Control Of Estrus Research Articles

Control of oestrus and ovulation in beef cattle in central Australia

Hormonal treatments were used to control the time of oestrus and ovulation in cattle in central Australia and to observe the efficacy of several luteolytic regimes under these conditions. All animals received intravaginal progesterone (PRID) for 7-14 days with 10 mg oestradiol benzoate (ODB) in a gelatin capsule attached to each PRID and 750 i.u. pregnant mare serum gonadotrophin (PMSG) by intramuscular injection 24 h before PRID removal. In addition half the animals received 25 mg dinoprost (PGF2�) at either 0 or 24 h before PRID removal. Differences in luteolytic treatments had no significant effects on calving rates to a single fixed-time insemination of acyclic animals (52%) or cyclic animals treated with PRID for 14 days (48%). In contrast the calving rate of cyclic animals treated with PRID for 7 days was depressed in all groups except that which received PGF2, 24 h before PRID removal (18 v. 56%, P<0.025). Independent of treatment effects lactating cows had a higher calving rate than non-lacting animals (50 v. 35%, 0.05 <P<0.10). These results indicate the importance of using effective luteolytic treatments in cyclic animals where short PRID treatments are used. The most appropriate regimes for use in extensive environments would appear to be based on a 14-day PRID treatment which eliminates the need for an injection of PGF2� before PRID removal while still producing acceptable fertility.

Automatic health and oestrus control in dairy husbandry through computer aided systems

Disturbances in health and reproduction are leading to immense economic losses in dairy husbandry. Improvements are possible by using computer and sensor technology in animal monitoring and herd management. The development and usefulness of sensors for automatic health and oestrus monitoring, integrated into a “computer aided management system”, are presented in this paper.

Hypothalamic control of ovulation and behavioral estrus in the cat

The estrous cat ordinarily ovulates only after a complex mating behavior pattern which involves an elaborate afterreaction. The present experiments were designed to determine whether identical or separate hypothalamic areas control mating behavior and the release of an ovulatory surge of pituitary gonadotropin. With stereotaxic methods under chloralose anesthesia the hypothalamic of naturally estrous or estrogen-gonadotropin-primed queens were stimulated bilaterally in one of the following regions: medial basal hypothalamus including the premamillary area (MBH) and the anterior hypothalamus including both medial and lateral divisions (AH, MAH, LAH). At the end of the stimulation period (5 V, 30 c/s, 5 ms duration, 30 s on and 30 s off for 30 min) bilateral anodal electrolytic lytic lesions were made at the stimulation sites (3 mA for 30 s) with the central tips of the bipolar electrodes. Characteristically, ovulation was induced by stimulating the MBH but not the AH. Furthermore, the MBH lesions usually caused ovarian atrophy which led to anestrus, but the cats mated normally if supplied with exogenous estrogen. The anterior lesions left the ovaries in good trophic condion, and they could be ovulated by stimulating the MBH. However, the cats with anterior hypothalamic lesions in either the medial or lateral position repeatedly refused to accept the male even primed with exogenous estrogen. The results from these combined stimulation and lesion experiments in the female cat indicate that a hypothalamic sex behavioral area lies rostral to and discrete from a tubero-mamillary area controlling the release of pituitary gonadotropin.

Differences in the rabbit uterine response to progesterone as influenced by growth hormone or prolactin.

The direct effect of growth hormone (GH) on the uterine response to progesterone was tested by using ovariectomized rabbits (at least 12 weeks) treated with GH; GH + progesterone; or progesterone alone. These results were compared with the effect of prolactin or prolactin + progesterone on the uterus. Prolactin treatment produced an increase (P less than 0.01) in the endometrial surface area and restored cytosolic oestrogen and progesterone receptor concentrations to oestrous control values. The sequential treatment of does with prolactin + progesterone stimulated uteroglobin production to a concentration equal to that found in intact rabbits on Day 5 of pregnancy. In contrast, GH treatment had no effect on endometrial surface area, produced an increase in the concentration of cytosolic oestrogen receptor but did not produce an increase in the concentration of progesterone receptor. The sequential treatment of does with GH + progesterone failed to stimulate uteroglobin secretion above control (progesterone alone) values. It is concluded that the action of prolactin in the rabbit uterus is no generally somatogenic; rather, prolactin increases the concentration of progesterone receptor and thereby enhances the uterine response to progesterone.

Effect of immunization against progesterone on oestrus, cycle length, ovulation rate, luteal regression and LH secretion in the ewe.

