Ask Horse Journal: 06/09

Pasture Plans. My horses love to eat pine needles. Is it OK’ Also, my new pasture has a huge black walnut tree that I don’t want to remove because it gives a lot of shade. Is it safe if the horses eat the bark or the leaves’

Horse Journal Response: A nibble or two on pine needles isn’t likely to cause a problem other than mouth irritation, but in large enough amounts they can cause colic.

It’s definitely not safe for the horses to chew on a black walnut tree or even eat the dirt around one. Juglone is the toxic, laminitis-inducing chemical in black walnut.

All parts of the tree contain the chemical, including leaves. While laminitis related to black walnut shavings had always been assumed to be from skin contact, efforts to reproduce this by exposure to shavings or juglone on the skin haven’t been successful. It may be that the horses on these shavings are eating some shavings and being poisoned.


My grandfather always had me put bluing (enough to turn the water to a sky blue) in the watering trough to keep the mosquito larva from developing in the trough. Does this work, or is it just an ”old farmer’s tale”’ What is the effect on the horses’

Horse Journal Response: We couldn’t find anything to confirm or deny that it would work. Laundry bluing is either the mineral ultramarine or Prussian blue. Prussian blue is an iron-and-cyanide compound that is potentially toxic. Prussian blue has been used to help discourage algae, which might be where this came from. One commercial product also contains oxalic acid (Mrs. Stewart’s Laundry Bluing) that will chelate with calcium in the intestines and prevent absorption.

Bluing is more safely used externally, to make white coats brighter. It’s why white-horse shampoos are often blue/purple. You can get the same effect by using a final bluing rinse after shampooing your horse. Wash thoroughly to remove stains, rinse off shampoo and do a final rinse of white areas with water (preferably distilled) that has bluing added at a rate of three to four drops per gallon.

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