Estrous Period Research Articles

Endocrinological Studies of Mares with Granulosa-Theca Cell Tumor.

To clarify the endocrinological characteristics of mares with granulosa-theca cell tumor (GTCT), 2 mares with GTCT and a long estrous period were investigated. Before removal of the GTCT in both cases, the concentrations of testosterone, immunoreactive (ir-) inhibin and follicle stimulating hormone (FSH) in the peripheral blood were higher than those of normal mares at the follicular phase, whereas the plasma concentrations of progesterone were constantly low. In Case 1 mare, the plasma concentrations of testosterone, ir-inhibin and follicle stimulating hormone (FSH) changed to significantly high levels. In Case 2 mare, plasma concentrations of all hormones except for progesterone changed to significantly high levels. After surgical removal of the GTCT, the circulating concentration of ir-inhibin decreased rapidly to the basal level. The ir-inhibin levels in GTCT tumor fluid were similar to the follicular fluid in healthy follicles 3.5-5.0 cm in diameter. Concentrations of estradiol in the GTCT tumor fluid were low, but testosterone levels were higher than those in healthy follicles 3.5-5.0 cm in diameter. These results suggest that high levels of circulating inhibin in addition to high levels of testosterone and low levels of progesterone may be used as a clinical sign in the diagnosis of GTCT in mares.

THYROID FUNCTION AND EFFECTS ON REPRODUCTION IN EWES EXPOSED TO THE ORGANOCHLORINE PESTICIDES LINDANE OR PENTACHLOROPHENOL (PCP) FROM CONCEPTION

There is concern over the potential endocrine-modulating effects of long-term exposure to pesticides. In this study, ewe lambs were exposed to lindane and pentachlorophenol (PCP) from conception to necropsy at 67 wk of age. The ewe lambs (and their mothers) were given untreated feed (n = 6) or feed treated with 1 mg/kg body weight/day of lindane (n=8) or PCP (n=13). Estrus was synchronized at 32 wk of age, and ewe lambs were exposed to vasectomized rams. Ewe lambs were then exposed to intact rams during the following two natural estrous periods and subsequent reproductive performance was monitored. Serum was collected every 2 wk during development, daily during the synchronized cycle and frequently (every 15-60 min) for 6-18 h either with or without stimulation with thyroid-stimulating hormone ( TSH) during the synchronized luteal phase or TSH/thyroid-releasing hormone (TRH) at 65-66 wk of age. Ewe lambs fed a PCP-treated diet had a significantly reduced serum concentration of both T4 and free T4, and a reduction in the magnitude and duration of the T4 and free T4 response to TSH, despite normal endogenous levels of TSH and a normal TSH response to TRH. PCP exposure had a less detrimental influence on unstimulated T 3 levels; however, the T3 (but not reverse T3) response to TSH was markedly reduced in PCP-treated ewe lambs. Ewe lambs given lindane also had a significantly reduced serum concentration of T4; however, despite continued exposure to lindane, T4 levels returned to normal by 10 wk of age. Detrimental effects on reproductive function were only seen following estrous synchronization when both PCP and lindane exposure reduced the number of corpora lutea (CL) and total CL volume and increased luteinizing hormone (LH) pulse frequency. In addition, lindane-treated ewes had shorter estrous cycles and lower luteal progesterone concentrations. No marked effects of pesticides were seen on fertility following mating during natural estrous periods. In conclusion, the pesticides affected reproduction only after estrous synchronization, whereas PCP consistently disrupted thyroid function, most likely through a direct effect on the thyroid gland.

Induction of ovulation with gonadotropin-releasing hormone during proestrus in cattle: influence on subsequent follicular growth and luteal function.

