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PubMed1998

Treatment with progesterone and 17 beta-oestradiol to induce emergence of a newly-recruited dominant ovulatory follicle during oestrus synchronisation with long-term use of norgestomet in Brahman heifers.

The aim of this study was to determine the effect on ovarian follicular growth and atresia, of acute treatment with either 100 mg of progesterone (n = 10), 200 mg of progesterone (n = 10), 10 mg of oestradiol + 100 mg of progesterone (n = 10), 10 mg of oestradiol (n = 10) or no treatment (n = 10), given on Day 10 of a 17-day treatment with a norgestomet implant in randomly cycling Bos indicus heifers. The fate of the dominant follicle on Day 10, emergence of the new cohort of follicles and the intervals from implant removal to ovulation were recorded by ultrasonography. Plasma concentrations of Luteinizing hormone (LH), progesterone and oestradiol were determined during the time when the norgestomet implant was in place. All treatments resulted in the emergence of a new cohort of follicles within 5 days of administration. The day of emergence of the ovulatory follicle tended to be delayed after treatment with 100 mg of progesterone (2.7 +/- 0.3 days after treatment), 200 mg of progesterone (3.7 +/- 0.5 days after treatment), 10 mg of oestradiol + 100 mg of progesterone (4.4 +/- 0.2 days after treatment) and 10 mg of oestradiol (4.6 +/- 0.4 days after treatment) compared to control heifers (1.4 +/- 1.4 days after time of treatment). The mean interval from implant removal to onset of oestrus was significantly shorter after treatment with 100 mg of progesterone (38.4 +/- 2.6 h) than after treatment with 200 mg of progesterone (61.5 +/- 3.9 h) but otherwise, the mean interval from implant removal to onset of oestrus did not differ. Oestrus synchrony, measured by the sample standard deviation of oestrus onset, was tighter in all treatment groups compared to untreated control heifers. The mean interval from implant removal to ovulation did not differ significantly between groups. The synchrony of ovulation, measured by the sample standard deviation of the interval from implant removal to ovulation, was significantly tighter after treatment with 100 mg of progesterone, 200 mg of progesterone and 10 mg of oestradiol compared to control heifers. Treatment with 10 mg of oestradiol resulted in ovulation in seven of 10 heifers before implant removal, three of which failed to ovulate after implant removal. Progesterone administered on Day 10 lowered plasma LH concentrations (P < 0.05), whereas treatment with oestradiol caused a surge of LH and ovulation. Progesterone administered with oestradiol prevented the LH surge. A combination treatment of oestradiol and progesterone given on Day 10 of a 17-day norgestomet treatment in a range of follicular states resulted in the consistent emergence of a new cohort of follicles which included the eventual ovulatory follicle.

Animals↗
PubMed1998

Presence of males affects the incidence of ovulation after pouch young removal in brushtail possums (Trichosurus vulpecula).

The traditional method for inducing and synchronising oestrus in the brushtail possum (Trichosurus vulpecula) is by removal of their suckling pouch young (RPY). However, our studies have recently shown that, in addition to wide variation between animals in the time of ovulation after RPY, a proportion of animals failed to ovulate. Evidence from several mammalian species indicates that the presence of males can stimulate ovarian activity and synchronise oestrus in females. The aim of this study was to determine the effect of the male on the oestrous cycle of the female brushtail possum after RPY. A total of 67 adult female brushtail possums were treated as three replicates. In order to observe the day of preovulatory follicle emergence and ovulation, animals underwent laparoscopic examination at 1-4 day intervals over a period from 0-21 days after RPY. The first replicate (N = 18, May/June 1995) involved only animals kept in isolation from males, whereas the two remaining replicates compared ovarian responses between animals kept with ( N = 10, July 1995; N = 14, June 1996) or in isolation from ( N = 10, July 1995; N = 15, June 1996) males. The incidence of ovulation after RPY was significantly higher in females that were housed with males than in those kept in isolation from males (100%, 92.8% vs. 50.0%, 66.7%, 14.3%; P < 0.001). Every animal that ovulated, had previously had a preovulatory follicle present at the site where the corpus luteum formed. Conversely, none of the animals that failed to ovulate, developed a preovulatory follicle during the period of the study. The range of mean day of preovulatory follicle emergence (6.00-6.86 days), of ovulation (11.80-12.20 days) and the synchrony of ovulation between animals (range 8-17 days) after RPY, were not significantly affected by the presence of males. This study demonstrates for the first time, that the presence of males significantly increases the incidence of ovulation after RPY in the brushtail possum. However neither the timing of reproductive events nor the synchrony of ovulation were affected by presence of the male.

