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PubMed1991

Effect of recombinant inhibin on gonadotropin secretion during proestrus and estrus in the rat.

This work investigated the ability of recombinant human (rh) inhibin A or the GnRH antagonist [Ac-D2Nal1, delta Cpa2, delta 3Pal3, Arg5 delta 5-(p-methoxyphenyl)5-oxo-2-aminopentanoic acid6, delta Ala10]GnRH to alter plasma immunoreactive LH and FSH levels in cycling female rats. In a first series of experiments, rh inhibin A (25 micrograms/kg) was injected iv between 0800 and 0830 h, or at 0800 and 1200 h, on proestrus, and plasma hormone levels were measured from 1200-1900 h. Both regimens of administration significantly (P less than or equal to 0.01) lowered mean plasma FSH levels but did not mask the primary FSH surge. This treatment also lowered the overall amount of LH released, although the difference between control and inhibin-treated rats only reached statistical significance (P less than or equal to 0.05) after two injections of the protein. Measurement of the number of tubal ova shed on the next estrus showed no difference between rats injected with the vehicle or inhibin at 0830 h. Finally, it was shown that administration of the GnRH antagonist (100 micrograms/kg) at 1200 h interfered with the primary surges of both LH and FSH. In a second series of experiments, rh inhibin A (25 micrograms/kg) was injected once at 2000 h on proestrus. In these animals, inhibin significantly (P less than or equal to 0.01) decreased mean plasma FSH levels between 2000 h on proestrus and 0500 h on estrus and totally suppressed the secondary FSH surge. LH secretion remained low in control animals, and no measurable changes were observed after inhibin treatment. Flushing of the ova 5 days later (i.e. during estrus of the subsequent cycle) showed no difference between control and inhibin-treated rats. Injection of the GnRH antagonist (100 micrograms/kg) at 2000 h on proestrus decreased the total amount of FSH secreted during late proestrus and early estrus. However, FSH secretion showed an increase at between 0100 and 0400 h of estrus despite blockade of GnRH receptors. These results indicate that administration of rh inhibin A interferes with both the primary and secondary FSH surges. In contrast to its inability to alter LH release by ovariectomized rats, inhibin also blunted LH secretion during the afternoon of proestrus. Whether these results represent differential effects of inhibin on LH secreted by intact and gonadectomized animals, or whether the documented changes in pituitary responsiveness to GnRH during proestrus are accompanied by an increased sensitivity to inhibin, needs further investigation.

Animals↗
PubMed1995

Induction of cyclooxygenase type-2 (COX-2) in rat endometrium at the peak of serum estradiol during the estrus cycle.

We investigated the induction of cyclooxygenase (COX) in rat endometrium during the estrus cycle. The estrus cycle was divided into five stages (proestrus, estrus, diestrus-1, diestrus-2, diestrus-3) by cytological observation of vaginal smears. COX-1 was detected in the endometrium during all five stages of the estrus cycle. In contrast, COX-2 in the endometrium was detectable only in three stages (diestrus-3, proestrus, estrus) and showed a peak at diestrus-3, coinciding with the peak in serum estradiol level, suggesting the estradiol-dependent induction of COX-2.

Animals↗
PubMed1991

Bulls show no preference for a heifer in estrus in preference tests.

The objective of this experiment was to determine whether sexually experienced bulls would demonstrate a preference (using primarily olfaction) between a heifer in estrus and a heifer in diestrus (luteal phase) when physical contact was denied. In Exp. 1, a heifer in estrus and a heifer in diestrus (n = 18 pairs) were individually enclosed in opposite ends of a pen. During each period (n = 18), three bulls were individually introduced into the pen and allowed 5 min to demonstrate preference between the heifer in estrus and the heifer in diestrus. The total time that a bull spent within 2.5 m of either heifer was used to evaluate his preference. The total time that bulls spent adjacent to the heifer in estrus was not greater (P greater than .05) than the total time that bulls spent adjacent to the heifer in diestrus. In Exp. 2, five bulls were used and were evaluated using the same method as in Exp. 1. In addition, the number of flehmen reactions were recorded for each bull. Six heifers were ovariectomized and each heifer was induced into estrus with one of three doses of estradiol 17 beta (5, 10, and 20 mg) over the 5-wk treatment period. Estradiol 17 beta-treated heifers were always paired with a non-estradiol-treated (control) heifer. The goal of Exp. 2 was to determine whether heifers treated with pharmacological doses of estradiol 17 beta would be preferentially selected from non-estradiol-treated (control) heifers by bulls.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Relative importance of vision and olfaction for detection of estrus by bulls.

