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PubMed2005

Influence of a prostaglandin synthesis inhibitor administered at embryo transfer on pregnancy rates of recipient cows.

Elevated uterine luminal concentrations of prostaglandin F(2alpha) (PGF(2alpha)) have been negatively associated with embryo quality and pregnancy rates. Two studies were performed in cows to determine PGF(2alpha) release from uterine endometrium following embryo transfer and to investigate administration of flunixin meglumine (FM), a prostaglandin synthesis inhibitor, on pregnancy rates following embryo transfer. In Experiment 1, blood samples were collected prior to and after embryo transfer from the posterior vena cava via saphenous vein cannulation. Serum profiles of PGF(2alpha) indicated that manipulation of the reproductive tract during embryo transfer was followed by increased release of PGF(2alpha) from the uterine endometrium. In Experiment 2, estrus (day=0) was synchronized in recipient animals and a single embryo transferred 7 days after estrus. At the time of non-surgical embryo transfer, animals were randomly assigned to receive either FM (FM; n=1300) or remain untreated (control (CON); n=797). Data collected at transfer included stage of embryo development, embryo quality, technician, and transfer quality score. Overall pregnancy rates of cows receiving FM (65%) were higher than control cows (60%; P<0.02). Pregnancy rates following transfer of quality 1 (good) embryos did not differ (P>0.05) between treatments. However, pregnancy rates of quality 2 (fair) embryos were higher in animals receiving FM than in CON (P<0.01). Moreover, pregnancy rates of transferred morula- and blastocyst-stage embryos were higher in FM-treated than in controls (P<0.06 and P<0.04, respectively). In conclusion, uterine release of PGF(2alpha) is elevated following embryo transfer and administration of a PGF(2alpha) synthesis inhibitor at the time of embryo transfer improved pregnancy rates in cows.

Animals↗
PubMed1999

Developmental competence, after transfer to recipients, of porcine oocytes matured, fertilized, and cultured in vitro.

The objective of this study was to evaluate the developmental ability of early porcine embryos produced in vitro and transferred to recipient gilts. Porcine cumulus-oocyte complexes were matured in modified North Carolina State University-37 solution for 44-46 h (in vitro maturation, IVM). In vitro fertilization (IVF) was performed with frozen-thawed epididymal spermatozoa. Inseminated oocytes were cultured in vitro (IVC) for 0, 24, or 48 h in modified NCSU-37 solution. Embryos were surgically transferred to the oviducts of recipients in which estrus had been synchronized with eCG and hCG. On the 29th day post-IVF, the uteri of some recipients were surgically examined for pregnancy; then pregnant females were hysterectomized in order to examine number and weight of the fetuses. Developmental rates to fetuses for IVM/IVF oocytes cultured for 24 and 48 h were significantly lower (p < 0.05, 1.7% and 2.0%, respectively) than that of IVM/IVF oocytes without IVC (6.7%). However, the weights of fetuses (1.0-1.2 g) did not differ among the experimental groups. The other recipients were examined for pregnancy using an ultrasound pregnancy detector, and pregnant females were allowed to go to term. Healthy piglets were delivered by some recipients to which embryos cultured for 0 or 24 h had been transferred; however, no farrow was obtained from embryos cultured for 48 h before the transfer. The results indicate that the viability of in vitro-produced porcine embryos is decreased by IVC after IVF; however, these embryos have competence to develop to term. An improved IVC system of porcine IVM/IVF oocytes is needed to generate advances in this field.

Animals↗
PubMed1994

Investigations into the control of litter size in swine: III. A reciprocal embryo transfer study of early conceptus development.

A reciprocal embryo transfer study with Meishan and Yorkshire pigs was conducted to examine the influence of embryonic genotype and uterine environment on preimplantation embryonic growth and development. Embryos were collected from gilts on d 2 of a spontaneous estrous cycle (d 0 = onset of estrus), transferred to synchronous recipients, and collected from recipients on d 12 to obtain measurements of embryonic diameter (size) and embryonic DNA, protein, and estrogen content. No difference was detected between Meishan and Yorkshire donors for number of ovulations, number of embryos recovered, or number of cells per embryo. Embryonic genotype affected (P < .01) d-12 embryonic characteristics; Meishan embryos (n = 101) were smaller (4.7 mm diameter) and contained less DNA (4.5 micrograms) and protein (104 micrograms) than Yorkshire embryos (n = 85; 5.9 mm, 6.1 micrograms, and 149 micrograms, respectively). Embryos (n = 80) transferred into a Meishan uterus were reduced (P < .001) in diameter (4.2 vs 6.4 mm) and in DNA (3.2 vs 7.2 micrograms), protein (103.8 vs 149 micrograms), and estrogen (352 vs 1,643 pg) content compared with embryos (n = 106) transferred into a Yorkshire uterus. These data indicate that the increased prolificacy of the Meishan breed may be due to an increased embryonic survival resulting from slower growing embryos and a suppressive effect of the uterus on embryonic growth rate and estrogen secretion.

