What to do with a frosted crop
Date: 17 Nov 2014
Once frost damage has been confirmed, there are a number of options for dealing with a frosted crop, each with advantages and disadvantages. Two of the most popular options are hay and livestock.
Agripartner Consulting livestock consultant Hamish Dickson says that whether cutting hay to use on farm or putting livestock on the crop, the key is aligning the feed quality to the class of stock. This means considering different metabolisable energy and protein requirements for different sheep and cattle classes (Table 1).
“It’s critical to do a feed test when considering using a frosted crop for feed. Depending on the growth stage when the crop was damaged the protein and metabolisable energy (ME) can be very different to normal hay,” he said.
“Once you’ve got feed test results, you can calculate for a target weight gain and the size of the crop, how many animals you can support and for how long.”
As digestibility, or energy, and protein levels decrease with plant maturity (Figure 1), growers should cut for hay as soon as possible after the frost is confirmed. If grazing, the decision to spray-top to ‘hold’ the crop maturity will depend on the stocking plan.
“If you can graze heavily immediately you may not bother with spray topping. However if you can’t graze heavily, it will often make sense to spray-top. The class of stock is also important; cattle are unable to efficiently utilise any grain that may develop in the head of a ripened crop, so there is no benefit to allowing the plant to mature and spray topping will likely be the best decision, however sheep can utilise the grain well, so when grazing sheep, allowing the crop to ripen can provide a boost in nutrition,” Mr Dickson said.
“If you’re feeding hay, use a hay feeder to get the best value out of a frosted crop. Trials have shown that up to 45 percent of hay is wasted from paddock placement. If you’re grazing, cropping paddocks are often too big to get the highest efficiency. A high stocking rate and small paddock size will make the best use of the crop, so consider using electric fencing to create more, smaller paddocks.”
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