|Feed budgeting in the dry period is inherently difficult due to the variability of the quality of dry feed and the value of the subsequent portion that the sheep choose to eat. The decline rate and pasture height differences between different pasture systems also affect the amount of energy sheep can gain from dry pasture. There are, however, some 'rules of thumb' that can be used as a guide for supplementary feeding in the dry period.
The general steps for feed budgeting at any time of the year are;
1. What they can eat - What they require = surplus or deficit of energy
2. If they aren't getting enough energy then how much to feed to meet the requirement.
It is important to remember too, that the energy requirements of sheep vary with the feed they are eating, the amount of grazing they are doing to find the feed and their current status of nutrition and whether they are dry, pregnant or lactating.
The tables presented below are general values only. It is important that these are used only as a guide and that regular condition scoring of the flock is the best way to tell if the feeding rates are adequate for their needs. These tables can also be printed out or saved as a PDF file.
Step 1. What they Need
Using either Table 1a. or 1b. select the column for the frame size and row for the pregnancy status of the flock, finding the value for maintenance energy required in MJ/day.
These values will vary slightly depending on the quality and quantity of feed the ewes are eating as well as the weather conditions and terrain of the paddock.
Example: medium frame ewes at condition score 3 with twins at day 100 of pregnancy need approximately 11.1 MJ/day to maintain their condition.
Step 2. What they can eat
Using Table 2 to identify the estimated metabolisable energy (ME) intake from dry paddock feed. Use Table 2a for perennial-annual mixed pastures and Table 2b for annual sub clover pasture systems. These vary due to the different height and quality characteristics of different pasture types. Weather also affects digestibility and therefore quality and is very variable throughout the season, so use this only as a guide. Sheep will also preferentially graze the higher quality fraction of the pasture first, which may cause higher intakes than expected at first.
Example: The ewes in step 1. are grazing pastures of 1500 FOO of dry 50% digestible pasture that has a mix of perennial grass and some clover. This means they can eat approximately 6.3 MJ/day.
Step 3. Losing or Gaining Weight?
This is calculated by subtracting the results of Step 1 from the results of Step 2, that is, what they can eat minus what they need. This is then either a surplus and ewes will increase in condition, or a deficit and ewes will lose condition. Table 3 shows the deficit or surplus in terms of grams per head per day and in change in condition score in 30 days for each frame size.
Example: The ewes from Step 1 (need 11.1MJ/d) and Step 2 (can eat 6.3 MJ/d) have a deficit of 4.6 MJ/d (11.1 - 6.3 MJ). This means the ewes will be losing about 140gms per head per day or half a condition score over the 30 days.
Step 4 How much to feed?
Use the Table below (from 'Managing Sheep in Dry Times' Bulletin, DAFWA) to obtain an estimate of the energy value of the feed expected to be fed. We suggest that feeds are tested as they can be variable, especially hays and silages.
Step 5: Determine how much feed to offer
Once a target condition for the ewe flock and how much energy is required to meet that target been decided, and the energy value of the feedstuff determined you need to calculate how much feed to offer.
Ewes in energy deficit:
Divide the deficit (MJ/day) by the energy value of the feed (MJ/kg). This gives the number of kilograms per day to be fed.
In our example the ewes need 4.6MJ/d. Using barley at 13MJ/kg they require 4.6/13 = 0.35kg of barley
These figures are expressed in dry matter per kilogram so it is important to convert the amount to 'as fed' kilograms which takes into account the moisture content of the feed.
To do this; Divide the kg/head/day to be fed by the dry matter % from Table 4. This is the weight to be fed out in the paddock.
barley at 90% Dry Matter and 0.35kg/hd/d required:
0.35kg / 0.90 = 0.39kg to be fed.
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