Animals↗
PubMed1998

Duration of ovulation suppression with subcutaneous silicone implants containing norgestomet in Bos indicus heifers and cows.

The aim of this study is to determine the duration of suppressing oestrus or ovulation in Bos indicus heifers and cows using norgestomet (N) incorporated into a silicone implant. Twelve heifers and 18 cows undergoing oestrous cycles were allocated to one of two treatment groups (6 heifers and 9 cows per group). Animals were treated with a single subcutaneous (s.c.) silicone implant containing 3 mg of N or two identical silicone implants (6 mg of N in two silicone implants) on day 0 of the study. An analogue of prostaglandin F2-alpha was administered intramuscularly, to all animals on days 0 and 6 to induce regression of corpora lutea. Implants were removed from all animals on day 21. Animals were observed for signs of behavioural oestrus while implants were in situ and for 6 d following implant removal. Blood samples were collected on alternate days from day 0 to 20 and again on day 21 and analysed for plasma progesterone (P4). Transrectal ultrasonography was performed on days 0, 6, 10, 14, 18, 21, 24, 26,27, and along with concentration of P4 in plasma was used to confirm ovulation during the treatment period. The cumulative percentages of animals ovulating during the 21 days implants were in situ were 6.7% (3 mg of N in one silicone implant) and 0% (6 mg of N in two silicone implants)Intervals from implant removal to oestrus (mean +/- S.E.M.) did not differ significantly among animals treated with either 3 or 6 mg of N in silicone implants (46.8 +/- 7.0 vs. 55.4 +/- 7.1 h, P = 0.398). Variances in interval from implant removal to oestrus among animals treated with 3 or 6 mg of N in silicone implants were also homogeneous (P = 0.942). The mean diameter of the ovulatory follicle on day 21 was larger in the animals treated with 3 mg of N compared to animals treated with 6 mg of N in two silicone implants ( 13.1 +/- 0.8 vs. 9.7 +/- 0.7 mm, P = 0.005). We conclude that treatment with 3 mg of N in a silicone implant will suppress ovulation in Bos indicus heifers and most cows for 21 d. Six mg of N in two silicone implants will suppress ovulation for 21 d in both cows and heifers.

Animals↗
PubMed1998

Effects of short-term treatment with progesterone superimposed on 11 or 17 days of norgestomet treatment on the interval to oestrus and fertility in Bos indicus heifers.

