Peripheral and intrauterine neutrophil function in the cow: the influence of endogenous and exogenous sex steroid hormones

It has been accepted for many years that the susceptibility of the genital tract to infection is reduced during the follicular phase compared with the luteal phase of the estrous cycle. Since the role of intrauterine neutrophils is paramount in the elimination of bacteria, it can be hypothesized that these differences in resistance to infection could be mediated by differences in uterine-derived neutrophil function. In order to test this hypothesis two groups of cows were used in this study. Group 1 cows (n=5) were studied at estrus, diestrus, after ovariectomy, after exogenous estradiol and after progesterone treatment, at which time they underwent intrauterine infusion with 1% oyster glycogen (OG) and a bacterial-free filtrate (BFF) of Actinomyces genes (BFF), the latter having been recovered from a clinical case of endometritis; neutrophils were harvested by flushing from the lumen 15 to 18 h later. A peripheral blood sample was collected at the time of flushing for the assay of estradiol and progesterone for a WBC and differential count and for the harvesting of neutrophils using a Percoll single-stage discontinuous gradient. After the recovery of the cells they were re-suspended in HBSS. Group 2 (n=4) were infused with BFF during during all reproductive states as Group 1, but with OG only after ovariectomy and after treatment with progesterone and estradiol. Neutrophil chemotaxis was assessed by measuring their migration using a modified Boyden chamber and Zymogen-activated serum as a chemoattractant. Phagocytic activity was measured by determining the number of Candida albicans ingested by each neutrophil after incubation. The percentage of kill was determined using a radiometric assay in which C. albicans was labeled with L-(5-3H) Proline. Peripheral WBC concentration was not influenced by the reproductive state of the cow; however, the mean neutrophil concentration was significantly different between the reproductive states (P<0.001) and between individual cows (P<0.001). In Group 1, there was little difference in the function of the peripheral and uterine neutrophils, and while there were differences in all 3 aspects of neutrophil function from both sources between reproductive states and individual cows, of which some were statistically significant, there was no consistent pattern. In Group 2, neutrophils recovered after the infusion of BFF had poorer function compared with those recovered after the infusion of OG. There was no consistent influence of the reproductive state or individual animal. The hypothesis that the influence of the reproductive state of the cow on the resistance of the uterus to infection is mediated by the inherent differences in either peripheral or intrauterine neutrophil function was not supported by this study.     

Variation in estrus-related odors in the cow and its dependency on the ovary

Urine samples were collected from 10 cows during the estrous cycle (Day 0=day of observed estrus) and investigated for pheromone activity using a quantitative rat bioassay. Pheromone activity in this assay was given in impulses/45 sec. Progesterone was measured in milk fat to verify the stage of cycle. The maximal response of rats was found on Day -1 (20.0 +/- 3.5 impulses/45 sec; x +/- SEM), and impulse rates were clearly higher (P 相似文献   

The regulation of precopulatory behavior by ovarian hormones in the female Mongolian gerbil

The hormonal regulation of precopulatory behavior in the female Mongolian gerbil was studied using two groups (N = 6) of sexually experienced females. A novel testing procedure was used which involved females living continuously with test males for several days. The test males showed either full sexual behavior (copulating males, C) or only precopulatory behavior (noncopulating males, NC). Experiment 1 investigated changes during the estrous cycle and following ovariectomy in females. Experiment 2 studied the effects of hormonal treatment of these ovariectomized females with 6 micrograms estradiol benzoate (EB) followed by 0.4 mg progesterone (P) or by 0.04 ml arachis oil. When tested with NC males, females displayed a greater range of precopulatory behavior. The patterns could be classified into three groups according to the manner of response to ovariectomy and hormone treatment. Group I patterns (approach, leave, and olfactory investigation of the male's head) were affected by neither ovariectomy nor EB treatment relative to Day 3 levels (Day 3, day preceding estrus; Day 4, estrus), but they were increased to estrous levels by EB and P. Group II patterns (darting, foot-stomping, and the present and piloerection postures) appeared only during estrus, did not appear after ovariectomy, and reappeared only after sequential EB and P treatment. Group III patterns (investigation of the male's anogenital area, allogrooming, ventral gland marking, and sand-rolling) were reduced relative to both estrus and Day 3 levels by ovariectomy and increased above Day 3 levels by EB alone; EB and P treatment further increased Group III patterns to the level of estrus. It is suggested that female precopulatory behavior patterns differ in their responsiveness to ovarian hormones. Estrogen appears to affect those patterns associated with the earliest stages of estrus (Group III).     

