|Abstract or Summary
- The first study utilized ova transfer in sheep and involved
hormonal treatments for synchronization of estrus and superovulation
in an investigation of crossbred maternal influences on inbred and
Synchronization of estrus in ewes was achieved effectively
with either oral progestogen, 6 α-methyl-17α-hydroxy-progesterone
acetate (60 mg./ewe/day), or intramuscular injections of progesterone
(10 mg./ewe/day), Satisfactory superovulation was not obtained with
pregnant mare serum preparations and alterations in oviduct morphology
were noted following oral progestogen therapy. After progesterone
injections, superovulation with a mean of 13.4 ovulations
per ewe was obtained using pituitary extracts. Successful treatments
began day after final progesterone injection with primary injection of
25 mg. followed in two days with 15 mg. of pituitary extract. An intravenous injection of 25 mg. pituitary leutinizing hormone followed
at onset of estrus.
Twelve Suffolk ewes of three inbred lines were bred to produce
fertilized ova from each of three lines and from each possible linecross.
Surgical transfers of ova from Suffolk donors were made to
nine recipients which were similar in size and consisted genetically
of Columbia, Dorset and Cheviot crosses.
Based on corpora lutea numbers, in vivo ova recovery rates
increased from 39 percent for the first year to 53 percent for the
second year. Cleavage rates were 54 and 52 percent for the two
The inbred line II lamb which developed in a crossbred maternal
environment weighed 12.3 percent more at birth than its non-transfer
line II counterpart. The transferred linecross III x II lamb
weighed 30.6 percent more at birth than its non-transfer counterpart.
The linecross took most advantage of prenatal nutrition. Adjusted
120-day weights, condition and conformation scores were similar for
transfer and non-transfer lambs at weaning. Under similar postnatal
environment, genotype for size is expressed in lambs at weaning.
In the second study effects of in vitro x-irradiation of fertilized
mammalian ova on their subsequent in vivo development were investigated
by means of rabbit ova transfer. Non-irradiated and irradiated two-cell ova were transferred to non-irradiated and irradiated uteri
of recipients to discriminate between embryonic and uterine injury.
Irradiation was applied to two-cell ova in vitro at levels of 0, 15.4,
61.2, 91.8, and 122.5 rads using a 100 kVp x-ray machine (1 ma.,
HVL 1 mm. Al., distance 37.4 cm., dose 14.5 r./min.), Ova were
transferred into oviducts of prepared recipients.
Uteri of recipients were exposed to the same radiation levels
as the ova and in addition to 250.2, 265.3, and 530.5 rads.
Combination of ova/uterus irradiation showed additive effects
of x-ray damage. One step increases of either ova or uterus above
61.2/250.3 rads caused 100 percent embryo mortality
Two-cell ova which were given 122.5 rads of irradiation failed
to develop into fetuses and uteri which were given 530.5 rads failed
to contain implantations. Irradiation with 91.8 rads killed all but the
most hardy ova and produced an all or none effect, while 61.2 rads
caused abnormal, dead, and resorbed fetuses as well as living offspring.
Two such newborn developed latent sequelae in the form of
spreading limbs. Deformities became obvious at one month and progressed
until death at four months.
Histological examinations of eight-day embryos which received
61.2 rads or no irradiation as two-cell ova revealed delayed development
in irradiated embryos. Mean
increase in weight for the first 50 days of surviving off-spring from irradiated ova was 6 gms./day more than that of controls.