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H Dobson

Publications and source records attributed to H Dobson.

At least 19 recordsLinked to original sources
PubMed2006

Oestradiol stimulates the release of AVP and GnRH from the ewe hypothalamus in vitro.

Oestradiol (E(2)) sensitizes the stress and reproductive axes in vivo. Our current aim is to investigate whether E(2) directly influences hypothalamic AVP and GnRH release in vitro. Within 10 min of ewe killing, saggital midline hypothalamic slices (from the anterior preoptic area to mediobasal hypothalamus, 2 mm thick, two per sheep) were dissected, placed in oxygenated MEM-alpha at 4 degrees C and within next 2 h were singly perifused at 37 degrees C with oxygenated MEM-alpha (pH 7.4; flow rate 150 microl/min) alone (vehicle; n = 15), with low (6 pg/ml; n = 14) or high E(2) (24 pg/ml; n = 13). After 5 h equilibration, 10 min fractions were collected for 3 h with exposure to 100 mm KCl for 10 min within the last hour. Concentrations of AVP and GnRH were measured by RIA. Baselines for AVP and GnRH were 7.0 +/- 1.1 and 17.4 +/- 0.8 pg/ml respectively. Basal values with low E(2) were similar to vehicle for AVP (7.5 +/- 1.2 pg/ml) and GnRH (17.5 +/- 1.1 pg/ml). However, high E(2) increased basal AVP (11.7 +/- 1.4 pg/ml; p < 0.05) and GnRH (23.7 +/- 1.4 pg/ml; p < 0.05). After KCl, AVP and GnRH respectively, increased (p < 0.05) to 25.6 +/- 7.5 and 38.2 +/- 5.6 (vehicle), 26.3 +/- 7.5 and 23.6 +/- 2.1 (low E(2)) and 24.1 +/- 5.4 and 41.3 +/- 6.6 pg/ml (high E(2)). After KCl, maximum values of AVP occurred at 20 and GnRH at 30 min. In conclusion, high E(2) concentration augments AVP and GnRH release by direct action on the ewe hypothalamus.

Animals↗
PubMed2005

Use of the cow as a large animal model of uterine infection and immunity.

For most of the reproductive cycle in both humans and animals, the uterus is clear of pathogenic bacteria. However, it is readily contaminated with pathogens, such as Escherichia and Tritichomonas species, during sexual intercourse and after parturition. Uterine infection is particularly common after parturition in cattle (Bos taurus), causing clinical disease and infertility. The endocrine and immune responses to uterine infection in cattle have been investigated in vivo and using tissue culture. Cattle are of sufficient size to permit monitoring of reproductive and immune function throughout uterine infections, and primary cell cultures are readily established. In the whole animal, uterine infections suppress GnRH and LH secretion, and inhibit the growth of ovarian follicles and their estradiol secretion. The immune response is characterized by an influx of neutrophils into the uterus and increased concentrations of acute phase proteins in peripheral plasma. In vitro, the endometrial and ovarian cell function is modified by challenge with bacteria, their products such as lipopolysaccharide or pro-inflammatory cytokines. However, it is interesting to note that the susceptibility to uterine infection and the immune response are partially regulated by the ovarian steroid hormone mileu. In conclusion, the ease of working with cattle, the availability of tissues and the similarity of uterine infection between mammals, make Bos taurus a good model for studying uterine infection and immunity.

Animals↗
PubMed2005

The usefulness of a single measurement of insulin-like growth factor-1 as a predictor of embryo yield and pregnancy rates in a bovine MOET program.

The objective was to determine if a single measurement of plasma insulin-like growth factor-1 (IGF-1) could predict the number of viable embryos obtained from donors and the likelihood of pregnancy in recipients in multiple ovulation and embryo transfer (MOET) programs in cattle. The embryo yields from 101 embryo recoveries were examined in maiden Holstein heifers (n=75) and multiparous Holstein cows (lactating cows n=20, dry cows n=6). Donors were super stimulated with FSH and embryo recovery was done non-surgically 7 days after artificial insemination. Embryos were classified according to the IETS criteria. Pregnancy rates in 100 maiden Holstein heifer recipients were analysed. Recipients were on day 7+/-1 of the estrous cycle at transfer. Pregnancy diagnosis was carried out at day 30 (PD 30) and rechecked at day 60 (PD 60) after transfer. Blood samples from coccygeal vessels taken at the time of embryo recovery (donors) and transfer (recipients) were analysed for IGF-1, insulin, beta-hydroxybutyrate (beta-OHB), non-esterified fatty acids (NEFA), urea and cholesterol. There was a negative correlation between the number of viable embryos and insulin (r=-0.33, P=0.025) in donor heifers. In donor cows, the number of viable embryos was correlated with IGF-1 (r=0.43, P=0.028) and cholesterol (r=-0.43, P=0.027). In recipients, PD30 and PD 60 were not affected by any of the circulating parameters analysed. Insulin, IGF-1 and cholesterol only explained 8.9, 13.9 and 15.8% of the variation in the production of viable embryos, respectively. Several factors affect MOET programs and under the circumstances of the present study the usefulness of hormonal and metabolic profiles as predictors of the outcome of this biotechnology was limited.

