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Using Potatoes For Cattle

14 May 2020

Stockfeed potatoes look plentiful at the moment and with prices currently around £18-25/t they are definitely worth consideration.

A few options for using potatoes:

 Ensiling raw potatoes and grass silage

 A well tried, tested and common procedure is to ensile potatoes with grass in a conventional silo.  The potatoes should be cleaned of soil as far as possible (as this causes bad patches in the silage) and either mixed in or put in alternate layers; about 0.6 m of grass followed by 0.15 m of potatoes. The usual recommended ratio of grass to potatoes is 5:1 but some authorities have suggested that a ratio as low as 3:1 is acceptable.

Ensiling raw potatoes and draff (please note draff is currently very limited in supply so may not be an option). Draff (or brewers grains or supergrains) and potatoes mixed in the ratio of 2:1 is also a safe and effective way of storing potatoes.  Ideally the mix should be ensiled when the draff is hot as the heat will partially cook the potatoes and reduce effluent flow.  These two feeds balance each other well as the low protein content of the potatoes is offset by the higher level in the draff.  Such an ensiled mix should have a dry matter content of about 250 g/kg, a protein of 170-200 g/kg DM and an ME of 11.6 MJ/kg DM.

Feeding potatoes to store/fattening cattle and cattle at grass

 With a good winter of feeding many store cattle may be further on than anticipated, rather than putting them out to grass perhaps keeping them in the house and finishing them would be an alternative? Potatoes may be a good option for a cheap addition to barley offering a welcome boost for cattle near finishing. Alternatively, if cattle are out for the summer and they need a push on to finish, perhaps feeding potatoes at grass would be worthwhile?

 Caution when feeding potatoes

  •  Make sure potatoes are as clean as possible
  • Green and sprouted potatoes contain chemicals – glycoalkaloids (GA), which are toxic to animals.  These toxins are similar to the ones found in Woody and Black Nightshade, which is not surprising since these plants are members of the same family as the potato. Potatoes always contain small amounts of GA’s – even if they are not green. Exposure to light and sprouting results in a large increase in the concentration of the toxins, with the sprouts containing up to 30 times as much as the green tubers. White sprouts contain about 30% to 40% less toxins than green sprouts so it is important to note that the sprouts do not have to be green to be toxic.  Cattle and sheep are more resistant to toxicity than pigs or humans and it appears that some of the toxin is destroyed in the rumen.
  • Ensiling also appears to destroy 30% to 40% of the toxins so that including slightly greened potatoes with grass silage should be safe. Ensiling badly greened or sprouted potatoes is therefore not without risk and every effort should be made to knock off the sprouts, which are the most toxic, before ensiling.
  • Always feed potatoes at ground level to avoid choking or chop them before feeding.
  • It should be noted if feeding potatoes at grass, if the grazing is in rotation with growing potatoes, there is a risk of contaminating the ground with powdery scab (14 years+ to eradicate) and potato cyst nematode (PCN) (7 years+ to eradicate). This also applies to cattle fed tatties indoors and the dung being spread on land for potatoes.

Karen Stewart, karen.stewart@sac.co.uk

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