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PubMed1979

[Possibilities of ovulation synchronization in puberty-induced gilts].

Puberty was induced in 39 clinically prepuberal gilts (two groups of three sub-groups each) by parallel but locally separated application of 500 IU PMSG ("Maretropin") and 250 IU HCG ("Gonadex"), with the view to testing ways to synchronise ovulation. Seventy-two hours were allowed to elapse, before 24 animals received another application of 500 IU HCG and 15 animals 250 IU HCG. The animals were slaughtered in consecutive groups of study ovulation and histolotically examined to disclose endometrial processes. Ovulations were found to be well synchronised in the recipients of a second injection of 500 IU HCG. Only sub-threshold effects with no synchronised ovulation were recorded from the animals that had received a second dose of 250 IU HCG. A second injection of 500 IU HCG should be given not until something between 78 and 82 hours after puberty induction for optimum follicle maturation and adequate proliferation of the endometrium.

Animals↗
PubMed2004

A comparison of diagnosis of pregnancy in the goat via transrectal ultrasound scanning, progesterone, and pregnancy-associated glycoprotein assays.

Real-time ultrasound scanning (US) via the transrectal route, progesterone (P4) assay, and pregnancy-associated glycoprotein (PAG) detection can be used to diagnose pregnancy at around 3 weeks after breeding. Although several studies have been carried out to evaluate each of these different methods individually, it is difficult to establish adequate comparisons due to differences, such as the breed of goat, age, and farming conditions, among others. The aim of the present paper is to compare the accuracy of diagnosis of pregnancy using transrectal US, P4 assay and PAG detection at the same time and on the same animals. Canary dairy goats (n=143) were synchronized with an 11-day fluorogestone acetate (FGA) intravaginal sponge followed by PGF2alpha and eCG 2 days before the FGA withdrawal. Blood samples were collected on Days 20, 22, 24, and 26 after mating to determine P4 and PAG concentrations. Transrectal US examinations were performed at the same time. There were 79 pregnant goats and another 64 non-pregnant. The US via the transrectal method and the determination of PAG concentrations provide very accurate pregnancy diagnosis at 24-26 days after breeding; on the contrary, P4 assay on plasma samples performed on Day 22 after breeding was accurate, in this case, in detecting pregnant animals but did not always detect the non-pregnant does.

Animals↗
PubMed2003

Regulation of gonadotropin releasing hormone release by neuropeptide Y at the median eminence during the preovulatory period in ewes.

The median eminence (ME) of the hypothalamus is known to be an important brain site where hypophysiotropic release might be regulated by excitatory and inhibitory signals impinging on their neuronal terminals. Since a role for neuropeptide Y (NPY) on preovulatory luteinizing hormone (LH) release has been suggested, we hypothesized that NPY might act at the ME to control preovulatory gonadotropin-releasing hormone (GnRH) release and thus the onset of the preovulatory surge of LH. To examine this possibility, we used the ewe as an animal model to determine: (a) immunocytochemical distribution of GnRH and NPY in the ewe ME; (b) changes in in vivo release of NPY and GnRH using ME push-pull cannula (PPC) perfusate samples, as well as in plasma LH, during the luteal, follicular and preovulatory phases of a synchronized estrous cycle, and (c) effects of ME perfusion of NPY or a Y1-NPY antagonist, or an NPY antiserum on in vivo release of ME-GnRH and plasma LH during a synchronized follicular phase. Immunolocalization reveals a dense plexus of beaded GnRH-containing neurites in the arcuate nucleus and in its vicinity, the pituitary stalk and the palisade. In contrast, a dense plexus of NPY-containing neurites occurs in the internal layer, with occasional fibers found in the intermediate and lateral external zone of the ME. In the area between the lateral internal and lateral external layers, both NPY and GnRH-containing processes were found, thus providing opportunities for synaptic and/or paracrine interactions between NPY- and GnRH-containing neurons. Hormonal analysis indicated that a synchronized preovulatory surge of LH is elicited within a 2-hour window by the sequential implantation and removal of silastic-encased estradiol (E2) or progesterone (P4) implants. In this paradigm, there was a parallel increase in ME release of both NPY and GnRH preceding the synchronized LH surge. The onset of this synchronized LH surge was advanced by ME perfusion of exogenous NPY and was both delayed and blunted by ME perfusion with the NPY antagonist (both were perfused through the PPC probe for 2 h, starting 2-3 h before the expected onset of the LH surge). In addition, NPY perfusion in the ME increases, while perfusion of the Y1-NPY antagonist or of the NPY antiserum decreases ME-PPC GnRH content and plasma levels of LH in early follicular ewes. Finally, perfusion of NPY antiserum during an ongoing LH surge disrupted LH release. These results suggest that interactions between NPY and GnRH neurons are important in controlling the timing, magnitude and maintenance of the preovulatory LH surge.

