult ewe base. The best way to do this is to let a few ewes run through the race at the start whose liveweight is not included (as the bigger ewes are generally at the front of the yard), then weigh a group of ewes (at least 50, depending on your flock size and the consistency of your ewe base). After you have determined your flock average liveweight on that day, adjust it based on the following factors:
- Deduct five per cent from the average liveweight if ewes have not emptied out to account for gut fill. If sheep have been yarded for four hours off feed and water you will not have to adjust for this.
- Add or subtract 19% from the average liveweight to account for any variation away from an average of CS 3 (e.g., if average CS of the mob is CS 2, and the average liveweight is 50 kg, add 9.5 kg, however, if the average CS of the mob is CS 4 and the average liveweight is 50 kg, subtract 9.5 kg from the average liveweight).
- Make an allowance for fleece weight if ewes are not bare shorn (e.g., for full wool deduct your average adult fleece weight, for six months’ wool deduct half your average adult fleece weight).
One condition score is equivalent to 19% of the SRW. The table below summarises the weight of one condition score for different sized sheep.
|
Standard reference weight |
40 kg |
50 kg |
60 kg |
70 kg |
|
One condition score |
7.5 kg |
9.5 kg |
11.4 kg |
13.3 kg |
Know the SRW for your flock
AWI’s Standard reference weight calculator allows you to calculate the SRW for your flock, allowing for more accurate feed budgeting and management decisions.
