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presence of urine which may often be detected
also by smell. A pinkish or reddish colour
indicates an admixture of fresh blood. while a
deep reddish-brown colouration probably indi
cates the presence of decomposed blood.
Specimens
showing
abnormal colour or
marked deficiency in density should not be used
for insemination.
Examination for Motility. A satisfactory ex
amination for motility can be made by placing
a drop of semen from a well-mixed sample on a
slide and placing a cover slip on it. For
routine examinations ⅔ and 1/6 objective lens are
required.
In examinations for motility, the following
precautions must be observed: (a) examination
should be carried out as soon as possible after
collection of semen; (b) care should be taken
that it is not exposed to a sudden temperature
fall between collection and examination; (c) the
sample should be mixed well before taking the
drop for examination; and (d) examination
should be made in a warm room.
Warming spermatozoa.
When examining
smears of sperm for motility immediately after
collection in cold weather, cooling takes place
so rapidly while handling it that often all the
spermatozoa appear motionless when examined.
Under these conditions it is advisable to hold
a lighted match under the slide to warm the
spermatozoa sufficiently to make them actively
motile, care being taken not to overheat and
kill them.
Types of motility.
According to Walton
[1933], three types of motility may be
recognized: —
(i) A progressive motion in which the sper
matozoon usually moves in a straight line.
(ii) A rotary motion in which the movement
is around the periphery of a circle whose dia
meter usually does not exceed the length of the
individual spermatozoon.
(iii) An oscillatory motion which consists of
a series of convulsive motions without change
of place.
Walton considers that a spermatozoon must
possess progressive motion if it is to meet and
fertilize the ovum.
No very satisfactory method of classifying
motality has yet been devised, but the following
system, introduced
by
Russian workers,
appears to be adequate for practical purposes.
It is based on a discrimination between the
various types of motility and the proportion of
spermatozoa exhibiting the respective types.
Thus: the highest rating, indicated by the figure
5, indicates that all or nearly all exhibit ener
getic progressive motion; 4, the majority of the
sperm have progressive motion; 3, there are
about equal proportions of sperm exhibiting
progressive motion and oscillatory motion or
are immotile; 2, oscillatory motion, with a large
number immotile; 1, immotile; and 0, comp
lete absence of spermatozoa.
Adopting the above ratings, it may be taken
that bulls giving specimens classed as 5 or 4 are
probably of normal fertility; samples classed as
3 indicate bulls of low fertility; while those
having ratings of 2, 1 or 0 are sterile.
The same classification may be applied for
evaluating the potential fertility of semen after
storage.
Detection of Extraneous Matter. Gross con
tamination of a semen sample with dirt from
the region of the prepuce will be recognized on
macroscopical examination.
Brown muddy
discoloration is evidence of this type of conta
mination.
Examination for cells may be done after
suitable staining, but for reliable bacteriological
examination,
sample are best sent to a
laboratory.
5. TECHNIQUE OF INSEMINATION
Semen can be, and often is, used immediately
after collection. If it is to be stored or trans
ported to a distance, it requires special treat
ment (see section dealing with Storage and
Transport).
Insemination should be carried out while the
cow is in oestrus or within about eight hours
after its cessation. If the cow is an uncertain
breeder it is recommended that she be insemi
nated as late as possible in the day in which she
is first observed to be in heat, and again the
following morning. This will entail keeping
semen overnight under suitable storage condi
tions or collecting afresh.
The cow for insemination should be secured
in a stall with, if possible, a good light directly
behind her. The lips of the vulva and surround
ing area should be thoroughly washed, using a
soft brush and warm water. No disinfectant or
soap should be used owing to the risk of con
taminating and so destroying the sperm. A
suitable speculum (Russian or tubular patterns)
is inserted into the vagina and held in position
with the left hand. For heifers a smaller type
speculum is necessary. The vagina is illuminat
ed with the light from a head lamp or by a