Animals↗
PubMed1979

Plasma progesterone levels in progesterone treated cows.

A technique for the radioimmunoassay of progesterone in plasma is described. In one trial the oestrous cycles of four cycling cows and in another trial of one non-cycling cow and two cycling heifers were synchronized by the administration of progesterone. Each female received either 50 mg or 0,1 mg/kg of progesterone intramuscularly on alternate days in two courses of four and six injections respectively. Blood samples of the animals were collected either daily or two-daily before, over the entire period of treatment and for eight days after the last progesterone injection. The results of the progesterone assays are represented graphically for each individual cow or heifer. The plasma progesterone levels during treatment were maintained reasonably well at levels corresponding to those normally encountered during the lluteal phase of the cycle. The progesterone levels, however, did not drop as rapidly as desired after the last injection but might have been influenced by a residual corpus luteum from a previous ovulation.

Animals↗
PubMed1989

Genital stimulation facilitates maternal behavior in estrous ewes.

Only a small proportion of ewes at estrus have been found to respond maternally to newborn lambs, and this low maternal responsiveness may be partially attributable to the absence of the genital stimulation which occurs at parturition. Therefore, the effect of artificial genital stimulation on maternal behavior of estrous ewes was investigated. Estrus was synchronized in 33 ewes by placement and withdrawal of progestin-saturated vaginal sponges. Estrous ewes were divided into two groups, a control group and a group receiving 5 min of artificial genital stimulation, and observed following presentation of newborn lambs. Significantly more stimulated ewes licked the lamb and emitted low-pitched bleats in a 30-min test. When genital stimulation was subsequently administered to control ewes, more of them also became maternal so that the two groups were no longer significantly different. These results indicate that absence of genital stimulation is one of the factors contributing to the low maternal responsiveness of estrous ewes. They also demonstrate for the first time that artificial genital stimulation is effective in eliciting maternal behavior in nonpregnant ewes even at physiological concentrations of estradiol.

Animals↗
PubMed2000

Effects of a single day of feed restriction on changes in serum leptin, gonadotropins, prolactin, and metabolites in aged and young mares.

In a variety of species, short-term feed restriction leads to rapid changes in the reproductive axis and reduces serum levels of leptin. Two experiments were performed to test the hypothesis that a single day of feed restriction in aged and young mares would cause a suppression of the gonadotropins and serum leptin concentrations. The estrous cycles of 12 aged (>eight years; Exp. 1) and eight young (<five years; Exp. 2) mares were synchronized and the mares were conditioned to twice-daily meal feeding. On the seventh day after synchronization, restricted mares (n = 6 for Exp. 1; n = 4 for Exp. 2) were not fed for 24 hr; all mares were fed the second day. In Exp. 1, serum leptin concentrations significantly decreased in restricted mares, but not in controls. In Exp. 2, serum leptin concentrations declined in restricted mares and no decline was seen in the controls. Serum glucose concentrations did not change in response to feed restriction or refeeding, but in both experiments feed restriction caused an increase in free fatty acids. For both experiments, prolactin, FSH, and LH serum concentrations were not significantly altered by feed restriction. The observed absence of suppression may reflect the maintenance of sufficient levels of metabolizable fuels, rather than a failure of leptin to signal nutritional status to the reproductive axis of the mare.

