Bog Asphodel (Narthecium ossifragum Huds.) has by some been regarded as a poisonous plant, and Müller says that the poisoning of cows has been recorded, and also that a cat died after drinking the milk of an affected cow. The toxic property is believed to be the glucoside Narthecin.
Molinia caerulea, Moench. A short account by Pott shows that when forming the principal part of moorland pasture grasses, and hence extensively eaten, this grass causes brittleness of the bones of stock, and in sheep chlorosis and wool eating. It also induces hæmaturia, but if free from parasitic fungi (e.g. Claviceps microcephala) and not covered with microscopic, sharp crystals, is quite harmless if only eaten as a secondary or incidental fodder. This grass seems to be very poor in lime (Immendorf, 1898), and Schulze and Castoro found the internodes of the stem to contain a considerable quantity of a pentosan (Xylan). It is poor in nutritive constituents. The harm done is due perhaps in part to this fact, and in part to more or less accidental or occasional constituents (as 0·046 per cent. of lead oxide in a case of the var. altissima near some lead works). Plants said to be occasionally similarly harmful are Juncus sp., Nepeta Glechoma, and Hieracium Pilosella.
CHAPTER VIII
THE EFFECTS OF PLANTS ON MILK.
A number of poisonous plants have a considerable influence on the milk yield of animals which eat them, reducing it in volume or in fat content, or imparting to it an unpleasant flavour which renders it unfit for human consumption, and even affecting the butter made from it. Other plants not actually poisonous also affect milk by “tainting” it, and must therefore be considered harmful otherwise than as mere weeds. Still others affect milk by causing it to be stained with blood, and in some cases the toxic principle of the plant concerned is even stated to have rendered the milk poisonous. It will be useful to give here a brief account of milk-affecting plants, though it is probable that there may be others which are not mentioned.
The plants best known in this connection are the Garlics (Allium oleraceum L., A. ursinum L., A. vineale L., and others), which impart to milk a strong “oniony” flavour. These plants also seriously affect the flesh of animals which eat them, even rendering it unfit for consumption. A case came before the author several years ago in which a considerable number of sheep had eaten a quantity of Allium ursinum, which was growing in a field in which they had been grazing for some days. The meat was so strongly tainted that, as the owner (a butcher) stated, it was quite unfit for sale. The only thing to be done was to pasture the sheep elsewhere for a time.
Pott notes that species of Ranunculus give rise to reddish or bitter milk (Mölkereizeitung, 1897), while Caltha palustris causes loss of milk production in cows.
Ranunculus repens imparts a strong unpleasant flavour to the milk of cows that have eaten it, and the butter made from such milk is distinctly bitter in taste (Güssow).
Ranunculus sceleratus causes a falling-off in milk-yield. (Cornevin.)
Alliaria officinalis Andrz, imparts an oniony flavour to milk.
Achillea Millefolium L. is stated to impart its bitter taste and strong odour to dairy products when eaten by cows. It contains an alkaloid, Achilleine (C20H38O15N2) having a peculiar odour and bitter taste.