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Biomedical subjects

L E Rowson

Publications and source records attributed to L E Rowson.

At least 19 recordsLinked to original sources
PubMed1980

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. The lowest pregnancy rate occurred in a group where pregnancy diagnosis was on day 42 by rectal palpation. The pregnancy rates of the highest and the lowest groups were significantly different. The pregnancy rate was increased in a group of heifers which were treated with human chorionic gonadotrophin from day 13 to 24 and palpated per rectum on day 42 to determine pregnancy. The presence or absence of penicillin and streptomycin in the medium and of passing differing volumes into the uterus after non-surgical transfer of single eggs using a glass pipette had no effect on pregnancy rate and there was no significant difference in pregnancy rate and there was no significant difference in pregnancy rate between the groups using different volumes of transfer media. The position of the egg within the uterine lumen after transfer contributes to the reduced pregnancy rate achieved after nonsurgical transfer when compared with the surgical method. The greatest proportion of embryonic death after non-surgical transfer occurs after day 17 and there is some evidence that human chorionic gonadotrophin treatment can improve embryo survival. The use of comparatively small volumes of medium to eject the egg into the uterus may be preferable to achieve maximum pregnancy rates.

Animals↗
PubMed1980

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. hCG daily from Days 13 to 35 after oestrus. At 42 days, pregnancy rate (N.S.) and fetal survival rate (P < 0.05) were greater when an embryo had been transferred to the tip rather than to the base of the ipsilateral horn, but the twin pregnancy rate was not improved. Treatment with hCG had no effect on these rates but the corpora lutea of treated animals were heavier (P < 0.02). Unilateral transfers of 2 embryos were made both to the tip of the ipsilateral uterine horn or one to the tip and one to the base (20 recipients/group). The pregnancy rate, fetal survival and twin pregnancy rate in each group were the same, but in the latter one of the embryos had migrated to the other horn in 5/9 animals with twin fetuses. The location of fetuses did not influence their rate of development as determined by fetal measurements. It is concluded that the tip of the ipsilateral uterine horn is the optimal site for fetal survival and that to ensure a high twin fetal survival one embryo must be in this site.

Animals↗
PubMed1979

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. There was a significant (P less than 0.02) fall in the mean ovulation rate at the second treatment when compared with the first but no significant difference between mean ovulation rate at the second and subsequent treatments. No significant difference between treatments in mean egg recovery rate or in the percentage of normal eggs recovered was demonstrated. Four heifers treated 10 times continued to respond with multiple ovulations on most occasions. At the end of the experiment 13 of the 14 heifers were inseminated and 12 conceived, requiring a mean of 1.67 services per pregnancy.

Animals↗
PubMed1979

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. Each animal was subjected to two consecutive but different treatments. A significant effect of dose was observed and there were fewer ovulations, but no reduction in the number of follicles, after the second PMSG treatment. There was no evidence that the ovarian response was affected by the PMSG batch used.

Animals↗
PubMed1979

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). Pregnancy rate was unaffected by progesterone treatments from Day 13 to the day before slaughter in Group 1b (8/10), or to Day 23 in Group 2b (2/10). Two of the conceptuses recovered in Group 1b were developing in the presence of regressed corpora lutea. There was, however, an increase in pregnancy rate in Group 2d (6/10) compared with Group 2a (2/10) when heifers were treated with hCG from Days 13 to 35 (P = 0.085). The results indicated that embryonic death is occurring after Day 24 and suggest that a change in the nature of the embryonic signal may be occurring at this time.

Animals↗
PubMed1978

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). Fertilised eggs were recovered from old (13 years) cows, some of which had ceased to breed normally. Pregnancy rate after transfer of these eggs was normal. Purebred Friesian calves out of Jersey recipients were Friesian weight (male, 44.8 kg; female, 37.4 kg) and contrary to experience with crossbreds caused severe dystocia problems. Severity of dystocia was related to birth weight and sex of calf.

Animals↗
PubMed1978

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. In a group of 42 heifers, superovulated on two occasions, embryos were recovered non-surgically on day 7 after the first superovulation (Day 0 = oestrus) and surgically after the second. Laparotomy was performed on each occasion and the number of corpora lutea counted. Ovulation rate was lower at the second superovulation and a correspondingly greater recovery of embryos was obtained surgically (P less than 0.02). Non-surgical recovery rates from anaesthetised cows and heifers and from standing sedated heifers were found to be similar. The distance of the catheter tip from the utero-tubal junction (UTJ) significantly affected recovery rate (P less than 0.001). Best results were obtained when the catheter tip was within 5 cm of the UTJ. Most embryos were recovered in the first 100 ml of recovered medium. The method compares favourably with other reported methods.

