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Biomedical subjects

J M Sreenan

Publications and source records attributed to J M Sreenan.

54 records · Page 3Linked to original sources
PubMed1983

Early embryonic mortality in the cow: its relationship with progesterone concentration.

For the cow, fertilisation rates are generally reported to be close to 90 per cent while average calving rates fall within the range of 50 to 60 per cent. Thus, embryonic and fetal deaths account for about 75 per cent of all reproductive wastage, following a single breeding. Early embryonic death (within 20 days of fertilisation) would seem to account for about 75 to 80 per cent of all embryonic and fetal deaths and results in a substantial loss in production. The literature relating to some possible genetic and environmental causes of embryo death is briefly reviewed. The relationship between progesterone level and the initiation and maintenance of pregnancy is discussed and some data are presented.

Animals↗
PubMed1983

Embryo transfer procedure and its use as a research technique.

The technique of superovulation and embryo transfer not only has the potential to increase the reproductive rate of the female but because the number, genotype, age of embryo, site of transfer and other factors can be controlled, also has the potential in a broad research context. The current efficiency of the total procedure involved, including superovulation, embryo recovery, embryo storage and embryo transfer is reviewed. Some of the main experimental uses that embryo transfer has already or may, in the future, be put to, are also reviewed.

Animals↗
PubMed1983

Fertilisation and embryonic survival rates in dairy cows culled as repeat breeders.

Seventy-three Friesian dairy cows culled as repeat breeders were slaughtered three to six, 16 to 19 or 40 to 49 days after insemination to establish fertilisation and embryo survival rates. Fertilisation rate following a single insemination was 72 per cent. The estimated embryo survival rates for days 16 to ¿19 and 40 to 49 were 67 per cent and 76 per cent, respectively. The previous breeding history of the cows showed that only eight (11 per cent) had consistently regular returns (18 to 24 days) to service. Fifty-three (75 per cent) had a combination of both long and short returns to service. Before service on experiment, 64 (89 per cent) cows had regular cycles and the six cows which repeated from the 40 to 49 days group, five (83 per cent) had regular return intervals. It is suggested that errors in oestrus detection contribute substantially to the problem of repeated returns to service of dairy cows in Ireland.

Animal Husbandry↗
PubMed1982

Induction of parturition in cows using betamethasone.

To avoid dystocia and calf mortality two groups of cows were induced to calve six or seven days prematurely. Group I consisted of none Hereford cross Friesian two-and-a-half-year-old recipient cows carrying Continental beef breed fetuses. Group 2 consisted of 10 four-year-old Continental beef breed cows carrying pure or crossbred fetuses of the same breeds. On day 280 of gestation a long-acting betamethasone formulation was injected into all 19 animals, followed five or six days later with an injection of short-acting betamethasone (15 animals) or prostaglandin F2alpha (one animal). Three cows calved before their second injection. Fourteen of the 15 animals given the short-acting betamethasone calved 26 to 70 hours later; the remaining animal was given prostaglandin at 72 hours and calved 36 hours later. The cow that received prostaglandin F2alpha instead of short-acting betamethasone calved after 11 hours. None of the calves in group I was born dead but three died within 36 hours. One calf was born dead in group 2. Cervical dilatation and slackening of pelvic ligaments were satisfactory in all animals. Although calf birthweights were between 39 and 60.5 kg, only two instances of dystocia were encountered. Thirteen of the 19 cows voided their fetal membranes within 12 hours of calving. Only two retained them for more than four days. All cows except two in group I showed good udder development and had a plentiful supply of colostrum at calving.

Animals↗
PubMed1981

Induction of twin-calving by non-surgical embryo transfer: a field trial.

Non-surgical embryo transfers were carried out on nine farms to 84 previously inseminated recipient cows. Insemination and transfers were at a fixed time after synchronisation. Forty-nine (58 pr cent) of the 84 cows calved to the fixed insemination and transfer, producing a total of 69 calves or 1.4 calves per cow calving. The twinning rate was 41 per cent in cows calving. Transferred embryo survival was high (59 per cent) in pregnant cows. Data on calf and calving performance are given.

Animals↗
PubMed1980

Fertilization and embryonic mortality rates in beef heifers after artificial insemination.

A total of 256 beef heifers, in 2 experiments, was used to establish fertilization rate and subsequent embryo survival rates. Fertilization rate following a single artificial insemination was 90%. Pooled estimates of embryo survival showed high survival rates up to Day 8 (93%) but markedly reduced (P < 0.001) survival at Days 12 (56%), 16 (66%) and 42 (58%). It is suggested that most embryonic mortality occurs between Days 8 and 16.

