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PubMed1993

[Estrus induction in bitches by the administration of PMSG and HCG].

Oestrus was induced in 14 anoestrous beagle bitches by intramuscular injection of PMSG in a dose of 20 I.U./kg once daily on five consecutive days, followed by an additional single i.m. injection of 500 I.U. of hCG on the fifth day. The day on which the first injection was given was counted as Day 1 of the experiment. Between the fourth and sixth day, the bitches began to attract the attention of male dogs and between Days 9 and 15 all bitches came in heat. Matings occurred on two to ten occasions, and six of the bitches conceived. The maximum concentrations of oestradiol in the plasma were in most cases reached on Days 10 or 12 and ranged from 42 to 195 pg/ml. In all cases progesterone concentrations rose sharply between Days 10 and 20. The incretion phase of the corpora lutea was noticeably brief in the non-gravid bitches; in five of these eight bitches, anoestrous values below 2 ng/ml were already obtained before the 65th day of the experiment. These results indicate that the administration of PMSG on five consecutive days supplemented by a final single injection of hCG stimulates the ovaries adequately to afford good prospects of conception. The concentrations of ovarian hormones are discussed.

Animals↗
PubMed1997

Determination of concentration of albendazole sulfoxide in plasma and uterine fluid of heifers.

OBJECTIVES: To determine time and concentration of peak plasma and uterine fluid concentrations of albendazole (ABZ) sulfoxide (ABZSO) in heifers after oral administration of ABZ. SAMPLE POPULATION: 25 young Angus and Simmental heifers maintained on pasture with ad libitum access to hay and water. PROCEDURE: Heifers were assigned at random to ABZ or control (water) groups, and were drenched with ABZ suspension at a dosage of 15, 30, 60, or 120 mg/kg of body weight, or with water. Plasma was collected hourly, from 14 to 25 hours after administration of ABZ or water. After a drug-withdrawal period, heifers were synchronized for estrus and drenched with 60 mg of ABZ/kg, or water (50 ml). Each uterine horn was flushed. All samples were extracted and subjected to high-performance liquid chromatography analysis. RESULTS: For all groups, highest mean +/- SEM plasma concentration of ABZSO was observed between 15 and 16 hours after ABZ administration, at 2.0 +/- 0.4 micrograms/ml (15 mg/kg), 5.3 +/- 1.0 micrograms/ml (30 mg/kg), 7.4 +/- 1.5 micrograms/ml (60 mg/kg), and 11.1 +/- 2.7 micrograms/ml (120 mg/kg). Mean concentration for all uterine horn fluid samples was 265 +/- 25 ng/ml/horn; range was 79 to 546 ng/ml/horn. The only significant (P = 0.0006) source of variation was the technician performing the flush. Mean concentration for each technician was 184 +/- 24 ng/ml/horn and 345 +/- 35 ng/ml/horn. CLINICAL RELEVANCE: Teratogenic and embryotoxic effects of ABZSO differ for ewes and heifers. Albendazole sulfoxide is detectable in the uterus of heifers; however, ABZSO peaks in heifer plasma earlier and at a lower concentration than that reported for ewes, perhaps contribution to differences in susceptibility at similar dosages.

Administration, Oral↗
PubMed1977

Practical experiences with prostaglandins in heifers and dairy cows.

This paper describes the extent to which utilisation of prostaglandins (PG) to achieve synchronisation of oestrus can influence certain economic results. Special attention is paid to the fertility status (FS) and calving index in dairy cows, where PG-treated groups are compared with untreated groups. With regard to these parameters a significant difference exists in favour of the PG treated group. In heifers the pregnancy rate after the first insemination has been determined in a PG treated group. The result compare very well with other published data. On large farms, where heat detection is poor, the routine use of PGs in the total herd is economically attractive. On those farms where the practitioner is involved in a fertility guidance system and where optimum heat detection takes place, the routine use of PGs in dairy cows would seem to offer advantages from a financial point of view.

Animal Husbandry↗
PubMed1979

[Estrogen determination in the urine of heifers during natural and CAP-affected sexual cycle].