Aging↗
PubMed2004

The "male effect" in sheep and goats: a review of the respective roles of the two olfactory systems.

In sheep and goats, exposure of seasonally anestrous females to sexually active males results in activation of luteinizing hormone (LH) secretion and synchronized ovulation. This phenomenon is named "the male effect" and seems to constitute a major factor in the control of reproductive events. This effect depends mostly on olfactory cues and is largely mimicked by exposure to male fleece only. In sheep, preventing the vomeronasal organ (VNO) from functioning does not affect the female responses to male odor suggesting that, unlike in rodents, the accessory olfactory system does not play the major role in the perception of this pheromonal cue. Female responses also seem to depend on previous experience, an effect that is not common for pheromones and renders this model of special interest. The aim of the present report is to summarize our current knowledge concerning the "male effect" and in particular to clarify the respective roles of the two olfactory systems in the processes involved in this effect.

Animals↗
PubMed2004

Advanced assisted reproduction technologies (ART) in goats.

Assisted reproduction technologies (ART) are reviewed with special emphasis on goat genetic improvement programs. Estrous synchronization and artificial insemination are the most commonly used ART worldwide because of their simplicity and excellent cost/benefit, especially when proven sires are used. Multiple ovulation and embryo transfer (MOET) has not become widely used due to its unpredictability. In vitro embryo production using oocytes collected by laparoscopy from valuable donors has the potential to improve the results obtained from MOET and expand its applications (for example, using prepubertal donors). However, the costs and inefficiencies of the system might restrict its use to special situations. Finally, transgenesis and cloning are expected to have a significant impact on the future genetic improvement of livestock. However, because of low efficiencies and high costs, their present use is restricted to applications with high returns such as the production of recombinant proteins of pharmaceutical and biomedical interest.

Animals↗
PubMed1994

Effect of exogenous progesterone on superovulatory response in heifers inseminated with fresh or frozen semen.

Superovulation in cattle normally involves the administration of gonadotrophins at specific times of the oestrous cycle, followed by the induction of luteolysis and insemination with high quality semen. The first aim of this experiment was to examine the effect of supplementary progesterone when used in conjunction with porcine FSH (pFSH) to induce superovulation in heifers. The methods compared were PGF2 alpha given at mid-cycle or a progesterone-releasing intravaginal device (PRID) inserted at different phases of the cycle. The second aim was to determine whether site of insemination or use of fresh or frozen semen affected embryo production. A factorial design was used involving 185 beef heifers. The main factors were (i) synchronization methods (PGF2 alpha or PRID); (ii) semen type (fresh or frozen); (iii) insemination regimens (involving two inseminations and variations in the sites) and number of straws used (one or two) at the second insemination. Eight injections of pFSH were given twice a day for 4 days starting either on days 9, 10 or 11 of the oestrous cycle or on the fourth day after insertion of a PRID. Heifers were checked for oestrus, inseminated twice and embryos were recovered on day 7 of the superovulated cycle. There was no difference between heifers given either PRID or PGF2 alpha in the oestrous response (93% versus 96%), number of ovulations (15.9 +/- 1.11 versus 13.4 +/- 1.06), large follicles (2.5 +/- 0.24 versus 2.3 +/- 0.23) or embryos recovered (9.1 +/- 0.77 versus 9.1 +/- 0.74).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2005

Veterinary clinical application of GnRH--questions of efficacy.