Animals↗
PubMed1979

Comparison of the embryo survival rate in heifers following artificial insemination, non-surgical blastocyst transfer or both.

In Exp. 1, embryo survival rates of 45 and 47% were recorded after artificial insemination and ipsilateral transfer respectively. In Exp. 2, pregnancy rates of 62 and 60% were recorded after artificial insemination and contralateral transfer to inseminated recipients respectively. In this experiment the contralateral transferred embryo survival rate was 44%. Transferred embryo survival was lower overall when donors and recipients were out of phase by 1 day than when exactly synchronous.

Animals↗
PubMed1977

The effects of progesterone and oestrogen treatment in heifers on oestrous cycle control and plasma progesterone levels.

Data are presented on the effects of a short-term progesterone treatment for oestrous cycle control in cattle. Progesterone was administered by intravaginal sponge pessaries inserted for a 10-day period. Progesterone pessaries alone did not affect oestrous cycle length or corpus luteum function at either early (day 2) or midluteal (day 12) cycle stages. However, when progesterone (250 mg) and oestradiol benzoate (7-5 mg) were given intramuscularly on the day of pessary insertion corpus luteum development was inhibited in animals treated at day 2 and was regressed in animals at day 12. This combined oestrogen-progesterone treatment efficiently controlled oestrous cycle length.

Animals↗
PubMed1975

The application of long- and short-term progestagen treatments for oestrous cycle control in heifers.

Progestagen-impregnated pessaries were inserted into 205 heifers on eight farms. Treatments were either pessaries only for 20 days or pessaries for 10 days combined with an intramuscular injection of 250 mg progesterone+7-5 mg oestradiol benzoate on the day of insertion. Pessary retention was low (86.7%) over the 20-day period, but high (93-6%) during the 10-day period. Calving rates of heifers inseminated in oestrus following the 20-day treatment were low, while those of heifers inseminated on a fixed-time basis with the 10-day treatment were slightly higher than those of control heifers.

Animals↗
PubMed1975

Effect of long- and short-term intravaginal progestagen treatments on synchronization of oestrus and fertility in heifers.

A total of 273 Herford cross heifers were treated with intravaginal progestagen pessaries to determine some of the factors affecting oestrous response and fertility following long-term (20-day) and short-term (10-day) treatments. Oestrous response and degree of synchronization were high after treatment for 20 days, but the fertility rate was lower than that of control heifers. There was no difference in the fertility of heifers inseminated artificially and those mated naturally. When the treatment period was reduced to 10 days and 900 mg progesterone and 5 mg oestradiol valerate given intramuscularly at the start, a high oestrous response and a low degree of synchronization resulted, but the conception rate was similar to that of the control animals. Reducing the dose of progesterone to 250 mg resulted in a high oestrous response and a high degree of synchronization. The stage of the cycle at the start of the 10-day treatment did not affect the oestrous response. Retention of the progesterone pessary was low (79-9%) in heifers treated for 2- days, but was 100% in those treated for 10 days.

Animals↗
PubMedDate not supplied

Expression and detection of oestrus in cattle.

For herds using AI heat detection rate and calving rate are the two major determinants of compactness of calving, of the proportion of cows that fail to conceive in a defined breeding season. Numerous factors affect the expression of heat including, housing arrangement, floor surface, feet and leg problems and status of herd mates. The number of mounts a cow receives increases with the number of cows that are in heat simultaneously up to about 3-4 cows in heat. Generally, cows that are themselves in heat, coming into heat or were recently in heat are most likely to mount a cow that is in heat. Cows that are at the mid-stages of their cycles (day 5 to about day 16) are least likely to mount a cow that is in heat and consequently could be termed "poor heat detectors". Similarly, cows that are pregnant show less interest in mounting other cows that are in heat. In smaller herds and as more cows become pregnant the likelihood of more than one cow being heat on any given day becomes less, consequently, making heat detection more difficult. The single most important factor affecting heat detection efficiency is that those responsible for checking for heat should fully understand the signs of heat and be fully committed to heat detection for as long as it is planned to use Al. Technological aids to improve heat detection include the use of tail paint, oestrous synchronisation, vasectomised bulls, pressure activated heat mount detectors, radio telemetric devices, pressure sensitive mount count devices and pedometers. As herd size increases and labour become more expensive there will be a greater adoption of some of these technological aids.

Animals↗