Since earlier investigations indicate that mares
with migrating amniotic sacs are more liable to develop
E.e.d. (Amoroso 1953), the material was examined with
this possibility in view.

Table 2.
The possible influence on early embryonic death of site
of pregnancy compared with site of ovulation.

e et e
Number E.e.d.

Pregnant on the ovulation side 25 2
Pregnant on the opposite side 14 5
Established cases of migrating
amniotic sacs 5 1
—_———
The migration observed was usually one from left to
right but migrations from right to left were also dis-
covered. In one case, a migration from left to right,
followed by a migration back to left, was noted. The
findings are in agreement with those made in earlier in-
vestigations (Day 1940, Amoroso, Hancock & Rowlands 1948).

Discussion. Various factors may cause E.e.d. in the mare:
15 defect ova and spermatozoaj 2) unfavourable conditions

in the uterus, esp. in connection with service during
foaling heat and in "windsucking" cases; 3) services in
the early seasong 4) the regular cycling of the mare dur-
ing the first 5 months of pregnancy combined with the
short life span of the corpus luteum of pPregnancy; 5)
wrong time of service, i.e. too late; 6) deficiencies

of minerals, minor elements (f. inst. Iodine), and vita-
mins (A,D,E); 7) parasitary infestations; 8) excessive
work and training.

In this material, foaling-heat-service was used to
a high degree and might, of course, be one of the major
causes of the comparatively many cases of E.e.d.
According to Trum (1950), the conception rate is only
43% at this time. The material was also thoroughly
checked for "windsucking", although this disturbance is
not so common in the Finnish draught horse as in the
Thoroughbred and the Standard bred.

The seemingly higher incidence of E.e.d. from ser-
vices early in the season may indicate that daylight
and, perhaps, temperature also affect embryo survival.

In the authors’ opinion, the more or less regular
cycling of the mare during early pregnancy might well
be one of the most important causes of E.e.d. In the
present material, most of the established cases of E.e.