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PubMed1976

[Results obtained after synchronisation of oestrus by prostaglandins in dairy cows (author's transl)].

Twenty-five mg. of PGF2 alpha were injected in forty-three lactating cows and eighteen young heifers at ten-day intervals to produce synchronisation of oestrus. Only twenty-four lactating cows (58 per cent) and fifteen young heifers (83 per cent) came on oestrus with two, three or four days after the second injection of prostaglandin. Within eighty hours after the second injection, all animals were inseminated with semen of good quality. This resulted in pregnancy in eight (19 per cent) dairy cows and ten (56 per cent) young heifers. Rectal examination at the time of the second injection revealed a number of changes in the lactating cows. There was undue follicular activity, follicular cysts were observed in several cases and a corpus luteum measuring more than 15 mm. in diameter was not present in 25 per cent of the animals. In addition, twenty-seven cows were synchronised by injection of 0.5 mg. of Estrumate (a synthetic prostaglandin analogue) during the puerperium. Injections were made twenty and thirty days post partum. Eighteen cows (67 per cent) came on oestrus within two, three or four days after the second injection. Insemination which was carried out during oestrus, resulted in pregnancy in five cows. Rectal examination did not reveal any abnormalities in these animals.

Animals↗
PubMed1999

Regulation of follicle waves to maximize fertility in cattle.

Cattle have recurrent follicular waves every 7-10 days in most physiological situations; an FSH increase is associated with emergence of the wave and LH pulse frequency determines the fate of the dominant follicle. To control oestrus with hormones it is necessary to ensure that either induced corpus luteum regression or the termination of a progestogen treatment coincides with the selection of the dominant follicle during the wave, to give a precise onset of oestrus and high fertility. The exogenous administration of progesterone or progestagen blocks the normal turnover of the dominant follicle once the corpus luteum regresses. Thus, the effects of duration of dominance of the preovulatory follicle on onset of oestrus and fertility were examined. The variation in onset of oestrus was reduced but occurred 5-9 h later after 4 versus 8 days of dominance; pregnancy rate was also affected with dominance periods of 2-4, 4-8 and > 10 days resulting in 0, 10-15% or 20-50% reduction in pregnancy rates, respectively. The necessity for short duration of dominance of the preovulatory follicle means that to ensure high fertility the follicular wave needs to be regulated when using hormones to control oestrus. Two approaches were examined, namely the use of GnRH or oestradiol at time of progesterone intravaginal releasing device insertion. The effect of 250 micrograms of synthetic GnRH on the fate of an existing follicle wave was to ovulate the dominant follicle (20/20 cows) and a new wave emerged 1.6 +/- 0.3 days later; however, there was no effect of GnRH on the wave if administered before dominant follicle selection. The effect of oestradiol concentrations on suppression of FSH in ovariectomized heifers showed that increasing oestradiol to 10-15 pg ml-1 caused a 37 +/- 6.9% decrease in FSH for 24 h, with a subsequent increase to pretreatment values by 57 +/- 13 h. In cyclic heifers, increasing oestradiol to > 10 pg ml-1 in conjunction with progesterone treatment at emergence of the first wave of the cycle affected the current follicle wave by either preventing dominant follicle selection or decreasing diameter of the dominant follicle, without consistently affecting the interval to new wave emergence. Increase of oestradiol after dominance, however, delayed new wave emergence by 2-5 days. A better understanding of the hormonal control of follicle waves will lead to development of improved hormonal regimens to control oestrus sufficiently to give high pregnancy rates to a single AI without recourse to detection of oestrus.

Animals↗
PubMed1999

Endocrine and reproductive responses of male and female cattle to agonists of gonadotrophin-releasing hormone.