Animals↗
PubMed2003

Effect of boar exposure at time of insemination on factors influencing fertility in gilts.

The effect of boar exposure during artificial insemination (AI) on semen backflow, fertilization, and embryo quality was evaluated. Gilts (approximately 170 d) were induced into estrus with PG600, and ovulation was synchronized using hCG 72 h later. Estrus detection was initiated after PG600 and continued at 12-h intervals. At estrus, gilts were allotted to receive boar exposure (BE, n = 20) or no boar exposure (NBE, n = 20) during AI. Gilts receiving NBE were identified to be in estrus prior to AI and the boar was then removed for 1 h, whereas gilts in the BE group received 15 min of exposure during AI. Insemination occurred in crates at 12 and 24 h after onset of estrus with 3 x 10(9) sperm/80 mL. Backflow was collected continuously with samples taken at time 0, (during AI), and at 0.25, 0.5, 0.75, 1, 2, 4, and 8 h after first and second AI. The effect of treatment was evaluated for time of insemination (min), backflow (mL), and sperm in backflow samples. Oviducts were flushed 2 d after first AI to evaluate the effect oftreatment on fertilization rate, accessory sperm numbers on embryos (scored 1 to 5), and embryo quality. There was no effect of first or second AI; therefore, data were pooled. Average duration of AI was 3.7 +/- 0.2 min and was not influenced by BE (P < 0.10). However, during the initial stage of AI, BE reduced the volume of semen (18.6 vs 32.4 +/- 3 mL) and the number of sperm lost (0.8 vs 1.3 +/- 0.15 x 10(9) sperm) compared to NBE (P < 0.05). There was a treatment x time effect (P < 0.05) for volume of backflow. By 45 min, the BE gilts lost more volume (9.0 vs 3.6 mL) compared to the NBE group, but sperm loss did not differ. Between 1 and 8 h after AI, neither volume nor sperm loss was influenced by treatment. By 8 h, total leakage (65 vs 63 mL) and total sperm loss (1.6 x 10(9) vs 1.8 x 10(9) sperm) were not influenced by BE (P > 0.10). However, more accessory sperm (P < 0.01) were found on embryos for the NBE (> or = 11 sperm/embryo) compared to BE embryos (< or = 10 sperm/embryo). Despite this observation, percentages of fertilized embryos (99.5 +/- 0.5 %) and number of embryos (11.5 +/- 0.1) were not different (P > 0.10). In conclusion, AI in the presence of a mature boar did not affect total semen leakage, sperm loss, fertilized embryos, or embryo quality. The importance of boar exposure during insemination was evident from less leakage during insemination, but had no effect on fertility; this suggests that the elimination of boar exposure during AI may not be deleterious to reproductive performance.

Animals↗
PubMed1976

Reproductive physiological responses of cattle to exogenous prostaglandin F2alpha.

Prostaglandin F2alpha caused rapid regression of the corpus luteum and initiated normal transitory hormonal patterns that culiminated in ovulation. PGF2alpha was effective in heat stressed heifers and a thermal stress of 32 C caused no major hormonal alterations from the time of CL regression to ovulation. A luteolytic dose of PGF2alpha tham salt (33.5 mg) given intramuscularly caused no major alterations in blood pressure, heart rate, and uterine or aortic blood temperatures. However, the same dose given as an intravenous jugular infusion over a 2 min period caused major alterations in circulatory homeostasis and body temperature. Treatment of all cattle twice with PGF2alpha tham salt (33.5 mg), 12 days apart, increased the number of responsive heifers at the second PGF2alpha injection. Synchronization of ovulation after the second injection is apparently precise enough to allow for a single timed insemination. Blood injection of estradiol benzoate and GnRH after PGF2alpha treatment will synchronize occurrence of estrus and the preovulatory surge of LH, respectively. However, GnRH treatment at 48 h lowers the frequency of PGF2alpha induced heats and this may be due to alterations in plasma progestins and estradiol.