The efficacy of GnRH treatments are reviewed in relation to prevention of embryo mortality, control of follicle development in synchronization programmes using PG as luteolysin, induction of ovulation in post-partum anoestrus and in bovine cystic ovarian disease. It is suggested that in cattle that GnRH is effective in increasing pregnancy rates when given either at the time of insemination (first or repeat) or between days 11 and 14 after insemination. Evidence is also presented for positive effects on pregnancy rates in sheep, mares and sows. Use of GnRH as an integral part of synchronising regimens where it is given 7 days before PG and then again 48-60 h after PG appears to be effective in increasing the synchrony of ovulation in controlled breeding programmes. The main synchronizing effect seems to reside in the second GnRH injection whereas the importance of the first is in prolonging the luteal phase in those cows treated late in the cycle. The published work on the potential use of GnRH to induce ovulation in anovulatory cattle is reviewed. Neither bolus dose injections, pulsatile, continuous infusion, nor controlled release formulations of GnRH, have yet proved effective in inducing fertile ovulations in a predictable or consistent manner. It is suggested that this is due to the variability of follicular status when treatment is initiated. GnRH is commonly used in the treatment of bovine cystic ovarian disease. However, although stimulating ovulation/luteinisation of a new follicle and luteinisation of the cyst, fertility of treated cattle remains very poor and it is suggested that a better understanding of the disease is needed before more effective treatments can be developed.

Animals↗
PubMed2004

The effect of a diet containing excess quickly degradable nitrogen (QDN) on reproductive and metabolic hormonal profiles of lactating dairy cows.

The objective of this experiment was to examine the effects of an excess intake of quickly degradable nitrogen (QDN) on metabolic and reproductive parameters in lactating dairy cows. Twenty-two lactating dairy cows were fed a total mixed ration once daily. The control diet was a typical ration for high producing cows in the UK (CP = 17.5%, ME = 11.8 MJ/kg DM). The cows were randomly divided into two groups, control diet (control; n = 12) and excess QDN diet (QDN; n = 10). The QDN group was fed an additional 250 g of urea per cow per day, from 10 days before insemination (day 0) until the end of the experiment, 17 days after the second insemination. Ten days before insemination, a synchronized oestrus was induced and the cows inseminated twice, 48 and 72 h after synchronization, with commercial frozen semen from a single sire. Ovaries were scanned using B-mode ultrasonography 10 days before insemination and then daily from 3 days before insemination. Eighteen of the cows (9 control and 9 QDN) were sampled more intensively to determine the pulsatile pattern of secretion of luteinizing hormone (LH) and growth hormone (GH). Cows were slaughtered 17 days after insemination, the reproductive tracts recovered and flushed to retrieve embryos. The excess QDN diet resulted in elevated (P < 0.05) plasma urea concentrations 3 days after starting urea feeding and these were maintained until the end of the experiment. However, the excess QDN diet did not significantly affect daily milk production or plasma concentrations of insulin and IGF-I. The QDN treatment did not significantly affect pulsatile patterns of secretion of LH and GH or the number of small (< 0.5 cm diameter) and medium to large follicles (> 0.5 cm diameter). Twenty cows ovulated following synchronization (control 11/12; QDN 9/10). There were no significant differences between the control and the QDN groups in the peak concentrations of oestradiol during the follicular phase or in the post-ovulatory pattern of plasma and milk progesterone secretion. Embryos and/or foetal membranes were recovered from 10 cows (5 control and 5 QDN). The results of the current study show that feeding excess QDN, as urea, for 27 days commencing 10 days before insemination had no effect on reproductive or metabolic hormonal parameters. Ovulation and the formation and function of the post-ovulatory corpus luteum were also unaffected by excess QDN. These data suggest that the harmful effects of excess intakes of QDN on fertility occur after 17 days following ovulation.

Animals↗
PubMed1997

Nonsurgical embryo transfer in the common marmoset monkey.