Inhibition of estrus and corpora lutea function with Norgestomet

Forty-five nonpregnant, nonlactating, Angus and Brangus cows were utilized to determine how long a Norgestomet ear implant would inhibit estrus when administered at various stages of an estrous cycle. All cows completed a nontreated estrous cycle to ensure normal cyclicity. At the second observed estrus (estrus = Day 1), cows were randomly allotted to be treated at metestrus (Day 3 or Day 4, n = 15); at diestrus (Day 9 or Day 10, n = 14); or at proestrus (Day 15 or Day 16, n = 16). All cows received a 2-ml intramuscular injection of 3 mg of Norgestomet accompanied by a 6-mg Norgestomet ear implant, which remained in situ for 21 days, or until individual cows were observed in estrus. Estrus was inhibited for a mean (+/- SEM) of 18.7 +/- 0.7, 19.9 +/- 0.8, and 17.0 +/- 0.8 days, respectively, when cows were treated at metestrus, diestrus, and proestrus (metestrus and diestrus vs proestrus; P < 0.05). Estrus was inhibited for an entire 21-day implantation period in 27, 50, and 38% of cows treated at metestrus, diestrus, and proestrus, respectively (P > 0.10). Norgestomet inhibited estrus in all cows for 11, 17, and 11 days after implantation when treatment was initiated at metestrus, diestrus, and proestrus, respectively (P > 0.10). These data indicate that a 6-mg Norgestomet ear implant effectively inhibits estrus in all cows for a maximum of 11 days, with some cows exhibiting estrus by Day 12 with the Norgestomet implant in situ.     

Effect of an implant containing the GnRH agonist deslorelin on secretion of LH, ovarian activity and milk yield of postpartum dairy cows

Prevention of high plasma progesterone concentrations in the early postpartum period may improve fertility. Our objective was to determine whether a Deslorelin implant (DESL; 2100 microg, s.c.) would reduce secretion of LH and alter follicle dynamics, plasma concentrations of progesterone, estradiol and PGF2alpha metabolite (PGFM) in postpartum dairy cows. Cows received DESL on Day 7 postpartum (Day 7, n=8) or were untreated (Control, n=9). All cows were injected with GnRH (100 microg, i.m.) on Day 14 to assess LH response. A protocol for synchronization of ovulation with timed AI was initiated on Day 60 (GnRH [Day 60], CIDR [Day 60 to Day 67], PGF2alpha [Day 67, 25 mg and Day 68, 15 mg], GnRH [Day 69] , AI [Day 70]). The LH response to injection of GnRH on Day 14 was blocked in animals treated with DESL. Numbers of Class 1 (<6 mm) follicles were unaffected (P > 0.05) whereas numbers of Class 2 (6 to 9 mm) (P < 0.01) and Class 3 (>9 mm) follicles were less (P < 0.01) in DESL cows between Day 7 and Day 21. From Day 22 to Day 60, DESL-treated cows had more of Class 1 follicles and less Class 2 (P < 0.01) and Class 3 (P < 0.01) follicles, and lower plasma concentrations of progesterone and estradiol (P < 0.01). Concentrations of PGFM between Day 7 and Day 42 were not affected by treatment (P > 0.05). All cows ovulated in response to GnRH on Day 69. Subsequent luteal phase increases in plasma progesterone concentrations (Day 70 to Day 84) did not differ. The use of the DESL implant associated with PGF2alpha given 14 days later suppressed ovarian activity and caused plasma progesterone concentrations to remain < 1 ng/mL between Day 22 and Day 51. The DESL implant did not affect milk production.     

