Brassica Fodder Crops

Things to know about Brassicas, which include: fodder kale, fodder rape and redstart.

• Brassicas are low in fibre and high in sugars, which can increase the chance of acidosis if not managed correctly with an overall balanced diet.
• Brassicas have a low Dry Matter content,
• It can take up to two weeks for an animal to adjust from grass to feeding brassicas
• Ensure animals are never hungry when entering the crop, allow them access for 1 -2 hours the first day and gradually build up the allowance over 10 days
• Maximum daily intake of brassica should not exceed 70% of an animal’s diet, hence concentrate & forage feeding is recommended.
• Brassicas contain low levels of some nutrients including Iodine, Selenium, Phosphorus and Potassium, its essential that supplementation is provided in the form of bolus, mineral buckets, blocks or minerals in the water, giving special attention to the iodine levels, as this is a deficiency that can manifest rapidly.

How to calculate daily feed allocation of Brassicas

Example: a weanling will eat 3% of their body weight in Dry Matter daily whilst being out wintered. Assume a weanling is 270 kg (x 3%) = 8 kg Dry Matter.

Remember a weanling can only consume a max of 70% of its diet in brassica so 8kg DM (overall req) x 70% = 5.6kg Dry Matter daily brassica requirement for 1 weanling.

Now assume we have 25 weanlings being grazed so we now require (25 x 5.6kg) = 140kg Dry Matter in total per day for 25 weanlings at 270kg weight.

Based on above figures and assuming crop yield of Redstart being 7 tons Dry Matter per hectare we can now calculate how many days a hectare of Redstart will last these 25 weanlings.

Because animals don’t graze these crops to the butt the assumption is the animal utilises approx. 80% of the crop. So overall yield of (7 tons x 80%) = 5.6 tons of utilizable crop per hectare.

140kg total daily brassica requirement (divided) by 5.6 tons or (5600 kg) of utilizable crop tells us that 1 hectare of brassica will keep 25 weanlings at 270kg weight going for 40 days.

Example above was based on a crop of redstart yielding 7 tons Dry Matter per hectare, please note that fodder kale has the potential to yield up to 10 tons Dry Matter per hectare while average yields of fodder rape will be limited to approx. 5 tons Dry Matter per hectare.