comprised 25 ml. yolk free CO, gassed IVT diluent containing 2000
million spermatozoa plus a further 25 ml. of the same diluent (not
gassed with CO,) added just before insemination. Semen was kept at
15 - 20°C during storage and transit to farms, All inseminations were
carried out with the rubber spiral catheter (Melrose & O'Hagan, 1961).

RESULTS Pre-paid postcards, requesting information on results, were
sent to users at the expected time of farrowing. The table shows that
the 'semen delivery'! service usage increased from 139 doses for the 4
months June - September 1965 to 2044 doses for the 3 months October -
December 1967 whereas the localised inseminator service increased from
179 to only 472 first inseminations over the same period. Use of the
'semen delivery' service varied from 1 to 214, (average - 9.2), doses
per breeder. The overall average farrowing rate of 50.5% with semen
dispatched direct to breeders was 19.4% lower than the 69.9% from
inseminations carried out by specialist pig inseminators. The aversge
total litter sizes at birth were 9.6 and 10.3 for the 'semen delivery!
and 'inseminator' services respectively. Farrowing rates reported by
users of the 'semen delivery' service ranged from 20 to 90%. The
centre veterinary officers are investigating this wide variation by
visiting all herds that have used more than 10 semen doses and where
the average farrowing is above 70% or below 40%. Investigations in
17 out of 61 herds with poor results revealed that 8 breeders were
possibly inseminating too early in oestrus, 2 breeders had experienced
difficulty in detecting oestrus in gilts and 7 breeders had found
difficulty in 'locking' the rubber spiral catheter in the cervix. In
spite of the written instructions, several breeders had not been
sterilising and drying their insemination equipment properly. In some
20 - 25% of the requests for the inseminator service the pig was not at
the correct stage for insemination and left uninseminated by the
inseminator,.

DISCUSSION The widespread demand for a 'semen delivery' service
appears to have been due to the increased awareness by breeders of the
potential benefits from the use of top performance tested boars. This
service was also used to introduce new blood lines into herds kept
strictly 'closed' for health control purposes and at the end of 1967
foot and mouth disease livestock movement restrictions increased the
usage of the 'semen delivery' service. The 'inseminator service' data
refer only to first inseminations whereas the data for the 'semen
delivery' service refer to semen used for first and repeat inseminatias
and the rejection by inseminators of pigs not considered to be at the
correct stage for insemination undoubtedly increased the 'inseminator!
service results. At other centres in Great Britain using the same
operators for pigs and cattle the farrowing rates over the same period
ranged from 40 to 55% which is no better than the farrowing rates
obtained with the 'semen delivery' service. The average farrowing rate
of 50% cannot be regarded as satisfactory but certain breeders obtained
farrowing rates comparable to those achieved by specialist inseminators
and to improve results it would appear that the field advisory staff
should concentrate on breeders of average ability. Breeders of poor

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