The objective of this experiment was to determine the relative importance of olfaction and visual observation of heifer mounting behavior to the detection of estrus by bulls. An observation pen was designed to allow the evaluation of the preference of five sexually experienced bulls under three sets of stimuli. The observation pen was 4 m x 17 m with a smaller enclosure (2 m x 4 m) at each end that housed either a pair of heifers in diestrus (D), a pair of heifers in estrus that were allowed to mount one another (EM), or a pair of heifers in estrus that were separated by an aluminum panel to prevent mounting behavior (E). The preference of bulls was determined between EM heifers compared to D heifers, EM heifers compared to E heifers, and E heifers compared to D heifers. Each bull was individually allowed 5 min inside the observation pen to demonstrate its preference. Preference was defined as the total time that bulls spent within 2.5 m of either pair of heifers. Each bull was subjected to 10 observation periods of each set of stimuli during a 4-mo period. Bulls preferred to be near EM heifers compared with either E or D heifers (P less than .05). However, the bulls demonstrated no preference (P greater than .05) for E heifers compared with D heifers. These data indicate that when physical contact is denied, bulls use visual observation of female homosexual behavior as the primary indicator of estrus and that olfaction alone provides insufficient stimuli for bulls to indicate preference toward heifers in estrus compared with heifers in diestrus.

Animals↗
PubMed1996

Acute and chronic changes in luteinizing hormone secretion and postpartum interval to estrus in first-calf suckled beef cows exposed continuously or intermittently to mature bulls.

The objective of this study was to determine whether patterns of LH secretion are acutely or chronically affected by the presence of mature bulls in postpartum first-calf suckled beef cows exposed to bulls either continuously or intermittently beginning on d 30 after birth. Crossbred cows were assigned randomly to be either continuously exposed to (BE; n = 20) or isolated from bulls (NE; n = 32) at calving, or exposed continuously (NEBE; n = 10) or intermittently (BEI; n = 21) to bulls beginning on d 30. The BEI cows were exposed to bulls for 2 h every 3rd d for 18 d. Ten cows from the NEBE, BEI, and NE treatments only were fitted with indwelling jugular catheters. Intensive blood sampling of NEBE and BEI cows began within 45 min after they were placed with bulls for 2 h on d 30, and for BEI cows on each d after 2 h exposure. Samples were collected at 15-min intervals for 6 h beginning on d 30 for NEBE, BEI, and NE cows; sampling continued at 3-d intervals until d 48. Samples were assayed for LH by RIA. Cows were observed twice daily (am:pm) for estrus. More (P = .07) BE and NEBE (75%) cows showed estrus by the end of the study than BEI and NE cows (48%). Interval to estrus was longer (P < .05) in BEI and NE cows (95.6 +/- 6.1 d) than in BE and NEBE cows (75.9 +/- 6.1 d). Baseline LH and amplitude and interpeak interval of LH peaks during the first 6 h after 2 h of bull exposure did not differ (P > .10) among treatments on d 30 after birth. However, mean LH and LH pulse frequency were higher (P = .06) for NEBE and BEI cows than in NE cows. Baseline LH and amplitude and duration of LH peaks did not differ (P > .10) over the seven sampling periods among NEBE, BEI, or NE cows. Mean LH and LH pulse frequency were higher (P < .05) in NEBE and BEI cows than in NE cows on each sampling period. Exposing first-calf suckled beef cows to bulls on d 30 after birth increased mean LH concentrations by increasing pulse frequency within a short period after a 2-h exposure. Thereafter, mean LH concentrations were higher in cows that were either continuously or intermittently exposed to bulls. Although mean LH and LH pulse frequency in NEBE and BEI cows were similar, intervals to estrus after bull exposure differed between treatments. The mechanism whereby bulls alter postpartum interval to estrus seems to involve other factors that may be related to but not directly linked with LH secretion.

Animals↗
PubMed1997

Estrus and luteal function in suckled beef cows that were anestrous when treated with an intravaginal device containing progesterone with or without a subsequent injection of estradiol benzoate.