Induction of ovulation by administration of gonadotropin-releasing hormone (GnRH) is commonly practiced in cattle to treat repeat breeders or cows exhibiting long estrous periods. This treatment may, however, disturb normal reproductive functions if timing is incorrect. The objective of the present study was to investigate the effect of exogenous GnRH on estradiol secretion of the ovulatory follicle, occurrence of ovulation, development and function of the corpus luteum (CL) and growth of a dominant follicle after ovulation in the bovine, when GnRH treatment was given before the expected physiological LH-surge. Luteolysis was induced by cloprostenol (PG) in three cows and six heifers. Every animal was assigned once to each of the following treatment or control manipulations, receiving either a single dose (0.1 mg) of GnRH (gonadorelin) at (1) 24 h (T1), (2) 48 h (T2), or (3) 72 h (T3) after PG, or (4) no gonadorelin (control manipulation, C). Ovaries were scanned by ultrasound and blood samples were collected for progesterone (P4) and estradiol-17beta (E-17beta) determination. Growth curves of dominant follicles between treatment I and the control differed significantly (P < 0.01). One day after ovulation, the diameter of the dominant follicle was almost 1 mm larger in T1. This difference remained almost unchanged during the entire follow-up period. The recruitment of a new follicular wave after ovulation seemed to occur earlier. Development of CL and levels and profiles of P4-production remained unaffected. When GnRH was given 1 day after PG injection, two animals showed significantly different development of CL (P < 0.05) and of P4-production (both in concentrations [P < 0.05] and profile [P < 0.01]). After normal ovulation and CL development, luteolysis took place on days 5 or 6 after ovulation, and animals ovulated on days 9 and 10. It is suggested that early induction of ovulation with GnRH can cause shortened luteal function in cattle and, ultimately, reduced fertility.

Identification of quantitative trait loci affecting female reproductive traits in a multigeneration Meishan-White composite swine population.

A multigeneration crossbred Meishan-White composite resource population was used to identify quantitative trait loci (QTL) for age at first estrus (AP) and the components of litter size: ovulation rate (OR; number of ova released in an estrous period) and uterine capacity (UC). The population was established by reciprocally mating Meishan (ME) and White composite (WC) pigs. Resultant F1 females were mated to either ME or WC boars to produce backcross progeny (BC) of either 3/4 WC 1/4 ME or 1/4 WC 3/4 ME. To produce the next generation (F3), 3/4 WC 1/4 ME animals were mated to 1/4 WC 3/4 ME animals yielding half-blood (1/2 WC 1/2 ME) progeny. A final generation (F4) was produced by inter se mating F3 animals. Measurements for AP and OR were recorded on 101 BC, 389 F3, and 110 F4 gilts, and UC data were from 101 BC and 110 F4 first parity litters. A genomic scan was conducted with markers (n = 157) spaced approximately 20 cM apart. All parental, F1, BC, and F4 animals but only 84 F3 animals were genotyped and included in this study. The QTL analysis fitted a QTL at 1-cM intervals throughout the genome, and QTL effects were tested using approximate genome-wide significance levels. For OR, a significant (E[false positive] < .05) QTL was detected on chromosome 8, suggestive (E[false positive] < 1.0) QTL were detected on chromosomes 3 and 10, and two additional regions were detected that may possess a QTL (E[false positive] < 2.0) on chromosomes 9 and 15. Two regions possessed suggestive evidence for QTL affecting AP on chromosomes 1 and 10, and one suggestive region on chromosome 8 was identified for UC. Further analyses of other populations of swine are necessary to determine the extent of allelic variation at the identified QTL.

Hypokalemia alters sex hormone and gonadotropin levels: evidence that FSH may be required for luteinization.

Hypokalemia produced different effects on steroid sex hormone concentrations in plasma and ovary in the mouse. Estradiol levels were slightly increased, whereas circulating progesterone was markedly decreased in all estrous periods. The preovulatory surge of gonadotropins and the secondary surge of follicle-stimulating hormone (FSH) at estrus were also decreased, but basal levels of both gonadotropins were unaffected. Supplementation with luteinizing hormone (LH), FSH, or gonadotropin-releasing hormone (GnRH) at proestrus rapidly normalized plasma and ovarian progesterone levels at this stage of the estrous cycle. Plasma progesterone levels at diestrus were restored only by combined treatment, at the periovulatory stage, with LH and FSH or GnRH but not by LH or FSH alone. The results demonstrate a lack of steroidogenic activity in the corpus luteum of the potassium-deficient mice and, furthermore, that FSH plays an important role in luteinization in the hypokalemic mice. We conclude that alteration of the transcellular potassium gradient may affect the regulation of the periovulatory surge of gonadotropins and progesterone secretion, probably by altering the release of GnRH from the hypothalamus. In addition, the results suggest that FSH may play a certain role as a luteotropic hormone in mice.