Pattern of sex steroids secretion and their relationship with embryo yield in Jersey cows superovulated with PMSG

The levels of progesterone and estrogen secretion were studied in relationship to the superovulatory response in Jersey cows. Progesterone and estrogen concentrations were measured in superovulated Jersey cows with the objective of correlating the patterns of steroid secretion with embryo yield and quality. Pregnant mare serum gonadotropin (PMSG) was used in combination with prostaglandin F(2) alpha analogue to induce superovulation in 18 multiparous, cyclic cows. Serum progesterone and estradiol levels from cows which exhibited estrus within 24 to 48 h after prostaglandin administration (n=13) were used to estimate the superovulatory response. Sex steroid concentrations at the day of estrus (Day 0) was a strong indicator of embryo yield. Progesterone was negatively (r=-0.56) and estrogen positively (r=0.80) correlated to the number of embryos collected. Dramatic increase in progesterone from Day 0 to Day 7 was a significant indicator of embryo yield. A higher rise of estrogen in the follicular phase was an indicator of a larger number of growing follicles and, consequently, better superovulatory response. Nonresponding animals did not show any significant change in the hormonal profile from the day of PMSG treatment to the day of embryo collection. The estimation of progesterone and estradiol concentrations, simultaneously, gave a more objective prediction of embryo yield.     

Chronic stress, hormone profiles and estrus intensity in dairy cattle

The objectives of the present study were to determine if lameness, a model for a natural chronic stressor, affects hormone concentrations in milk prior to estrus and/or the subsequent expression of estrus in the postpartum period. Dairy cows>20 days postpartum were scored for lameness and observed for estrus intensity using a weighted scoring system (>100 points=estrus=Day 0). Increasing lameness score was not associated with daily profiles of milk progesterone (throughout Days -18 to 0), estradiol (Days -6 to 2) or cortisol (Days -18 to 2) around estrus, maximum estradiol values or estradiol concentrations on Day 0. However, post hoc pair wise comparisons revealed that prior to estrus, severely lame cows had lower maximum progesterone concentrations compared to nonlame cows (1.3+/-0.1, 1.2+/-0.2, 0.7+/-0.1 ng/ml milk; P=0.042). Furthermore, severely lame cows expressed behavioral estrus with lower intensity (284+/-128 points, n=9) compared to moderately lame (662+/-310 points, n=9) or nonlame animals (583+/-275 points, n=18; P=0.05 and P=0.02, respectively). Resting concentrations of cortisol (Days 20-80 postpartum) did not vary between days postpartum or lameness score. The incidence of behavioral estrus was not affected by increasing lameness score, as 54.2%, 56.2% and 50.0% periods with low progesterone were associated with spontaneous estrus expression, respectively. Concluding, in this biological model of chronic stress, lameness did not affect the incidence of behavioral estrus but did reduce estrus intensity once ovarian cyclicity had resumed after calving. This reduced intensity of estrus was associated with lower maximum progesterone values prior to estrus but not abnormal daily cortisol or estradiol values in milk.     

Effect of ACTH (tetracosactide) on steroid hormone levels in the mare. Part B: effect in ovariectomized mares (including estrous behavior)

The mare is the only non-primate species known to display estrous signs after ovariectomy and adrenal hormones have been implicated as a possible cause. Moreover, in several species, estradiol seems to have a stimulatory effect on the hypothalamic-pituitary-adrenal axis. The aim of the present study was to compare the effect of ACTH (tetracosactide) on pertinent hormones [cortisol, progesterone, androstenedione, testosterone (intact and ovariectomized mares) and estradiol (ovariectomized mares only)] in intact mares in estrus with the same mares after ovariectomy (n=5). Blood samples were collected hourly from 12:00 until 14:00 h the following day (half-hourly between 14:00 and 17:00 h) on two occasions, with saline or ACTH treatment at 14:00 h (saline treatment day or ACTH treatment day). The mares, both when intact and after ovariectomy, showed a significant increase in all measured hormones, except estradiol (not measured in intact mares), after ACTH treatment, lasting at least 3h post-treatment (P<0.001). On the saline treatment day, cortisol levels in ovariectomized mares were lower than in intact mares in the evening (18:00-23:00 h), but higher at night (24:00-05:00 h). No differences in cortisol response between mares, when intact and after ovariectomy, were found after ACTH treatment (P=0.3). Androstenedione levels were lower (P<0.001) and increased less after ACTH treatment in ovariectomized mares, as compared to when intact (P<0.05). Progesterone concentrations were lower in the ovariectomized mares at night (24:00-05:00 h) on the saline treatment day and at all times on the ACTH treatment day (P<0.05). Testosterone concentrations were lower in ovariectomized mares on both treatment days, as compared to when intact (P<0.001). It was concluded that ovariectomy affected basal cortisol pattern. Ovarian androstenedione and testosterone contributed to the basal circulating levels and, in the case of androstenedione, was stimulated by ACTH. Endogenous estradiol did not act stimulatory on adrenal gland hormone production in the mare.     