With all differences due to environmental effects and individuality, oestrogen secretion actually follows a typical line of dynamics during one normal sexual cycle. Oestrogen curves were found to rise on the seventh and ninth days of the sexual cycle and to reach a maximum level on the last day. Cycle-depending differences between oestrogen concentrations were found to be leveled on the eighth day, when the oestrus had been synchronised by means of CAP. Oestrogens then went down, in response to synchronisation, up to the 15th day. Both the curve proper and the amount of oestrogens in the given cycle, following synchronised oestrus in heifer, practically were congruent with the values recordable from a normal sexual cycle. Two daily CAP doses of 10 mg per individual did synchronise oestrus in heifer and had no side effects on ovarian function over the following sexual cycle.

Animals↗
PubMed1998

Oocyte transfer in mares.

Oocytes were collected from dominant preovulatory follicles of donor mares 24 hours after administration of human chorionic gonadotropin. Oocytes were incubated in vitro for 12 or 18 hours before transfer to recipient mares, representing maturation times after human chorionic gonadotropin administration of 36 and 42 hours, respectively. Pregnancy rates after transfer were 4 of 5 in the 36-hour group and 2 of 3 in the 42-hour group. The overall pregnancy rate achieved (6/8 mares) indicated that oocyte transfer may be useful clinically.

Animals↗
PubMed1981

Ovarian activity and hormonal patterns in gilts fed allyl trenbolone.

A study was conducted to establish the profile of reproductive hormones and the degree of ovarian activity in gilts fed either 2.5 or 15.0 mg of allyl trenbolone (AT) daily. Progesterone levels following regression of corpora lutea remained low (less than 1 ng/Ml) during progestin treatment. In gilts given 2.5 mg AT, plasma estradiol (E2) levels fluctuated between 7 and 13 pg/ml during treatment and began to decrease by day 2 after withdrawal of AT. Gilts given 15 mg of AT had lower (P less than .01) plasma concentrations of E2 (2.5 pg/ml) during treatment; concentrations began to increase the day after withdrawal of AT, reaching a maximum of 13.1 pg/Ml in 3.5 to 4.0 days. Luteinizing hormone (LH) levels were low (less than 1.5 ng/ml) during AT treatment. Daily feeding of AT prevented estrus in all gilts. A preovulatory surge of LH (4 ng/ml) was observed on the first day of the first post-treatment estrus. Gilts given 2.5 mg of AT daily had more (P less than .01) follicles of ovulatory size during treatment and a higher frequency of cystic follicles after withdrawal than gilts given 15 mg of AT daily. Estrus was effectively synchronized in gilts given 15 mg of AT daily, whereas the feeding of 2.5 mg AT daily resulted in an increased incidence of anestrus.

Animals↗
PubMed1979

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.

Animals↗
PubMed2005

Effect of administration of human chorionic gonadotropin after artificial insemination on concentrations of progesterone and conception rates in beef heifers.

The objective of this study was to determine whether administration of hCG approximately 5 d after AI would increase plasma progesterone concentrations and conception rates in beef heifers. Heifers from two locations (Location 1: n = 347, BW = 367 +/- 1.72 kg; Location 2: n = 246, BW = 408 +/- 2.35 kg) received melengestrol acetate (0.5 mg.heifer(-1).d(-1)) for 14 d and an injection of PGF2alpha (25 mg i.m.) 19 d later. Heifers were observed for estrus continuously during daylight from d 0 to 4.5 after PGF2alpha and artificially inseminated approximately 12 h after the onset of estrus. Half of the heifers inseminated at Location 1 were assigned randomly to receive an injection of hCG (3,333 IU i.m.) 8 d after PGF2alpha, and a blood sample was collected from all heifers 14 d after PGF2alpha for progesterone analysis. Half of the heifers inseminated at Location 2 were administered hCG on d 9 after PGF2alpha, and a blood sample was collected from all heifers 17 d after PGF2alpha. Heifers at Location 1 had a 94% synchronization rate, exhibited estrus 2.45 +/- 0.03 d after PGF2alpha, and received hCG 5.55 +/- 0.03 d after AI. Heifers at Location 2 had an 85% synchronization rate, exhibited estrus 2.69 +/- 0.03 d after PGF2alpha, and received hCG 6.31 +/- 0.03 d after AI. Progesterone concentrations were greater (P < 0.01) for hCG-treated heifers than for controls at both locations (8.6 vs. 4.6 ng/mL for treatment vs. control at Location 1, and 11.2 vs. 5.6 ng/mL for treatment vs. control at Location 2). Pregnancy status was determined by ultrasound approximately 50 d after AI. Conception rates (65 vs. 70% for treatment vs. control, respectively) did not differ at Location 1. Conception rates tended (P = 0.10) to be increased with hCG treatment at Location 2 (61 vs. 50% for treatment vs. control, respectively). A second experiment was conducted with 180 heifers at a third location to determine the effects of hCG administration 6 d after timed insemination at approximately 60 h after PGF2alpha in heifers synchronized as in Exp. 1. Pregnancy rate to timed AI did not differ between hCG-treated (62%) and control heifers (59%). Final pregnancy rate after timed AI and bull exposure (92%) was not affected by treatment. In summary, administration of hCG 5 to 6 d after AI did not improve conception or pregnancy rates at two out of three locations evaluated, suggesting insufficient progesterone is not a major factor contributing to early pregnancy failure in beef heifers.