Reproductive performance of lactating dairy cows treated with gonadotrophin-releasing hormone (GnRH) and/or prostaglandin F2a (PGF2a) for synchronization of estrus and ovulation

The objective of this study was to determine the reproductive performance of lactating dairy cows treated with GnRH and/or PGF2a for synchronization of estrus and ovulation. Between Days 43 and 57 post partum, a total of 374 dairy cows was divided into 4 groups. Cows in Group 1 (n=62) were treated with 25 mg, im PGF2a on Days 43 and 57; cows in Group 2 (n=65) were not treated at this time; cows in Group 3 (n=118) were treated with 100 μg, im GnRH on Day 50, 25 μg, im PGF2a on Day 57, 100 μg, im GnRH on Day 59, and time-inseminated 16 h later; cows in Group 4 (n=129) were treated with 25 mg, im PGF2a once on Day 57. Cows in Groups 1 and 4 were inseminated at an induced estrus within 7 d after the last PGF2a treatment, and cows in Group 2 were inseminated at a noninduced estrus within a corresponding period of time. Conception rate, estrus detection rate and pregnancy rate were analyzed using logistic regression, and controlled for lactation number, body condition score and time of year. Days from calving to conception were analyzed using the GLM procedures of SAS, and the model included group, body condition score, lactation number, time of year, and their interactions. Cows in Group 3 had a significantly higher pregnancy rate than cows in Groups 1, 2 and 4. Orthogonal contrasts of mean days from calving to conception showed that cows in Group 3 had significantly (P<0.01) less days from calving to conception than cows in Group 1 and Group 4. There was a significant effect of time of year on pregnancy rate and days from calving to conception, but there was no interaction between time of year and these reproductive characteristics. There was no effect of body condition score and lactation number on the reproductive characteristics evaluated. From the results of this study, it was concluded that better reproductive performance was observed in cows inseminated at a synchronized ovulation than in those inseminated at a synchronized estrous period.

Measurement of vaginal temperature by radiotelemetry for the prediction of estrus in beef cows

Peaks in vaginal temperature were assessed as predictors of estrus in 22 suckled beef cows during 2 breeding seasons. A flexible plastic anchor was used to retain a temperature radiotransmitter within the cow vagina and vaginal temperature was monitored at 4-min intervals. Blood was collected twice weekly for analysis of serum progesterone to confirm the occurrence of estrus and ovarian status was checked weekly using transrectal ultrasonography. Visual observations of estrous behavior were made for 20 min/h between 0400 and 0800 h and casually from 0800 to 1600 h (4 to 6 times). Values for vaginal temperature were available for 47 estrous periods. The prediction of estrus based on vaginal temperature was excellent when an estral peak in vaginal temperature was defined as an increase of at least 0.4°C for 3 or more consecutive hours using the corresponding hourly means of a 2 or 3-d baseline. Combining the results of 2 separate years and using a 3-d baseline, a peak in vaginal temperature was found for 42 of 47 confirmed estrus periods (detection sensitivity of 89.4% and prediction power positive of 85.7%). Corresponding detection sensitivity and prediction power positive for visual observations of standing estrus were 53.2 and 96.2%, respectively. The mean maximal increase in vaginal temperature at estrus was 0.9 ± 0.3°C and the mean duration of the estrual peak in vaginal temperature was 6.5 ± 2.7 h. In addition, vaginal temperature was found to be significantly depressed for 3 d prior to estrus and significantly elevated at mid-cycle.

Canid Reproductive Biology: an Integration of Proximate Mechanisms and Ultimate Causes