Synchronization of estrus with PGF2 alpha administered 18 days after a progesterone treatment in lactating dairy cows

In a previous study we showed that estrus synchronization with 2 treatments of PGF2 alpha 13 d apart reduced conception rate at the synchronized estrus and that this reduction occurred mainly in cows in the early luteal phase at the second PGF2 alpha treatment. The objective of the present study was to determine the efficacy of a synchronization regimen in which PGF2 alpha was administered during the mid- to late-luteal phase to cows that had previously been synchronized with progesterone. Spring-calving cows from 6 dairy herds were used in this study. On Day -32 (Day 1 = the start of the breeding season), cows that had calved 2 or more weeks ago were randomly assigned to a synchronization (S, n = 732) or control (C, n = 731) group. Cows in Group S were treated with an intravaginal progesterone device (CIDR) for 12 d from Day -32 to Day -20, while those in Group C were left untreated. Similar percentages of cows in Group S (80.6%) and C (82.9%) had cycled by Day -7. The CIDR treatment synchronized the onset of estrus, resulting in 92.9% of cows in estrus being detected within 7 d after CIDR removal. Cows in Group S that had cycled by Day -7 were treated with PGF2 alpha (25 mg, i.m., Lutalyse) on Day -2. Cows in both groups that were anestrous on Day -7 were treated with a combination of progesterone and estradiol benzoate (EB) to induce estrus and ovulation (CIDR and a 10 mg EB capsule on Day -7, CIDR removal on Day -2, and injection of 1 mg EB 48 h after CIDR removal). The PGF2 alpha treatment synchronized the onset of estrus in 87.5% of the cows. Group S and C cows had similar conception rates to first (61.0 vs 58.3%) and second (58.4 vs 60.9%) AI; similar pregnancy rates over the AI period (82.8 vs 79.2%) and over the whole breeding season (91.9 vs 90.6%); and required a similar number of services per pregnancy to AI (1.7 vs 1.8). The interval from the start of the breeding season to conception for cows conceiving to AI or to combined AI and natural mating was shorter (P < 0.001) by 5.7 and 6.2 d, respectively, for the Group S cows. It is concluded that the treatment regimen tested in the present study achieved satisfactory estrus synchronization, had no detrimental effect on fertility at the synchronized estrus, and shortened the interval from start of the breeding season to conception.     

Incorporation of a rapid pregnancy-associated glycoprotein ELISA into a CIDR-Ovsynch resynchronization program for a 28 day re-insemination interval

