Untersuchungen zur Eignung von Empfängertieren im Rahmen des Embryotransfers

The aim of this study was to test the possibilities of
ultrasonography in the examination of recipient animals during
commercial embryo transfer in cattle. Altogether 257 animals have
been synchronised by a single or a double injection of
Prostaglandine F2alpha, 33 potential recipients showed spontaneous
heat. On 200 of the animals actually being used as embryo
recipients, a rectal palpation as well as an ultrasonographic
examination of the ovaries was performed on the day of the transfer
and on day 21 of the cycle. The recipients were examined again for
pregnancy by ultrasound on day 35 (28 days after the transfer) and
by rectal palpation on day 49. A blood sample (plasma) was taken on
day 0 (oestrus), 7 (transfer) and 21, in order to mesure the
progesterone concentration (P4). An enzyme-based immunological
assay was used to evaluate the plasma samples for P4 concentration.
The ultrasonographically defined area of the largest cross-section
of the corpus luteum was significantly correlated (r = 0,22 ; p
< 0,001) with the corpus luteum size evaluated by rectal
palpation. There was no relation between the scoring of the corpora
lutea performed by palpation and the average P4- concentration (r =
0,13 ; p > 0,05), whereas on day 7 the luteal tissue area
measured by ultrasonography was significantly correlated with the
P4 values (r = 0,40 ; p < 0,001). In 55 % of the recipients, a
sonographically detectable cavity within the corpus luteum was
found on the day of transfer. Corpora lutea with a cavity were
bigger than those without ( 3,8 cm2 vs. 3 cm2; p < 0,001),
however the luteal tissue area of corpora lutea with or without
cavity was not significantly different (p > 0,05). On day 21,
136 animals out of 200 (69 %) having received an embryo, showed no
signs of oestrus. On day 35 and 49 pregnancy was diagnosed in 50 %
and 47 % respectively. The highest pregnancy rate (60 %) was
obtained in the group of recipients, with the best score evaluated
by rectal palpation. However, there was no significant difference
in pregnancy rate between animals with different corpora lutea
scores. The pregnancy rate on day 35 was 56 % in animals with a
compact corpus luteum and 45 % when a cavity was present in the
corpus luteum. The mean P4 value on day 7 of animals later
diagnosed as pregnant or not was not significantly different (2,1
ng/ml vs. 2,2 ng/ml). 54 animals showing clear signs of heat 21
days after the last oestrus, had a P4 value of < 1 ng/ml. The
area of compact corpora lutea of recipients having a P4 content of
< 1ng/ml on day 21 was significantly smaller than that of
animals having a P4 value > 1 ng/ml (1,5 cm2 vs. 3,5 cm2 ; p
< 0,001). The average area of compact corpora lutea on day 21
(3,6 cm2 vs. 2,3 cm2; p < 0,05) was significantly bigger in
pregnant than in non-pregnant animals. The percentage of presumably
(day 21), respectively definitely pregnant animals (day 35 and 49),
was 86 %, 65 % and 63 % respectively with fresh embryos of good
quality, 57 %, 38 % and 34 % respectively with fresh embryos of
poor quality and 66 %, 45 % and 44 % respectively with
frozen/thawed embryos. The use of ultrasonography in the evaluation
of the corpus luteum quality of recipients prior to the transfer is
of limited value in commercial embryo transfer. A good oestrus
detection on day 21 is useful to get the animal pregnant as early
as possible; the determination of the plasma progesterone content
on this day could contribute to obtain this goal. The
ultrasonographic examination of the recipients for early pregnancy
diagnosis (day 35 and earlier) can help, to re-use the non-pregnant
animals again as soon as possible.