The objectives in this study were to determine whether treatment with progesterone (P4) via an intravaginal device would induce estrus and development of corpora lutea (CL) with typical life spans and whether treatment with estradiol benzoate (EB) following device removal would enhance the responses. At treatment initiation (d 0), suckled beef cows (n = 362) that were anestrous received one of the following: 1) an intravaginal device containing P4 for 7 d plus an injection of 1 mg of EB 24 to 30 h after device removal (P4+EB), 2) an intravaginal device containing P4 for 7 d (P4), 3) a sham device for 7 d plus an injection of 1 mg of EB 24 to 30 h after device removal (EB), or 4) a sham device for 7 d (control). Progesterone treatment increased the proportion of cows that formed CL with a typical lifespan (P < .001) and exhibited behavioral estrus (P < .05). Treatment with EB in combination with P4 increased (P < .001) the proportion of cows that exhibited estrus. Treatment with P4 alone had no effect, but the combination of P4 and EB increased (P < .01) the proportion of cows that formed short-lived or typical lifespan CL by the end of the experiment compared with untreated cows. In summary, treatment with P4 increased the incidence of estrus and the proportion of cows that formed CL with a typical lifespan. Treatment with P4 resulted in resumption of luteal function in suckled beef cows that were anestrous, with most cows developing CL with a typical lifespan, whereas EB enhanced the expression of estrus.

Administration, Intravaginal↗
PubMed1999

Impact of amino acid nutrition during lactation on luteinizing hormone secretion and return to estrus in primiparous sows.

The impact of the dietary amino acid regimen of primiparous sows on LH secretion and weaning-to-estrus interval was evaluated. Thirty-six sows, nursing litters of 13 pigs, were allocated daily 6 kg of a corn-soybean meal diet containing a high (HP, 1.20% lysine) or low (LP, .34% lysine) protein content during a 23-d lactation. Dietary lysine concentration was achieved by altering the ratio of corn and soybean meal in the diet. Plasma LH, ACTH, and estradiol-17beta were evaluated at 15 min, hourly, and at 6-h intervals, respectively, during 6-h periods on d 0, 5, 10, 15, and 20 of lactation. Sows were checked daily for estrus from weaning to 45 d postweaning. Sows fed the LP and HP diets consumed 4.41 and 4.98 kg of feed daily during lactation. The LP sows weighed less (P < .05), had lighter (P < .05) litters at weaning, and had (P < .05) extended weaning-to-estrus intervals. Mean and baseline LH concentrations and LH pulses/6 h were lower (P < .01) in LP sows, and the differences between LP and HP sows were established by d 10 of lactation. Plasma estradiol and ACTH concentrations were not altered by diet. Mean LH concentrations on d 5 and 10 of lactation were correlated (r = -.54 and -.56, respectively, P < .01) with weaning-to-estrus interval. Also, mean LH concentrations on d 10 were correlated (P < .05) with the magnitude of dietary lysine deficiencies relative to demand for milk synthesis on d 0 to 5 and d 5 to 10 (r = -.39 and -.49, respectively). Inadequate dietary amino acid intake in sows during early lactation results in lower LH secretion by d 10 postpartum and is associated with increased weaning-to-estrus interval.

Adrenocorticotropic Hormone↗
PubMed2001

Efficacy of an intravaginal progesterone insert and an injection of PGF2alpha for synchronizing estrus and shortening the interval to pregnancy in postpartum beef cows, peripubertal beef heifers, and dairy heifers.