The objective was to compare two resynchronization programs; one that used a blood-based ELISA for pregnancy-associated glycoproteins (PAG) for pregnancy diagnosis so that non-pregnant cows were re-inseminated at 28 d after first TAI, and another that used transrectal ultrasonography for pregnancy diagnosis so that non-pregnant cows were re-inseminated at 35 d after first TAI. The PAG_resynch cows (n = 103) began CIDR-Ovsynch resynchronization on Day 18 after first TAI (Day 0). On Day 25, the CIDR was removed and pregnancy diagnosis with a PAG ELISA was performed. If a cow was not pregnant on Day 25, she was treated with PGF_2α, treated with GnRH 2 d later (Day 27), and TAI on Day 28. Control cows (n = 99) were observed for estrus until Day 25, when they began an identical CIDR-Ovsynch program with pregnancy diagnosis by transrectal ultrasonography on Day 32. If a cow was not pregnant on Day 32, then she was treated with PGF_2α, treated with GnRH 2 d later (Day 34), and TAI on Day 35. There was no difference in pregnancy per AI (P/AI) for either group at first or second insemination. For cows without pregnancy loss, the interval between first and second (P < 0.001) or second and third (P < 0.016) TAI was shorter for PAG_resynch cows compared with Control cows. The interval between first and second or second and third TAI was not different if pregnancy loss cows were included in the analysis. Plasma progesterone concentrations were similar at PGF_2α treatment, and plasma estradiol concentrations increased similarly after PGF_2α treatment for PAG_resynch and Control cows. In conclusion, the 28 d CIDR-Ovsynch resynchronization protocol was comparable to a 35 d CIDR-Ovsynch resynchronization protocol that also included estrus detection. Shortened resynchronization protocols that do not require estrus detection may improve reproductive efficiency in dairy cattle.     

Capability of ovarian steroids in inducing LH surges in acutely ovariectomized rats.

The capability of estradiol (E2) or E2 and progesterone (P4) in inducing luteinizing hormone (LH) surge in acutely ovariectomized (Ovx) rats was studied. In group I, rats were Ovx on estrus and were implanted with E2 capsules and atrial cannulae immediately after operation for blood samplings. In group II, rats were also Ovx on estrus but were implanted with E2 capsules and sampling cannulae the next day (the expected diestrus day 1, D1). In group III, rats were Ovx on D1, and were implanted E2 with capsules and atrial cannulae immediately after operation. All surgical operations were done around 1000h in the morning. On the expected diestrus day 2(D2) at 0930h, one half of the rats in each group received an oil vehicle or 2mg of P4 subcutaneously. Blood samples were taken from the indwelled cannulae at 1300, 1500, and 1700hrs in the afternoon. Results showed that P4 treatment amplified LH release in all three groups of rats primed with E2, and that the oil vehicle did not assist in LH release in E2 primed rats of group I and group II, but it did in 8 out of 10 rats in group III in the late afternoon of D2. Results suggested that the estradiol alone was capable in inducing LH surge on the expected D2 afternoon, and that under estradiol-primed conditions, P4 can trigger neural initiators to advance LH surge, but that the internal hormonal milieu at the time of ovariectomy may affect the influence of ovarian steroids in inducing LH release.     

The effect of aspirin administration and parity on plasma salicylate concentrations and postpartum reproductive parameters in Brahman cows

Forty pluriparous (M) and 20 primiparous (P) suckled Brahman cows were used to evaluate the effect of aspirin and parity on plasma 13,14-dihydro-15-keto-prostaglandin F2alpha (PGFM) and progesterone (P4) concentrations and some reproductive parameters. On Day 7 after calving (PP), the cows were allocated within parity into 2 groups: the aspirin group received concentrate containing aspirin at a rate of 100 mg/kg of body weight every 12 h until Day 13 PP; and the control received concentrate every 12 h for the same interval. Blood samples were collected after first and last aspirin feeding and daily from Day 1 PP to Day 6 PP and from Day 14 PP to Day 21 PP, twice daily from Day 7 PP to Day 13 PP, and weekly until first non-return to estrus. Plasma salicylate concentrations in the aspirin group cows were affected by parity (P < 0.01) and time after feeding (P < 0.0001). P cows showed higher plasma salicylate concentrations with a later peak and slower decrease than M cows. Aspirin-treated P cows had longer PP intervals than either control P, control M, or aspirin-treated M cows. Cows receiving aspirin had a lower pregnancy rate, an increased incidence of abnormal estrous cycles, and a decline in the presence of corpora lutea after estrus. Cows that formed a corpora lutea and had received aspirin had higher P4 release between Day 6 and 14 after estrus. Aspirin-treated cows that did not form corpora lutea had lower P4 release between Days 9 and 14 after estrus. A treatment by parity interaction affected mean PGFM proportions (P < 0.01) during the treatment period. Aspirin-fed P cows increased PGFM release as measured by mean proportion of Day 6 PP values. Aspirin-fed M cows showed a decrease in mean PGFM proportions. Aspirin feeding during the early PP showed different effects on some reproductive parameters in P and M Brahman cows, indicating differences in PP physiology between parities.     