3-Hydroxybutyric Acid↗
PubMed2005

Expression of the GLUT1 and GLUT9 facilitative glucose transporters in embryonic chondroblasts and mature chondrocytes in ovine articular cartilage.

Glucose transport across the chondrocyte membrane is essential for chondrogenesis and the development of the skeletal system. We have previously used RT-PCR to show that fully developed human articular chondrocytes express transcripts for the GLUT1 and GLUT9 glucose transporters. In this study we report on the expression and immunohistochemical localization of the GLUT1 and GLUT9 proteins in embryonic and mature ovine cartilage. We also provide Western blot evidence for GLUT1 and GLUT9 expression in mature ovine chondrocytes. Ovine embryos (developmental stages E32 to E36 and E42 to E45) were obtained from pregnant ewes humanely killed by injection with sodium pentobarbitone. Embryos were fixed and processed for immunohistochemistry. Polyclonal antibodies to GLUT1 and GLUT9 revealed that both transporters are expressed in developing chondrocytes in ovine embryos and in the superficial, middle and deep layers of ovine cartilage from mature animals. GLUT1 expression was observed in erythrocytes and organs including heart, liver, and kidney. GLUT9 was also found in heart, kidney and liver. Western blotting confirmed the presence of the GLUT1 protein which migrated between the 50 and 64 kDa markers and two specific GLUT9 bands migrating under the 50 and 60 kDa markers, respectively. The presence of GLUT1 and GLUT9 in developing joints of ovine embryos suggests that these proteins may be important in glucose delivery to developing chondroblasts. Expression of these GLUT isoforms may be an important bioenergetic adaptation for chondrocytes in the extracellular matrix of developing cartilage.

Animals↗
PubMed2004

Effect of intrauterine administration of oestradiol on postpartum uterine bacterial infection in cattle.

After parturition fewer first dominant follicles are selected in the ovary ipsilateral to the previously gravid uterine horn in cattle. However, the presence of a large oestradiol-secreting follicle in the ipsilateral ovary is a predictor of fertility, possibly due to a localised effect of oestradiol which increases the rate of elimination of the ubiquitous uterine bacterial contamination that occurs after calving. The present study tested the hypothesis that oestradiol reduces uterine bacterial contamination when administered into the uterine lumen around the expected time for selection of the first postpartum dominant follicle. Animals were infused with saline (n=15) or 10mg oestradiol benzoate (n=15) into the previously gravid uterine horn on Days 7 and 10 postpartum. Peripheral coccygeal blood samples were collected daily and oestradiol concentrations measured by radioimmunoassay (RIA). Uterine lumen swabs were collected 7, 14 and 21 days postpartum for aerobic and anaerobic culture, bacteria were identified and growth scored semi-quantitatively. Plasma oestradiol concentrations were higher for treated animals between Days 7 and 14 (1.4+/-0.1 versus 2.0+/-0.2 pg/ml, P<0.05). Control animals had a similar bacterial growth score on Days 7 and 14, with a lower value on Day 21 (5.7+/-1.0 and 6.1+/-0.7 versus 0.3+/-0.1, P<0.05). However, treated animals had a surprising higher bacterial load on Day 14, than on Days 7 or 21 (7.1+/-0.9 versus 4.0+/-0.6 or 3.6+/-0.6, P<0.05). The increased score was attributable to more pathogens associated with endometritis on Day 14 than Day 7 (5.1+/-1.0 versus 2.5+/-0.5, P<0.05), in particular Prevotella melaninogenicus (1.5+/-0.5 versus 0.7+/-0.2, P<0.05) and Fusobacterium necrophorum (1.5+/-0.4 versus 0.3+/-0.2, P<0.05). In conclusion, administration of oestradiol into the uterine lumen surprisingly increased uterine pathogenic anaerobic bacterial contamination. Thus, it is unlikely that increased fertility associated with a first dominant follicle in the ipsilateral ovary is a consequence of the elimination of bacterial contamination by ovarian oestradiol.