SYNOPSIS. The canid reproductive system includes many features that are unusual or even unique among mammals. Focusing on gray wolves, for example, these include monogamy, monestrum with exceptionally long proestrous and diestrous phases, a copulatory lock or tie, incorporation of adult young into the social group, behavioral suppression of mating in these subordinate young, obligate pseudopregnancy in subordinate females, and alloparental care. These features can be analyzed on the levels of both proximate and ultimate causation by considering them in the context of the reproductive system as a whole. First, when assessing possible proximate mechanisms, monestrum appears to be pivotal. It is probably accomplished by the extremely long luteal or diestrous phase, which is followed by a seasonal peak in prolactin. Two sequellae of the extended diestrus (or pseudopregnancy) in non-pregnant subordinate females are to 1) suppress any subsequent cycles, and 2) hormonally prime them to behave maternally. The prolactin peak in all adult pack members, coincident with the birth of pups, also may stimulate parental behavior. The risk of monestrum (limited chance for conception) appears to be reduced by the relatively long proestrous and estrous periods, as well as by monogamy. The adaptive value, or ultimate cause, of this reproductive system is most obvious for the more social canid species, such as the gray wolf. That is, advantages to sociality, such as cooperative hunting, may have driven development of the anomalies of the reproductive system.

In vitro maturation and fertilization techniques for assessment of semen quality and boar fertility.

The reliability of using different in vitro-derived measures of sperm quality to predict boar fertility was examined. On three occasions during a 20-wk period of breeding, special collections of the first sperm-rich fraction of the ejaculate from six boars were carried out. After in vitro capacitation procedures, three dilutions (5 x 10(5), 1.25 x 10(5), and 3.125 x 10(4) sperm/mL) of these semen samples were used in a standardized in vitro fertilization (IVF) test with oocytes recovered from prepubertal slaughterhouse ovaries and matured in vitro. Routine assessments of sperm motility, concentration, and morphology were also carried out for all collections used for AI during the 20-wk period. Semen from the same ejaculate, processed according to normal commercial practice using the AndroHEP extender, was used to inseminate equal numbers of recently weaned sows with either 3 x 10(9) or 2 x 10(9) total sperm, three times during the estrous period. Data from a total of 444 sows were used to determine boar fertility; between 12 and 54 sows were bred with each semen dose across the six boars. All measures of sperm fertilizing ability in vitro were different among boars (all P < .05) and use of different semen dilutions for IVF allowed further discrimination of apparent sperm quality among boars. The laboratory evaluation of semen collected during the period of breeding indicated effects of boar on ejaculate volume, total number of sperm per ejaculate, motility, and the percentage of sperm with normal morphology (all P < .01). Sperm dose used in AI had no effect on farrowing rate (80.7 vs 81.5%), but the lower AI dose resulted in a reduction (P < .05) in total numbers born (10.8 vs 10.0). For all three semen dilutions, estimated potential embryo production rate accounted for up to 70% of the variation in litter size obtained with 3 x 10(9) sperm per AI dose, and the number of sperm attached per oocyte was a major factor accounting for variation in litter size obtained with 2 x 10(9) sperm per AI dose. These IVF variables may, therefore, be effective indicators of boar sperm quality for use in AI. With 2 x 10(9) sperm per AI dose, the percentage of sperm with normal morphology also explained a large part of the variance in litter size born (R2 = .59), indicating that morphological characteristics are a useful measure of semen quality.

Alteration of Ingestive Behavior and Plasma Metabolites by Estrogen in Ovariectomized Goats.

Ovariectomized goats were treated with subcutaneous implants containing ovarian steroid hormones and their effects on ingestive behavior and plasma metabolite concentrations were examined along with those on reproductive function. Sequential administrations of progesterone (P) and estradiol (E) reproduced steroidal milieu during the luteal through the follicular phases. Around 35 hours after the commencement of the E administration, estrous behavior appeared, and almost simultaneously the luteinizing hormone surge occurred. During the estrous period, amount of food intake and duration of rumination markedly decreased, whereas plasma concentrations of glucose and free fatty acid increased. These changes lasted until the E-implant was removed. The E administration without P pretreatment induced similar changes in reproductive, ingestive and metabolic parameters, although the occurrences of these were all advanced. In contrast, the administration of P alone had no such effect on any parameter. These results demonstrate that estrous behavior is accompanied by changes in feeding behavior and metabolism, and suggest that E is playing essential roles to prepare female for mating by coordinating diverse physiological functions in the goat.

Influence of mating frequency on sow reproductive performance.

