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

Morphological changes of the acrosome of boar spermatozoa during
aging and cold shock

J. BOENDER
Research Institute for Animal Husbandry '"Schoonoord"
Department of Animal Reproduction and A.I.

Driebergseweg 10 d, Zeist, Netherlands

Introduction

It is generally known that during storage of spermatozoa in vitro the
fertilizing capacity is slowly declining, The causes responsible for
this phenomenon are as yet unknown, In recent years however it be-
came apparent - as several papers pointed out (1 - 9) - that the acro-
some plays an important role during the first period of the fertiliza-
tion (i.e. the moving around and the penetration of the egg). Morpholo-
gical changes of the acrosome of bull and boar spermatozoa lead to
sterility (2, 3, 4).

Material and methods

The spermatozoa needed for this experiment were obtained by means
of an artificial vagina from some 1 - 2 years old Great Yorkshire
boars with a good fertilizing capacity. For the purpose of storage, the
sperm was diluted 1 : 1 in the modificated IVT diluent, saturated with
CO, up to pH 6.2 (10) at 23°C, then shed in Kimax tubes, hermetical-
ly glosed and kept at a constant temperature of isc (+0. 5°C). Cold
shock experiments were carried out with the adding of 3 ml fresh un-
diluted sperm to 2, 5 ml precooled spermplasma of the same ejacula-
tion. The following staining technique was used: immediately after mi-
croscopical observation of the sperm, smears were made and dried in
the air during% an hour at 30°C. Then fixated during 1 an hour at 30°C
in Hancock's isotonic fixation liquid (11), next rinsed in running water
and afterwards stained for 45 minutes in a Giemsa solution.

Results

Aging symptoms during storage of spermatozoa

From earlier experiments it already appeared (12) that boar sperma-
tozoa kept in a CO, saturated IVT diluent, maintained its fertilizing ca-
pacity for 3 - 4 days. After this period a reduction of the fertilization
results and the numerical strength of the farrow appeared. The percen-
tage of living spermatozoa is practically identical in comparison with
that at the beginning of the storage. After 10 days the percentage of
living spermatozoa is + 70%. When we examine the spermatozoa
coloured by means of a Giemsa staining, the following can be observed.
In normal fresh spermatozoa one may be able to distinguish: a distinct,
lightly coloured apical border area, a crescent shaped acrosome, an
aequatorial plate and a post nuclear cap (p.n.c.) (series 1, fig. 1y
Some days later the apical border area however is not visible any more.
It proves to have a very tender structure and is the first change to be
observed. The tenderness of this structure is such that two times of
washing are sufficient for its disappearance., After a 4 days' storage it

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