Anesthesia↗
PubMed1978

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. Bacterial contamination of the instrument on withdrawal after transfer was not related to the success or failure of pregnancy. Maintenance of pregnancy to term and calving appeared to be normal. It is suggested that this method could be used for the routine transfer of eight and nine day embryos.

Animals↗
PubMed1978

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 0.1 degrees C/min between -36 and -60 degrees C before being plunged directly into liquid nitrogen. They were subsequently thawed (rapidly to -50 degrees C, at 4 degrees C/min from -50 to -10 degrees C, and rapidly again) to room temperature. Embryonic viability was tested by four different transfer techniques. Maximum pregnancy rate (8/12) was obtained with surgical transfer immediately after thawing and dilution of DMSO.

Animals↗
PubMed1977

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.u. oxytocin on 3 consecutive days, commencing on Days 1-6 after oestrus, and the levels of prostaglandin (PG) F in posterior vena cava plasma were compared with pretreatment values. An increase of PGF in response to oxytocin was significantly influenced by day, with the greatest response occurring on Day 3 after oestrus. In an ovariectomized heifer the levels of PGF in posterior vena cava plasma increased 24 h after priming with oestradiol, but no further increase occurred after oxytocin injection. Peak levels of PGF were higher in the plasma of the posterior vena cava than in the jugular vein. Various storage conditions of the blood before centrifugation and freezing (--20 degrees C) produced significant differences in plasma levels of endogenous PGF, but storage experiments with added labelled PGF-2alpha indicated that the PG was stable in plasma and whole blood.

Animals↗
PubMed1977

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. Sperm penetration was observed in 49% of oocytes in the cow oviduct, but although 47% had undergone development 96 h after transfer few developed to morulae and blastocysts, confirming the impaired ability of oocytes matured in vitro, as assessed by nuclear change, to develop normally. Oocytes obtained from heifers slaughtered 24 h after HCG developed normally when transferred to the oviduct of inseminated heifers. Of the oocytes with an activated cumulus, 39% developed to blastocysts and of 16 blastocysts transferred to suitable recipients, 13 developed to normal fetuses at 13-17 weeks gestation.

Animals↗
PubMed1976

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. 1, Days 5-8 embryos survived for at least 15 min at 0 degrees C in the presence of 1-5 M-DMSO. In Exp. 2, 12/14 Days 5-8 embryos survived after being frozen in 1-5 M-DMSO at 0-3 degrees C/min to temperatures ranging between-15 degrees and -60 degrees C and then thawed at 12 degrees C/min. In Exp. 3, Days 5-8 embryos were frozen in 1-5 M-DMSO at 0-3 degrees C/min to below-65 degrees C before being transferred to liquid nitrogen (-196 degrees C), and stored for 12 hr to 1 month. The embryos were thawed at 3 degrees C/min, 12 degrees C/MIN or 360 degrees C/min and, after transfer to rabbit oviducts, 0/4, 10/36 and 1/4, respectively, developed normally. The 11 embryos which were considered normal when recovered from the rabbit oviducts plus 1 slightly retarded embryo were transferred to 7 recipient ewes. Four ewes subsequently lambed, producing 5 lambs. In addition, 8 embryos were transferred to 4 ewes directly after thawing. Three of these ewes subsequently lambed, producing 3 lambs.

Animals↗
PubMed1976

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. Some retardation of development occurred in Day-3 eggs after 96 hr in the rabbit oviduct when compared to Day-5 eggs after 48 hr. Cooling of Day-5 and Day-6 eggs to 0-7-5 degrees C resulted in degeneration of a large proportion of eggs. Of the factors examined, storage medium (PBS or PBS+20%FCS), storage time (2 min, 24 hr) and storage temperature (0, 2, 5 or 7-5 degrees C) had little effect, but slower cooling rates tended to improve survival of eggs although the differences were not significant. More morulae (greater than 32 cells) than 8-to 24-celled eggs developed normally.

Animals↗
PubMed1975

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. Similarly, progesterone levels were raised in the superovulated animal presumably due to production by the numerous corpora lutea. In two heifers, in which overstimulation of follicular development had occurred, there were no ovulations in one of the animals while in the other animal there were 16 ovulations but early regression of corpora lutea was indicated. It is concluded that the poor recovery of eggs on day 6 after superovulation could have been due to deleterious effects of high levels of oestrogen on either the motility of the genital tract causing the premature transport of eggs, or the properties of the zona pellucida.

Animals↗