Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~ ~5~93
2M139-057
"Method of castration and contraception''
The invention relates to a method of chemical
castration of and contraception in male mammals with
external testes. More particularly in this method
a suitable preparation may be injected into the vasa
deferentia, the testes or the epididymides of the
male mammals.
]0 The castration of male mammals may be performed
by surgery, but an open wound can lead to complications
and infections such as tetanus, and may consequently
cause death. As a result of the stress and pain
connected with surgical castration, the animals are
frequently retarded by at least two weeks in their
physical development.
A number of attempts have already been made
to perform castration by a chemical method. A number
of chemical reagents and mixtures, both natural and
synthetic, have been tried. Thus, agents with a
sclerotic activity have been applied to the male
reproductive organs in order to prevent the passage
of semen. All the processes hav~e some disadvantages,
manifested by either inefficiency and/or undiminished
libido and/or the formation of uncontrollable necrotic
tissue damage.
The testes have two main functions. I'he Eirst
is the production of semen which runs away through
the seminiferous tubules and the second is the production
of the androgens (testosterone and dihydrotestosterone)
which run away in the interstitial cells (I.eydig's
cells).
~ fter being produced in the testes, the sperms
are released in the top of the epididymis and travel
from there to the end of the epididymis, a cavernous
network of convoluted tubes. The function of the
epididymis is to transport the semen, develop it
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to maturity, concentrate it and store it. On ejaculation,
the spermatozoa are released ~rom the epididymides
into the vasa deferentia and finally through the
penis to the outside. The function of the two vasa
deferentia is to ensure the supply of, gas exchange
in and thermo-regulation of the testes via the p:Lexus
pampiniformis.
We have now developed a method, employing a
suitable agent, which interferes with this complex
interplay. In our method, on being injected into
the two vasa deferentia, the agent used destroys
the vascular system and thus produces atrophy of
the testes and hence loss of spermatogenesis and
loss of libido. Alternatively, when injected directly
into both testes, the agent causes atrophy and loss
of spermatogenesis and libido or, when injected into
the epididymides, causes sterilisation (contraception~
but leaves the libido undiminished.
~ccording to one aspect of the invent;on, therefore,
we provide a method for the castration of or of contra-
ception in male mammals which comprises in~ecting
;nto the genital organs of said mammals an effective
amount of castrating or contraceptive agent.
The method can be used on a wide range of mammals,
provided that it is not restricted by the siæe and
unfavourable shape of the male gen;tals as is the
case in boars, stallions and male cats. It is oE
particular application on dogs, cattle, sheep and
goats.
~ particularly pre~erred agent used in the
invention may be selected from an aqueous solution
of a mono- or dicarboxylic acid with up to ~ carbon
atoms, a hydroxy-substituted analogue or an anhydride
thereof. Included amongst the acids which may be
used are acetic, propionic, butyric, glycolic, oxalic,
malonic, succinic, malic and tartaric acid, acetic
anhydride and, more particularly, lactic acid and
lactic acid lactide. A 1 - 90~ aqueous lactic acid
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solution in a dosage of from 0.l to 20 ml, more parti-
cularly from 0.25 to 16 ml has been found to be parti-
cularly suitable. A 5 to 85% aqueous lactic acid
solution has been successfully used for the sterilisation
of bulls and male dogs. When injected into the vasa
deEerentia or the epididymides of male dogs, a 5
to 25~ aqueous lactic acid solution has proved particularly
effective. The lactic acid solutions used showed
few side effects and no ulceration whilst giving
reproducible results. T.actic acid is a naturally
oceurring non-toxic reagent which is also easily
detected in tissue samples and residues.
The optimum method of administration has proved
to be by injeetion through the two vasa deferentia,
since with this method oE injection only a small
area is destroyed, as opposed to the entire testes.
However, in bull calves weighing less than ~5 kg
injection into the testes is preferable since the
injection can be given more easily and only a little
tissue is destroyed. This method of chemical castration
ean be used particularly successfully and economically
in bulls and male dogs. In the U.S.A. alone about
20 - 30 million bull calves per year have to be castrated.
The method according to the invention is highly useful
for restrieting the dog population; it may be used,
for example, as an economical method of sterilising
male dogs in dog homes.
The method according to the invent;on has proved
to be a sa~e, rapid, economical, practical method
which is simple to perform after a single demonstration.
The complications which occur in surgical castration
do not arise and eonsequently chemical castration
is cleaner, safer and consequently more comfortable.
Moreover, the retarded growth which occurs in surgical
castration does not happen with chem;cal castration.
In comparison with earlier methods of chemical casl:ration,
the invention provides a dosage-dependent effect,
high efficiency, the avoidance of uncontrollable
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tissue damage, versatility in its range of applications,
with the possibility of either maintaining or suppressing
the libido as required and adaptabil;ty for the treatment
of different animals, for example by modifying the
volume administered and the size of the needle, to
suit different animals.
The method according to the invention is hereinafter
illustrated more fully with reference to the Examples,
which should not be taken as limiting~
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Example 1
The effect of reagent containing lactic acid was
tested on a total of 173 bulls weighing between 45
and 286 kg. Different concentrations and volumes
of the reagent were injected into hoth vasa deferentia.
As controls, 4 bulls were castrated surgically.
37 of the 173 bulls weighed more than 225 kg. The
tests showed that better results were obtained when -
the process was used on bulls with a body weight
of less than 225 kg. Thus, the treatment was successful
in 98 out of 136 bulls (72%) weighing less than 225
kg, whereas in the 37 bulls with a body weight of
more than 225 kg the process was successful in only
24 animals (~5%). Moreover, there was found to be
a clear dosage-dependent effect proportional to the
body weight, and as a result a dose of 2 ml is recommended
for bulls weighing up to 90 kg (93~ efficiency),
a dose of 4 ml (100% efficiency) for body weights
from 90 to 135 kg and a dose of 8 ml (82% ef~iciency)
of 85% lactic acid solutions Eor body weights of
from 135 to 225 kg.
If the efficiency rate is to be increased,
higher doses should be administered.
~ ple 2
The aim was to determine the most favourable injection
site by injecting 8 ml of an 85% lactic acid solution
into both vasa deferentia. For this purpose, the
substance was injected into the vasa c7eEerentia oE
20 bulls, on the one hand directly above the testes
and on the other hand 2.5 to 3.75 cm above the testes.
The results showed that injection directly above
the testes was more favourable, with an efficiency
rate of 95, as opposed to 80g.
Example 3
1 and 2 ml of an 85~ lactic acid solution were injected
directly into the testes of 5 Holstein bull calves
(between 0 and 33 days old). The positive results
in all the calves show that the process according
to the invention can be used even in very young calves.
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Example 4
Lactic acid was tested as a possible chemical steriliser for dogs.
I'he results obtained from injecting a dose of 0.25 ml to 1 ml of lactic acid
into the epididymides and the plexus pampiniformis of the vasa deferentia
clearly show that a 5 to 25 % lactic acid solution is an effective chemical
steriliser. For 25, 20, 15 and 10 % lactic acid, the results show percentage
efficiencies of 82% (14 out of 17), 100 % (6 out of 6), 92 % (12 out of 13)
and 80 % ~4 out of 5).