The effects of active immunization against progesterone on reproductive activity were studied in Merino ewes. Immunization against progesterone caused a shortening (P less than 0.01) of the interval between ovulations from 17-18 days (controls) to between 6 and 10 days (immunized group); this was associated with a corresponding reduction in the interval between LH surges. The immunized ewes also had higher (P less than 0.05) ovulation rates (1.72) than controls (1.25) and exhibited a reduced (P less than 0.01) incidence of oestrus (26% v. 95%). Many immunized ewes continued to ovulate despite the persistence of corpora lutea from earlier ovulations which led to an accumulation on the ovaries of many corpora lutea of different ages. The frequency of LH pulses in ewes immunized against progesterone (1.8 +/- 0.2 pulses/4 h) was significantly (P less than 0.001) higher than that of control ewes (0.3 +/- 0.1 pulses/4 h). This study highlights the importance of progesterone in the control of oestrus, ovulation, ovulation rate, luteal regression and the secretion of LH in the ewe.

Reproductive efficiency and feasability of oestrus control prior to artificial insemination in crossbred bovine females in India

Reproductive efficiency and feasability of oestrus control prior to artificial insemination in crossbred bovine females in India

Control of ovulation, vaginal estrus, and behavioral receptivity in voles (Microtus)

Rodents of the genus Microtus provide an excellent focus for the study of the effects of environmental and behavioral influences on reproductive physiology. Despite some early reports, there is little definitive evidence of truly spontaneous ovulation in Microtus. Stimuli from copulation with males appear capable of triggering ovulation in all species: the requisite amount of stimulation for ovulation and a functional luteal phase varies with the species. In addition, however, a certain percentage of the females of some, but not all, species ovulate when placed in proximity to males when copulation is prevented. There are few reports of regular cycles of cell types in the vaginal smears of Microtus females; the relative preponderance of cornified, nucleated, and leukocytic cells varies with species and conditions. Behavioral receptivity is not invariably correlated with smear type. The complexity of environment-behavior relationships in different species suggests the need for a more comprehensive classification schema for systems of female reproductive physiology and a study of their adaptive significance.

The control of undesirable behaviour in male dogs using megestrol acetate

ABSTRACTMegestrol acetate is widely used for oestrus control in the bitch and cat. Field reports suggested that the compound may also be used successfully in male animals for the control of undesirable behaviour. Previous surveys have indicated that the following signs or combinations of signs presented a real problem to the owners of male dogs: aggression (dominant or fear‐induced), mounting, territory marking by urination, roaming, excitability and destructiveness. In the present study the efficacy of megestrol acetate was assessed using a defined dosage regime in 163 dogs exhibiting one or more of the above signs. Seventy‐five per cent of dogs improved during treatment, and 64 per cent of dogs assessed three months after the end of treatment had maintained their improvement. The incidence of side effects was found to be low.

A comparison of cloprostenol and dinoprost tromethamine for the control of estrus in bovine embryo transfer

Cloprostenol (500 ug) and dinoprost tromethamine (65 mg in three doses) were similarly effective in controlling estrus during superovulation with FSH-P. Estrous response was 97.3% and 99.5%, respectively. Embryo production was the same measured in terms of the number transferable, total, percent transferable and number of ova cleaved. The percent cleaved was higher in the dinoprost group (75.5%) than the cloprostenol group (67.4%, P=0.019). The number (P=0.04) and proportions (P=0.009) of degenerate embryos were higher in the dinoprost group as compared to the cloprostenol group (2.9 and 27.9% vs 2.2 and 20.5%).

Field Trials in Fixed Time Sheep A.I. in Ireland

Studies reported from this laboratory in the mid seventies showed that it was possible to achieve a conception rate of 73% to a single fixed-time insemination in the autumn breeding season in ewes previously treated with intravaginal progestagen and pregnant mare serum gonadotrophin (PMSG). The present work was aimed principally at an examination of the AI technique in commercial flocks when applied over a period of three years (1979–81) and when applied in sheep of different breeds (Galways and Suffolk-cross).In the course of three successive breeding seasons, a total of 2,704 cyclic ewes in 87 farm flocks were bred to Texel or Suffolk rams by A.I. using a sperm dose of 400 million in 0.2 ml volume of a skim milk diluent; only semen samples showing a wave motion rating of 3.5 or higher were used and accepted samples were pooled. A further 525 ewes in 20 farm flocks were bred by natural service (ratio of 1 ram: 10 ewes) in one area covered by the AI work. Control of oestrus and ovulation was achieved by a 12-day treatment using commercially available progestagen sponges (Chronogest, Intervet. Ltd.; Veramix, Upjohn Ltd.); at sponge withdrawal a single intramuscular injection of 500 i.u. PMSG (Intervet. Ltd.) was administered.

