Stubble grazing over summer - tips and tricks
Stubbles are the major feed source for sheep during the summer-autumn period.
There are some general principles for managing livestock grazing stubbles.
Observe carefully
The feed value of stubbles is hard to estimate so there is no substitute for actually going into the paddock and observing the animals, the amount of grain on the ground, the amount of green regrowth and the amount of bare, potentially eroding land.
The grain on the ground and the green and dry regrowth (grasses, legumes and weeds) are the most energy dense components of the stubble. These energy sources will determine how long sheep can graze stubble before they start to lose weight.
For hoggets and older sheep, regular condition scoring of 25 animals per mob is the most accurate way to monitor livestock grazing stubbles.
For weaners, it is preferable to weigh a sample of the mob, as this will give earlier warning than condition scoring of declining body weights. For a weaner, a decline of one condition score (6-7 kg) can be critical.
Observe frequently
Check stubble paddocks and the stock on them at least weekly.
Stubble grazing is not a matter of “set and forget” for some predetermined period.
That practice can lead to numerous problems, including low conception rates, poor lamb survival, slow weaner growth (or deaths), assorted poisonings, vitamin and mineral deficiencies, or soil erosion.
When animals are on stubbles, you cannot relax: their welfare is always your responsibility.
The grain matters most
The amount of grain on the ground can be measured using a quadrat, tossed repeatedly across the paddock at random, each time counting the grain within it.
Alternatively, for cereals and lupins, you can get a rough but quicker estimate by counting the grain within the square made standing with your feet at right angles, heels together. This area is ~ 0.1m2.
Canola stubble is an exception to the rule that it’s the residual grain that matters most for stock. The best part of canola stubble for stock is green leaf, on standing stems or seedling regrowth. So, for the best return from canola stubble, graze it early, while there is still green leaf present.
Stubble quality and safety can’t be assumed
The quality of grain in stubble is a variable that shouldn’t be assumed.
Test results on harvested grain on delivery are certainly important for the cropping enterprise; however, for the animals which will graze the stubbles, those tests provide only part (the protein level) of the information required.
Stubble quality mainly relates to energy content, although the protein content is also important for young animals and breeders.
If growing conditions included frost, severe water deficit, waterlogging or disease, grain quality can be affected in unpredictable ways.
Rainfall after harvest also may affect the overall stubble value, including the grain, causing more rapid deterioration and fungal growth (beware lupinosis).
Toxic plants that may germinate or regrow in stubbles following summer rain include caltrop, heliotrope, Gastrolobium or poison species, Duboisia hopwoodii or pituri, and Lythrum hyssopifolia or lesser loosestrife.
Slender ice plant is an unusual toxic plant in that it is most toxic and palatable when it is dead and dry in summer. It is often found in medium-heavy soils, including cereal paddocks.
Not all new summer weed growth is poisonous though, and some plants are usually safe and possibly nutritious, such as wireweed, various native grasses and melons.
Supplementation, especially on cereal stubbles, will help stock
Additional feed from chaff cart heaps, or from grain or pellets in self feeders, lick feeders or trail-fed, will prolong the stubble grazing period.
Pellets or grain (especially lupins or peas) supplemented to sheep on cereal stubbles will usually improve weight gains and potentially conception rates or lamb survival.
Hay can be useful for adult dry stock but it is usually of little value to improve performance of young animals and breeders on stubbles.
Mineral-vitamin licks and loose mixes can be useful
Cereal stubbles are likely to provide inadequate sodium, calcium and probably magnesium.
Depending on farm location some trace elements may be beneficial also, but beware of copper supplementation without veterinary advice.
If protein in the stubble is low, it’s better to supplement with a legume grain or high protein pellets rather than a urea-fortified lick.
Vitamins E and A are often inadequate in summer-autumn stubbles and can be supplemented in mixes/blocks or other ways (talk to your vet).
The Department of Agriculture and Food, Western Australia has a range of information on stubble grazing at its Grazing stubbles and dry pasture webpage.
For more information contacts Roy Butler, Veterinary Officer, Merredin on +61 (0)8 9081 3111, 0427 197 242 or Danny Roberts, Veterinary Officer, Albany on +61 (0)8 9892 8535, 0429 084 710.