Animals↗
PubMed2004

Postpartum uterine health in cattle.

Uterine health is often compromised in cattle because postpartum contamination of the uterine lumen by bacteria is ubiquitous, and pathogenic bacteria frequently persist causing clinical disease. The subfertility associated with uterine infection involves perturbation of the hypothalamus, pituitary and ovary, in addition to the direct effects on the uterus, and appears to persist even after clinical resolution of the disease. Absorption of bacterial components from the uterus can prevent the follicular phase LH surge and ovulation. In addition, the first postpartum dominant follicle has a slower growth rate and secretes less estradiol at the end of the growth phase. There are also localised ovarian effects of high uterine bacterial growth density, because fewer first dominant follicles are selected in the ovary ipsilateral than contralateral to the previously gravid uterine horn. Thus, it is important to diagnose and treat uterine disease promptly and effectively. Examination of the contents of the vagina for the presence of pus is the most useful method for diagnosis of endometritis. The character and odor of the vaginal mucus can be scored and this endometritis score is correlated with the growth density of pathogenic bacteria in the uterus, and is prognostic for the likely success of treatment. The challenge for the future is to design prevention and control programs to reduce the incidence of disease, and understand how the immune and endocrine systems are integrated.

Animals↗
PubMed2004

Effect of heel elevation on forelimb conformation in horses.

OBJECTIVE: To determine the conformational changes in the distal forelimb of horses following heel elevation of 15 degrees and greater. An experimental study with repeated, within-horse measurements. PROCEDURE: Five clinically normal, mixed-breed horses were used to determine distal forelimb conformation following heel elevation from 0 to 45 degrees in 15 degree increments. Data were also compared to conformation of the limb in a Kimzey splint. Conformation was determined using lateral to medial radiographic projections. Conformation parameters assessed included measurement of apparent lengths of digital flexor tendons from the origin of their accessory ligaments to the points of insertion, and the joint angles of the distal limb. RESULTS: For angles of heel elevation from 15 to 45 degrees, the degree of joint angulation increased (increasing flexion) with heel elevation for the metacarpophalangeal, and proximal and distal interphalangeal joints. Conversely, the measured apparent lengths of the digital flexor tendons in the distal limb, decreased. CONCLUSION: The data supports the practice of elevating the heel (greater than 15 degrees) for conditions in which decreased fetlock extension may be desired such as with laceration or injury to the digital flexor tendons. Further study is required to determine whether heel elevation greater than 15 degrees reduces in vivo digital flexor tendon tension and also to ensure that the marked flexion of the distal interphalangeal joint with greater heel elevation is not detrimental over a prolonged period that may be required for the rehabilitation of flexor tendon injuries in the horse.

Animals↗
PubMed2003

The effect of oestradiol on postpartum uterine involution in sheep.

The present study tested the hypothesis that ovarian oestradiol increases the rate of uterine involution after parturition in sheep. The day after parturition, ewes were randomly assigned as un-operated controls (n=5), or a 3 cm silastic implant containing oestradiol (n=8) or empty (n=7) was sutured within the bursa of the ovary ipsilateral to the previously gravid uterine horn. Blood samples were collected daily for measurement of PGFM and acute phase proteins until 17 days postpartum when the ewes were slaughtered and the genital tract was collected. There was no consistent effect of treatment group on uterine involution determined by the collagen density, dry matter content, width, length, or weight of the genital tract. Furthermore, there was no evidence of a localised effect of oestradiol on involution as there were no significant differences between the previously gravid and non-gravid uterine horns. However, oestradiol-treated ewes had lower plasma concentrations of 15-keto-13,14-dihydro-prostaglandin F2alpha (P<0.01), alpha1-acid glycoprotein (P<0.05) and ceruloplasmin (P<0.001); but, not haptoglobin. These observations could reflect a direct effect of oestradiol on inflammatory mediator synthesis or secretion because, in the absence of parallel physical measurements, it is unlikely that these observations reflect a beneficial effect of treatment on uterine health.

Animals↗
PubMed2003

Identification of stimulatory and inhibitory inputs to the hypothalamic-pituitary-adrenal axis during hypoglycaemia or transport in ewes.