Gilts and sows were bred one, two, or three times during a single estrous period in a commercial herd for evaluating the effect of mating frequency on reproductive performance. Estrus detection started at approximately 0630 daily by applying back pressure to females with the presence of a mature boar. Natural mating was used. Gilts detected in estrus were mated in the morning of d 1 (AM), the morning of d 1 and 2 (AM-AM), and the morning and afternoon of d 1 and morning of d 2 (AM-PM-AM) for mating frequencies 1, 2, and 3, respectively. Sows were bred in the AM, AM-AM, AM-PM-AM (1), and morning of d 1 and morning and afternoon of d 2 [AM-AM-PM (2)] for mating frequency 1, 2, 3 (1), and 3 (2), respectively. Breeding events in the morning and afternoon started at approximately 0730 and 1530. Females were randomly assigned to a mating frequency. Boars were randomly assigned to each breeding event. In total, 256 gilts and 766 sows were involved in the study. Gilts with a single mating (76.5%, P = .06) and triple matings (80.4%, P < .05) had higher farrowing rates than those with double matings (65.3%). No differences (P > .1) in the farrowing rates of sows were observed between mating frequencies 1, 2, 3 (1), and 3 (2). Double-mated gilts had more (P < .03) total born (9.7 vs 8.6) and pigs born alive (9.3 vs 8.2) than did single-mated gilts. There were no differences (P > .3) in total born and pigs born alive in sows between mating frequencies. We concluded that triple-mating gilts and sows did not improve farrowing rate and litter size compared with single and double matings. There were no differences in farrowing rate and litter size between double- and single-mated sows. Gilts with double matings had a larger litter size than those with a single mating.

Synchronization of estrus in sheep using progestagen and inseminating with chilled semen during the breeding season

The efficiency of synchronization following the use of halved or whole (60 mg) MAP sponges and 300 IU PMSG during the breeding season was evaluated using 111 Merino ewes. Artificial insemination was performed with chilled semen (stored as 15 °C for 3 h) at 55 h following sponge withdrawal in the progestagen treated ewes and at 12 h following the onset of natural estrus in the control group. Estrous occurrence from time of sponge withdrawal, the interval from sponge withdrawal to estrus (mean of 30.5 vs 27.5 h for the whole and halved sponges, respectively) and the duration of the induced estrous period (mean of 25.1 vs 28.3 vs 35.0 h for the whole, halved sponges and control groups, respectively) was not significantly different in the groups. A high percentage of MAP was still present in the whole (76.6%) and halved (49.3%) sponges following withdrawal after 14 days. The mean serum progesterone concentration during the estrous period was higher ( P < 0.01) in the control group. No significant difference was found in the peak serum LH concentrations and the position of the LH peak relative to estrus. The conception rate was higher ( P < 0.01) in the halved sponges and the control (70.5 and 64.0%, respectively), compared with the whole MAP sponges (54.8%). Similarly the lambing rate was also higher ( P < 0.01) for the halved sponges and control group, compared with the whole sponges (106.8 vs 104.9 vs 85.9%, respectively). Halving of 60-mg MAP sponges is warranted in the breeding season and fertility results obtained with chilled semen are satisfactory.

Non-invasive detection and monitoring of estrus, pregnancy and the postpartum period in pygmy loris (Nycticebus pygmaeus) using fecal estrogen metabolites.

Estrone-conjugates (E1C) were measured in the feces of six female pygmy lorises (Nycticebus pygmaeus) during estrus (n = 12), pregnancy (n = 4) and the postpartum period (n = 3). Noninvasive feces collection permitted frequent sampling throughout estrus and pregnancy, without disturbance of animals. The estrous period was defined as an increase in fecal E1C levels above an average of 70 ng/g feces with peaks above 100 ng/g feces obtained in consecutive fecal samples collected over a 6- to 11-day period between the end of July and the first third of October. Comparison of the periovulatory profile of E1C and the stage of labial opening of the vagina revealed a high agreement (P < 0.001). In all pregnant females, an E1C rise was found approximately 47 days postestrus, the source of which may be the growing fetal placental unit. Estimated gestation lengths ranged between 187 and 198 days (n = 4).