Animals↗
PubMed2001

Standardization of the Whitten Effect to induce susceptibility to Neisseria gonorrhoeae in female mice.

Female mice (Mus musculus) frequently are used to study hormonally related differences in susceptibility to infectious organisms or response to pharmaceutical agents. Cyclical variation in hormone levels within a group of mice, however, challenges the experimental design of such studies in that it is often difficult to obtain sufficient numbers of mice in the desired phase of the estrous cycle at the time of treatment. The purpose of this work is to provide investigators with a standardized protocol for inducing estrus in mice through exposure to male urine (Whitten Effect). In addition, we demonstrate how the Whitten Effect can be used to induce susceptibility of mice to Neisseria gonorrhoeae infection. Female BALB/c mice were exposed to male urine via soiled bedding for 0, 24, 48, 72, or 96 h. The effect of exposure on the reproductive cycle was monitored by cytologic examination of vaginal smears and measurement of serum 17-b estradiol levels by using a nonradioactive immunoassay kit. In a separate experiment, mice were exposed to male-urine-soaked bedding for 0, 24, 72, or 96 h prior to intravaginal inoculation with Neisseria gonorrhoeae. Infection was monitored by using vaginal culture for 5 consecutive days. We found that the highest percentage of mice in estrus occurred among mice that were exposed to male-urine-soaked bedding for 96 h. Consistent with this finding was the demonstration that mice were more susceptible to gonococcal infection after exposure to male urine for 3 to 4 days. We conclude that exploitation of this natural murine behavioral response is a simple and inexpensive method by which estrus can be synchronized in a group of mice within a defined period of time. In addition, this protocol can be used to increase mouse susceptibility to experimental gonococcal infection.

Animals↗
PubMed1995

Effect of norgestomet treatment after insemination on the calving rate of postpartum suckled beef cows.

Two experiments were conducted on postpartum suckled beef cows synchronized with Syncro-Mate B and artificially inseminated approximately 48 h after implant removal. In Exp. 1, cows (> or = 42 d postpartum at the timed AI) were randomly assigned to treated (n = 101) and control (n = 85) groups on d 12 after the timed AI. Treated cows received norgestomet/silicone implants that were left in situ for 9 d. Norgestomet treatment had no effect (P > .25) on the calving rates from the initial timed AI or from the return estrus. Nonpregnant norgestomet-treated cows returned to estrus in a more (P < .05) synchronized manner than the nonpregnant control cows. In Exp. 2, early postpartum cows (< 42 d postpartum at the first AI; n = 30) were included and all 118 cows (88 cows were > or = 42 d postpartum) received norgestomet/silicone implants as in Exp. 1. Of the 30 early postpartum cows, eight (19 to 41 d postpartum at the time of the first AI; mean = 29.3 d) calved to the first AI and nine calved to the second synchronized estrus. The calving dates at the next calving season for these 17 cows (57% of the cows in this group) was advanced an average of 46 d (319-d calving interval). The calving rates for the two timed insemination periods were similar (P > .25) for early and later (> or = 42 d postpartum) postpartum cows. Treatment with norgestomet implants on d 12 through 21 had no detrimental effects on established or subsequent pregnancy, synchronized the return estrus of nonpregnant cows, and was efficacious in establishing pregnancy early postpartum.

