2, Lactating sows with litters (154 animals), Large White,
Essex and Welsh cross-bred stock, individually fed, were

allocated to one of three treatments,
(a) Methallibure (Group LM). Thirty four sows received
in their morning feed a premix containing 150 mgm of
methallibure, for 7 successive days starting 4-7 days
before weaning,
(b) Methallibure + PMS (Group LMP)., Thirty eight sows
treated as in 2(a) received additionally 1000 i,u, PMS
subcutaneously on the last day of treatment (day 7Ye
(c) Methallibure + PMS + HCG (Group IMPH). Nineteen
sows treated as in 2(b) were given 500 i, u, HCG intra-
muscularly, 72 hours later (day 10 of the treatment),
(d) Untreated (Group U). Sixty three sows were weaned
conventionally to obtain additional control data on
breeding performance,
All animals were artificially inseminated, Those receiving
HCG were inseminated 24 hours after injection of this hor-
mone, All other groups were inseminated 24 hours after the
onset of a 'standing reflex!, The dates of onset of the
reflex, insemination, return to service or farrowing, and
litter-size 24 hours post-partum were recorded,

RESULTS, Table I shows, for each group, the interval bc.ween
the last day of methallibure treatment and the onset of oes-
trus, and the fertility and fecundity of animals artificially
inseminated at the controlled time,

In the gilts and dry sows, 71% of Group MPH first showed
a standing reflex on the 6th day after treatment; without
administered gonadotrophins Group M)the maximum synchronised
on one day was 35% on the 6th day, Of the lactating sows,
6% in Groups LMP and LMPH showed oestrus on the 4th day
after stopping methallibure, whereas in Groups LM and U the
corresponding results were 37% on the 5th day after methal-
libure or weaning., These differences between Groups M and
MPH, and between Groups LM, U and LMP, LMPH are significant
(P <0,001), The differences in farrowing rates and mean
1itter sizes between the gilt Groups, or the lactating sow
Groups are not significant (P ¢0,005), Thus, neither the
use of gonadotrophins as described, nor fixed-day insemina=-
tion had an adverse effect on the reproductive capacity of
the animals,

DISCUSSION. The experimental basis for the technique used
in gilts and dry sows in these trials has been discussed (3).
The results described confirm the applicability of the tech-
nique to field conditions,

Equivalent experimental information is not available for
the lactating sow; the treatment applied was empirical and

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