Animals↗
PubMed1999

Effect of calcium soaps of fatty acids and administration of somatotropin on milk production, preovulatory follicular development, and plasma and follicular fluid lipid composition in high yielding dairy cows.

The effect of fat and bovine somatotropin (bST) on preovulatory follicular hormones and lipids was evaluated by feeding cows for 150 d from parturition a control diet, a control diet plus 0.55 kg/d of calcium soaps of fatty acids, or a control diet with 500 mg of bST injected every 14 d. Fourteen days after a synchronized or natural estrus, cows were injected with a PGF2 alpha analogue; 48 h later, follicular fluid from all ovarian follicles > 8 mm was aspirated. Cows fed fat or injected with bST produced more milk and milk solids than did control cows, and cows on the bST treatment lost more body condition after calving than did cows on the other treatments. Both treatments changed the proportion of estradiol-active follicles (> 400 ng of estradiol/ml of follicular fluid) and the correlation between follicular fluid estradiol concentration and the total number large follicles per cow. In follicles aspirated between 60 and 90 DIM the percentage of estradiol-active follicles was 67, 40, and 0 for cows on the control, calcium soaps of fatty acids, and bST treatments, respectively. After 90 DIM, no differences existed between treatments in the percentage of estradiol-active follicles. Estradiol concentration in follicular fluid was correlated with DIM at follicle aspiration (r = 0.51). The proportion of oleic acid in free fatty acids in plasma at 50 DIM was lower in control cows and was lower in follicular fluid of estradiol-active follicles. Both calcium soaps of fatty acids and bST had a considerable effect on follicular development and activity and the composition of fatty acids in follicles.

Androstenedione↗
PubMed1994

Growth and ovarian function of weanling and yearling beef heifers grazing endophyte-infected tall fescue pastures.

Growth and ovarian function of crossbred beef heifers grazing low and high endophyte-infected tall fescue pastures were studied for 2 successive years. In April of each year, 20 weanling and 20 yearling heifers were included in the study. All heifers were weighed at 28-d intervals for 112 d. Blood samples were collected from each heifer on Day 0 and +7 of each of five 28-d periods and analyzed for progesterone concentration. Heifers with progesterone concentrations >/= 1.5 ng/ml on either or both Day 0 and +7 were classified as having normal cyclic ovaries. High endophyte-infected fescue pastures adversely altered the ovarian activity (P < 0.05) of weanling heifers in both years. In each trial, average weight gains were lower (P < 0.05) in yearling and weanling heifers grazing the high endophyte-infected pastures than in heifers grazing low endophyte-infected pastures. In 1992, heifers were synchronized with PGF(2alpha) administered on Days 101 and 112. Blood samples were collected on 0, 4, 8 and 12 d after the second PGF(2alpha) injection for progesterone analysis. Heifers grazing high and low endophyte-infected pastures were pastured separately with 4 bulls each and were given heatmount detectors. At 96 h, less estrus activity was observed (P < 0.10; power=0.63) in weanling heifers grazing the high vs. low endophyte pastures although pregnancy rates were similar for all groups. Progesterone concentrations suggested that weanling heifers on the high endophyte pastures had a higher incidence of luteal dysfunction after PGF(2alpha) synchronization. In summary, high endophyte-infected pastures decreased growth in both weanling and yearling heifers, ovarian activity and luteal function were adversely altered in weanling heifers with subsequent decreased estrus response to estrus synchronization.

Journal Article↗
PubMed1999

Factors affecting pregnancy rate following nonsurgical embryo transfer in buffalo (Bubalus bubalis): a retrospective study.