The pituitary response in cattle to treatment with GnRH agonist has two phases. In the acute phase secretion of LH is increased, while the chronic phase is characterized by a downregulation of GnRH receptors and insensitivity of gonadotrophs to natural sequence GnRH. After long-term treatment with GnRH agonist, cattle do not have pulsatile secretion of LH but maintain basal LH. This is associated with reduced pituitary contents of LH, LH mRNA, FSH and FSH mRNA. Long-term treatment of bulls with GnRH agonist results in an increase in testicular LH receptors and high plasma testosterone. Heifers treated with a GnRH agonist from early in the oestrous cycle develop a larger corpus luteum and secrete more progesterone. Increased steroidogenesis is reflected in increased steroid acute regulatory (StAR) protein and steroidogenic enzymes in the testes and corpus luteum. GnRH agonists have potential as novel strategies for reproductive management in cattle. A GnRH agonist bioimplant was recently used to block the LH surge after FSH stimulation of follicle growth in heifers. Ovulation was induced by injection of LH, and heifers were inseminated relative to the LH injection. This GnRH agonist-LH protocol provides a model for studying the gonadotrophin requirements for follicular growth and oocyte maturation in cattle, and will enable controlled in vivo maturation of oocytes before recovery for in vitro procedures.

Animals↗
PubMed1999

Reproduction in water buffalo: comparative aspects and implications for management.

The domestic buffalo occupies an important niche in many ecologically disadvantaged agricultural systems, providing milk, meat and draught power. Although buffalo can adapt to harsh environments and live on low quality forage, their reproductive efficiency is often compromised by such conditions. Climatic stress depresses ovarian cyclicity, oestrous expression and conception rates. Poor nutrition, usually related to seasonal fluctuations in availability and quality of feed, delays puberty and increases the duration of postpartum anoestrus. Management factors such as the system of grazing (free, tethered or none) and sucking by calves (restricted or ad libitum) also modulate reproductive functions. Finally, the skills and capabilities of farmers as well as the quality of support services such as artificial insemination and disease control also influence fertility. The relative importance of these factors vary greatly depending on ecological conditions and production systems. Improvement of reproductive efficiency therefore requires the identification of specific limiting factors under a given situation and the development and field testing of strategies for improvements and interventions that are sustainable with available local resources. The application of modern reproductive technologies in buffaloes requires an appreciation of their biology and reproductive physiology as well as the potentials and limitations under each specific production system.

Animal Husbandry↗
PubMed2000

Expression of mRNA encoding insulin-like growth factors I and II and the type 1 IGF receptor in the bovine corpus luteum at defined stages of the oestrous cycle.

Previous studies have implicated insulin-like growth factors I and II (IGF-I and -II), in the regulation of ovarian function. The present study investigated the localization of mRNA encoding IGF-I and -II and the type 1 IGF receptor using in situ hybridization to determine further the roles of the IGFs within the bovine corpus luteum at precise stages of the oestrous cycle. Luteal expression of mRNA encoding IGF-I and -II and the type 1 IGF receptor was detected throughout the oestrous cycle. The expression of IGF-I mRNAvaried significantly during the oestrous cycle. IGF-I mRNA concentrations were significantly higher on day 15 than on day 10, and IGF-I mRNA in the regressing corpus luteum at 48 h after administration of exogenous prostaglandin was significantly greater than in the early or mid-luteal phase (days 5 and 10). In contrast, there was no significant effect of day of the oestrous cycle on expression of mRNA for IGF-II and the type 1 IGF receptor in the corpus luteum. Expression of IGF-II mRNA was localized to a subset of steroidogenic luteal cells and was also associated with cells of the luteal vasculature. mRNA encoding the type 1 IGF receptor was widely expressed in a pattern indicative of expression in large and small luteal cells. These data demonstrate that the bovine corpus luteum is a site of IGF production and reception throughout the luteal phase. Furthermore, this study highlights the potential of IGF-II in addition to IGF-I in the autocrine and paracrine regulation of luteal function.

Analysis of Variance↗
PubMed1975

[Combined artificial insemination and synchronisation of oestrus in sheep (author's transl)].

A brief introduction is followed by a description of artificial insemination in sheep, based on a review of the literature. A number of experiments are then discussed, which were mainly concerned with the possibilities arising when artificial insemination and synchronisation of oestrus are combined. It is concluded that satisfactory results (70-80 per cent pregnant) may be obtained, provided a large number of live spermatozoa (500 x 10(6)) are inseminated at the right time.

