gilts. The only exception were herds 1 and 14, in which the
inseminations were carried out by a trained inseminator. Co=-
operating breeders were also asked to complete a treatment record
sheet for each gilt in the trial.

RESULTS The table shows that the number of gilts treated in any one
herd ranged from 5 to 21. The average farrowing rate to first
insemination was 53.6% with a total of 7.1 pigs born. The level of
fertility varied on different farms and the herds with the lower
farrowing rates tended to have lower average litter sizes, Few
breeding gilts were available in each herd after the groups of gilts
for treatment had been selected but limited control data were obtained
on gilts inseminated or served naturally in 10 herds during the six
months before and after this trial. From 130 normal inseminations
performed on 4 different farms the farrowing rate was 66.9% with an
average total litter size of 9.7 piglets at birth. Natural mating
data on 440 gilts from 9 farms showed a farrowing rate of 87% with an
average total litter size of 9.7 piglets at birth but these data were
in most cases based on the results of a double service, which could
increase fertility (Pitkjanen, 1955). Statistical analysis of these
limited data showed that the differences in litter size and conception
rate between the methallibure treated and natural mated group were
highly significant but between the methallibure treated and normal
ingeminated groups these were not significant.

DISCUSSION With the farm application of a technique evolved at a

research station there are invariably problems, often due to deviations
from the prescribed treatments. For example, in herd 16 data from
some 20 gilts had to be excluded as these were fed methallibure at a
level different from that prescribed. Six breeders observed that
some gilts exhibited symptoms of inappetance to a varying extent, this
did not appear to materially affect their results, but 3 gilts with
marked depression of appetite returned to oestrus 10, 11 and 15 days
after being inseminated. Six breeders noticed that the treated gilts
had been more difficult to inseminate and only shown partial signs of
oestrus. Two breeders reported that in 3 cases when attempting to
inseminate the spiral catheter did not lock in the cervix and all 3
animals returned to oestrus 20 - 21 days later. The field reports
indicated thet partial signs of oestrus at the time of insemination or
irregular returns to oestrus were more common in herds with the lower
farrowing rates, suggesting that in these herds the gilts had not
received the prescribed amount of methallibure. Also many breeders
found the incorporation of methallibure in the food a tedious and time
consuming process. The conception rate in the treated groups vwas
encouraging but the lower litter size in the treated groups, although
not significant when compared with the limited control A.I. data, was
noticeable to the herd owners. Since the reduced fertility appeared
to be associated with faults in treatment with methallibure it might be
necessary for breeders to become proficient in the use of methallibure
alone before embarking on its use in conjunction with hormones.
Further field trials are required, with particular attention being

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