Crop growth this year has been lower and depending on where you are and your paddock soil type, you may be looking to salvage crops that have suffered from the late and dry season or frost.
A tool to help you decide the crop outcome is the ‘Salvaging crops for fodder, grain or grazing – costs and income calculator’.
Using your own input, harvesting costs and potential value for each product, the calculator helps you compare the various management options, to make an informed decision on the best crop outcome. Other factors include potential weed seed set, presence of herbicide resistance and the amount of grain that can be picked up by the header.
If your crop is not suitable for hay or harvesting, here are some considerations for grazing different crop types.
Canola will likely be one of the first crops you graze and usually has a high feed value (high energy, protein and digestibility), but animals may take some time to adapt the new feed. At mid to late flowering crops can have energy of 11-13% MJ ME/kg, and above 18% protein.
If nitrogen fertiliser was applied prior to becoming moisture stressed, plants are at risk of having high nitrate levels. Rumen bacteria are highly effective at using plant nitrates, but in excessive amounts the bacteria are overwhelmed, resulting in accumulation and toxicity. However, a gradual increase in available nitrate levels can be well tolerated by ruminants.
Poor gut adaptation to canola can result in a neurological condition, polioencephalomalacia (PEM). The effect of this can also be induced or exacerbated by high plant sulphur.
To help prevent animal health issues from grazing canola, follow the recommendations:
- Test the crop nitrate (don’t exceed 0.5%, over 1% dangerous) and sulphur (don’t exceed 0.4%) levels
- Ensure animals do not graze the crop hungry – fill with hay prior to introduction to the crop
- Graze between 10am-2pm each day for seven days to ensure gradual adaption to the change in diet
- Provide ad lib access to hay or straw (for fibre) or a neighbouring standing crop paddock at all times while grazing the crop. Canola should not be more than 60% of the diet.
- After seven days animals can be left on the crop provided they have on-going access to hay.
- Continue to monitor stock daily. Remove stock immediately if they show any unusual behaviour.
Grazing legumes
If grazing a standing, green legume crop, the leaf material can only be eaten until dry conditions set in. Once mature, leaf material drops off the plant and quality deteriorates. Cutting or desiccating helps to preserve the quality, and may allow the leaf to be grazed, particularly if in a windrow.
Forage yield of a frosted legume crop may be 1.0 to 1.5 times the anticipated grain yield of the crop before the frost. Any unfrosted grain present in pods will boost the forage yield. The grazing value of a standing, mature crop or legume stubble is mostly in the grain. Stock can be finished on legumes if the stocking rate is managed to have enough grain remaining until the stock are ready for slaughter. Feed test to determine the feed value for livestock
Chickpeas have a malic acid coating on the leaves, making them unpalatable for grazing or hay production. Stock will graze some new growth, flowers or pods in some varieties more than others (kabuli are better than desi types), but the greatest value will be in the weeds around them. Once weeds have been grazed, remove stock before they begin to lose weight.
Beans are unpalatable when green, but once dried off can be grazed and have 9 MJ ME/kg DM and 13-17% protein. Some varieties have high-tannin levels (which reduce feed intake and digestibility), but recent breeding of beans for feed use have produced low-tannin cultivars with reduced anti-nutritional factors. If unsure of tannin levels, supplement with other feed so that beans are no more than 50% of the diet.
If there’s not enough biomass for hay, rather than turning the stock straight in, cut into a windrow and then graze to reduce trampling and wastage. Cut with a mower conditioner to speed up stem drying. Be careful of rain on the windrow (although unlikely in a poorer season) causing microbial growth/mould that can affect palatability and produce mycotoxins that affect stock health. Alternatively, hay freeze the crop then strip graze using electric fencing.
Lupins are usually grown on lighter soils and in drought conditions will have lower biomass, so be mindful about the erosion risk. Lupins have a high stem to leaf ratio so graze before the leaves fall off. Lupinosis usually occurs following summer rain on stubbles and trash but could potentially be an issue on a dried failed crop. Some varieties have better resistance, but none are immune. Alkaloids are low in Southern Australia varieties with ‘sweet’ low-alkaloid types most commonly grown.
A failed cereal will often have 6-10 MJ ME/kg DM energy and 8-16% protein, depending on how mature the crop is. Feed test to know for sure. Supplement stock with a limestone:causmag:salt mix 2:2:1 continually while grazing, and vaccinate stock for enterotoxaemia prior to entering the crop if it’s a change of feed.
Withholding periods on chemicals:
For all crops, adhere to grazing withholding periods for any seed dressings, herbicides, insecticides and fungicides applied to avoid chemical residues. That includes pre and post-emergent herbicides like atrazine and/or simazine used on TT canola varieties.
National Vendor Declarations (NVDs) for both sheep and cattle ask specific questions about observance of feed withholding periods. Financial penalties, including buyer avoidance or discounts, may be incurred if stock isn’t declared as having grazed only ‘clean’ feed in the 60 days before sale.
Withholding periods for seed dressing and pesticides can be found in Grazing Cropped Land, pg. 59.