A technique for nonsurgical embryo transfer in common marmosets was developed. Transfers were either synchronous (ST) or asynchronous (AT). Synchronous transfers (embryo donor and the embryo recipient ovulated on the same day) were performed 5 to 8 days post-ovulation. Asynchronous transfers (embryo donor had ovulated at least 2 days before the embryo recipient) were performed when the recipient was 2 to 4 days post-ovulation (donor was 6 to 8 days post-ovulation). Four pregnancies from nine transfers (44%) were established by AT, and three pregnancies were carried to term. Only 1 of 11 transfers (9%) from ST resulted in a pregnancy, which was lost by Day 40 of gestation. Significantly more infants were born from AT (6 infants from 17 embryos; 35%) than from ST (0 infants from 22 embryos; 0%; p < 0.005). This technique allows experimental analysis of primate postimplantation development and provides a tool for conservation of endangered Callithrichid species.

Animals↗
PubMed2002

Improving reproductive performance in lactating dairy cows by synchronizing ovulation or inducing oestrus.

Lactating crossbred Holstein-Friesian dairy cows (n = 331) were started on an Ovsynch regimen 68 +/- 8.2 days after calving; 200 micrograms GnRH intramuscularly (i.m.) on Days 0 and 9, and 35 mg prostaglandin F2 alpha i.m. on Day 7. Thirty-eight and 31 cows (11.5 and 9.4%, respectively) were in oestrus on Days 0 to 6 and 7 to 8, respectively, and inseminated, and the remainder were fixed-time inseminated (on Day 10). For these three groups, pregnancy rates (60-65 days after breeding) were 31.6, 38.7 and 34.0%, respectively (P = 0.82) and calving rates were 100, 100 and 89.9% (P = 0.23). In a preliminary trial, twelve lactating cows (45 to 60 days postpartum) with inactive ovaries were given 1500 IU eCG i.m.; 10 were in oestrus within 10 days after treatment (and inseminated) and eight of these were pregnant (30 days after breeding). The Ovsynch program resulted in acceptable reproductive performance in cyclic cows and eCG treatment has considerable promise for inducing oestrus in anoestrous cows.

Animals↗
PubMed2001

An attempt to detect oestrus from changes in Fourier transform infrared spectra of milk from dairy heifers.

This study was carried out to investigate if there were systematic changes in milk Fourier transform infrared (FT-IR) spectra relative to stage of the oestrous cycle in cattle. Oestrous cycles of 22 lactating heifers were synchronized with two injections of prostaglandin F2alpha (PGF) administered 11 days apart. The heifers were milked twice daily, and milk samples were collected from each heifer at each milking for a period of 70 days, starting on the day of the second PGF injection. Oestrus was diagnosed by visual detection in conjunction with monitoring rectal temperature. Milk samples were analyzed by FT-IR spectroscopy and the spectra data were analyzed using partial least squares (PLS) methods in relation to time of observed oestrus in heifers. In this investigation, it was not possible to identify reliable changes in milk FT-IR spectra in relation to oestrus on a single heifer basis, though there was a weak correlation between FT-IR spectra and expected time of oestrus when the analysis was carried out across all the heifers.

Animals↗
PubMed1982

Influence of sperm number and seminal plasma on fertility of progestagen-treated sheep in confinement.

Progestagen-impregnated vaginal sponges + PMSG were used to synchronize oestrus in crossbred adult ewes which were inseminated 56 h after sponge removal with 0.5 ml diluted semen containing 400, 200, 100, 50 or 25 x 10(6) spermatozoa per insemination. The diluent was skim milk-citrate or pooled seminal plasma. There was no difference in reproductive performance due to the insemination medium. Fertility (no. of ewes lambing) after insemination of 400 or 200 x 10(6) spermatozoa was 68% and was similar to that observed after natural service at progestagen-induced oestrus. When less than or equal to 100 x 10(6) spermatozoa were inseminated, fertility fell markedly and the number of lambs per ewe inseminated decreased. A decrease in litter size also occurred. The data indicate that insemination of 200 x 10(6) spermatozoa, i.e. less than 10% of the number in a single ram ejaculate, allows normal conception rates in progestagen-treated ewes.

Animals↗
PubMed1990

Temporal relationship between the onset of oestrus, the preovulatory LH surge and ovulation in farmed fallow deer, Dama dama.