The aims of this study were to determine: (1) if short-term treatment of Bos indicus heifers with progesterone (P4) while implanted with a s.c. norgestomet implant for 17 days would influence the time interval to oestrus and increase fertility of the synchronised oestrus, and (2) whether the response to treatment with P4 would differ between heifers treated with a norgestomet implant for 17 vs. 11 days when short-term treatment with P4 is applied 3 days prior to implant removal. B. indicus heifers at two separate sites (A and B) were allocated to three groups at each site. Heifers in two groups (NG and NGP4 groups) were given a single s.c. norgestomet implant on the first day of treatment (day 0) while heifers in a third group (NGP4PG group) were implanted on day 6. A single P4 releasing Controlled Internal Drug Release device (CIDR) was inserted on day 14 in heifers in the NGP4 and NGP4PG groups and was removed 23.5 +/- 0.07 h later (day 15). Heifers in the NGP4PG group were administered an analogue of prostaglandin F2 alpha (PGF2 alpha) at the time of CIDR removal to regress corpora lutea. Implants were removed from all heifers on the same day (day 17) and a 400 IU of equine chorionic gonadotrophin (ECG) was administered s.c. Animals were artificially inseminated 11.1 +/- 0.17 h after detection of oestrus, using frozen semen from one bull at site A and one of five bulls at site B. Inseminations were carried out by one of two technicians. Treatment with P4 delayed oestrus and reduced the synchrony of oestrus at site A (hours to oestrus +/- SD: NG group, 39.0 +/- 13.7; NGP4 group, 66.3 +/- 24.4; NGP4PG group, 58.9 +/- 20.5 h; P < 0.05) but not at site B (41.4 +/- 15.2, 42.5 +/- 10.1, 45.4 +/- 10.3 h; P > 0.05). Pregnancy rates 6 weeks after insemination were found to be significantly associated with bull (P < 0.001), treatment group (P = 0.013) and insemination technician (P = 0.033). Pregnancy rates were greater in the heifers in the NGP4 group than heifers in the NG group [50.3% (78/155) vs. 36.4% (60/165); odds ratio = 1.83, 95% CI = 1.14 to 2.96] and similar between heifers in the NGP4 and NGP4PG groups [50.3% (78/155) vs. 51.1% (63/117); odds ratio = 1.06, 95% CI = 0.67 to 1.69]. It was concluded that acute treatment with P4 can improve pregnancy rates in B. indicus heifers treated for 17 days with norgestomet implants. Reducing the duration of norgestomet treatment to 11 days and administration of PGF2 alpha at the time of ending treatment with a CIDR device resulted in no differences in fertility, mean intervals to oestrus or synchrony of oestrus.

Analysis of Variance↗
PubMed1998

Development of a nutritional strategy for increasing lamb survival in Merino ewes mated in late spring/early summer.

A nutritional strategy for increasing lamb survival in Merino ewes mated in late spring/early summer was evaluated in a commercial flock over two consecutive years (Year 1, n = 680; Year 2, n = 325). The strategy combined the 'ram effect' to synchronise oestrus and hence parturition, plus supplementary feeding of lupin grain for 14 days in the expected early post-parturient period. Supplementary lupin feeding commenced 12 days after the expected start of lambing. Lambing was highly synchronised over a 14-day period commencing 17-19 days after the expected start of lambing, in both years. Supplementary feeding did not affect lamb birthweight in either year but subsequent increases in weight were observed at weaning in Year 1 (1.4 kg; P = 0.06) and tail docking in Year 2 (1.3 kg; P < 0.05). Lamb survival was increased by 7 lambs per 100 ewes exposed to rams in both years. (Year 1 at weaning, NS; Year 2 at tail docking, P < 0.001). It was concluded that the strategy improved both lamb survival and lamb performance possibly due to an effect of lupin supplementation on colostrum and subsequent milk production.

Animal Feed↗
PubMed1998

Successful embryo transfer in the silver fox (Vulpes vulpes).

Surgical embryo transfer in the silver fox was investigated as part of a larger project concerning the conservation of endangered canine species using modern artificial reproduction techniques with the farmed fox as a model. The animals were chosen on the basis of synchrony in natural oestrus. The timing of ovulation and artificial insemination was determined by measuring electrical resistance in the vagina. Twenty-nine embryos were flushed from eight humanely killed donor females and transferred surgically into the uteri of eight recipients. One recipient female gave birth to two male pups 47 days after the transfer of four expanded blastocysts and one embryo at the 16-cell stage derived from a donor female flushed 10 days after artificial insemination.

Animals↗
PubMed1999

Effect of roughage type and concentrate supplementation on follicle numbers and in vitro fertilisation and development of oocytes recovered from beef heifers.