Animals↗
PubMed1988

Timing of preovulatory endocrine events, estrus and ovulation in Brahman x Hereford females synchronized with norgestomet and estradiol valerate.

The purpose of these studies was to investigate the pattern and timing of preovulatory endocrine events, estrus and ovulation in Brahman X Hereford (F1) heifers synchronized with norgestomet and estradiol valerate. In Exp. 1, 66 nulliparous and 191 primiparous Brahman X Hereford (F1) heifers were used to estimate the interval from norgestomet implant removal to onset of estrus. The mean interval from implant removal to onset of estrus was 29.8 +/- .5 h, with 80.9% exhibiting estrus within 48 h. Endocrine and reproductive characteristics were examined in detail during Exp. 2 with 37 primiparous heifers. Continuous observation for estrus, 6-h or 2-h blood sampling and ovarian palpation per rectum were employed. All animals were artificially inseminated 48 h after implant removal. Mean interval from implant removal to onset of estrus and to onset of the luteinizing hormone (LH) surge were closely related (r = .91; P less than .0001). Mean intervals from implant removal to ovulation, onset of estrus to ovulation and onset of LH surge to ovulation were 59.1 +/- 2.5 h, 23.3 +/- 1.4 h and 23.1 +/- 1.6 h, respectively. Approximately 73% of heifers exhibited estrus within 54 h after implant removal (optimal timing); conception rate was 59.3% in this subgroup. Conception rate of heifers that did not exhibit estrus within 54 h after implant removal or exhibited an LH surge later than 12 h after estrus (delayed timing) was 10%. Assessment of plasma estradiol-17 beta concentrations suggested that retarded selection and(or) maturation of the preovulatory follicle following implant removal delayed estrus and lowered conception in up to 28% of females timed-inseminated at 48 h.

Animals↗
PubMed2005

The effect of synchronization on genetic parameters of reproductive traits in dairy cattle.

Genetic evaluation and selection is one strategy for improving female reproductive performance. Many producers use synchronization of ovulation or estrus to manage reproduction. The objective of this study was to examine the effects of reproductive synchronization on genetic parameter estimates of days to first breeding (DFB), days open (DO), and pregnancy rate at 120 d postpartum (PR120). Data were collected from 64 producers participating in an artificial insemination progeny testing program and using Dairy Comp 305 herd management software to record reproductive treatments and events. Data included 18,359 records for DFB and 16,379 records for DO and PR120. Synchronization was classified by breeding codes at time of insemination. The traits DFB and DO were analyzed using a linear model with age at calving, herd-year-season, and parity as fixed effects and sire and residual as random effects. For PR120, a threshold sire model was used with fixed effects as in the DFB and DO models. Three models were applied to the complete data sets of all traits; a base model with no synchronization effect, an expanded model with a fixed synchronization effect, and an interaction model with a random sire by herd management interaction. Herd management categories were based on an individual herd's use of synchronization protocols. Also, data subsets were analyzed separately based on cow synchronization treatment and herd management categories. Synchronized records for DFB had on average 40% higher sire variance and 60% lower residual variance than nonsynchronized records. Heritability for DFB ranged from 0.01 to 0.09. Sire variance was 40% lower for DO and 25% lower for PR120 in first synchronized records than either later-synchronized or nonsynchronized records. Residual variances for DO varied by 3% among cow treatment categories and 14% for herd management categories. Heritabilities ranged from 0.03 to 0.07 for DO and 0.10 to 0.26 for PR120. Including a fixed effect for synchronization in the DO model reduced sire variance by 33% and residual variance by 10%. Sire by herd management interactions were less than 2% of the total variance for all traits. Accounting for synchronization, especially for DFB, may improve accuracy of genetic parameter estimates and animal evaluations.

Analysis of Variance↗
PubMed2004

Artificial insemination following observational versus electronic methods of estrus detection in red deer hinds (Cervus elephus).