Superovulatory responses in dairy cows following ovulation of the dominant follicle of the first wave

In the present study we investigated the effect of hCG administration on Day 7 (Day 0 = day of standing estrus) to ovulate the dominant follicle of the first wave and the associated increase in progesterone concentration on subsequent superovulatory response in dairy cows. Twenty cyclic lactating cows were allocated at random to 2 groups: control (n = 10) and hCG-treated (n = 10). The ovaries of each cow were scanned using an ultrasound scanner on Day 7, to confirm the presence of the dominant follicle and thereafter every other day until embryo recovery. All cows received a total dose of 400 mg Folltropin-V in decreasing amounts for 5 days (Days 9 to 13) and 35 mg PGF(2alpha) on Day 12. In addition, the treated cows received 1000 IU hCG on Day 7. All cows were inseminated twice during estrus, and the embryos were collected 7 days later by a nonsurgical procedure. Blood smaples were taken at different times of the treatment period for progesterone determination. All cows possessed a dominant follicle at Day 7, and all but one of the hCG-treated cows ovulated the dominant follicle and formed an accessory corpus luteum. Plasma progesterone concentrations were significantly higher (P<0.01) in hCG-treated cows than control cows on the first day of Folltropin treatment and on the day of PGF(2alpha) injection. The mean number of follicles at estrus, the number of ovulations, the total number of embryos and the number of transferable embryos were not different (P>0.05) between control and hCG-treated cows.     

Comparison of two estrus synchronization and resynchronization treatments in lactating dairy cows

Reproductive performance in cows following synchronization of estrus with intravaginal progesterone releasing devices (IVD) has varied with the length of treatment, cyclic status and prolonged return to estrus intervals in some cows following first AI. The objective of this study was to compare two methods of synchronizing and resynchronizing estrus on the reproductive performance of lactating dairy cows. Cows were treated with an IVD (Day 0) for 7 days (n = 350) or 8 days (n = 350), cloprostenol (0.5 mg i.m.) at the time of device removal and estradiol benzoate (EB) at the time of device insertion (1.5mg i.m.), and again 9 days later (1.0 mg i.m.). Cows were also resynchronized starting on Days 23 and 46 by reinsertion of IVDs for either 7 or 8 days and treatment with EB (1mg i.m.) at the time of device insertion and again 9 days later. Cows were inseminated on detection of estrus for 4 days after removal of devices at each of the synchronized estrous cycles. No significant differences in reproductive performance were detected between each treatment throughout the study period. Synchrony of estrus was more precise at the first and second estrus after treatment with an IVD for 8 days compared to 7 days. Cows classified as anestrous had lower reproductive performance than cows classified as cycling and had longer intervals to estrus at the second (P < 0.001) and third estrus (P < 0.06), but not at the first estrus (P = 0.09). Mean time to onset of estrus after IVD removal was less in cows treated with an IVD for 8 days compared to 7 days at each synchronized estrus (P < 0.01). More Holstein-Friesian cows were classified as non-pregnant and not detected in estrus than crossbreed cows (15.7%, 54/343 versus 9.0%, 24/266; [P < 0.05). The results of the study suggested that the main effects of the treatments that were used to synchronize and resynchronize estrus were to alter the timing and synchrony of estrus without affecting fertility.     

