Vle CONG. INTERN. REPROD. ANIM. INSEM. ARTIF, PARIS, 1968, VOL. II ‘

Relation between the day of the oestrual cycle at the time
of the intravsginal application of a MAP impregnated sponge |
and synchronisation rate and conception rate in Texel sheep.

A.H. WILLEMSE

 

Clinic for Veterinary Obstretics & Gynaecology
State University, Utrecht, Netherlands.

Oestrus synchronisation in ewes by means of the vaginal
application of a sponge impregnated with a progestational
compound involves an artificial lengthening of the luteal
phase. The extent of this lengthening depends on the day
of the oestrual cycle on which the sponge is inserted and
varies from one to thirteen days, assuming that the sponge
remains intravaginally for 13 days. When the sponge is
inserted during the follicular phase there is a short
interruption between the luteal phase and the progestational
phase caused by the sponge.

The aim of this experiment was to study the influence of this
artificial lengthening of the progestational phase on
synchronisation rate and on the fertility of the synchronized
oestrus.

Material and method. Seventeen days prior to sponge insertion
a number of vasectomized and apronized rams was added to the
flock of 229 two to three years old Texel ewes. Once a day
the mated ewes were checked. On the moment of sponge insertion
(T 0) the day of the oestrual cycle of each animal was known.
The sponges used were impregnated with 60 mg MAP and were
kindly supplied by the Upjohn Co. 110 ewes did not receive
any further treatment, while 119 ewes received a subcutaneous
injection with 750 IU PMS on T 11. On T 13 the sponges were
removed. Twentyfive fertile rams were added to the flock.
Twice a day the number of mated ewes was noted down.

Results and discussion. Four ewes showed no oestrus symptoms
during the seventeen days prior to sponge insertion, so in
these animals the sponges were inserted at an unknown stage
of the cycle. Two animals lost their sponges.

Synchronisaticn. The PMS injection appears to have a

significant influence on synchronisation rate: 48 hours

after sponge removal 85% of the PMS treated ewes had been

mated against 51% of the non-PMS treated group (P 0.001).

To study the influence of the day of the cycle at the moment

of sponge insertion, the ewes were divided in three groups:

1. a group which received their sponges during the first half
of the luteal phase, i.e. between day 1 and day 7. (day O
being the first day of oestrus). In these ewes the

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