Cornevin remarks that _Melampyrum arvense_ is considered to influence cows to produce more milk.
According to some authorities species of _Equisetum_ check milk production or cause it to cease, and _E. palustre_ is stated by Weber to cause the milk of affected cows to become watery, poor in fat, and give rise to a greasy and unappetising butter, while the yield may soon quite fail.
The ingestion of the foliage of the oak (_Quercus_ sp.) is stated by Cornevin to induce _Maladie des Bois_, with reduction or entire loss of milk production (see p. 69). Acorns have also affected milk production, and a case is recorded (_The Dairy_, 1913) in which it is stated that cheese made from the milk of cows which had fed on acorns developed a sharp acid flavour when about four weeks old, though the texture was good. It is not clear, however, how it was proved to be due to the acorns.
In one case recorded a reddish tinge was observed in the milk of a cow suffering from Rhododendron poisoning (p. 46), and in general reduced milk production appears to occur.
In addition to the foregoing, there is good authority for saying that the following plants may impart a disagreeable flavour to milk, and in many cases the butter made from it:—
_Anthemis arvensis_L. (Corn Chamomile). _Anthemis Cotula_L. (Stinking Mayweed). _Artemisia Absinthium_ L. (Wormwood). _Conium maculatum_ L. (Hemlock). _Hyoscyamus niger_ L. (Henbane). _Matricaria Chamomilla_ L. (Wild Chamomile). _Pinguicula vulgaris_ L. (Butterwort). _Senebiera didyma_ Pers. (Lesser Wartcress). _Sium angustifolium_ L. (Lesser Sium). _Sium latifolium_ L. (Water Parsnip). _Tanacetum vulgare_ L. (Tansy). _Thlaspi arvense_ L. (Penny Cress).
(See also Index “Milk, plants affecting,” p. 117.)
There are a number of plants which, while not necessarily physiological poisons, may induce injuries of a severe character when taken by animals, and by causing festering may bring about septic poisoning. For example the sharp pointed fruits of _Stipa pinnata_ and _Nardus stricta_ may cause injury to the skin and mouth, piercing the palate and causing inflammation, and when eaten may even perforate the wall of the intestine and cause death; and the awned glumes of species of _Bromus_ or the spikelets of Hordeum may injure the gums, causing inflammation, ulceration, sores, the formation of pus, and loss of teeth. The _Bromus_ and _Hordeum_, also, together with over-matured “heads” of _Trifolium incarnatum_, may give rise to Phytobezoars or balls in the stomach of horses and cattle (60, 119). The sharp pointed fruits of _Erodium cicutarium_ may cause local irritation by working into the wool of sheep. _Aira caespitosa_ may also cause injury to the mouth of stock.