Evaluation of steroid microspheres for control of estrus in cows and induction of puberty in heifers

Two trials were designed to test whether a single treatment with a microsphere formulation of progesterone (P) could simulate the luteal phase of the estrous cycle and lead to estrus and subsequent luteal development. The first experiment was to characterize the pattern of serum P concentrations and estrus in cows treated with a microsphere formulation (P + E) that contained 625 mg P and 50 mg estradiol (E). Four cows with palpable corpora lutea were treated with 25 mg prostaglandin F2 m. Each cow was given P + E (i.m.) 12 h later. Tail vein blood samples were taken on Days 1 and 2 following P + E treatment and then three times weekly for 24 days. Serum P increased from 0.8 +/- 0.1 ng/ml at P + E treatment to 4.7 +/- 0.6 ng/ml on Day 1, declined gradually to 4.1 +/- 0.3 ng/ml on Day 7 and then declined more rapidly to 0.6 +/- 0.1 ng/ml on Day 13. Treated cows showed estrus 16.25 +/- 0.7 days after P + E treatment. Thereafter, serum P increased beginning on Day 20 after P + E treatment, as expected following estrus. In Experiment 2, Angus and Simmental heifers (10.5-11.5 months of age) were administered i.m. either the vehicle (controls), E (50 mg), P (625 mg) or P + E (n = 13 per group). While treatment with E resulted in behavioral estrus (1-2 days after treatment) in each treated heifer, it did not (P > 0.5) initiate estrous cycles as indicated by subsequent increased serum P. In contrast, the P and P + E treatments increased (P < 0.05) the proportion (11/13) of heifers that showed estrus by 21 days after treatment followed by elevated serum P. We conclude that the microsphere formulation of P simulated the pattern of serum P concentrations during the luteal phase of the estrous cycle and initiated estrous cycles in peripubertal heifers with or without E.     

The effect of exogenous estradiol benzoate and altrenogest on uterine and ovarian blood flow during the estrous cycle in mares

In recent years, a positive relationship between genital perfusion and fertility has been established; in species other than horses, uterine and ovarian perfusion was improved by exogenous estrogen but impaired by exogenous progestin. The goal of the present study was to investigate the effect of exogenous estrogen and progestin on uterine and ovarian blood flow in cycling mares. Five Trotter mares were examined daily during three estrous cycles. Mares were given no treatment, altrenogest (0.044 mg/kg BW) orally from Day 0 (ovulation) to Day 14 and estradiol benzoate (5mg i.m.) on Days 0, 5, and 10, in three cycles, respectively. There was no difference ( P > 0.05 ) in the length of untreated versus estrogen-treated cycles ( 22.8 +/-1.3 days and 23.2 +/= 1.5 days, respectively), but cycle length was increased (P < 0.05) in progestin-treated cycles (26.0 +/- 1.2). To facilitate comparisons among cycles with different lengths, data from Days 0 to 15 (diestrus) and from Days -6 to -1 (estrus) were analyzed. Transrectal Doppler sonography was used to evaluate blood flow in both uterine arteries and in the ovarian artery ipsilateral to the preovulatory follicle during estrus and ipsilateral to the corpus luteum during diestrus. Blood flow was assessed semiquantitatively using the pulsatility index (PI); high PI values indicated high resistance and a low perfusion and vice versa. An immediate effect of treatments occurred only after the administration of estradiol benzoate on Day 0; uterine PI values decreased (P < 0.05) between Days 0 and 1 and estrogen-treated mares but increased (P < 0.05) at the corresponding time in untreated cycles. Mean PI values for the uterine and ovarian arteries during both diestrus and estrus were higher (P < 0.05) in estrogen-treated versus untreated mares. Furthermore, mean uterine PI values during diestrus and estrus were higher (P< 0.05) in altrenogest-treated versus untreated mares. Neither estrogen nor altrenogest treatments had a significant immediate effect on ovarian PI values. Compared to untreated cycles, mean ovarian PI values were elevated (P < 0.05) only in the estrus following altrenogest administration. In conclusion, exogenous estrogen and progestin both decreased genital perfusion in cycling mares.     