Estrous expression in dairy cows and heifers ( Bos taurus) following repeated PGF 2α injection and choice of selecting a mounting partner

Research findings on the behavioral patterns of animals in estrus have indicated a strong relationship between social structure of the herd and estrous expression. It was therefore of interest to know if the liaisons established during a previous heat are maintained through subsequent estrous periods, particularly with respect to the choice of mounting partners. Fourteen Holstein cows and ten heifers were synchronized on six occasions. Every 11 days, each animal received an i.m. injection of 25 mg PGF 2α, except for the fifth and sixth trials, when only half of the animals were treated. Sexual behavior of both groups was observed continuously from 40 to 100 h following injection. The ‘consistency value’ representing the repeatability of mounting behavior during estrus was higher in cows than in heifers (0.18 ± 0.1 vs. 0.13 ± 0.01; P < 0.05). Cows in estrus formed a greater number of sexually active groups (3.5 ± 1.2 vs. 2.0 ± 0.6; P < 0.05), with fewer members (2.65 ± 1.52 vs. 3.30 ± 1.36; P < 0.05) than heifers. The length of the estrous periods were 17.6 ± 1.96 h in cows and 20.6 ± 2.54 h in heifers ( P < 0.05). Mounting behavior was equally distributed between day and night. Sexual activities showed marked contrasts between groups and among trials. It was concluded that cows form more stable social groups than heifers, as shown by a greater consistency in their choice of mounting partners.

Changes in uterine secretion of prostaglandin F2 alpha in response to oxytocin during the estrous cycle, early pregnancy, and estrogen-induced pseudopregnancy in swine.

Thirty-one sows were used in an experiment designed to determine whether the ability of the porcine uterus to release prostaglandin (PG) F2 alpha in response to oxytocin was suppressed in pregnancy and pseudopregnancy. Sows were assigned to one of three treatment groups: nonbred (nonpregnant) controls (n = 8), pseudopregnant (5 mg estradiol benzoate, i.m., daily on Days 11-15 postestrus; n = 8), or bred (bred once daily throughout the estrous period; n = 15). Jugular venous blood samples were collected daily for quantification of progesterone. Pregnancy was determined by uterine examination at slaughter 51-72 days postmating. On the basis of progesterone and embryo recovery, bred sows were classified into three subgroups: confirmed pregnant (n = 4), suspected pregnant based on delayed luteal regression (n = 5), or bred/not pregnant (n = 6). All sows received an injection of oxytocin (30 IU, i.v.) on Days 12, 15, and 18 postestrus. Jugular venous blood samples were collected from 60 min prior to through 120 min after injection of oxytocin for quantification of 13, 14-dihydro-15-keto-PGF2 alpha (PGFM). Magnitude of response above baseline and area under the PGFM response curve (AUC) were calculated for each sow on each day and compared among treatment groups by analysis of variance. Responses in pregnant and suspected-pregnant sows were not different on any day examined; therefore the two groups were combined (n = 9) and considered pregnant for all subsequent analyses. Responses in the nonpregnant and bred/not pregnant sows were pooled and compared to the responses in the pregnant and pseudopregnant sows. Magnitudes of response were similar between these pooled groups on Day 12 (p > 0.5), but were less in pregnant and pseudopregnant sows on Days 15 and 18 (p < 0.01). When nonpregnant and bred/not pregnant sows were compared to each other, the magnitudes of the response were similar on Days 12, 15, and 18 (p > 0.3 on each day). In contrast, when pregnant and pseudopregnant sows were compared, pseudopregnant sows had a lower magnitude of response that was consistent across all 3 days (p < 0.02). Similar relationships were apparent for the AUC. These results demonstrate that uterine secretory responsiveness to oxytocin is suppressed during early pregnancy and that this effect may be mediated through estrogen secreted by conceptuses.

Immunohistochemically-determined changes in the distribution of insulin-like growth factor-I (IGF-I) and epidermal growth factor (EGF) in the bovine endometrium during the estrous cycle.

