If managed appropriately, stubbles and crop residues can provide a valuable nutritional source for sheep and lambs.
But many producers can use stubbles for longer than they are providing adequate energy for the sheep often leading to a decrease in condition score in breeding ewes and under performance in young stock.
CSIRO agriculture and food scientist Dr Dean Thomas said stubbles are a feed source that start as high quality, but depletes quickly.
"Because sheep clean up the spilt grain quickly, producers need to keep this characteristic in mind to ensure a good source of nutrition is maintained," Dr Thomas said.
"Grazing stubbles is often done when ewes are pregnant so it's important they're kept in good condition.
"Producers should aim for a condition score of three and have them on a rising plane of nutrition."
So how do we know when to remove the sheep from the stubble before the grain is exhausted?
Nutritional value in stubble predominantly comes from spilt grain and green pick, as opposed to the straw and stubble and the nutritional value of the stubble will decline once the grain has been consumed.
Elders livestock production manager Rob Inglis said although grazing crop stubble on a mixed farming production system provides free energy, particularly in seasons of very heavy crops, it is important to work out how much grain is in the stubble crop in order to determine how long to leave the sheep to graze.
"A portion of a crop will be damaged or laid down by weather and machinery so there will be quite a few unharvested heads as well as a lot of spilt grain coming out of the header," Mr Inglis said.
"That cereal grain is a very good source of fermentable carbohydrate which really improves ruminant efficiency."
Mr Inglis said as a rough guide, in an average cereal crop or average wheat or barley crop, there will be about 100 kilos per hectare of unharvested or spilt grain.
"The sheep will recover about 70pc of that so the sheep will get about 70 kilograms per hectare of grain from the stubble," Mr Inglis said.
"To work that out in DSE days, with sheep eating about half a kilo of grain per day, that's about 130 DSE days per hectare and that also includes a little bit of roughage they are consuming as well.
"So 130 DSE days per hectare, assuming you were running three DSE per hectare, you would divide 130 by three.
"That equates to about 40 to 50 days of grazing before the grain is exhausted."
Mr Inglis said stock that need high quality feed such as weaners would benefit from stubbles with a high amount of grain on it.
"In terms of priority it would be young sheep (weaners), then pre-joining ewes and for those that have joined earlier, possible pregnant ewes," he said.
"Weaners have the highest energy requirements, but ewes pre-joining would also benefit."
But he warned if joining ewes on stubbles, to make sure rams were imprinted as well.
"If you suddenly throw the rams in with ewes on stubbles, if they haven't been imprinted you could give them sever Laminitis or poison them, so introduce the rams the same you do as the ewes.
"Having too much grain, there needs to be big importance placed on imprinting the animals so their system doesn't get a shock moving on to a heavy grain load."
Weighing young sheep frequently would be the best way to ascertain that the pasture is producing as expected and with mature sheep, conditioning scoring as often as possible to ensure they are not losing any condition, Mr Inglis said.
"When managed correctly, with the grain being the principle energy source, in young sheep, 100 to 150 grams per head per day would be achievable," Mr Inglis said.
"In older sheep, probably 50 to 100 grams per day.
"But in younger sheep, if the nutrient balance is right between carbohydrates and protein you could get in excess of 200g per day."
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