Control of oestrus in ewe lambs and yearling ewes with medroxyprogesterone acetate and fluorogestone acetate

Two experiments were conducted in a large flock of Berrichon purebred and Romanov × Berrichon F 1 crossbred ewes. In experiment 1, 157 ewe lambs were placed in six groups according to season of mating and maternal breed. Within each group equal numbers of females were treated with either medroxyprogesterone acetate (MAP) or fluorogestone acetate (FGA)-impregnated sponges for 14 days; dosage of PMSG at the time of sponge removal was 500 and 300 I.U. respectively for pure and crossbred. In experiment 2, 111 dry yearling ewes of the Berrichon breed were involved, of which 35, 51 and 25 had either a short lambing to treatment interval (approximately 3 months), a long lambing to treatment interval (approximately 6 months), or were primiparous or nulliparous. They were also treated either with MAP or FGA. The conception rates were extremely high (overall near 86%) in ewe lambs and not significantly affected by seasons or breeds or treatments. Prolificacy and number of lambs per ewe mated were higher in the F 1 crossbred group than in pure Berrichon females (respectively 1.91 vs. 1.34 lambs/mated ewe). No significant difference between the two progestagens could be observed for any of the productivity criteria. Fertility was equally satisfactory in yearlings (overall near 85%) irrespective of the interval between lambing and mating. However, the fertility of the nulliparous ewes (those that failed to conceive as ewe lambs) was significantly lower (72%). The number of lambs per ewe mated was 1.78 in yearlings with a 6-month interval from lambing to mating but was not significantly different from the numbers recorded in the other two groups (1.37 and 1.36). As in experiment 1, there was no difference in the results obtained after either of the two progestagen treatments. In conclusion, progestagen treatment has been shown in both ewe lambs and yearlings to be a very effective means of increasing lamb production in large flocks. This was achieved in ewe lambs regardless of the season and, in dry yearling ewes, regardless of the interval from lambing to mating in the anoestrous season.

Control of estrus and pregnancy in dairy heifers treated with Syncro-Mate-B

Control of estrus in dairy heifers with Syncro-Mate-B was evaluated in five experiments with a total of 393 Holstein heifers. Estradiol-17β at implant removal or gonadotropin releasing hormone 40 hr after implant removal did not cause any beneficial effect on fertility. In heifers implanted on selected days of the estrous cycle, 88.3% of heifers treated with SMB only were in estrus within 5 days of implant removal and fertility was not significantly different from that of control heifers. In heifers implanted at random stages of the estrous cycle, estrus occurred within 5 days of implant removal in 88.7% of 159 SMB treated heifers. First service conception rates (heifers pregnant of heifers inseminated) and pregnancy rates (heifers pregnant of heifers assigned) were 72.7% and 60.8% for heifers inseminated 8 to 16 hr after estrus within 5 days of implant removal, 55.0% and 55.0% for heifers inseminated 48 hr after implant removal without regard to estrus and 71.6% and 67.1% for control heifers inseminated over a 25 day period.

Oestrus control in bitches with chlormadinone acetate

ABSTRACTA clinical study of oestrus control in bitches with chlormadinone acetate (CMA) is reported. The commercial 1‐0 per cent crystalline suspension of CMA was injected subcutaneously at a dose of 3 mg/kg, or somewhat lower for the largest animals. Treatment was initiated always in anoestrus and was repeated twice annually for as long as requested. The longest, 9‐year, period of anoestrus was achieved by twenty repeated treatments. A total of 2,471 treatments were given to 568 bitches (an average of 4‐4 treatments per bitch) during a period of over 10 years, with an efficacy of 98 per cent. The incidence of false pregnancy, uterine inflammatory disorders and mammary nodules in the treated group were compared to those of an age‐related control group of 487 bitches that did not receive hormonal treatment. A lower incidence of false pregnancy and the two clinical entities was observed in the group of treated animals. It is concluded that CMA can be used safely and reliably for oestrus control in bitches and is therefore, an appropriate alternative for ovariohysterectomy.

Ovariectomy as a means of abortion and control of estrus in feedlot heifers

Three hundred and six heifers were randomly assigned to treatment groups in a three by six factorial design. Treatments were ovariectomy, melengestrol acetate (MGA), manual abortion, intramuscular estradiol cypionate (ECP) or Prostaglandin F2α and untreated controls. The Average Daily Gain (ADG) of the Ovariectomized Group was less (p < .01) during the first 24 days and not different (p > .05) for the total feeding period. Feed intake of the Ovariectomized Group was less (p < .05) than Manual Abortion, Prostaglandin or Control Groups during the first 24 days but essentially the same (p > .05) for the total period. The Prostaglandin Group required fewer days to reach slaughter condition than the Ovariectomy or MGA Groups (p < .05). The only difference in the cost/benefit analysis was in the direct cost of the treatments. Factors other than the various treatments interrupted many pregnancies. The effects of treatments varied with 100% of pregnancies terminated only in the Prostaglandin F2α Group.