A study was conducted to determine the timing of ovulation relative to the onset of oestrus and the preovulatory LH surge in fallow deer. Mature fallow does were randomly allocated to two treatments (N = 10 per treatment) designed to synchronize oestrus on or about 17 May. Does assigned to Group 1 (prostaglandin-induced oestrus) each initially received single intravaginal CIDR [Controlled Internal Drug Release] devices for 13 days followed by an i.m. injection of 750 mg cloprostenol on Day 12 (15 May) of the subsequent luteal cycle. Does assigned to Group 2 (progesterone-induced oestrus) each received CIDR devices for 13 days, with withdrawal occurring on 15 May. All does were run with crayon-harnessed bucks (10:1 ratio) from the start of synchronization (18:00 h 15 May). Ten does (5 per group) were blood sampled via indwelling jugular cannulae every 2 h for 72 h from cloprostenol injection or CIDR device withdrawal and the plasma was analysed for concentrations of progesterone and LH by radioimmunoassay. Does within each treatment were randomly allocated to an ovarian examination time of 12, 16, 20 or 24 h after the onset of oestrus. Laparoscopy was repeated at 12-h intervals until ovulation was recorded. The ovaries of does failing to exhibit oestrus were examined 72 and 86 h after cloprostenol injection or CIDR device withdrawal. A total of 17 does were observed to exhibit oestrus at a mean (+/- s.e.m.) interval from treatment of 44.6 +/- 3.6 h for Group 1 (N = 9) and 34.1 +/- 2.5 h for Group 2 (N = 8).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2001

Hormonal characterization of the reproductive cycle and pregnancy in the female Mohor gazelle (Gazella dama mhorr).

The oestrous cycles of seven captive Mohor Gazelles (Gazella dama mhorr) were investigated. Hormone profiles obtained from faecal samples collected each day from cyclic females indicated that the mean duration of the oestrous cycle was 18.62 +/- 0.26 days (range 16-22 days; n = 37 oestrous cycles). No inter-individual differences in the concentration of faecal progestagen metabolites excreted were observed, but mean faecal oestrogen excretion during both the luteal and inter-luteal phases of the oestrous cycle varied among females (P < 0.001 and P = 0.070, respectively). Oestrous cycles were synchronized using controlled internal drug release (CIDR) devices, before natural mating with an intact male. Concentrations of faecal progestagen metabolites remained approximately constant for the first 10 weeks of gestation (mean +/- SEM = 4048 +/- 407 ng g(-1) faeces), before increasing to a mean of 23 556 +/- 1176 ng g(-1) faeces. Two of seven female gazelles conceived immediately after removal of the CIDR device, a similar proportion to that conceived at the postpartum oestrus under natural conditions. Life history data for these individuals indicated that the mean time to conception in female gazelles is positively correlated with peak values in the ratio of excreted oestrogen : progestagen during the inter-luteal period of their oestrous cycles (R(2) = 0.58; P < 0.05). This finding indicates that interactions between steroid production and metabolism may influence the likelihood of conception occurring in this species.

Animals↗
PubMed2006

Role of the olfactory systems and importance of learning in the ewes' response to rams or their odors.

In sheep, exposure of seasonally anestrous females to the male or its fleece results in activation of luteinizing hormone (LH) secretion and synchronized ovulation. The study of the neural pathways involved in this phenomenon, commonly named "male effect", show that the main olfactory system plays a critical role in the detection and the integration of the male odor. The accessory olfactory system participates in the perception of the ram odor but does not seem necessary for the endocrine response. According to the hypothesis that the neuroanatomical differences between the two olfactory systems could be associated with different functional roles, we investigated the importance of sexual experience and learning processes in the male effect. Our results showed that female responses depend on previous sexual experience. We also demonstrated that the LH response to male odor could result from an associative learning process. The aim of the present report was to summarize our current knowledge concerning the "male effect" and in particular to clarify the role of sexual experience and learning in the processes involved in this effect.

Animals↗