The objective was to test the efficacy of an intravaginal progesterone insert and injection of PGF2alpha for synchronizing estrus and shortening the interval to pregnancy in cattle. Cattle were assigned to one of three treatments before a 31-d breeding period that employed artificial insemination. Control cattle were not treated, and treated cattle were administered PGF2alpha or an intravaginal progesterone-releasing insert (CIDR) for 7 d and treated with PGF2alpha on d 6. The treatments were applied in one of three experiments that involved postpartum beef cows (Exp. 1; n = 851; 56+/-0.6 d postpartum), beef heifers (Exp. 2; n = 724; 442.5+/-2.8 d of age), and dairy heifers (Exp. 3; n = 260; 443.2+/-4.5 d of age). Luteal activity before treatment was determined for individual cattle based on blood progesterone concentrations. In Exp. 1, there was a greater incidence of estrus during the first 3 d of the breeding period in CIDR+PGF2alpha-treated cows compared with PGF2alpha-treated or control cows (15, 33, and 59% for control, PGF2alpha, and CIDR+PGF2alpha, respectively; P < 0.001). The improved estrous response led to an increase in pregnancy rate during the 3-d period (7, 22, and 36% for control, PGF2alpha, and CIDR+PGF2alpha, respectively; P < 0.001) and tended to improve pregnancy rate for the 31-d breeding period for cows treated with CIDR+PGF2alpha, (50, 55, and 58% for control, PGF2alpha, and CIDR+PGF2alpha, respectively, P = 0.10). Improvements in rates of estrus and pregnancy after CIDR+PGF2alpha, were also observed in beef heifers. Presence of luteal activity before the treatment period affected synchronization and pregnancy rates because anestrous cows (Exp. 1) or prepubertal heifers (Exp. 2) had lesser synchronization rates and pregnancy rates during the first 3 d of the breeding period as well as during the entire 31-d breeding period. The PGF2alpha, and CIDR+PGF2alpha but not the control treatments were evaluated in dairy heifers (Exp. 3). The CIDR+PGF2alpha-treated heifers had a greater incidence of estrus (84%) during the first 3 d of the breeding period compared with the PGF2alpha-treated heifers (57%), but pregnancy rates during the first 3 d or during the 31-d breeding period were not improved for CIDR+PGF2alpha compared with PGF2alpha-treated heifers. In summary, the concurrent treatment of CIDR and PGF2alpha improved synchronization rates relative to PGF2alpha alone or control. Improved estrus synchrony led to greater pregnancy rates for beef cows and beef heifers but failed to improve pregnancy rates for dairy heifers.

Administration, Intravaginal↗
PubMed1981

Estrus and fertility in lactating sows and piglet performance as influenced by limited nursing.

Seven trials were conducted with 126 sows and their litters to determine the influence of limited nursing (LN), starting on day 21 of lactation, on estrous activity and conception rate during lactation and on piglet performance. One-half of the sows in each of the first three trials were allowed to nurse their piglets four times daily for 30-min periods for 12 days. In the last four trials, half of the sows nursed their piglets four times daily for the first 3 days and then three times daily for 4 days (7-day limited nursing). The remaining sows in each trial were allowed to nurse their piglets in a normal manner. All piglets were weaned at the end of the LN period. Piglets were weighed at the start of the study, at weaning and at 14 days postweaning. Creep intake was measured during the LN period. In the first three trials, eight of the 26 LN sows were in estrus before weaning, whereas no control (C) sows were in estrus during lactation (P greater than .01). The average interval from weaning to breeding was 1.7 and 6.6 days for LN and C sows, respectively (P greater than .01). In the last four trials, five of 37 LN sows were in estrus before weaning, whereas no C sows were in estrus during lactation (P greater than .07). The average interval from weaning to estrus was 3.3 and 4.3 days for LN and C sows, respectively, (P greater than .05). Conception rate did not differ between trials or between treatment groups. Weight gain during the treatment period was lower and creep feed intake greater (both P greater than .01) for pigs reared by LN sows than for piglets reared by C sows. Weight gained after weaning was greater (P greater than .05) for piglets reared by LN sows than for those reared by C sows in the first three trials, but was similar for the two groups in the following four trials. Piglet death loss was similar for the two groups throughout the experiment.

Animal Population Groups↗
PubMed1982

Synchronization of estrus and reproductive performance of ewes treated with synthetic progestogens administered by subcutaneous ear implant or by intravaginal sponge pessary.

