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Migration of embryos in the anastomosed uterine horns of the pig.

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Migration of Embryos in the Anastomosed
Uterine Horns of the Pig'
0. C. MILLER AND P. J. DZIUK
Department of Animal Science, University of Illinois, Urbana, Illinois
ABSTRACT
One ovary was removed from 28 gilts and the uterus was transected,
closed and anastornosed in one of four patterns. In three of the patterns the uterine
horns were jointed near the uterotubal junction and in the fourth pattern the uterus
formed one continuous tube from one oviduct to the cervix. Gilts were mated, then
killed at 15 to 60 days of gestation when fetuses were located. The proportion of gilts
pregnant was lower (P < 0.05) in the two groups requiring passage of sperm through
an anastomosis than in the two groups where fertilization did not require that sperm
traverse an anastomosis. Ten gilts were pregnant when killed and embryos were
distributed in both horns in each gilt. Embryos can pass through an anastomosis and
migrate and are spaced quite evenly even after disturbance of the normal anatomical
relationships between uterine horns.
Intrauterine migration and mixing of
embryos is well known to occur in the pig
(Corner, '21; Dziuk, Polge and Rowson,
'64; Dhindsa, Dziuk and Norton, '67). The
normal pig uterus can be considered as one
unit with the body connecting the two
horns. Krehbiel ('46) surgically anastomosed the two separate uterine horns of
the rat and obtained intrauterine migration
in some types of joinings. He concluded
that in the normal duplex rat uterus, embryo migration was controlled by the individual horn whereas the anastomosed
uterus usually acted as one unit. The following experiments were performed to determine whether disturbing normal relationships between the two horns of the pig
uterus by anastomoses would affect distribution and migration of embryos.
as in type I but sperm had to traverse the
anastomosis to reach the oviduct. The two
horns formed one continuous tube from
oviduct to cervix in type 111. In type IV the
cervical end of one horn was anastomosed
to the upper end of the other horn. There
were eight gilts each of types I and I1 and
six gilts each of types I11 and IV.
After laparotomy the gilts were penned
with a fertile boar in groups of 10 or 12
and mating allowed. Gilts were killed at
times ranging from 15 to 60 days after
mating when corpora lutea were counted,
pregnancy determined and embryos or fetuses identified and located. The uteri of
nonpregnant gilts were filled with water
to check the anastomoses for patency and
leaks. Data were analyzed for statistical
significance by chi-square.
MATERIALS AND METHODS
RESULTS
The experimental animals were 28 sexuThe ovaries at autopsy had a mean of 13
ally mature gilts of Duroc, Yorkshire or corpora lutea, confirming previous observaDuroc x Yorkshire breeding. Laparotomies tions that one remaining ovary will comwere done aseptically while the animals pensate (Dhindsa et al., '67). Ten of the
were under general anesthesia (Dhindsa 28 gilts were pregnant when killed. Eight
et al., '67). One ovary was removed and of the ten had a mean of seven fetuses and
the uterus anastomosed or closed with con- the other two had elongated chorionic
tinuous sutures of black silk, size 0, in one membranes characteristic of day 15 of gesof four patterns (I, 11, I11 or IV) as shown tation making precise count of embryos
diagrammatically in figure 1. In type I the difficult. The proportion of gilts pregnant
uterine horns were joined at the ovarian in each treatment group is shown in table
end, sperm could go from cervix to oviduct
1 This investigation was supported in part by Public
Health Service Research grant HD01987 from the
without passing through an anastomosis. National
Type I1 gilts had the uterine horns joined velopment.Institute of Child Health and Human DeANAT. REC., 162: 137-138.
137
138
0. C. MILLER A N D P. J. DZIUK
TABLE 1
Pregnancy in gilts with uterine anastomoses
Type of
Number
of gilts
Number
pregnant
I
8
6
14
3
anastomosis
IV
I plus 1v
I1
I11
11 DlUS 111
5
8
1
1
21
8
6
14
1 Lower than types
I plus N (P < 0.05).
1. There were no significant differences between types I1 and I11 nor between I and
IV in the proportion pregnant. A greater
proportion of types I and IV combined,
were pregnant than types I1 and I11 combined (P < 0.05).
The distribution of fetuses is shown in
figure 1. At least one fetus was in each
uterine horn in all pregnant animals. Embryos and sperm could both pass through
anastomoses. There was no indication that
embryos had an affinity for one horn or the
other. Horns ending blindly at one end did
not preclude pregnancy.
\Severed
And
Closed
TYPE
I
TYPE Ip
TYPE I
TYPE Ip:
TYPE
TYPE
IL:
IE
TYPE 3 l I
TYPE Ip.
Fig. 1 Location of fetuses following transection and anastomosis of uteri of gilts.
The uteri of some of the nonpregnant
gdts contained accumulated fluid and pus
which probably prevented pregnancy.
DISCUSSION
Disruption of the normal anatomical relationships between the two uterine horns
and establishment of abnormal ones did
not prevent pregnancy. Blind uterine horns
per se were compatible with pregnancy
which is Merent from naturally occuring
blind horns that can not be pregnant and
may exert an indirect effect preventing
pregnancy from being maintained in the
normal horn (Nalbandov, '52).
Sperm could pass a n anastomosis but
perhaps the difference between groups I
and N combined as compared to groups
I1 and 111 combined in conception rate
was due to more frequent failure of
sperm transport across anastomoses. Embryos readily migrated across anastomoses
and there was no indication that conception rate was affected by the frequency of
failure of embryo migration. Embryos were
quite evenly spaced regardless of which
end of the horn the embryo entered, confirming the previous observation (Dziuk
et al., '64) that uterine migration is not
unidirectional.
Distribution of embryos seemed normal
even though the embryos entered midway
between the two ends of the uterus (types
I, I1 and IV) rather than at both ends of
the uterus as would occur normally. This
observation suggests that spacing and migration are random processes and that the
pig uterus can be regarded as one continuous unit in spite of abnormal anatomical
relationships such as were created in this
study.
Work reported by Dhindsa and Dziuk
('68) has shown that when one half the
uterus is unoccupied before day 14 pregnancy does not continue. Whether failure
of maintenance of a unilateral pregnancy
was the reason 18 gilts were nonpregnant
in this study is not known. All pregnant
gdts in this study had at least one fetus in
each uterine horn.
LITERATURE CITED
Comer, G. W. 1921 Internal migration of the
ovum. Johns Hopkins Hospital Bull. NO. 32:
78-83.
Dhindsa, D. S., and P. J. Dziuk 1968 Influence
of varying the proportion of uterus occupied by
embryos on maintenance of pregnancy in the
pig. J. Animal Sci., 27: 668-672.
Dhindsa, D. S., P. J. Dziuk and H. W. Norton
1967 Time of transuterine migration and distribution of embryos in the pig. Anat. Rec.,
159: 325-330.
Dziuk, P. J., C. Polge and L. E. A. Rowson 1964
Intrauterine migration and mixing of embryos
in swine following egg transfer. J. Animal Sci.,
23: 3 7 4 2 .
Krehbiel, R. H. 1946 Distribution of ova in the
combined uteri of unilaterally ovariectomized
rats. Anat. Rec., 96: 323-340.
Nalbandov, A. V. 1952 Anatomic and endocrine causes of sterility of female swine. Fert.
Steril., 3: 100-120.
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