Animals↗
PubMed2002

Fertility rate evaluation by laparoscopic approach in the experimental animal.

PURPOSE OF INVESTIGATION: The aim of the present study was to evaluate the effect of laparoscopic insemination (LAP) and natural mating (NM) on fertility rate in experimental animal (Ovis Aries Comisana) during the month of June. METHODS: For the experiment, 97 ewes were used. Laparoscopic insemination was performed with the frozen semen of three different Romanov rams: Laparoscopic insemination I (n = 24); Laparoscopic insemination 2 (n = 26); and laparoscopic insemination 3 (n = 28), and natural mating was performed with two different Ovis Aries Comisana rams with proven fertility: Natural mating I (n = 10); Natural mating 2 (n = 9). Estrus was synchronized with fluorogestone acetate impregnated intravaginal sponges (40 mg, 14 days). Pregnant mare serum gonadotrophin (Folligon, Intervet International) at a dose of 400 UI was given intramuscularly at sponge removal. Artificial insemination was carried out 60 hours after the removal of the sponges in the laparoscopic insemination groups. RESULTS: The mean pregnancy rate at ecographic diagnosis performed at about 36 days from sponge removal for the laparoscopic insemination and natural mating groups were respectively, 62.8% and 78.9% with no significant difference. CONCLUSION: The mean fertility rates for the LAP and NM groups were 56.0 and 73.4, respectively, with no significant difference.

Animals↗
PubMed2002

Effects of oestradiol and progesterone on secretion of gonadotrophins and health of first wave follicles during the oestrous cycle of beef heifers.

Antral follicle development in cattle is initially FSH dependent and then LH dependent. The aim of the present study was to determine the effects of oestradiol- and progesterone-induced suppression of FSH and LH on growth and differentiation of first wave follicles. Cyclic heifers (n = 45, n = 6-10 per group) received the following i.m. injections or treatments beginning 30 h after oestrus: (i) saline (controls); (ii) 0.75 mg oestradiol benzoate (ODB); (iii) insertion of a progesterone-releasing intravaginal device (PRID) for 42 h (progesterone); (iv) 0.75 mg oestradiol benzoate plus PRID (ODB plus progesterone); (v) 0.75 mg ODB plus injection of 1 mg Ovagen(TM) at 33, 39 and 45 h after onset of oestrus (ODB plus FSH). In Expt 1, follicle development was monitored by ovarian ultrasonography once a day. In Expt 2, heifers were ovariectomized. Emergence of the first follicle wave and dominant follicle selection were delayed in ODB plus progesterone-treated heifers compared with controls. Interval to nadir FSH concentration was shorter in ODB-, progesterone- and ODB plus progesterone-treated heifers compared with controls. Frequency of LH pulses was unaffected in ODB- or ODB plus FSH-treated heifers, decreased in progesterone-treated heifers and further decreased in ODB plus progesterone-treated heifers. Intrafollicular oestradiol concentrations were lower in the largest follicle from ODB plus progesterone-treated heifers compared with control (66 h) heifers, but follicle diameter and concentrations of insulin-like growth factor binding proteins (IGFBPs) and inhibin forms were unaffected. Treatment with ODB decreased follicular oestradiol concentration in smaller follicles in the cohort. It is concluded that growing cohort follicles are uniformly responsive to increased FSH concentration but differentially responsive to suppressed FSH and LH release, which is consistent with an LH-mediated survival advantage of the largest follicle in the cohort before cessation of the growth of remaining follicles in the cohort occurs.

Animals↗
PubMed1976

[Use of prostaglandins in suboestrus cows (author's transl)].

One hundred and fifty lactating, suboestrus cows with palpable corpora lutea from twenty herds were treated by intramuscular injection of prostaglandins. The expected date of oestrus was predicted in 150 suboestrous controls of the same herds on the basis of ovarian findings. The average interval between treatment and insemination was 8.8 days in the prostaglandin-treated and 17.6 days in the control group. The interval between treatment and insemination was shorter than eight days in 74 per cent of the prostaglandin-treated cows. Pregnancy rates in the treatment and control groups were 56 per cent and 58 per cent respectively.

