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

Ovulation in She-Mules: A report of two cases.

W. BIELANSKI and Z. ZAPLETAL
Coll. Agr., Dept. of Reprod., Krakow, Poland

Our own studies on the function of the ovaries and sexual behaviour
in she-mules.istarted in 1951 (1, 2). The subjects studied were 10
animals born in 1946 and 1947. This group was investigated over three
periods of time, the method of examination and the system of recording
being constantly the same. During most of the periods of heat the she-
mules were naturally served by stallions and sometimes by jack.

In the first period, extending from January 1, 1951 to July 31, 1952
(10 animals studied), as well as in the second period from January 1,
1958 to September 30, 1960 (6 animals studied), stress was puf on clini-
cal changes in reproductive organs during oestrus. The third period
(October 1, 1960 to December 31, 1962) consisted of long-day treat-
mentwith two trials in autumn 1960 and 1961 with prolonged artificial
daily light (3). This experiment was carried out on she-mules (4).
About two years later (1964-65) 3 animals were slaughtered just 2 days
after ovulation had taken place.

In the cases presented below, it was possible to find egg cells in 2
mules, but none in the third mule.

Case N° 1 (MUR/IV) was a good strong draft mule, born in 1946,
black, height in withers in 1951, 148 cm; in 1961, 151 cm.; weight
in 1951, 477 kg; in 1961, 472 kg. During the first years she showed
nearly regular 22-day cycles, with longer intervals in the summer. The
follicles developed and ovulation took place in 502 of the examined
heats.

This situation gradually changed in the second period when only
17 oestruses were examined, 5 of which were with ovulation. Prior
to the long-day treatment she showed no sign of heat for 224 days.
This state persisted on into the first 165 days of the experiment.

The oestrus which followed a 380-day-long continuous anoestrus,
initiated a 16-day cycle. Ovulation took place in both heats. The
treatment with prolonged light, repeated the next autumn, stimulated
heat after 56 days and was followed by two cycles of 37 and 21
days long.

Atresia occurred once, and ovulation twice.

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