She-Mule MUR/IV

Mt number of

Observatio of oestruses
period months ; , number of
ovulation | atresia follicles

(false atresia)

Control of ovaries

exam-
ined

total

On September 7, 1964 the mule showed heat and on the fourth day
a follicle in the right ovary grew to 6-7 cm in diameter. The she-mule
was served by a stallion. The next day, post-ovulatory changes in the
ovary were observed.

Two days later (September 14, 1964) the mule was slaughtered,
and the sectioned tubes were flushed. From the right tube (1/3 uterine
part) one egg cell was flushed (Photo N° 1), No spermatozoa were
observed in the fluid or in the zona pellucida. The egg cells were
136 x 122p in diameter with the zona about 11p  thick. The structure
looked delicate,but similar to that of the normal mammal egg.

Case N° 2 (MUL/1) was also a draft mule, but of a light type, born
in 1946, black-bay, height in withers in 1951, 145 cm; in 1961, 146 cm;
weight in 1951, 425 kg; in 1961, 387 kg. In the beginning she showed
pretty regular 20-day cycles. In 21 examined oestruses ovulation took
place in 60%. In the second period, the length of the cycles was found
to be irregular (14-43 days), and passed into periods of long anoestrus.
Complete five-year observations gave only 6 examined oestruses, 4 of
which ended with ovulation and 2 with atresia. Before the experiment
with prolonged daily light no oestrus was recorded during a period of
about 3 years (1035 days of anoestrus). 22 days from the start of lighting
she came into heat, but the follicle did not rupture (atresia).

Next, after 82 days new heat and ovulation were observed. In the

second long-day treatment the next autumn, she showed heat on the
69th day from the start of the experiment (after 287 days of anoestrus).

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