Ma. Akinbami et al., EMBRYONIC SURVIVAL IN THE UTERUS OF EWES INSEMINATED AT THE UTEROTUBAL JUNCTION ON DAY 32 POST-PARTUM, Theriogenology, 45(6), 1996, pp. 1129-1139
Experiments were conducted to determine 1) if pregnancy initiated on D
ay 32 post partum would be maintained until lambing, 2) if there is a
difference in the ability of the previously gravid or nongravid uterin
e horn to maintain pregnancy, and 3) if season has an effect on embryo
loss. Estrus was induced in ewes on Day 32 post partum. At estrus, ew
es were inseminated surgically at the uterotubal junction and assigned
to the following groups: 1) inseminated at estrus and laparotomized o
n Day 3 to collect embryos for determination of fertilization rate (C)
, 2) inseminated in the previously gravid uterine horn (PG), 3) insemi
nated in the previously nongravid uterine horn (NG), and 4) inseminate
d when both horns were previously gravid (BG). Ewes pregnant in the PG
, NG and BG groups were allowed to lamb. Conception rate in Group C at
embryo collection was 70%. Embryo loss, based on concentrations of pr
ogesterone at Day 18 post insemination, was 43, 19 and 18% in the BG,
NG and PG group, respectively. The high embryo loss in Group BG occurr
ed only during the breeding season. Only 24% of the ewes that had been
inseminated lambed. This was due to the prepartum loss of embryos and
fetuses (47, 48 and 33% in Group BG, NG and PG, respectively. In conc
lusion, the detrimental effects of the uterus on embryo survival was e
vident within 18 d post insemination in Group BG (breeding season), an
d embryo loss prior to lambing was high in all the treatment groups (b
oth seasons).