This study used the novel approach of statistical modelling to investigate the control of hypothalamic-pituitary-adrenal (HPA) axis and quantify temporal relationships between hormones. Two experimental paradigms were chosen, insulin-induced hypoglycaemia and 2 h transport, to assess differences in control between noncognitive and cognitive stimuli. Vasopressin and corticotropin-releasing hormone (CRH) were measured in hypophysial portal plasma, and adrenocorticotropin hormone (ACTH) and cortisol in jugular plasma of conscious sheep, and deconvolution analysis was used to calculate secretory rates, before modelling. During hypoglycaemia, the relationship between plasma glucose and vasopressin or CRH was best described by log10 transforming variables (i.e. a positive power-curve relationship). A negative-feedback relationship with log10 cortisol concentration 2 h previously was detected. Analysis of the "transport" stimulus suggested that the strength of the perceived stimulus decreased over time after accounting for cortisol facilitation and negative-feedback. The time course of vasopressin and CRH responses to each stimulus were different However, at the pituitary level, the data suggested that log10 ACTH secretion rate was related to log10 vasopressin and CRH concentrations with very similar regression coefficients and an identical ratio of actions (2.3 : 1) for both stimuli. Similar magnitude negative-feedback effects of log10 cortisol at -110 min (hypoglycaemia) or -40 min (transport) were detected, and both models contained a stimulatory relationship with cortisol at 0 min (facilitation). At adrenal gland level, cortisol secretory rates were related to simultaneously measured untransformed ACTH concentration but the regression coefficient for the hypoglycaemia model was 2.5-fold greater than for transport. No individual sustained maximum cortisol secretion for longer than 20 min during hypoglycaemia and 40 min during transport. These unique models demonstrate that corticosteroid negative-feedback is a significant control mechanism at both the pituitary and hypothalamus. The amplitude of HPA response may be related to stimulus intensity and corticosteroid negative-feedback, while duration depended on feedback alone.

Adrenal Cortex Hormones↗
PubMed2003

Reproductive challenges facing the cattle industry at the beginning of the 21st century.

The aim of this review is to pinpoint the areas that require further research for greatest impact to improve the efficiency of dairy and beef production. Increased knowledge about the principal causes of reduced fertility is essential. Increases in milk yield have been at the expense of reduced fertility in dairy cows and although diet has a major impact, the precise interaction between nutrition and reproduction still needs to be characterized in both beef and dairy cows. Furthermore, during periods of inadequate nutrition or stress, the intensity of oestrus is reduced by inadequate exposure to oestradiol. However, it is still unclear which pheromones are involved at oestrus, how synthesis is controlled and how pheromones are detected in herd-mates. GnRH may be involved in behaviour but the brain centres that translate hormonal messages are unknown. Attempts to overcome poor oestrous detection include measurements of milk progesterone, telemetric pressure detectors and devices that record the extra activity at oestrus. Substitution of heat detection by 'hormone treatment remedies' has met strong consumer resistance in Europe. The creation of larger cattle units and increased movements world-wide render herds more susceptible to infectious agents, such as Neospora, Leptospira, Trypanosoma and Bovine Viral Diarrhoea virus (BVDv), but it is unclear how other clinical conditions, such as lameness or endometritis, also interfere with ovarian function. The future of dominant follicles selected within 14 days after parturition is crucial--normal ovulation, prolonged persistence or atresia. Calving carries the greatest risk in the reproductive life of a cow and yet little work has focused on reducing the frequency of this event. For dairy cows, a greater understanding about induced or extended lactation is required. For beef animals, precise induction of twinning and nutritional adjustments could produce two offspring per pregnancy. At the start of pregnancy, the trophoblast produces interferon to prevent luteolysis, but the immunological implications are unknown and it is not clear how the rest of pregnancy is maintained. Profiles of pregnancy specific protein B (PSPB) have increased understanding of embryonic death. However, 25% of cows in abattoirs are pregnant, even though 30% of involuntary cullings are 'for failing to conceive'. Clearly, this is an area of wastage that requires urgent resolution. It is unknown why undernutrition at the time of insemination or in early pregnancy leads to delayed births, low fetal weights and later adverse health. At the end of pregnancy, the fetus controls the onset of parturition, but very little is known about the biochemical control of cervical dilation and placental separation. On the male side, bulls are selected for optimal freezability of semen; however, there is as yet no reliable predictor for semen fertility. Methods for accurately pre-determining the sex of both semen and embryos will revolutionize the dairy and beef industries.

Animal Nutritional Physiological Phenomena↗
PubMed2003

Stress and the control of LH secretion in the ewe.

