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

THE EFFECT OF LENGTH OF STORAGE TIME AND
NUMBERS OF SPERMATOZOA ON THE FERTILITY
OF DILUTED BOAR SEMEN

G.H.BENNETT, C.0'HAGAN and D.L.STEWART,
Ministry of Agriculture, Fisheries and Food,
Cattle Breeding Centre, Shinfield, Reading,

England.

The modification of the Illini Variable Temperature
diluent for use in the preservation of boar semen (1) was a
major advance in the development of pig A.I. Subsequently it
was shown that this diluent would maintain satisfactory
fertility when boar semen was stored for a period of three days
and the number of spermatozoa per insemination was reduced to
2,000 x 10® in a volume of 50 ml. of modified I.V.T. (2).

An increase in the utilisation of boar semen is still
required to facilitate the further development of the artificial
insemination of pigs and a series of field fertility trials have
been made at Reading in an attempt to achieve this objective by
lengthening the time semen is stored before use and by reducing
the number of spermatozoa per insemination.

MATERIALS AND METHODS.

In the series of fertility trials described in this paper
semen was collected from Large White and Landrace boars, using
the spiral artificial vagina (3), the number of spermatozoa in
each ejaculate was determined by using a specially calibrated
photo-electric absorptiometer and diluted to obtain the required
number of spermatozoa per insemination volume in modified I.V.T.
according to the method previously described (2). The
insemination volume was standardised at 50 ml., stored at between
150C and 200C until used and all the inseminations were made by
using the rubber spiral catheter (4).

The results are based on first inseminations of sows and
gilts only, and are given as the farrowing percentage. The
average litter size includes all piglets whether born alive or
dead.

RESULTS AND DISCUSSION.
(a) Length of storage time.

2,000 x 106 spermatozoa per insemination volume were employed in
this field fertility trial and the diluted semen was used on the
day of collection (Day 1), on the subsequent day (Day 2) and on

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