In the
first half of the nineteenth century the cause of blue milk was a subject of
much speculation. Several authors
supposed that the eating of plants that contain indigo-like compounds was the
cause of this phenomenon, that was considered a disease by some and someething
outside the cow by others. Chabert and Fromage in 1805, in a book that I
discussed in the two preceding blogs, tried to connect the blue milk to
abnormal digestion and metabolism of the cow.
In Gellé
(1841) other theories were discussed. Gellé wrote a book (1), devoted to
diseases of cattle. In a long paragraph (p.695-701) he discussed the alterations
of the secretion of the milk, the main subjects being red milk and blue milk.
Red milk was a less important problem, mainly caused by blood in the milk of
which the origin was uncertain; Gellé cites, without giving the source, a
certain M(onsieur) Serain who in 1805 had a couple of cows, some of which gave
milk full of blood; it appeared to be some kind of epidemic in the field that
was called “vaches harondelées”
because it was thought that the udders of these cows were picked at by swallows
(hirondelles).
With regard
to blue milk Gellé included in his review quite a number of reports of persons
who had observed blue milk occurring in practice and had tried to explain and
cure or prevent it. Of the many theories described and commented upon by him I
want to concentrate on a report by Monsieur Sarin, a health officer in Saintes,
in France, who did some
investigations in Normandy.
As with the others, the source of the report is not given by Gellé; it may have
been oral. Sarin had observed in a certain, not specified, year that during the
months June, July and August, when blue milk was expected to manifest itself as
usual, he could not find it, because, as he speculated, the weather was rather
cold then. In addition, he observed that in regions where it was a custom to
tie the cows to a stake during the whole day and right in the sun, blue milk
was seen frequently. Sarin concluded from these observations that an excess of
atmospherical heat should be the cause. He described that he had met a
farm-maid (bonne femme) who had told
him that she protected the tied cows against blue milk by pouring three or four
buckets of cold water on the back of the cows, in the morning and in the
afternoon. Sarin believed he had found the cause and the remedy and was
supported in this belief by an experiment he performed in which he produced blue milk in cows in a
very warm cow-shed; subsequently he got rid of the blue milk by the cold water
treatment. When he repeated this “protocol” by heating the shed again and then
cooling the cows in the shed by cold water, the blue milk returned and disappeared
as before.
Gellé did
not believe it, he prefered the other theories, given by his sources: either
nutrition is the cause because the cows eat plants containing substances that
give a colour to the milk, or it is the consequence of irritations of the udder,
developed during the parturation process.
I think the
report of monsieur Sarin is interesting for two reasons.
First he is
trying to confirm an hypothesis, based on field observations, of heat as a
cause of blue milk, by performing an experiment. I our view it may be a sloppy
experiment; it lacks at least one necessary control, i.e. cows in the same shed
not treated with cold water. But nevertheless it is an experiment as a step in
scientific reasoning that was absent in most of the other theories that were
based on observations and subsequent correlations alone. Gellé thought it was a
mistake to adhere to the heat theory because in other regions in France with
“atmospherical heat” no blue milk was found. Sarin’s theory was rejected, not
because his experiment was wrong but because the hypothesis that was the
starting point for his experiment was considered not plausible and was not
supported by other evidence, apart from his experiment.
Second,
Sarin’s report is interesting because he tells us about farming practices of
the early 19th century, that we easily forget since we are used to
machine milking and farms with tens or hundreds of cows. In Sarin’s days cows
were sometimes tied to a stake and left on their own for the whole day. What
did they eat? I suppose the plants that were in their reach, but probably also
all kinds of vegetable feedstuff that was collected by the farmer or his wife
and his employees in the direct environment of the farm: plants from fallow
land and sides of ditches, containing weeds and contaminations, sometimes causing
the milk to be coloured blue, red or yellow. Compared to what we are used to
now, farming practices were different, housing of cows was different and what
cows were given to eat was also different.
And
concepts of disease were different.
1. P.-B.Gellé. Pathologie bovine ou traité complet des
maladies du boeuf. Tome
troisième.
Paris, Bouchard-Huzard, 1841