Experiments were conducted to compare the efficacy of synthetic progestogens administered by subcutaneous ear implant or intravaginal sponge to induce a synchronized estrus in adult ewes and ewe lambs and to evaluate reproductive performance (fertility and litter size) to breeding at the synchronized estrus. Experimental animals were representative of three strains maintained in total confinement and exposed to a synthetic light regimen which alternated at intervals of 4 mo from 18 h day length to 10 h day length/24 h. Treatments were applied at different times of the year at the end of a low light cycle. Implants contained Norgestomet (3 mg) impregnated in a polymethacrylate polymer (Implant H) or impregnated in a silastic polymer containing 1.05 (Implant S1), 1.78 (Implant S2) or 2.60 mg (Implant S3) Norgestomet, respectively. Intravaginal sponges contained 40 mg Fluorogestone Acetate. Implants or sponges were left in situ for 12 d and 500 IU pregnant mares' serum gonadotropin was injected im at the time of removal. Following treatment with Implant H, 96% of ewes were judged to be in estrus at 48 h after implant removal. Fertility of adult ewes and ewe lambs (6 to 7 mo of age at time of breeding) at the synchronized estrus were similar after implant H or sponge treatment, but litter size was higher (P less than .05) for adult ewes treated with sponges. The percentages of adult ewes marked by rams within 60 h after removal of silastic implants or intravaginal sponges were similar. There was a tendency for ewe lambs to be marked later than adult ewes and for adult ewes treated with Implant S1 and Implant S2 to be marked earlier than ewes treated with Implant S3 or sponges. Higher percentages (P less than .05) of adult ewes and ewe lambs lambed to breeding at the synchronized estrus after treatment with Implant S2 or Implant S3, respectively, than after treatment with Implants S2 or sponges.

Animals↗
PubMed1989

Conception rate in Bos taurus and Bos indicus crossbred heifers after postweaning energy manipulation and synchronization of estrus with melengestrol acetate and fenprostalene.

Conception rate in heifers after synchronization of estrus with melengestrol acetate (MGA) and fenprostalene (a prostaglandin F2 alpha analogue; PGF) was determined in pubertal Bos taurus and Bos indicus crossbred yearling heifers. Angus x Hereford (AH, n = 137) and Brahman x Hereford (BH, n = 97) heifers were sorted by body weight after weaning into light (LW) and heavy (HW) weight blocks. Heifers were assigned by age to diets to reach a target weight of 55% (LE) or 65% (HE) of their projected mature weight by the start of breeding. Heifers that exhibited estrus and had serum progesterone greater than or equal to 1 ng/ml (0 or 10 d before estrous synchronization treatment) were assigned randomly within breed and nutritional groups to either an estrous synchronization (S) or control (C) group. Heifers in the S group were fed .5 mg of MGA for 7 d and injected s.c. with 2 mg PGF on d 7 of MGA. All heifers were inseminated 12 h after first detected estrus. A greater proportion of AH (P less than .01) than of BH heifers were in estrus within 6 d after PGF, and more S heifers than C heifers (P less than .01) were in estrus. Conception rate at first service was proportionately higher (P less than .001) in AH than in BH heifers and lower (P less than .02) in S than in C heifers. There was a breed x energy level interaction (P less than .01) for conception rate at first service. Stage of the estrous cycle at the time treatment with MGA was initiated influenced (P less than .05) conception rate at first service in the S, AH heifers, with lower conception rates among heifers beginning treatment late in their estrous cycles (greater than or equal to d 12). Pregnancy rates after 21 d were higher (P less than .01) in AH than in BH heifers and higher (P less than .01) in HW than in LW heifers. More HE than LE heifers (P less than .02), and more AH than BH heifers were pregnant after 45 d. Pregnancy rates at the end of 21 d were higher among HE, BH heifers than among LE contemporaries. A higher (P less than .02) percentage of HE, HW, BH heifers were pregnant at the end of 45 d compared with other BH groups. Results indicated that a 7-d MGA-PGF treatment reduced conception rates at first service in pubertal yearling heifers. Pregnancy rate was affected by prebreeding nutrition in BH yearling heifers at the end of 45 d.

Administration, Oral↗
PubMed1989

Induction of fertile estrus in prepuberal gilts by treatment with a combination of pregnant mare's serum gonadotropin and human chorionic gonadotropin.

Ten trials involving 678 presumed prepuberal gilts (5.5 to 7.5 mo old) were conducted in North Carolina, Illinois and Missouri to evaluate the reproductive performance of gilts given a combination of 400 IU of pregnant mare's serum gonadotropin and 200 IU of human chorionic gonadotropin (P. G. 600). Gilts that were presumed to be prepuberal received P. G. 600 or no treatment (control) on the day of movement from finishing facilities to pens for breeding. Detection of estrus, with the aid of mature boars, was conducted daily for 28 d; gilts in estrus were mated naturally. Treatment with P. G. 600 increased the percentage in estrus within 7 (57.5 vs 40.9%) or 28 d (72.9 vs 59.5%); average interval to estrus was reduced (P less than .05) from 10.4 to 7.5 d. Farrowing rate (78.5 +/- 3.1%), number of pigs born alive (8.6 +/- .2) or dead (.26 +/- .06) and number of pigs weaned (8.0 +/- .2) were unaffected by treatment. Gilts that were heavier than the median for each farm were in heat sooner and more were detected in heat, but no other reproductive traits differed between heavy and light gilts. Overall, the results reveal that P. G. 600 was useful for induction of fertile estrus in prepuberal gilts.