Pharmacologic Control of Estrus in the Bitch and Queen

Pharmacologic Control of Estrus in the Bitch and Queen

Estrus and ovulation in gilts fed a synthetic progestogen

A synthetic progestogen, allyl trenbolone (AT), was fed to sexually mature gilts to determine the effective doses for the control of estrus and ovulation. Gilts were assigned to a control group and 5 treatment groups receiving 10.0, 12.5, 15.0, 17.5 or 20.0 mg of AT mixed in .45 kg of feed/head/day for 18 consecutive days. Ovarian morphology was determined by laparotomy following estrus or at 10 days post-treatment. AT suppressed estrus in all gilts during treatment. Estrus was effectively synchronized in treated gilts. The average interval from withdrawal of progestogen treatment to estrus was 4.5 days for 48 of 50 treated gilts that were in estrus within 10 days after treatment. The average ovulation rate in treated gilts was similar to control gilts. No detrimental side effects, due to treatment, were observed with the possible exception of a slight increase in the incidence of cystic follicles.

Oestrus control and the incidence of mammary nodules in bitches, a clinical study with two progestogens.

The incidence, size and location of mammary nodules were established in 10 practices in The Netherlands by the clinical examination of bitches in which oestrus was controlled with proligestone (P), 331 animals, or medroxyprogesterone acetate (MAP), 341 animals and in 339 animals never medicated with such compounds. In comparison with the unmedicated control and the P-medicated animals of comparable age the incidence of mammary nodules of all sizes was significantly increased in the MAP-medicated animals. There was no significant difference in nodule incidence between the P-medicated animals and the control animals. Based on the assumption that nodules above a certain size are most likely tumours, these results indicate that oestrus control with MAP stimulates tumour development even in animals medicated for less than four years. The practical value of the reported differences, especially in relation to the subsequent requirement for surgical removal of tumours in bitches, medicated for oestrus control, is discussed.

Control of estrus in gilts with a progestogen.

Two trials were conducted to evaluate the effectiveness of a synthetic progestogen, allyl trenbolone, for control of estrus and ovulation in gilts. Estrus was effectively synchronized with 33 of 38 gilts exhibiting estrus 2 to 7 days after last progestogen feeding. There was no effect on fertilization rate in gilts free of ovarian abnormalities. Ovulation rate was higher in gilts fed the progestogen in both Trial 1 (P less than .01) and Trial 2 (P less than .10). Progestogen treatment caused an increase (P less than .01) in the incidence of cystic follicles which resulted in a decrease (P less than .01) in conception rate in Trial 1.

Preventive medicine for cattle

The third annual conference under this general theme was held by the British Cattle Veterinary Association at the University of Nottingham School of Agriculture, Sutton Bonington. Items were included under various subjects such as mastitis control, oestrous control, calf management and disease, computer utilisation, minerals, beef preventive medicine and parasites. About one hundred and thirty veterinary surgeons attended each day and they were augmented by about fifty farmers on the second day.

Oestrus control and early pregnancy diagnosis in the swamp buffalo: Comparison of enzymeimmunoassay and radioummunoassay for plasma progesterone

A preliminary study has been undertaken, in order to investigate the suitability of a progesterone assay in blood plasma for oestrus control and pregnancy diagnosis in the swamp buffalo ( Bubalus bubalis ). Progesterone was determined both by radioimmunoassay (RIA) and by enzymeimmunoassay (EIA). Values obtained by EIA were considerably lower than values obtained by RIA. This may be partly due to the fact that only RIA values were corrected for procedural losses. Blood samples were taken on day 1 (= day of insemination) and on days 24, 27 and 30 after insemination (p.i.). Additional samples from pregnant animals were taken around day 170 p.i.. Normal progesterone values during oestrus were lower than 0.5 ng/ml, and generally the same low values were found in case of non-pregnancy at days 24, 27 and 30 p.i.. Pregnant animals showed in all cases progesterone concentrations higher than 0.5 ng/ml at days 24, 27 and 30, as well as around day 170 p.i.. These preliminary results indicate that the analysis of progesterone in plasma may be suitable for fertility control in the swamp buffalo. Furthermore we suggest that a modified EIA method can be used as a simple and rapid oestrus detection test under field conditions.