The objectives were to determine the efficacy of the HeatWatch (HW) electronic estrus detection system for monitoring behavioral estrus (including duration and intensity) in red deer hinds and to evaluate pregnancy rate to AI after detected estrus. Red deer hinds (Cervus elephus; n = 50) were allocated into two treatment groups: AI following synchronization (CIDR/PMSG) and observed estrus (induced estrus group: IE; n = 25) or AI following the detection of natural estrus (NE; n = 25) without hormonal treatment. Hinds were fitted with two HeatWatch (HW) electronic estrus detection transmitters, one above the tail (bottom) and one between the tuber coxae of the pelvic girdle (top), and visual observations for mounting activity began with the aid of young sterile red deer stags (18 months old) fitted with marking harnesses. Hinds in both groups were inseminated (10-12h after observed estrus) with frozen-thawed red deer semen using a transvaginal/cervical AI approach. Following a 26-day period of AI, hinds were placed with a mature fertile stag for an additional 30-day natural breeding period. Pregnancy diagnosis was performed 57 and 86 days after the start of AI. While the hinds were housed with the young stags, 82% were detected in estrus by visual appraisal of stag crayon marks, but only 32% of these were detected by HW. In contrast, in the hinds housed with the mature stag, 93% detected in estrus by crayon marks were also detected by HW. The top HW transmitter consistently recorded more mounts (P < 0.05) than the bottom transmitter. The pregnancy rate was numerically better in IE versus NE hinds (42% versus 29%, P > 0.10). In summary, there were no differences (P > 0.10) in the intensity (number) or duration of mounts (detected by HW) during estrus in IE versus NE hinds, and HW was most effective in detecting estrus in the presence of a heavier, mature stag versus a younger stag. When used in combination with transvaginal AI, an overall first-service pregnancy rate of 36.6% was achieved with AI of frozen-thawed semen in red deer hinds following detected estrus.

Animals↗
PubMed2005

Induction of estrus in suckled female yaks (Bos grunniens) and synchronization of ovulation in the non-sucklers for timed artificial insemination using progesterone treatments and Co-Synch regimens.

The objectives of the present study were to evaluate the induction of estrus and fertility in yak cows treated with Co-Synch regimens or progesterone (P(4)). In Experiment 1, postpartum suckled yaks were assigned to three treatments: (1) A (n=28), insertion of an intravaginal device containing P(4) (CIDR) on Day 0, PGF(2alpha) (i.m.) on Day 6 and PMSG (i.m.) at the time of CIDR removal on Day 7 (P(4)-PGF(2alpha)-PMSG); (2) B (n=21), PGF(2alpha) (i.m.) on Day 6 and PMSG on Day 7; (3) C (n=26), control group. Seven yak bulls were grazed with the cows for natural breeding. Rate of estrus within 96h of the end of treatment was greater (P<0.05) in A (100.0%) than in B (28.6%) or C (0.0%). First service conception rate (CR) determined by serum P(4) on Day 21 after breeding was greater (P<0.05) in A (78.6%) than in B (22.2%). Also, pregnancy rate (PR) during the breeding season was greater (P<0.05) in A (82.1%) than in B (19.0%) and C (7.7%). In Experiment 2, non-suckled yaks that calved in previous years but not in the current year were assigned to three treatments: (1) A (n=31), GnRH (i.m.) on Day 0, followed by PGF(2alpha) on Day 7 and timed artificial insemination (TAI) concurrently with GnRH treatment on Day 9 (Co-Synch regimen); (2) B (n=50), a CIDR device for 7 days plus PGF(2alpha) and PMSG at the time of CIDR withdrawal on Day 7 and TAI on Day 9 (P(4)-PGF(2alpha)-PMSG); (3) C (n=50), yak cows were artificially inseminated at spontaneous estrus. Frozen semen of Holstein and Jersey were used for insemination in Experiment 2. The CR assessed by rectal palpation 35 days after TAI was not different in A (22.6%), B (30.0%) and C (33.3%), but PR was greater in A and B than in C, when based on those cows presented for estrous synchronization programs. It is concluded that P(4)-PGF(2alpha)-PMSG protocol could efficiently induce estrus and result in an acceptable pregnancy rate in postpartum suckled yak cows. This technique and Co-Synch regimen can be applied successfully for TAI of non-suckled yak cows.

Animals↗