To ensure your sheep maintain a healthy body condition score and are provided with adequate feed, it is critical to understand the individual nutritional requirements of your sheep. You can then provide adequate nutrition with the pastures you have available and supplement their feed if necessary.
This fact sheet will explain the nutritional essentials and provide resources that allow you to calculate a feed budget for your farm which will help anticipate how much home-grown feed is available and how much supplementary feed is likely required at different times of the year.
Sheep’s nutritional requirements depends on:
· The life stage of the animal
· Live weight
· Condition score
· Whether that animal is growing or at maintenance
· Whether that animal is pregnant or lactating
Need help understanding or calculating a ewe’s condition score? Click here
Energy Requirements
An animal’s requirement for energy is measured in megajoules (MJ) and expressed as metabolisable energy (ME). Metabolisable energy is the amount of total energy that can be utilised by the animal.
Digestibility refers to how much of the feed is retained and used by the animal. If the digestibility of a feed is 75 percent, then for every kg of dry matter (DM) eaten, 750g is retained by the animal and 250g is excreted.
Digestibility and the available energy of feed is directly related. The higher the digestibility, the higher the quality of pasture and available energy for your stock.
Carbohydrates (water-soluble carbohydrates, sugars, starch, cellulose and lignin) are the main component of the dry matter of plants. The water-soluble carbohydrates are the most digestible and the lignin component is largely indigestible.
This means young actively growing pastures such as grasses, perennials, legumes etc., have a higher digestibility and therefore higher ME as they are made of mostly water-soluble sugars. However, dry stalk grasses that have lost their green colour have a lot of lignin causing them to have low digestibility and low ME values.
Protein
Protein, measured as crude protein (CP%), is the percentage of protein in dry matter. It is most important for young lambs and weaners when they are growing. Green pasture is high in protein (leafy pasture is 25-30% protein) so supplement feeding is often not required if lambs are born in late winter and spring. However, when no green pasture is available such as in summer, protein intake may be below the requirements for some classes of stock. If the diet’s crude protein content drops below 7 percent, the microbes in the rumen struggle to reproduce and effectively utilise carbohydrates. Consequently, both the feed intake and the growth rate of the sheep begin to decline. Lick blocks with urea can be a protein source to assist in the animal utilising carbohydrates in their feed.
Vitamins and Minerals
Calcium and magnesium are two of the most important minerals for pregnant and lactating ewes. Both are needed for the growth of the unborn lamb and milk production. Legumes are high in calcium, but cereal grains are deficient so ensure you supplement this if feeding a high ration of cereal grains.
Most vitamins required by sheep are produced by the rumen microbes. Vitamin A and E are found in green pastures, however during periods of drought when there is a lack of green feed, deficiencies could occur in young sheep.
Fibre and Roughage
If sheep are grazing pastures and stubbles, lack of fibre is generally not an issue. However, if sheep are on a grain dominant diet, they may not be consuming enough fibre to slow the passage of food in the rumen for stable digestive function. Hay will have lower digestibility and more fibre slowing the passage of food in the rumen and encourage saliva production which can reduce the risk of acidosis on high grain diets.
Feed Budgeting
Now you know the basic nutritional terms it is time to focus your attention on feed budgets. Feed budgeting is an important tool that calculates the amount of feed you have. It is used for two things:
1. It allows you to work out how much feed supply you have and if it meets the nutritional demands of your stock
2. It can help you calculate the optimal stocking rate different times of year, which will tell you the cost to supplement feed during periods of low feed availability.
Feed budgets can be created for different classes of stock at different times of the year so you can prepare accordingly.
There are two ways of calculating a feed budget:
1. Using Dry Sheep Equivalent (DSE) – Dry sheep equivalents (DSEs) are the most common unit used when comparing the feed and energy requirements for different classes of stock, including cattle. It is also a valuable measure when matching stocking rates to available pasture.
2. Megajoule (MJ)/Metabolisable Energy (ME) per day method (using NDF value from a feed test)
The result will be similar regardless of which you use.
To calculate a feed budget, you need the following four things:
1. Sheep feed requirements
2. Pasture quantity
3. Pasture quality
4. Pasture growth rate.
SHEEP FEEED REQUIREMENTS
Click here for a Sheep Feeding Guide
This information will assist in sheep feed and energy requirements. Chapters 2, 3 and 4 have helpful information regarding setting nutrition targets based on condition score, what to feed sheep and how much/how often.
PASTURE QUANTITY
Click here for Pasture Growth Rate Guide for Victoria
Click here for Pasture Growth Rate Guide for Different Species and Parts of Victoria
To assist in calculating pasture quantity – the above resources will assist in working out the typical growth rate for different parts of the state for different times of the year.
The below tools also help to measure pasture quantity:
Tool 8.6 – Pasture rulers, sticks and meters (makingmorefromsheep.com.au)
PASTURE QUALITY
Click here for the Feed on Offer Library
For calculating pasture quality – this can assist farmers in calculating their Feed on Offer (FOO) and nutritional value of pastures.
If you are unsure of the nutrient value of your pastures, identify the species present and feed test.
PASTURE GROWTH RATE
Click here for a feed budget template with steps
With the above resources you should now be able to calculate a feed budget for different times of the year.