results following both the induced and first subsequent oestrus are com-

bined, the difference between treatments is not significant.

(v) Timing of PMS Treatment:

Table 2 shows the significance of the time of PMS administration
in relation to progestogen treatment, Group 1 ewes were injected with
PMS 2 days prior to withdrawal of the vaginal sponge (day -2) while
group 2 were injected at the termination of progestogen medication (day
0). Though the differences between treatments are not statistically sig-
nificant, the results agree with the findings of Roberts and Edgar (1966)
in that the earlier PMS treatment did have a favourable effect on fer-
tility at the induced oestrus, However, when the lambing results are
assessed on the outcome of both induced and first subsequent oestrus,
the advantages of PMS treatment prior to withdrawal of the wvaginal
sponges have almost disappeared. Furthermore, the proportion of births
resulting in more than two lambs was higher following the day -2 PMS
treatment, and in view of the high mortality rate among triplets, quads
and quintuplets, this advantage in fecundity is likely to be smaller at

the time of weaning,

(¢) Timing Introduction of Rams:

The data in Table 3 shows the effect of omitting breeding at the
induced oestrus and delaying the introduction of rams until prior to
the second post-treatment oestrus. The results given refer to the out-
come of the induced plus the first repeat oestrus for the immediate join-
ing as compared with first repeats only in the case of the other group.
A significant difference (P<.0l) is shown in favour of joining the rams
as soon as pessaries are withdrawn, The evidence indicates that the
stimulating effect of the ram may play an important role in establishing
cyclical breeding in sheep subjected to hormonal therapy.

(d) Mating Management:

Table 4 shows the effects of management at mating time on the lamb-
ing performance following treatment for early breeding. A one ram relay
system was compared with the situation where three rams were continually

present with a flock of ewes following treatment (groups 1 & 2). The

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