Hormone response of dairy cows with ovarian cysts after treatment with HCG or GnRH

Twenty lactating Holstein and Guernsey cows, diagnosed by rectal palpation as having ovarian cysts, were randomly divided within breed into two groups to receive either a single intramuscular injection of 100 μg of synthetic gonadotropin releasing hormone (GnRH) or an intravenous injection of 10,000 IU of human chorionic gonadotropin (HCG). The objective was to compare hormonal and clinical changes in cows with ovarian cysts following treatment with GnRH and HCG. Eight of ten and nine of ten cows given either GnRH and HCG, respectively, responded to treatment and subsequent fertility was not different between the two groups. Pre-injection plasma levels of LH, progesterone, and estradiol were highly variable. Mean plasma levels of LH, progesterone and estradiol did not differ between groups either following treatment (days 1–17 post-treatment), at the subsequent estrus, or during days 1–13 following the subsequent estrus. Mean LH levels did not differ significantly on the days either post-treatment or post-estrus except that levels were higher (P < .01) at the subsequent estrus as compared to the other days. Mean progesterone levels increased after treatment with either GnRH or HCG and were higher on days 5, 9 and 13 post-estrus and post-treatment as compared to the subsequent estrus. Mean levels of estradiol were higher (P < .05) at the subsequent estrus than any other time post-treatment or post-estrus. No other days were significantly different. In conclusion, GnRH and HCG are effective treatments for ovarian cysts in cattle. Endocrine response on days following treatment are similar for both compounds.     

Cyclic estradiol treatment normalizes body weight and restores physiological patterns of spontaneous feeding and sexual receptivity in ovariectomized rats

Hypothalamic-pituitary-gonadal axis function strongly influences feeding and body weight in cycling females in many species. To test the sufficiency of cyclic variations in plasma estradiol to reproduce normal patterns of spontaneous feeding, food intake, and body weight, ovariectomized Long-Evans rats were subcutaneously injected every fourth day with 2 microg estradiol benzoate or with the oil vehicle alone. Cyclic estradiol treatment completely normalized the trajectory of body weight gain and total food intake through seven treatment cycles. The hyperphagia of ovariectomized rats was expressed as an increase in spontaneous meal size. Meal frequency decreased, but not enough to compensate for the increase in meal size. Estradiol treatment normalized both parameters. In addition, cyclic estradiol treatment produced a further phasic decrease in meal size (and increase in meal frequency) and a decrease in food intake during the second night after injection. This phasic change is similar to the feeding changes occurring during estrus in intact rats. Sexual receptivity was measured during the eighth estradiol treatment cycle, 4 h after injection of 0.5 mg progesterone. Lordosis scores at the time of the treatment cycle modeling estrus were maximal, and scores at the time modeling diestrus were slightly increased over those of rats that did not receive estradiol. Finally, plasma estradiol levels, measured during the ninth treatment cycle, revealed a near-normal cyclic pattern of plasma estradiol levels. These results provide the first demonstration that the induction of a cyclic, near-physiological pattern of plasma estradiol is sufficient to maintain normal levels of body weight, spontaneous feeding patterns, total food intake, and (together with progesterone) sexual receptivity in ovariectomized rats.     

Critical progesterone requirement for maintenance of pregnancy in ovariectomized rats

The minimum progesterone concentration required to maintain the pregnancy was studied by varying doses of progesterone given subcutaneously to rats ovariectomized on Day 8 of pregnancy. Injecting 3 mg progesterone plus 200 ng oestradiol benzoate daily provided serum progesterone values between 25.4 +/- 7.0 and 35.2 +/- 6.2 ng/ml throughout Days 10-19 which were significantly lower than normal levels (P less than 0.05), but resulted in 93.6% of fetal survival on Day 19 which was not significantly different from 93.3% in the control group. Injecting 2 mg progesterone plus 200 ng oestradiol benzoate daily gave progesterone values between 13.2 +/- 4.6 and 19.0 +/- 6.2 ng/ml and could not maintain fetal viability to Day 19 (14.2%, P less than 0.05 compared with control group). Critical times to supplement progesterone in rats ovariectomized on Day 8 or Day 15 were studied by varying the time of progesterone implantation after ovariectomy. Progesterone implants were administered 8, 12 and 24 h after ovariectomy on Day 8 and 24, 36 and 48 h after ovariectomy on Day 15. On Day 8, progesterone replacement could be delayed to 8 h but not 12 h, while on Day 15, progesterone replacement could be delayed up to 36 h but not 48 h after ovariectomy without affecting fetal survival.