30 June 1998
Potato skins as cattle feed
WE have been offered the chance to feed our cattle potato skins from a commercial processing plant. These potatoes have been steamed to have the skins removed and we would like to know if the steaming process effectively kills off eelworm, or if it is killed in the cattle gut. Are these potato skins of any nutritional value; and would they be of any use as cattle feed?
Mitch Lewis, Animal Biology Division, SAC, Penicuik.
THE potato skins may be nutritious, and eelworms would be killed off by the steaming or in the gut of the cattle. But the almost indestructible eelworm cysts are another matter.
The nutritional value of potato skins would differ from that of whole potatoes. The skins would have a lower energy value but a higher fibre and protein content. I suggest you ask the supplier whether an analysis is available. If not, get a sample analysed for dry matter, protein and an estimate of energy (ME) to make the best use of them.
Whether eelworms would be killed by the steaming process depends on the temperature of the steaming process. However, feeding the skins to cattle would kill the eelworms because of the combined (but sequential) effects of
- the anaerobic conditions in the rumen, which would starve them of oxygen, and
- the acidic environment and the digestive juices of the lower gut.
However, besides eelworms, the cattle may ingest eelworm cysts, which seem to be extremely tough and able to resist almost anything thrown at them, due to their chitin exoskeleton. They can withstand a short period of high temperature without damage and would certainly be able to suvive (and even
enjoy!) a journey through the digestive tract of a ruminant. However, since cysts tend to be associated with the soil rather than the tubers, well-washed potatoes should be free of cysts.
It is impossible therefore to give a cast-iron guarantee that the dung will be cyst-free. If this is important on this farm, then my advice is not to bother with the skins – the risk is not worth taking.