Fetal survival rate after the surgical transfer of two bovine embryos.

Single embryos were bilaterally transferred on Day 7 to the tip of the uterine horn ipsilateral to the corpus luteum and to the tip of the opposite horn, to the tip and contralateral base, base and tip and base and base (20 recipients/group). Ten of the recipients in each group were treated with 1000 i.u.

Non-surgical transfer of bovine eggs: investigation of some factors affecting embryo survival.

In an investigation on the effect of position of deposition of the egg within the uterus, surgical transfer of single eggs to the tip of the horn resulted in a significantly higher pregnancy rate than transfer to the base. To determine embryo survival at differing times after transfer single eggs were transferred non-surgically to the base of the uterine horn. The highest pregnancy rate occurred in a group of heifers slaughtered 16 to 17 days after oestrus followed by heifers slaughtered on days 24 to 26.

Embryo survival in heifers after transfer of an egg to the uterine horn contralateral to the corpus luteum and the effect of treatments with progesterone or hCG on pregnancy rates.

Day 7 eggs (oestrus = Day 0) were surgically transferred singly to the uterine horn contralateral to the CL and heifers were either slaughtered on Day 24-26 (Group 1) or palpated per rectum on Day 42 (Group 2) to determine the presence of a developing conceptus and a maintained corpus luteum. There was a fall in pregnancy rate of the control heifers in Groups 1a (6/10) and 2a (2/10) (P = 0.085).

Influence of dose, repeated treatment and batch of hormone on ovarian response in heifers treated with PMSG.

The effect of two dose levels (1000 and 2000 i.u.) of three different commercially available batches of PMSG on the ovarian response (ovulations and follicles greater than 10 mn) of 42 heifers was examined in a randomized incomplete block experiment.

Ovulation rate and egg recovery in cattle treated repeatedly with pregnant mare serum gonadotrophin and prostaglandin.

Fourteen heifers were superovulated five to 10 times using pregnant mare serum gonadotrophin (PMSG) and prostaglandin in a standardised regime which resulted in a mean interval of 42.1 days (SEM +/- 0.97) between treatments.

The Sacrewell project: an on farm demonstration of the potential of egg transfer.

A surgical demonstration of the potential use of egg transfer for converting a herd of cattle from one breed to another (Jersey to Friesian) was undertaken on farm. Friesian donors were non-lactating but 50 per cent failed to respond adequately (greater than 3 ovulations) to treatment with PMSG (1500 to 3000 iu). Heifers yielded more ovulations and eggs than cows, but recovery rate was higher from cows (80 per cent cf 60 per cent).

Non-surgical recovery of bovine embryos.

The non-surgical recovery of bovine embryos was examined using a three-lumen PVC catheter passed to the tip of each uterine horn. The recovery of eggs placed in Dulbecco's phosphate buffered saline, with protein was very efficient whether in boiling tubes or funnels. In the absence of protein egg recovery was considerably lower.

Comparison of the fetal survival rate in heifers after the transfer of a embryo surgically to one uterine horn and non-surgically to the other.

When transfer of Day 7 embryos was surgically to the horn ipsilateral to the CL and non-surgically to the contralateral horn, fetal survival rate was 85 and 35% respectively. After non-surgical transfer to the ipsilateral and surgical transfer to the contralateral horn, fetal survival rate was 20 and 30% respectively.

The viability of deep-frozen cow embryos.

Day 7 cow embryos were frozen in 1.5 M-DMSO in PBS at 0.3 degrees C/min to -36 degrees C and at 0.

Non-surgical transfer of bovine embryos.

Bovine embryos obtained from donors six to nine days after oestrus were transferred non-surgically at a rate of one per recipient using a sterile insemination instrument, protected from contamination by the vagina with a plastic sheath. The percentage of recipients pregnant increased with the age of embryo transferred and for day 6 and 7 embryos was 33% compared to 58% for day 9 and 8 embryos. This difference approached statistical significance.