The aims of this study were to investigate whether there are cell-specific distributions of insulin-like growth factor I (IGF-I) and epidermal growth factor (EGF) in the endometrium, and to determine whether or not the expression of these factors varies with the stage of the estrous cycle. Fifty-four endometrial biopsy specimens were collected from normal cycle Holstein-Friesian heifers. The endometrial specimens were divided into nine groups (at least five different animals per group) corresponding to the following days of the cycle: days 20-0, 1-3, 4-5, 6-7, 8-10, 11-13, 14-15, 16-17, and 18-19 (day 0 = estrus). IGF-I and EGF were localized by immunohistochemistry in the intact heifer endometrium throughout the estrous cycle. Throughout the estrous cycle, IGF-I was localized in the luminal epithelium and stroma with a little staining in the glandular epithelium (P < 0.01). In the luminal epithelium, the number of IGF-I-positive cells increased on days 1-3, 6-7, 11-13, and 16-17. In the stroma, the number of IGF-I-positive cells increased on days 8-10 and 20-3. The number of positively stained cells in the glandular epithelium increased around the estrous period. EGF stained intensely in the stroma but very little in the luminal and glandular epithelia (P < 0.01). In the stroma, three peaks in the number of EGF-positive cells were observed: on days 1-3, 6-7, and 11-13. These results demonstrate cyclical changes in the endometrial cell types localization of IGF-I and EGF.

Use of behavioral measures to assess reproductive status in maned wolves (Chrysocyon brachyurus)

Captive breeding efforts of the threatened maned wolf (Chrysocyon brachyurus) have been plagued by a lack of reliable reproduction and a high rate of neonatal mortality. A particular problem for animal managers has been the ability to detect pregnancy in a noninvasive manner. Pseudopregnancies are common, and many staff hours are expended preparing for a birth that may not occur. The objectives of our study were to document changes in behavior during the breeding season in captive maned wolves in order to determine if behaviors other than sexual (i.e., copulation) could be used to distinguish nonbreeding from breeding pairs and, further, whether successful breeding pairs (young born) could be distinguished behaviorally from breeding pairs that did not produce young (pseudopregnant). Between 1988 and 1994, behavioral data were collected during the annual reproductive season from 52 maned wolf pairings (27 males, 26 females) housed at 17 North American institutions. Breeding animals showed significant increases in rates of affiliative behaviors (approach, friendly) and the amount of time spent in close association (social) during the estrous period, compared to pre- and post-estrous periods. In contrast, the behavior of nonbreeding pairs varied little throughout the breeding season. Discriminant function analysis (DFA) showed that several behavioral measurements during certain reproductive periods were useful in discriminating between nonbreeding and breeding animals (rates of friendly and social behavior for males, marking and social behavior for females). Unsuccessful (pseudopregnant) and successful breeding pairs could be further distinguished on the basis of agonistic and approach behavior frequencies (successful females showed higher rates of agonistic and lower rates of approach behavior during certain periods; successful males had higher rates of both behaviors). Discriminant equations for key behavioral measurements and examples of their practical application are presented. DFA provides animal managers with an effective, noninvasive technique for assessing the reproductive status of maned wolf pairs. © 1996 Wiley-Liss, Inc.

Growth and estrous behavior of heifers actively immunized against prostaglandin F2 alpha.

To determine the effects of active immunization against prostaglandin F2 alpha (PGF) on estrous activity and performance traits of beef heifers, 50 14-mo-old cyclic heifers (358 +/- 3.3 kg) were assigned to two treatments (n = 25 per treatment): 1) heifers (controls) given 3.3 mg of human serum albumin (HSA) on d 0 (primary) and 27 (booster), and 2) heifers (PGF-immunized) given 3.3 mg of PGF-HSA on d 0 and 27. The adjuvant was DEAE-dextran, and the duration of the experiment was 167 d. Plasma progesterone concentrations (every 3 to 4 d) were used to monitor corpus luteum (CL) presence; PGF antibody titers were determined every 2 wk. Heifers were checked twice daily for estrous behavior and were weighed every 2 wk. Data were analyzed using ANOVA. Antibody titers for PGF-immunized heifers increased to a peak (43 +/- 2.9% binding at a plasma dilution of 1:1,250) on d 55 +/- 4.6. Antibody titers were greater (P = .02) in PGF-immunized than in control heifers by d 15 and remained elevated (P < or = .001) throughout the experiment. Twenty-four of 25 PGF-immunized heifers formed persistent CL with a mean duration of 129 +/- 6.4 d. The mean number of estrous period per heifer were less for PGF-immunized (1.5 +/- .27) than for control heifers (7.0 +/- .32). Mean daily live weight gain of the PGF-immunized heifers was decreased (P < .05; .75 +/- .024 kg) compared with that of controls (.83 +/- .014 kg), largely due to a 31.5% decrease during the 28-d period after booster.(ABSTRACT TRUNCATED AT 250 WORDS)