Stress influences the activity of the reproductive system at several sites. One of the most significant effects is at level of the GnRH secretory system to reduce GnRH pulsatility and thus LH pulsatility. This in turn reduces the oestradiol signal that stimulates the GnRH-LH surge in the follicular phase. Three sequential phases have been identified in the induction of the GnRH-LH surge by oestradiol: (i) activation, (ii) transmission and (iii) surge secretion. There is evidence that administration of endotoxin prevents activation but not transmission, hypoglycaemia blocks both activation and transmission, whereas truck transport is effective during the late, but not early, transmission phase. Opioids mediate the suppressive effects of hypoglycaemia on both LH pulsatility and the delayed onset of the LH surge in ewes. The exact neurocircuitry used in sheep is yet to be identified but many of the connections that are proposed as important in rats are present in sheep. Corticotrophin-releasing hormone (CRH) neurones in the paraventricular nucleus that project axons to the median eminence probably do not directly inhibit GnRH, but either afferent or parallel central pathways are involved. New members of the CRH peptide and receptor families have been identified, but roles in the control of reproduction have yet to be determined.

Adrenocorticotropic Hormone↗
PubMed2002

Effect of postpartum manual examination of the vagina on uterine bacterial contamination in cows.

Twenty-one days after they had calved, the vaginas of 34 cows were examined with a clean gloved hand, and 26 cows were left unexamined. Swabs were collected from the lumen of the uterine body of the cows on the same day and seven days later; bacteria were identified by aerobic and anaerobic culture, and bacterial growth was scored semi-quantitatively. On the same days, blood samples were collected and the concentrations of acute phase proteins were measured, and the diameters of the cows' uterine horns were measured by transrectal ultrasonography. The vaginal examinations did not result in uterine bacterial contamination or an acute phase protein response, and they did not affect the diameters of the uterine horns.

Animals↗
PubMed2002

Support needs of veterinary surgeons during the first few years of practice: perceptions of recent graduates and senior partners.

Postal surveys or personal interviews of 76 recent veterinary graduates and their 49 employers were undertaken to establish their perceptions of good practice when integrating a new graduate into a business and their preferred methods of assessment and development. Practice type and location were the main influences on graduates looking for their first job. Interviews were mostly informal. Employers expected basic veterinary competence and candidates expected good quality support. Most graduates (93 per cent) had their own consultations on the first day. During early consultations 2 per cent of senior vets accompanied the new graduate, 95 per cent of practices provided senior back-up either in person or by telephone but in 3 per cent no back-up was available. Most new graduates (90 per cent) were satisfied with their workload. Three-fifths were on-call within the first week, and 95 per cent within a month. Graduates received calls directly in 45 per cent of practices, in 9 per cent seniors screened the calls, and the remainder used a third party. Assistance from experienced lay staff varied greatly. Discussion of problems was mainly informal. There was little spontaneous feedback and problems resulted from inadequate communication. One in three new graduates left their first job within two years, and one in six identified lack of support, heavy workload, stress or clashes with staff as a primary reason. This high turnover was a problem for employers. From the new graduates' perspectives, initial problems included: being on call (59 per cent), financial aspects (47 per cent) and surgery (43 per cent). Communicating with clients and learning to prioritise jobs were also difficult. New graduates took longer over procedures (79 per cent of employers commented) and required extra back-up (91 per cent) both of which reduced income (59 per cent). Nearly all the seniors felt that their current new graduates had coped 'quite well', although it was claimed that new graduates lacked the ability to talk to clients at the appropriate level, wanted to bring all their scientific knowledge to bear on every case, and often failed to consider the obvious or to appreciate clients' needs. Only 18 per cent of practices had formal and regular review procedures but all monitored the response of clients and watched the new graduate perform. Feedback to their new colleague was considered 'adequate' by 85 per cent of seniors, although 45 per cent of graduates felt they had not received enough. Eighty-three per cent of new graduates felt 'moderately prepared' by their undergraduate course, and 76 per cent of senior vets were 'generally satisfied' Both wanted improvements in extramural studies and increased exposure to routine cases. Senior partners sought greater commitment in the undergraduate curriculum to financial/legal issues and communication skills. Over a third of employers (38 per cent) had a 'great influence' on the choice of continuing professional development courses for their recent graduates. New graduates chose courses to deal with a perceived weakness, or to specialise, and welcomed opportunities to meet other new graduates and share early experiences. It was concluded that turnover and staff problems would be reduced if practices became more effective in coping with new arrivals, especially by supporting their development.