Fertilization and development capability of bovine follicular oocytes matured in vitro and in vivo and transferred to the oviducts of rabbits and cows.

Follicular oocytes were cultured for 24 h in vitro or obtained 6-24 h after HCG injection from cows pretreated with PMSG, and transferred to the oviducts of oestrous rabbits or heifers, inseminated with bull spermatozoa, to determine their capability for normal development. More than 65% of oocytes cultured in fetal calf serum, equilibrated with 5% CO2 + 5%O2 + 90% N2, matured to metaphase II within 24 h. Fertilization was not obtained in the rabbit oviduct but about 8% of oocytes matured in vitro underwent parthenogenetic cleavage.

The effect of oxytocin treatment on the levels of prostaglandin F in the blood of heifers.

Six heifers with normal oestrous cycles were treated i.m. with 100 i.

The influence of in-vitro culture and cooling on the survival and development of cow embryos.

Cow morulae cultured in a phosphate-buffered medium containing serum developed normally and retained viability when transferred to recipients. Unlike earlier cleavage stages, cow blastocysts tolerated cooling to 0 degrees C and retained viability after storage for 48 hr at 0 degrees C when transferred to recipients.

The storage of cow eggs at room temperature and at low temperatures.

The survival and development of cow eggs in the rabbit oviduct after storage at room temperature and after cooling and storage at 0-7-5 degrees C was examined. In PBS medium at room temperature 88% of Day-5 and 85% of Day-3 eggs showed normal development, but in TCM 199, 71% of Day-5 and only 49% of Day-3 eggs showed normal development. Duration of storage (1 1/2-2 hr or 6 1/2-7 1/2 hr) and cleavage stage before storage had no appreciable effect on development.

Deep freezing of sheep embryos.

Sheep embryos, collected 1-8 days after oestrus, were placed in Dulbecco's phosphate-buffered saline medium (PBS). After treatment, the viability of the embryos was tested by temporary transfer to ligated rabbit oviducts. In Exp.

Plasma oestrogen and progesterone in relation to superovulation and egg recovery in the cow.

Pregnant mares serum gonadotrophin (PMSG) was used in combination with prostaglandin F2alpha or its analogues to induce superovulation in 25 heifers. Total unconjugated oestrogen and progesterone were determined in peripheral plasma of these superovulated animals, and the levels compared with those found during the normal oestrous cycle. A very high level of oestrogen was found between day 3 and 6 after superovulation, and it seems likely that large unovulated follicles were responsible for the excess steroid.

Experiments on egg transfer in the cow and ewe: dependence of conception rate on the transfer procedure and stage of the oestrous cycle.

The effects on embryo survival of procedures used in transferring eggs non-surgically were investigated in three experiments in ewes and heifers. In Exp. 1, two techniques for introducing eggs into the uterus through the cervix in heifers were compared; namely (i) deposition of the eggs high into the uterine horn or (ii) into the body of the uterus.

Surgical and non-surgical egg transfer in horses.

Surgical and non-surgical methods used for the recovery and transfer of fertilized horse eggs are described. Sixteen of the twenty-three zygotes recovered surgically between Days 1 to 6 after ovulation from thirty donor mares were transferred surgically to synchronized recipients; seven pregnancies resulted. Seven of the eleven zygotes recovered non-surgically between Days 6 to 8 after ovulation from twenty-eight donor mares were transferred non-surgically to synchronized recipients; five pregnancies resulted.

Tetraparental sheep chimaeras induced by blastomere transplantation. Changes in blood type with age.

The blood groups are described of three sheep chimaeras produced by injection of blastomere cells into fertilized eggs of different parental origin. Evidence is presented that these chimaeras had a blood type which could only have been derived from both sets of parental genes. Two antigenically distinct red cell populations were identified in all three sheep and chimaerism of serum transferrin and albumin types was also present in two of them.