Increasing dietary energy tends to decrease the ovulatory response and produce fewer viable embryos following superovulation of beef cattle. Data in sheep indicate that high energy intake can decrease progesterone concentrations (P4), although effects in cattle are not as clear. The objectives were to evaluate the effects of roughage type and concentrate supplementation on P4 concentrations, follicle growth and subsequent oocyte fertilisation and embryo development in vitro. Forty-two beef heifers were allocated to 3 treatment groups: (i) silage ad libitum plus 6 kg concentrates (silage + conc.; n = 14); (ii) silage ad libitum (silage; n = 14) or (iii) hay ad libitum (hay; n = 14) for 40 days. Oestrus was synchronised using a controlled intravaginal progesterone releasing device (CIDR) for 7 days plus prostaglandin F2 alpha (15 mg luprostiol) administered 2 days before CIDR withdrawal. Ovaries were stimulated with 600 i.u. of follicle stimulating hormone (pFSH) administered in 6 equal doses at 12-h intervals, starting 12 days after CIDR withdrawal. Daily blood samples were collected from 3 days after CIDR insertion until CIDR withdrawal, and for another 3 days prior to pFSH, for P4 determination. Oocytes were recovered postmortem 12 h after the last pFSH injection, matured, fertilised and cultured in vitro. There was no overall effect of diet (P > 0.05) on P4 concentrations. The number of follicles grown in heifers on silage + conc (18.8 +/- 3.3), silage (23.5 +/- 3.4) or hay (18.1 +/- 2.6) were not affected by the dietary treatment (P > 0.05). The percentage of oocytes fertilised from heifers on hay (88%) was higher compared to oocytes from heifers on silage (79%; P < 0.05), but was not different (P > 0.05) compared to the proportion of oocytes from heifers on silage + conc. (86%). The percentage of fertilised oocytes that cleaved was higher from heifers on silage (94%; P < 0.01) compared with oocytes from heifers on hay (82%) or silage + conc. (86%). The proportion of embryos that developed to blastocyst was not different (P > 0.05) between groups of oocytes from heifers on silage + conc. (8%), silage (14%) or hay (15%). Heifers on silage produced numerically more blastocysts (silage: 19 from 14 heifers; silage + conc.: 8 from 14 heifers; hay: 12 from 14 heifers). These results suggest that dietary treatment used prior to oocyte recovery did not significantly influence the developmental competence of the oocytes in vitro.

Ammonia↗
PubMed1999

Understanding maternal contributions to fertility in recipient cattle: development of herds with contrasting pregnancy rates.

Causes of variation amongst recipients within a herd in their ability to initiate and maintain pregnancy is largely unknown. In order to develop an experimental resource to understand the biology of recipient reproductive performance, each of 155 contemporary yearling heifers received 2 in vitro-produced embryos on 6 separate occasions during a 26-month period. Sixty days after transfer, pregnancy and the number of foetuses were determined ultrasonically and then pregnancies were terminated and the process was repeated. Heifers were ranked on their aggregate pregnancy rate performance, and the highest (High) and lowest (Low) 25 were retained. Mean pregnancy rates of all recipients ranged from 0.20 to 0.67 depending on transfer occasion. The mean +/- s.e. pregnancy rate of the High and Low sub-herds were 0.76+/-0.04 vs. 0.11+/-0.03, respectively (P<0.001), with 55% and 37% of this difference due to differences in Day 25 return to oestrus rates and losses between Day 25 and Day 35, respectively. We suggest that failure in the mechanism involved in maternal recognition of pregnancy was a major cause of the difference between the two sub-herds. These sub-herds are a unique experimental resource for understanding the early pregnancy process in cattle.

Animals↗
PubMed1999

The role of luteal oxytocin in episodic secretion of prostaglandin F2alpha at luteolysis in the ewe.