Attitude of Health Personnel↗
PubMed2002

Hormonal interactions within the hypothalamus and pituitary with respect to stress and reproduction in sheep.

Endocrine systems may be used as indicators of stress in two ways. The primary role of a hormone may be as part of the homeostatic response to a stimulus (e.g., adrenaline, corticosteroids). The amplitude of hormone response may correlate with the severity of the stimulus and any change indicate that the body is responding. Alternatively, a hormone may have a key role in normal body function (e.g., reproduction) and stress may deleteriously alter the hormone signal prevent normal function. This demonstrates that the stimulus was sufficiently severe that homeostatic mechanisms were unable to maintain normal function. Stress may effect reproduction by reducing both LH pulse amplitude and frequency. The LH surge may also be delayed. Several mechanisms may account for these effects both at the hypothalamus and pituitary. Corticosteroids have a broad, yet fundamental, role in homeostasis and have been used as primary indicators of stress for many years. Excess corticosteroid can be detrimental so the concentration is controlled via the hypothalamus-pituitary-adrenal (HPA) axis by multi-level feedback mechanisms. Under field and experimental conditions, after an initial large response prolonged stimulation leads to a gradually reducing plasma corticosteroid concentrations. This has been interpreted as a reduction in perceived stimulus severity or habituation to the stimulus and the animal deemed "less stressed" and its welfare "better." However, this reduction may be due to the intrinsic control mechanisms designed to prevent prolonged increases in corticosteroid concentrations. The stress signal at higher brain levels may still be present and the animal may still be experiencing the stimulus as aversive. Thus, the welfare interpretation of a corticosteroid concentration may differ during the time course of a stress response. A greater understanding of the mechanisms controlling corticosteroid secretion at each level of the HPA is required to determine what is the correct interpretation at any time point. To address these issues, we have used mathematical modelling to produce representations of possible control mechanisms at each level of the HPA. The starting point was to measure AVP and CRH concentrations in hypophysial portal blood and ACTH and cortisol concentrations in jugular blood in conscious sheep during 2h road transport (a cognitive stimulus). Modelling identified the signal inputs that were most likely to explain the secretion rate of each hormone. Modelling suggested that the reduction in AVP and CRH secretion observed during transport was most likely due to a reduction in stimulus input, with a significant contribution from cortisol negative feedback only on AVP secretion. At the pituitary level, ACTH secretion was stimulated more by AVP than by CRH (ratio 2.3:1) and there was also a stimulatory effect related to cortisol concentration at the time of sampling. However, the responses to both stimuli were curtailed by cortisol negative feedback and an inhibitory effect of prior CRH concentration. These are complex effects, but the modelling does suggest that while "stress" inputs may reduce over time hormone negative feedback is a major factor reducing hormone responses. When interpreting hormone data for animal welfare purposes, it is important not to interpret a reduction in hormone concentration due to intrinsic hormone control mechanisms as a reduction due to a decrease in the stress stimulus.

Adrenal Glands↗
PubMed2002

Influence of uterine bacterial contamination after parturition on ovarian dominant follicle selection and follicle growth and function in cattle.

First postpartum dominant follicles are preferentially selected in the ovary contralateral to the previously gravid uterine horn. The aim of the present study was to test the hypothesis that uterine bacterial contamination alters the location of ovarian follicle emergence and selection, and inhibits follicle growth and function. Swabs were collected from the uterine body lumen of cattle on days 7, 14, 21 and 28 after parturition. Bacteria were identified by aerobic and anaerobic culture; bacterial growth was scored semiquantitatively and animals were categorized into standard or high bacterial contamination categories on the basis of the number of colonies detected. Follicular growth and function were monitored by daily transrectal ultrasonography, and estimation of plasma FSH, oestradiol and progesterone concentrations. There was no effect of bacterial contamination on plasma FSH concentration profiles or emergence of the ovarian follicle wave. When uterine bacterial growth scores were high on day 7 or day 21 after parturition, fewer first (1/20 versus 15/50; P < 0.05) or second (1/11 versus 13/32; P < 0.05) dominant follicles were selected in the ipsilateral compared with the contralateral ovary, respectively. The diameter of the first dominant follicle was smaller in animals with a high day 7 bacterial score (P < 0.001), dominant follicle growth was slower (P < 0.05) and oestradiol secretion was decreased (P < 0.05). The present study provides evidence for an effect of the uterus on the ovary after parturition, whereby uterine bacteria have a contemporaneous localized effect on ovarian follicle selection and subsequent growth and function, but not on initial emergence.

Animals↗