The objectives of this study were to determine the pregnancy rate and factors affecting it following nonsurgical embryo transfer in buffalo. Donor buffalo were superovulated with FSH, and embryos collected nonsurgically were evaluated for stage of development and quality. They were transferred nonsurgically to 91 recipients on Days 5 to 7 of the natural (n = 52) or induced (n = 39) estrus (estrus = Day 0). The overall pregnancy rate of 24/91(26.4%) was higher than in earlier reports for buffalo but was much lower than in cattle. Pregnancy rates were not affected by season (autumn vs winter), side of transfer (right vs left uterine horn), or type of estrus (spontaneous vs induced). The pregnancy rate was high 11/27(40.7%) when donors and recipients were closely synchronized, while it was compromised when recipients were in estrus at +12 h (1/7, 14.3%) and at -12 h (5/27, 18.5%). Asynchrony beyond 12 h on either side resulted into conception failure. The pregnancy rate tended to increase with the increase in CL size of recipients, while stage of embryonic development had no effect. The transfer of an 8-cell embryo with a 16-cell embryo led to the birth of heterosexual twins, indicating that the uterine milieu of Day 5 to 6 recipients may be tolerated by the out-of-phase 8-cell embryo, at least in the presence of a more mature embryo. Embryo quality had the greatest effect on pregnancy rate as it was higher (P < 0.005) after the transfer of Grade I than Grade III embryos (6/10, 60.0% vs 3/36, 13.9%). Assessment of returns to estrus indicated that among nonpregnant recipients, 17/67 (25.4%) embryos never matured sufficiently to prevent luteolysis through maternal recognition of pregnancy (MRP), while 14/67 (20.8%) embryos probably died following MRP. These results indicate that efforts to increase pregnancy rate following embryo transfer in buffalo should include prevention of luteolysis during the first week of transfer and a reduction in the incidence of embryonic mortality.

Animals↗
PubMed2000

Ovarian consequences of low dose peroral Fusarium (T-2) toxin in a ewe and heifer model.

The effect of low dose peroral Fusarium produced T-2 toxin intake upon the ovarian function was evaluated in ewes (n = 30; Trial 1) and heifers (n = 7; Trial 2). Half of the ewes and all of the heifers were fed rich, acidosis-inducing concentrate. The 30 ewes were divided into 6 groups of 5 animals each. They were given 0, 0.3 or 0.9 mg/day (0, 5 or 15 ug/kg) purified T-2 toxin per os for 21 days (3x2 factorial design). Four of the 7 heifers were fed 9 mg/day (25 ug/kg) of the same purified T-2 toxin for 20 days while 3 remained untreated. The estrus cycles in all animals were synchronized prior to the trials and the T-2 exposure was started in the mid-luteal phase. The acidic condition in the rumen was estimated by the determination of urinary net acid-base excretion. The ovarian activity was followed with blood sampling for progesterone on alternate days (Trial 1) or with ultrasonography and sampling for progesterone daily (Trial 2). All of the heifers and concentrate-fed ewes showed a compensated acidosis, during first two thirds of T-2 exposure. In Trial 1, ovarian malfunction manifested as lower P4 peak concentration in the midluteal phase, shortening of the CL lifespan and prolonged follicular phases. These malfunctions were detected in 3 and 3 ewes fed concentrate and 0.3 mg and 0.9 mg T-2 toxin. Lower P4 peak concentration was observed in 1 ewe fed regular diet and 0.9 mg T-2 toxin. None of the control and acidotic groups (0 mg T-2), or ewes fed regular diet with 0.3 mg T-2 showed any ovarian malfunction. In Trial 2, after PGF2, administration the ovulation occured later and the plasma progesterone level remained low (< 3 nmol/l) for a longer period in T-2 treated heifers, than their untreated control mates (5.0+/-0.7 vs 3.7+/-0.5 d, P<0.05 and 8.3+/-0.4 vs 6.3+/-0.9 d, P<0.01, respectively). These results show that the peroral T-2 intake can significantly retard the folliculus maturation and ovulation and perhaps the subsequent luteinisation also in ruminants kept on concentrate-rich diet.

Acidosis↗
PubMed2005

Pattern of circulating luteinizing hormone isoforms during the estrous and luteal phases in Holstein heifers.

