Vie CONG. INTERN. REPROD. ANIM. INSEM. ARTIF., PARIS, 1968, VOL. Il

ceived.One could attribute this result to the lack of
proper timing of insemination in relation to the time
of ovulation.However,the successive inseminations,which
were repeated every I2 hours during the whole period of
the probable time of ovulation,eliminate this possibili=-
ty.Moreover,the abnormal duration of induced oestrus
was not the only phenomenon produced by the high dose
of PMS.The milk production also of the individuals in
groups B & C,which exhibited prolonged oestrus and did
not conceive,dropped sharply in contrast with the ewes
of the group A and these of groups B & C which conceiv-
ed,the milk production of which extended over a period
of two more months,

Another indication of the unfavourable influence of
the high PMS,dose,is the low conception rate (42,8%) in
group C by natural mating during the returns(Fig.I/B).
The above agree with Lamond(3),who suggested that the
inceased PMS dose may cause hormonal imbalance leading
not only to prolonged oestrus but also to genital tract
abnormalities that may reduce fertility.

As for the lambing percentage the differences between
the experimental groups were not significant(TableZ).
Nevertheless,if it is taken into consideration that
group C consisted of ewes which had single lambs in the
previous year,it could be said that a certain positive
influence of the increased PMS dose on lambing percent-
age was revealed,

No significant differences were observed in the length
of the gestation period and the sex-ratio between the
experimental groups(Table 4),The mean gestation period
in the experimental groups was 2,5 days shorter than
that of control M,Although the difference is highly si-
gnificant(P<0,0I),this might be due to the effect of a-
nother factor not directly related to the hormonal
treatment,

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.Lamond,D.R.I963.J.Repr.Fertil.?,171-183.

.Lamond,D.R.I96h.J.Repr.Fertil.S,IOI-IIh.

,Robinson,T.J,I195I.J.,Agr,.Sci.,4I,G.

.Robinson,T.J.I954a,Austr,.J,Agr,Research5,

.Robinson,T.J,I1959.Cole &nd P.T.Cupps,Academic Press
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