Analysis of Variance↗
PubMed2004

Resynchronizing estrus with progesterone or progesterone plus estrogen in cows of unknown pregnancy status.

Two experiments were conducted to test 2 progesterone (P4)-based treatments that were applied to lactating dairy cattle of unknown pregnancy status to resynchronize estrus of nonpregnant cows. In experiment 1, cows were assigned randomly before a timed AI (TAI) to 1) treatment with a CIDR (controlled internal drug-releasing intravaginal insert containing P4) for 7 d starting on d 13 after TAI (CIDR; n = 300) or 2) no P4 treatment (control; n = 330). Compared with controls, P4 increased the synchrony of those detected in estrus, but failed to increase the overall return rates of non-pregnant cows during the 6 d after CIDR removal (27% vs. 31%; d 20 to 26 after TAI) and did not alter synchronized conception rates (32% vs. 20%) of those inseminated. Use of P4 did not compromise pregnancies resulting from TAI compared with controls (38% vs. 42%), but increased embryo survival between d 29 and 57 after TAI (65.5% vs. 44.3%). In experiment 2, on d 13 after TAI, 196 cows were treated with a CIDR insert for 7 d. Controls received no further treatment. Remaining cows were treated with 1 of 3 estrogen regimens: 1 mg of estradiol benzoate (EB), 0.5 mg of estradiol cypionate (ECP), or 1 mg of ECP on both d 13 and 21. Only 60% of nonpregnant, estrogen-treated cows were detected in estrus between d 20 and 26, and rates of return and conception did not differ among treatments. Estrogen on d 13 did not consistently turn over the dominant follicle when given at CIDR insertion but did increase concentrations of estradiol and reduced luteal function when administered on d 13 and 21 (24 h after CIDR removal). Treatments had no negative effects on milk yield, dry matter intake, or established pregnancies. Use of P4 alone had little effect on overall rates of return to estrus or conception at the first eligible estrus in experiment 1. Combining estrogen with P4 in experiment 2 had no detrimental effects on established pregnancies or subsequent conception and failed to improve return rates beyond P4 alone.

Administration, Intravaginal↗
PubMed1978

Estrus in relation to time of administration of prostaglandin F2alpha to heifers.

Holstein heifers (95) were given two injections of prostaglandin F2alpha, the first on day 0 and the second either at 0600 h or 1800 h on day 12. Interval from the second treatment to first observation of estrus did not differ between heifers treated during the morning (69.8 +/- 4.4 h) or evening (72.7 +/- 5.2 h). However, estrus was detected sooner after treatment of heifers during July 1975 (49 +/- 2 h) than after treatment during June 1976 (85 +/- 8 h). Estrus began at 64 +/- 5, 73 +/- 7, and 76 +/- 7 after the second injection during August 1975, October 1976, and December 1975. Heifers treated during the morning in October were detected in estrus sooner (57 +/- 3 versus 95 +/- 13 h) than those treated during the evening. An interaction of season by time may affect interval from prostaglandin F2alpha treatment to onset of estrus.

Animals↗
PubMed1979

Prostaglandin in milk, days open, and estrus detection in dairy cows treated with prostaglandin F2 alpha.