The role of luteal oxytocin in the generation of luteolytic episodes of prostaglandin F2alpha at luteolysis was investigated. On day 10 of the cycle Dorset ewes underwent either surgical removal of the corpora lutea (lutectomy; n = 4) or sham operation (sham; n = 4). Lutectomised ewes were then administered progesterone by twice daily i.m. injection in corn oil (20 mg/day) until day 14 when treatment was ceased to simulate luteolysis. The concentration of 13, 14 dihydro-15-keto prostaglandin F2alpha (PGFM) was measured in peripheral blood samples collected at 20-min intervals for 8 h on days 12-16 of the cycle. Progesterone and oestradiol concentrations were similar in the two groups over the whole experimental cycle while oxytocin fell dramatically following lutectomy. No prostaglandin F2alpha release episodes were seen on day 12 or 13, while from days 14-16 both groups exhibited a similar episode frequency (lutectomy 0.9/ewe/8 h; sham 0.8/ewe/8 h). Analysis of episode characteristics revealed lower episode amplitude (p<0.05) but longer episode duration (p<0.05) in the lutectomy group. The results demonstrate that a normal frequency of prostaglandin F2alpha release episodes occurs independently of luteal oxytocin secretion. However, luteal oxytocin is involved in regulating the pattern of release, perhaps causing the release of episodes of the magnitude required for the successful completion of luteolysis.

Animals↗
PubMed2000

Effects of vitrification medium composition on the survival of bovine in vitro produced embryos, following in straw-dilution, in vitro and in vivo following transfer.

This study examined the effects of adding a macromolecule, polyvinylpyrrolidone (10% PVP) and a sugar (0.3 M trehalose) to vitrification solutions (VS) containing either one (40% ethylene glycol [EG], two (25% EG+25% DMSO) or three (20% EG+20% DMSO+10% 1, 3-butanediol [BD]) permeable cryoprotectants on the survival and hatching of IVP bovine embryos, following vitrification, warming and in-straw cryoprotectant dilution. Grade 1 and 2 compact morulae and blastocysts were selected on Day 7 (Day 0=IVF) of culture in SOFaaBSA and equilibrated for 10 min at room temperature in 10% EG. Following exposure, for up to 1 min at 4 degrees C, to one of the above VS (with or without PVP+trehalose), the embryos were loaded into straws and immersed in liquid nitrogen. Following warming and in-straw cryoprotectant dilution, the embryos were cultured for 48 h to assess hatching. There was no effect of VS on the survival of embryos after 24 h, however fewer compact morulae than blastocysts survived after 24 h (24% vs. 75%; P<0.001) or hatched after 48 h (15% vs. 59%; P<0.001). When blastocysts only were considered, an interaction between VS and additional PVP+trehalose was also observed (P<0.01). Hatching was reduced when they were added to 25% EG+25% DMSO (70% vs. 45%) but was not affected for either 40% EG (44 and 49%) or to 20% EG+20% DMSO+10% BD (72 and 72%). Pregnancy rates (Day 90 ultrasound) of recipients that were transferred either two non-vitrified or two vitrified (20% EG+20% DMSO+10% BD) blastocysts, did not differ (3/6 [50%] and 11/20 [55%]). However, significantly (P<0.02) fewer recipients that received compact morulae maintained pregnancy to Day 90 although this was not affected by vitrification (fresh vs. vitrified; 1/5 [20%] vs. 3/18 [17]). These data demonstrate that a VS comprising three cryoprotectants, rather than one, enables more embryos to hatch during post-thaw culture and that the survival, following direct transfer of these vitrified embryos, is not different to non-vitrified embryos.

Animals↗
PubMed2000

Embryo and foetal loss in beef heifers between day 14 of gestation and full term.

Following insemination, reproductive failure in cattle is largely manifested as embryo mortality and is a major source of financial loss to livestock producers. Ongoing studies at this laboratory into factors affecting embryo mortality have facilitated the collection of new data on the extent and timing of embryo and foetal mortality in cattle. Oestrus was synchronised in 158 beef cross heifers and following artificial insemination, embryo and foetal survival rates were determined on days 14 and 30 after insemination and subsequently at calving. Embryo survival rates measured on days 14, 30 and at full term were similar at 68%, 76% and 71.8%, respectively (P0.05). Based on morphological examination, all the 14-day-old embryos recovered were assessed as grade 1. These results provide new information indicating that most embryo losses in heifers have occurred before day 14 after insemination.