Responses of Free-ranging Rhesus Monkeys to a Natural Form of Social Separation. I. Parallels with Mother-Infant Separation in Captivity

Observations of 23 free-ranging rhesus monkey infants on Cayo Santiago, Puerto Rico, indicated that mothers' first postpartum estrous periods were marked by large increases in the amount of time infants were separated from their mothers, by disturbances in mother-infant relationships, and by increases in infant distress behavior. When their mothers resumed mating, most infants showed signs of agitation; a few briefly showed indications of depression. Male infants responded to their mothers' resumption of mating by playing more, whereas females engaged in less play and more allogrooming. The results suggest (a) that basic parallels exist between the behavioral responses of rhesus infants to their mothers' resumption of mating in the field and to forcible separation from their mothers in captivity and (b) that early separation experiences may play a role in the normal development or manifestation of sex differences in behavior.

Follicular development, oocyte viability and recovery in relation to follicular steroids, prolactin and glycosaminoglycans throughout the estrous period in superovulated heifers with a normal LH surge, no detectable LH surge, and progestin inhibition of LH surge

Estrous cycles of heifers (n = 137) were synchronized with prostaglandin (PGF 2α) and follicular development stimulated with follicle stimulating hormone. Twenty-eight animals were administered Norgestomet implants 12 hr prior to the initial PGF2α injection to suppress the LH surge that initiates ovulation. Animals were ovariectomized every 12 hr after the initial PGF2α (7–9/time, 12–108 hr and at 192 and 240 hr post PGF2α) and divided into three treatment groups to consist of: 1) animals exhibiting a normal luteinizing hormone (LH) surge (n = 86), 2) animals in which no LH surge was detected (n = 23), and 3) suppression of the LH surge via Norgestomet implants (72–108 hr, n = 28). Follicular diameter was measured and follicular fluid was collected for analysis of prolactin, estradiol, progesterone and glycosaminoglycan concentrations. Progesterone concentrations were increased in animals exhibiting an LH surge as compared to animals in which no LH surge was detected; primarily in large follicles (> 8 mm diameter) after the LH surge. Animals not exhibiting an LH surge also had increased follicular progesterone concentrations compared to Norgestomet-implanted animals (242.3 ± 36.3 vs 86.7 ± 6.4 ng/ml, respectively, P < .01), indicating some LH stimulation. Follicular estradiol in animals exhibiting an LH surge increased up to the time of LH surge detection and then declined whereas animals with no LH surge detected had follicular estradiol concentrations that declined after the PGF 2α injection. No differences were noted between those that did not exhibit an LH surge or in which the LH surge was suppressed with Norgestomet in relation to follicular estradiol concentrations. Follicular estradiol concentrations increased with follicular size in all treatment groups (P < .01). Follicular concentrations of prolactin were increased in small follicles (P < .05; ≤ 4 mm diameter) and follicular prolactin increased from 12 to 36 hr post PGF2α injection, then declined after the LH surge. Follicular glycosaminoglycan concentrations decreased with increases in follicular size (P < .01) and were higher in animals that did not exhibit an LH surge (P < .01). No differences in follicular glycosaminoglycans were noted between Norgestomet-implanted animals and those not exhibiting an LH surge. In the animals representing days 4 and 6 of the subsequent estrous cycle (192 and 240 hr post PGF2α), numbers of small-sized follicles were increased. Follicular progesterone and estradiol concentrations were related to atretic large follicles unovulated from the prior estrus and a wave of growth in small and medium follicles. Follicular prolactin and glycosaminoglycans increased with time of the new estrous cycle and were increased in smaller follicles (P < .01). Suppression of LH with progestin implants (Norgestomet) may relate to early effects of progesterone, which may not be totally eliminated at target tissues and subsequently alters the LH surge, steroidogenesis of the follicle, and ovulation. Oocytes were predominantly found in the follicular fluid from animals in which an LH surge was detected and in the buffer wash of follicles in which no LH surge was detected. Oocyte viability was higher in animals exhibiting an LH surge (75% viable) whereas the oocytes of Norgestomet-implanted animals were 75% degenerate.