Vie CONG. INTERN. REPROD. ANIM. INSEM. ARTIF., PARIS, 1968, VOL. I

this tendency can be reduced if the proportion of eosinophilic
spermatozoa in any slide is unknown until all the counting has

finished.

The sudden exposure of fresh ejaculated ram and bull spermatozoa
to temperatures between 0°C and 10°C resulted in an immediate rise in
the proportion of eosinophilic spermatozoa (2) but if a spermatozoon
survived the first shock it did not become eosinophilic in the suc-
ceeding 15 minutes. None of the other factors tested altered this
effect appreciably, although dilution of ram semen with this diluent
produced a slight increase of the shock effect.

The extraordinary variation in the proportion of eosinophilic
spermatozoa in bull semen exposed to 7.5°C suggests that this is a
critical temperature for whatever mechanism normally prevents the
entry of eosin into the spermatozoon. Therefore this temperature
will be used in future studies on susceptibility of spermatozoa to
cold shock, at least in the bull.

 
 

BULL

  
  

RAM

e undiluted
e diluted

   

  

o
O

perm

5

N
O

%6 Stained S

10 20 30 10 20 30
Temperature °C Temperature °C

o

Fig. 1. The proportion of eosinophilic spermatozoa (Z stained sperm)
after sudden exposure to various temperatures. The diluted samples
were diluted 1:4 with phosphate buffered saline. Each point is the
mean of 5 samples. (8 counts/sample).

1237

27