Nightshade Berries Contaminating Livestock Feed: Worry or Don't Worry?
Q: Find enclosed a sample of oats that I harvested with a considerable amount of eastern black nightshade berries. Is it alright to feed this to my beef cows?
A: If your desire is to have no risk of negative health impacts on your livestock, then do not feed the contaminated oats to your beef cows. However, we can draw on past experience with feed samples contaminated with eastern black nightshade to provide some indication of potential risks.
Plant species from the nightshade family often contain glycoalkaloids, which are bitter tasting and poorly absorbed from the gastrointestinal tract, causing gastric irritation and symptoms that range from "tummy rumbling" to vomiting and diarrhea. Many of you have seen green parts of a potato, or a potato chip with a tinge of green. When a potato has green skin, it contains the glycoalkaloid "solanine". Many of us though, don't toss out a potato with green skin but rather cut the green part off and use the rest. After all, a University of Nebraska, Lincoln report indicated that one would have to consume 1% of our body weight in green potatoes to get sick1, which for many of us would represent well over 1 lb of green potatoes.
In 2015 an oat sample was sent to me that contained dried up eastern black nightshade berries at 1% of total sample weight (Figure 1 & 2). Previous reports have indicated that dried berries of black nightshade do not contain toxic alkaloids while the immature green berries of eastern black nightshade may contain small amounts of toxic alkaloids2 so presumably the risk of feeding this sample would be low given the berries in the sample were mature and dried. Nonetheless the feed sample was sent to a diagnostic lab to see if any toxic alkaloids could be found. While awaiting results from a diagnostic lab, the farmer decided to feed a small amount of the contaminated oats to his cattle. He reported back that "the calves' manure became loose and some bloody, so (I) backed off the amount fed and have slowly increased the amount but not to the levels I would normally feed with and have seen no side effects". When the lab report came in, it had tested positive for toxic alkaloids, which would seem consistent with the side effects observed by the farmer. Once again, this illustrates that "the dose makes the poison" but the challenge with poisonous plants contaminating animal feed is that there is little information available as to what dose will cause problems. Therefore, it's best to be cautious. Either compost the oats so that you have a chance at killing the viability of the weed seeds or clean the seed as best you can to remove the berries and re-purpose as cover crop seed, keeping a keen eye on any germinating nightshade plants so that you can remove them when young.
Figure 1. Sample of oats sent in that contained "nightshade" berries
Figure 2. Berries were sorted out of the oat sample and weighed, revealing that the nightshade berries comprised 1% of the total sample weight.
1 O'Connor, A. (2007, July 3). The Claim: Green Potatoes Are Poisonous. New York Times.
2 Canadian Biodiversity Information Facility. (n.d.) In: Black nightshade (common name). Retrieved December 3, 2015.
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