Animals↗
PubMed1992

Influence of hormonal secretion and fertility in merino mutton sheep by exogenous pheromone application during the breeding season.

The effect of a ram-pheromome extracted from the wool of insemination rams with excellent libido sexualis of the merino mutton sheep breed was examined with respect to the hormonal secretion and fertility of adult ewes during the breeding season. A control group (untreated animals) was at disposal for every experiment. There were significant differences between the ewes treated with pheromone and the controls in the course of the preovulatory LH wave and the oestradiol concentration of the oestrus sheep at the beginning of the breeding season. The ovulation in ewes after prostaglandin application was stimulated by pheromone applications. The regime practised in the experiment on pherome application had a positive influence on the conception rate of the inseminated ewes and resulted in a significant increase of the lambing results (lambs/birth).

Aerosols↗
PubMed2004

Luteolysis, onset of estrus, and ovulation in Holstein heifers given prostaglandin F2alpha concurrent with, or 24 hours prior to, removal of an intravaginal, progesterone-releasing device.

The objective was to determine the effects of giving prostaglandin F2alpha (PGF) concurrent with, or 24 h before, removal of an intravaginal, progesterone-releasing (controlled internal drug release [CIDR]) device, on luteolysis, the synchrony of estrus and ovulation. Eighteen postpubertal Holstein heifers were given a CIDR and 100 microg gonadotropin releasing hormone (GnRH) and equally allocated to 3 groups. The PGF was given concurrently with CIDR removal after 7 or 8 d (groups D7/D7 and D8/D8, respectively) or given 1-d before removal of CIDR after 8 d (group D7/D8). There was no difference (P > 0.75) among groups in the intervals (h) from CIDR removal to onset of standing estrus and to ovulation (49.3 h+/-6.2 h and 77.5 h+/-9.0 h, respectively; least squares means+/-standard error of means). We also determined if stage of the estrus cycle influenced the synchrony of estrus or ovulation. In heifers in metestrus at CIDR insertion (versus those at estrus or diestrus), intervals from CIDR removal to estrus and to ovulation were longer by 33.4 h (P < 0.05) and 38.5 h (P = 0.01), respectively. However, the interval from standing estrus to ovulation was not affected. Giving PGF concurrent with CIDR removal did not affect luteal regression, the synchrony of estrus, and ovulation; but heifers in metestrus at the initiation of treatment had longer intervals from CIDR removal to estrus and ovulation.

Animals↗
PubMed2005

The effect of intramuscular injections of boar pheromone 5alpha-androstenol on the hormonal regulation of the estrous cycle in hypoosmatic gilts.

Until 1999 it was accepted that pheromones act exclusively by stimulating the dendritic receptors present in olfactory epithelium. Cycling gilts with an experimentally-disrupted neural olfactory pathway were used to test the hypothesis that boar pheromone 5alpha-androstenol may affect the secretion of hormones involved in the regulation of the estrous cycle by the humoral pathway. On day 12 of the estrous cycle the nasal cavity of gilts (n=15) was irrigated with zink sulfate solution. From day 16 to 20, the experimental group (n=10) was injected intramuscularly with 5alpha-androstenol (20 microg) twice a day. Blood samples were collected from the jugular vein at 4 h intervals on days 17-21 to estimate plasma concentration of LH, oxytocin, estradiol-17beta, testosterone and progesterone. The experimental group displayed a significantly lower mean concentration of LH than the control animals (P<0.0001). The decrease in concentration of LH was accompanied by the reduction of oxytocin (P<0.001), estradiol-17beta (P<0.001) and testosterone (P<0.01) secretion. These results demonstrated that 5alpha-androstenol influenced hormonal regulation by humoral pathway and might be considered to be the priming pheromone in gilts.

Androstenols↗