The pattern of distribution of circulating luteinizing hormone (LH) isoforms in cattle during estrus and the luteal phase was investigated. In each stage, the stage of the estrous cycle was synchronized in seven Holstein heifers with a prostaglandin analogue. After estrus was detected, blood samples were taken at 2-h intervals for 24h. In the luteal phase, animals received 250 microg i.v. of GnRH and blood samples were collected every 15 min for 5h. LH concentration in the samples was determined. Samples with the greatest LH concentration in estrus (pre-ovulatory peak) and those collected 60 min after GnRH administration (luteal phase) were analyzed by chromatofocusing, eluted with a pH gradient from 10.5 to 3.5. Eluted LH was grouped into basic (pH > or = 7.5), neutral (pH 7.4-6.5) and acidic isoforms (pH < or = 6.4) as well as by pH unit. In both phases, basic forms were the most abundant, and these were greater (P < 0.05) during the luteal phase (78.4 +/- 4.2%) as compared with during estrus (57.1 +/- 6.2%); the proportion of neutral and acidic isoforms in estrus (13.7 +/- 2.6%; 28.5 +/- 2.8%) was greater (P < 0.05) as compared with the luteal phase (3.0 +/- 0.7; 18.7 +/- 3.4). These results indicate that the relative proportion of LH isoforms secreted by the adenohypophysis differ by stage of estrous cycle. The addition of excess of NaCl to the column modifies the antigen-antibody binding in the RIA, and the proteins eluted are erroneously quantified as LH; this is an artifact of the technique.

Animals↗
PubMed2004

Developmental competence of bovine oocytes: effects of follicle size and the phase of follicular wave on in vitro embryo production.

Developmental competence of bovine oocytes collected from follicles of different size categories (in either the growth or the dominant phase of the first follicular wave) was studied, with the aim of improving in vitro embryo production. Estrus and ovulation of 39 cyclic Holstein dairy cows were synchronized by two prostaglandin F2alpha treatments at 11-day intervals and one hCG treatment on the day of onset of estrus (Day 0). Cows with follicles in either the growth (Day 3, n=25) or the dominant phase (Day 7, n=14) were slaughtered, and follicles >5 mm were counted. Three oocyte populations were recovered separately from large (11-15 mm), medium (6-10 mm) and small (2-5 mm) follicles in both follicular phases. All collected cumulus-oocyte complexes (COC), except for markedly atretic oocytes without cumulus cells, were used in experiments. Oocytes were matured, fertilized and cultured by standard methods. There were no significant differences between the growth and the dominant phases for mean numbers of large follicles, usable oocytes and embryos per donor. Generally, those numbers were low, but the development rates of oocytes into blastocysts were high, particularly in the growth phase (60.0%). Mean (+/- S.E.M.) numbers of medium follicles, oocytes and embryos per donor were higher in the growth as compared with the dominant phase; in the usable oocytes and embryos, this difference was significant (9.6 +/- 1.4 and 3.5 +/- 0.6 versus 3.9 +/- 0.6 and 1.1 +/- 0.3; P<0.01). The development rates of oocytes into blastocysts, however, did not differ significantly between the growth and the dominant phases (36.7% versus 27.8%). Mean numbers of usable oocytes and embryos per donor recovered from small follicles in both follicular wave phases were similar. The development rate of oocytes into blastocysts was generally low, but higher (P<0.01) in the growth than in the dominant phase (24.5% versus 11.7%). Comparison between the two phases showed that mean number of all counted follicles and all usable oocytes collected per donor were similar, but the mean number of embryos per donor and the development rate of oocytes into blastocysts were higher in the growth phase than in the dominant phase (8.0 +/- 1.2 versus 3.8 +/- 2.4; P=0.012 and 30.3% versus 14.9%; P<0.01). The interaction between follicle size and the phase of follicular wave affected the efficiency of embryo production. The yield of embryos was primarily influenced by the number of oocytes collected from medium follicles and the developmental competence of oocytes from small follicles. The growth phase was more effective for oocyte collection; the number of oocytes from medium follicles and the developmental competence of oocytes from small follicles decreased in the dominant phase.

Animals↗
PubMed1981

Fertilization and embryonic survival in ewes synchronized with exogenous hormones during the anestrous and estrous seasons.

