Matching production cycle to feed quality and quantity
MLA & AWI July 31, 2024
To meet productivity targets, it is important to know when feed supply and demand are at their highest and identify any shortfalls. Pastoral grazing businesses are often governed by other significant factors, such as access to markets and well as seasonal feed availability, in determining when key livestock operations are carried out. Therefore, supply and demand may not always match up perfectly.
Undertake fodder budgeting regularly to match periods of peak feed demand with periods of peak supply. Feed demand is calculated based on:
- the number of stock grazing (including non-domesticated animals)
- their physiological state (dry, pregnant, lactating, weaned)
- production requirements (maintenance or finishing).
Recording rainfall and stocking rates over time can help build a profile of how a property’s stocking rate is tracking according to rain received, which will enable informed decisions regarding stocking rates and formulate strategies to manage tight periods. This activity may be of limited use in areas with ‘aseasonal’ rainfall patterns (where there is no seasonality to rainfall patterns).
Energy
The amount of energy derived from a feed is related to the digestibility of the feed. Digestibility is the percentage of the feed converted to energy when consumed. The higher the digestibility, the higher the energy in the feed. The lower the digestibility, the lower the amount of energy in a feed, and more is passed through the animal and removed as waste product.
Less-than-optimum levels of energy lead to performance issues for sheep flocks, which include:
- lower conception rates
- rapidly falling condition scores for pregnant ewes, leading to pregnancy toxaemia, lower than ideal birth weights for lambs and increased ewe mortality
- poor growth and increased mortality of weaners and replacement stock
- not meeting key marketing opportunities due to not being finished (or sale ready).
To calculate the feed requirements of livestock grazing, the digestibility, metabolisable energy and protein content of the feed need to be determined, as these factors impact the amount of feed livestock can be eat and utilise.
This information can be obtained by sending feed to a feed testing service to analyse the levels of dry matter, energy, protein, digestibility and minerals. Local advisors may also be able to provide data on local feed quality.
Stock will selectively graze certain parts of the plants (for example, leaves as opposed to stem) and therefore may be able to consume higher levels of energy or protein than an ‘average’ feed test result indicates is present.
Digestibility can also be estimated by observing pasture characteristics such as:
- availability of green material
- whether the plants are in a reproductive phase
- the colour of dead material.
Protein
Protein is an essential component of the diet of sheep. Just like energy, the level of protein in different species varies through the growing season. Many pastoral plant species contain high levels of protein.
As is the case for energy, the level of protein in grazed plants varies due to growth stage, rainfall, season and the area in which they are growing. Green plants generally contain sufficient protein to maintain ruminants. When pastures dry out, protein decreases to sub-optimal levels for maintenance of sheep.
Minerals and trace elements
An important nutritional factor regarding the nutritional value of grazing plants is the level of minerals and trace elements that plants contain.
Even though old man saltbush (Atriplex nummilaria) has high levels of energy and crude protein, stock may not perform as well as expected due to the mineral and trace element imbalance. For example, the high salt level requires energy to be expended to excrete this through the kidneys. This issue can be further exacerbated when sheep are drinking water with a moderate or high salt content. Other saltbush species may lead to similar outcomes.
In a situation where lower production has been observed, consider the potential for mineral imbalances and possible options for remediation or supplementation to avoid significant production losses.
Different types of perennial grasses
Perennial grasses are extremely important in grazing systems and are a key focus for grazing management and landscape function; they assist in reducing wind and water erosion, provide litter for recruitment of new seedlings and are often the most responsive species to rainfall.
Native perennial grasses can be divided into warm-season and cool-season grasses.
Warm-season grasses do most of their growing and seed set during summer and are better adapted to high temperatures and light intensities. They are frost susceptible and can be winter dormant.
Cool-season grasses grow and set seed during the cooler months (winter–spring). They are frost tolerant, provide green feed during winter when temperatures are low and moisture is not limiting. During summer they have reduced growth and survive high temperatures and low rainfall by entering a drought-induced dormancy.