Prostaglandin F2 alpha was used to induce estrus in postpartum dairy cows to decrease calving interval and time spent on heat checks. The amount of prostaglandin residue in milk after treatment also was investigated. Twenty-two control cows, checked for heat twice daily, were bred at estrus after 55 days postpartum. Sixty-three cows checked on days 55 to 60 were either bred if in estrus or treated with 30 mg of prostaglandin F2 alpha injected intramuscularly on day 60 and bred at induced estrus or at 75 h posttreatment. Twelve cows were in heat between days 55 and 60 and were bred. Twenty-nine of 51 treated cows were seen in estrus; all of these were bred and 51.7% conceived at this time. Treated cows had fewer days to first service than did controls, but days open were not different, 105.7 versus 101.8. Fertility was similar. Controls required more heat checks than did treated cows (39 to 8.2). Milk from 17 cows at two milkings before and ten milkings after treatment had similar concentrations of prostaglandin (698 +/- 27 pg/ml) except for the first posttreatment milking when prostaglandin concentration almost doubled (1.293 +/- 143 pg/ml).

Animals↗
PubMed1987

Comparison of on-farm laboratory milk progesterone assays for identifying errors in detection of estrus and diagnosis of pregnancy.

A field study was conducted in 10 commercial dairy herds to test the efficacy of a rapid enzyme-linked immunosorbent assay to identify errors in detection of estrus and diagnosis of pregnancy. Milk samples were collected at the milking following detection of estrus and on d 21 postinsemination. Progesterone was measured on-farm by an enzyme-linked immunosorbent assay and in the laboratory by radioimmunoassay. Agreement between the two methods of progesterone analysis (n = 820) was 89.8%. There were 93 cows (18.7%) by laboratory analysis and 126 cows (25.4%) by on-farm analysis for which concentration of progesterone in the sample collected at suspected estrus (n = 497) was higher than normal estrual values. Exclusion of these cases increased the overall accuracy of pregnancy diagnosis by 6.8 and 6.4% for laboratory and on-farm methods. Overall agreement between pregnancy diagnosis by milk progesterone at d 21 postinsemination and diagnosis by return to estrus or palpation of reproductive organs was 80.5 and 75.8% for laboratory and on-farm methods (75.0% and 69.7% for pregnant cows and 94.5 and 93.9% for nonpregnant cows). These results indicate that an enzyme-linked immunosorbent assay for milk progesterone performed on-farm was equal in accuracy to a laboratory radioimmunoassay for identifying errors in detection of estrus and diagnosis of pregnancy.

Animals↗
PubMed1991

Use of Chronogest implants and Folltropin for estrus synchronization and superovulation in goats.

Six Barbari goats each were assigned randomly to treatments 1,2 or 3, comprising im injections of FSH (folltropin) at 12, 14 or 16 mg dose level respectively. Estrus was synchronized with intravaginal sponge impregnated with flugestone acetate (30 mg; chronogest) inserted for 12 days and cloprostenol (125 micrograms) im at the insertion as well as at removal of sponge. FSH treatment started 48 hr before the sponge removal as 4-day declining dose scheme. Estrus could be effectively synchronized in all goats under the study, with significant difference (P less than 0.05) in the onset of estrus between the treatment groups. All goats were administered with 750 IU hCG i.v. at estrus. Recording of ovarian response and embryo recovery was done 45 hr after the onset of estrus. The prime aim of superovulation was effectively achieved in Barbari goats with the use of chronogest implants and folltropin. There was no difference (P greater than 0.05) between the treatment groups in recovery of transferable embryos, however, 14 mg folltropin appeared to be near optimal dose. There was no adverse effect on the quality of recovered embryos with high doses of folltropin.

Animals↗
PubMedDate not supplied

Delay of behavioral estrus in hamsters and phenobarbital.

The onset of behavioral estrus was used as a phase marker of the hamster timing system in SLD 16:8 (dark 20:00-04:00). TZ was injected between 11:00 of cycle day 3 and noon of cycle day 4 when onset of estrus was determined. At no time did injection of TZ cause a phase advance in SLD 16:8. Small delays of estrus resulted from 11:00-16:00 injections but marked delays began with the 17:00 injection. Phenobarbital was injected between noon and 19:30 on cycle day 3. Injections between noon and 16:00 had no effect but all later injections beginning at 17:00 delayed estrus, the 17:30 injection causing the greatest delay. Diazepam also markedly delayed estrus when tested at 17:30. These results with three drugs support results with light pulses that 18:00 in SLD 16:8 marks the same phase of the 24-h hamster timing system as the onset of wheel running does in DD, LL, and WLD. These findings with three GABA potentiators extend to SLD previous evidence based on the onset of wheel running in DD, LL and WLD that GABA may be involved in hamster timekeeping and its responses to light and drugs.

Animals↗