Causes of reproductive loss in ewes synchronized and mated during the anestrous season and during the normal breeding season were compared with those for natural cyclic ewes mated in season. Synchronization of ewes in season and out of season with progestogen: pregnant mare serum gonadotropin (PMSG) increased ovulation rate, but the percentage of ewes ovulating did not differ from that noted for untreated ewes mated in season. However, synchronized ewes exhibited markedly higher total reproductive losses, both in season (49%) and out of season (58%), than did untreated ewes mated in season (25%). The two primary sources of the increased reproductive loss in synchronized ewes were increased fertilization failure and increased embryonic mortality, regardless of season. The increased fertilization failure was accompanied by a decrease in the number of accessory sperm per ovum and decreased tubal sperm numbers. The increased embryonic mortality among treated ewes was associated with increased variation in stage of embryo development within ewe and advanced stage of embryo development, which indicated that asynchronies of timing of onset of estrus, ovulation and fertilization may have occurred in synchronized ewes. The high reproductive losses for ewes treated out of season was characterized by a marked increase in fertilization failure, compared with that observed for ewes treated in season, in addition to the relatively high embryonic mortality associated with the synchronization treatment. Semen quality of rams was lower out of season than in season. It was concluded that the reduced and more variable lambing response often obtained for ewes treated with progestogen: PMSG during anestrus may be due to decreased semen quality of rams and increased asynchrony of events in the ewe reproductive tract.

Animals↗
PubMed2000

Use of a small dose of estradiol benzoate during diestrus to synchronize development of the ovulatory follicle in cattle.

We tested the hypothesis that a small dose of estradiol benzoate (EB) at the midstage of the estrous cycle in cattle would synchronize the subsequent pattern of ovarian follicular development, estrus, and ovulation. Nonlactating Friesian cows received either 1 mg of EB i.m. on d 13 of the estrous cycle (T; n = 12; estrus = d0) or served as untreated controls (C; n = 12). Their ovaries were examined daily with transrectal ultrasonography from d 7, and blood samples were collected 0, 2, 4, 8, 24, and 48 h after treatment on d 13. Plasma concentrations of estradiol-17beta were elevated to 12 pg/mL during the initial 24 h following treatment, compared with a baseline of 1 pg/mL in untreated controls (P < .001). Progesterone concentrations in cows of the T group declined between 24 and 48 h after treatment (-3.2 +/- .5 ng/mL) compared with little change in concentrations of progesterone in cows of the C group at this time (P < .01). This difference was coincident with an earlier time to regression of the corpus luteum in cows of the T group. Disregarding treatment groups, the second dominant follicle of the estrous cycle (DF2) emerged on d 10.6 +/- .3 and was 9.4 +/- .4 mm in diameter on d 13. Further growth of the DF2 was halted by EB treatment on d 13. Cessation of growth occurred irrespective of whether the DF2 was in the early or late growth phase, and a new follicular wave emerged 4.5 +/- .2 d later. The dominant follicle from this wave (DF3) ovulated 5 d after emergence in most cases. During the estrous cycle of every cow in the T group, there were three waves of follicular development (3-wave), whereas the ratio of 2:3 waves of follicular development in cows of the C group was 1:3. Consequently, the interval from emergence to ovulation of the ovulatory dominant follicle in cows of the C group ranged from 3 to 11 d. The dynamics of ovarian follicular wave development during the estrous cycle can be strategically manipulated by treating with a small dose of EB to synchronize proestrous development of the ovulatory follicle.

Animals↗
PubMed1990

Management of reproduction in dairy heifers based on the synchronization of estrous cycles.

Israeli-Holstein breed dairy heifers (n=571), 13 to 15 mo old, were utilized in two experiments. In Experiment 1, the reproductive performance of synchronized heifers was compared with that of untreated controls. The heifers in both groups were inseminated following the detection of estrus. In Experiment 2, all heifers were synchronized and inseminated following the detection of estrus. Half of the animals in this experiment also received one or two fixed-time inseminations 72 and 96 h after the last synchronization treatment. Synchronization of estrous cycles was performed by two prostaglandin F2alpha (PG) injections given 12 d apart. In the control group of Experiment 1, observation of estrous behavior and insemination of heifers detected in estrus were carried out daily throughout the experiment. In the synchronized groups of Experiments 1 and in 2, the management of reproduction consisted of estrus detection followed by the insemination of heifers in estrus carried out only during 6 d of every 3 wk. Five days following the second PG injection, 86% of the heifers were detected in estrus, 71% of them at 49 to 96 h after treatment. In Experiment 1, age at first insemination, age at conception, and conception rate were, respectively, 425 d, 446 d and 54% in the control group vs 432 d (P<0.02), 449 d and 62% in the PG-treated group. In Experiment 2, the respective figures were 436 d, 462 d and 59% in the group inseminated following the detection of estrus vs 427 d (P<0.002), 464 d and 51% (P<0.05) in the group in which heifers were inseminated at estrus and also received one or two fixed-time inseminations.