Abortion, Veterinary↗
PubMed2000

Norgestomet- and oestradiol valerate-induced luteolysis is dependent upon the uterus.

Beef heifers were assigned to three groups: (1) untreated controls (n=4), (2) Syncro-Mate B(R) (SMB)-treated (n=5), and (3) hysterectomized and SMB-treated (n=4). SMB was administered 8 or 9 days after oestrus, approximately 30 days after hysterectomy. This study was conducted to determine if the uterus was necessary for SMB to induce luteolysis. SMB induced premature luteolysis as only 20% of the intact SMB-treated heifers had >/=0.75 ng/ml of progesterone 7 days after the time of SMB treatment, compared to all (100%) of the untreated heifers (p<0.05). By 9 days after the time of SMB treatment, 25% of the untreated heifers and none (0%) of the intact SMB-treated heifers had >/=0.75 ng/ml of progesterone; however, all (100%) of the hysterectomized SMB-treated heifers had >/=0.75 ng/ml of progesterone (p<0.05). Therefore, SMB-induced luteolysis required the involvement of the uterus. The luteolysin, prostaglandin F(2alpha), is probably the secretion from the uterus that mediates the SMB-induced luteolysis. SMB treatment, however, required 7-8 days to induce luteolysis.

Animals↗
PubMed2001

Reproductive techniques in sheep.

This article reviews current methods of evaluating reproductive performance in the sheep industry. The reproductive technologies of breeding soundness examination, reproductive ultrasonography, estrus manipulation, artificial insemination, and embryo transfer are also extensively discussed. The veterinarian's current and future role in the application of these technologies is discussed.

Animals↗
PubMed1992

Management of replacement breeding animals.

In conclusion, replacement gilts should be finally selected before 110 kg body weight and should have been stimulated to reach puberty by this time. Currently, the best method for achieving this is ad libitum feeding and the correct use of boar exposure. However, whether ad libitum feeding will always be the best feeding strategy remains to be seen. The impressive success of selection programs and the potential for the use of growth promoters and repartitioning agents in the feeder barn may require that future replacements be identified at an early stage and raised under a separate feeding regimen. To produce a large first litter, gilts should be bred at their second estrus. There is unlikely to be any further increase in litter size by delaying mating to third estrus. A major consideration when choosing when to breed replacements is the length of their productive life. For many farms, this may be maximized by delaying breeding until the sow is 120 to 130 kg body weight with a minimum backfat depth of 18 mm. For the producer who is able to exert control over lactation condition loss, however, breeding replacements at about 110 kg body weight with backfat depths of 14 to 16 mm should not adversely affect long-term performance. Although it is true that, under some conditions, the lean gilt may become a problem, it is equally true that her potential is as great as her fatter contemporaries. Whether this potential is realized is largely under the producer's control. Regarding the boar, nutritional management need not vary from that provided for gilts. However, if replacement boars are raised on-farm, it is of great importance that they be allowed to socially interact with other pigs. Failure to provide this opportunity will result in a boar with reduced libido.

Animal Husbandry↗
PubMed1990

Out-of-season breeding in goats.

Maintenance of winter milk production and the production of meat kids for seasonal specialty markets are two major reasons for out-of-season breeding. Strategies include the manipulation of light cycles and the administration of exogenous gonadotrophins following progestogen priming with either vaginal sponges or subcutaneous implants. A number of does in excess of expected need should be prepared. Excess numbers of bucks also are advisable, because libido and fertility often are lower out of season.

Animals↗
PubMed1999

Equine reproductive pharmacology.

This article reviews therapies and strategies commonly used to treat diseases of the mare's genital tract and modulate the reproductive cycle of the mare. Many reproductive treatments are based on historical use and empirical evidence rather than well controlled clinical studies. This article attempts to present practical information in a summary form while highlighting the need for continued research documenting the efficacy and safety of reproductive therapies.

Abortion, Veterinary↗