Journal Article↗
PubMed1994

Placental lactogen and somatotropin: hormone binding to the corpus luteum and effects on the growth and functions of the ovary in heifers.

The effects of recombinant bovine placental lactogen (rbPL) and recombinant bovine somatotropin (rbST) on development of ovarian follicles and CL were tested in heifers. Estrus (day = 0) was synchronized and heifers were treated (Days 0-21) with either saline (control; n = 7), rbST (25 mg/day; n = 6), or rbPL. (50 mg/day; n = 8). Blood was collected daily for analyses of progesterone, estradiol, ST, PL, and insulin-like growth factor (IGF)-I; ultrasound was performed daily for measurement of follicles and CL. PL in plasma (mean +/- SE; ng/ml) averaged 4.1 +/- 0.2 for rbPL-treated heifers, and ST in plasma (ng/ml) averaged 2.7 +/- 0.3 for rbST-treated heifers. IGF-I in plasma (ng/ml) was increased for rbST-treated (198 +/- 10; p < 0.001) and rbPL-treated (143 +/- 9; p < 0.06) heifers compared to controls (117 +/- 9). After Day 9 of the estrous cycle, heifers treated with rbPL had larger CL (p < 0.001) and more progesterone in plasma (p < 0.001) than controls, whereas rbST-treated heifers were intermediate for these measures. Largest follicles were decreased in size (mm) throughout the estrous cycle for rbPL-treated heifers (12.9 +/- 0.4) compared to controls (14.2 +/- 0.5; p < 0.06) or heifers given rbST (14.0 +/- 0.5; p < 0.11). After Day 17 (preovulatory period), concentrations of estradiol in serum (pg/ml) were decreased for rbST-treated (2.7 +/- 0.3; p < 0.01) and rbPL-treated (2.9 +/- 0.2; p < 0.02) heifers compared to controls (3.8 +/- 0.3).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1981

Synchronization of ewes during anestrus: influence of time of year and interval to onset of estrus on conception rate.

The effects of progestogen-gonadotropin treatment on estrous response, ovulation rate and lambing response of crossbred ewes were examined at two times during the anestrous season (May-June and July-August). Each ewe group was treated with progestogen pessaries for 16 days and injected with 750 IU pregnant mare serum gonadotropin (PMSG) on days 17 and 32 to induce two consecutive estrous periods. Data accumulated from single-sire matings of 500 ewes indicated that estrous, ovulation and lambing responses did not differ (P less than .10) between ewes treated in May-June (92%, 2.5, 66%) and ewes treated in July-August (93%, 2.5, 67%). We concluded that there were no significant differences between reproductive responses of ewes synchronized during mid-anestrus (May-June) and those of ewes treated during late anestrus (July-August). For the May-June and July-August groups combined, estrous, ovulatory and lambing response were higher (P less than .05) during the first induced estrous period (76%, 3.0, 62%) than during the second (33%, 1.9, 43%). In both the first and second induced estrous periods, as interval from PMSG injection to onset of estrus increased, significant declines in ovulation rate, conception rate and ram marking activity were observed, particularly when onset of estrus occurred 72 hr or more after PMSG injection. These results indicate that the reduced lambing responses reported for ewes synchronized during anestrus may be due to increased asynchrony of reproductive events in the ewe, or decreased ram aggressiveness and fertility, or a combination thereof, as the interval from PMSG injection to the onset of estrus increases.

Animals↗
PubMed1975

Fetal cardiovascular and other defects induced by thalidomide in cats.

Timed pregnancies were induced in cats by synchronizing gonadotropin-stimulated estrus and ovulation with natural mating. The cats were given daily oral doses of thalidomide as follows: 10 mg/kg on days 10-20 of pregnancy, 240 mg/kg on days 10-14, and 120, 240, and 480 mg/kg on days 15-17 or 18-20 of pregnancy. Fetuses were delivered by cesarean section on day 44 or 45 or earlier if threatened abortion was considered imminent. A wide variety of cardiovascular anomalies was observed on gross and microscopic examination including the following ventricular septal defect, right atrial distension primarily involving the coronary sinus, malpositioned great vessels, and narrowed left ventricular chamber with hypertrophied walls. The overall incidence of these anomalies appeared related to dose and treatment period.

Animals↗