Scalp and Source Power Topography in Sleepwalking and Sleep Terrors: A High-Density EEG Study

STUDY OBJECTIVES

To examine scalp and source power topography in sleep arousals disorders (SADs) using high-density EEG (hdEEG).

METHODS

Fifteen adult subjects with sleep arousal disorders (SADs) and 15 age- and gender-matched good sleeping healthy controls were recorded in a sleep laboratory setting using a 256 channel EEG system.

RESULTS

Scalp EEG analysis of all night NREM sleep revealed a localized decrease in slow wave activity (SWA) power (1-4 Hz) over centro-parietal regions relative to the rest of the brain in SADs compared to good sleeping healthy controls. Source modelling analysis of 5-minute segments taken from N3 during the first half of the night revealed that the local decrease in SWA power was prominent at the level of the cingulate, motor, and sensori-motor associative cortices. Similar patterns were also evident during REM sleep and wake. These differences in local sleep were present in the absence of any detectable clinical or electrophysiological sign of arousal.

CONCLUSIONS

Overall, results suggest the presence of local sleep differences in the brain of SADs patients during nights without clinical episodes. The persistence of similar topographical changes in local EEG power during REM sleep and wakefulness points to trait-like functional changes that cross the boundaries of NREM sleep. The regions identified by source imaging are consistent with the current neurophysiological understanding of SADs as a disorder caused by local arousals in motor and cingulate cortices. Persistent localized changes in neuronal excitability may predispose affected subjects to clinical episodes.

High Resolution Topography of Age-Related Changes in Non-Rapid Eye Movement Sleep Electroencephalography

Sleeping brain activity reflects brain anatomy and physiology. The aim of this study was to use high density (256 channel) electroencephalography (EEG) during sleep to characterize topographic changes in sleep EEG power across normal aging, with high spatial resolution. Sleep was evaluated in 92 healthy adults aged 18–65 years old using full polysomnography and high density EEG. After artifact removal, spectral power density was calculated for standard frequency bands for all channels, averaged across the NREM periods of the first 3 sleep cycles. To quantify topographic changes with age, maps were generated of the Pearson’s coefficient of the correlation between power and age at each electrode. Significant correlations were determined by statistical non-parametric mapping. Absolute slow wave power declined significantly with increasing age across the entire scalp, whereas declines in theta and sigma power were significant only in frontal regions. Power in fast spindle frequencies declined significantly with increasing age frontally, whereas absolute power of slow spindle frequencies showed no significant change with age. When EEG power was normalized across the scalp, a left centro-parietal region showed significantly less age-related decline in power than the rest of the scalp. This partial preservation was particularly significant in the slow wave and sigma bands. The effect of age on sleep EEG varies substantially by region and frequency band. This non-uniformity should inform the design of future investigations of aging and sleep. This study provides normative data on the effect of age on sleep EEG topography, and provides a basis from which to explore the mechanisms of normal aging as well as neurodegenerative disorders for which age is a risk factor.

Direct Observation of Melting in Shock-Compressed Bismuth With Femtosecond X-ray Diffraction

The melting of bismuth in response to shock compression has been studied using in situ femtosecond x-ray diffraction at an x-ray free electron laser. Both solid-solid and solid-liquid phase transitions are documented using changes in discrete diffraction peaks and the emergence of broad, liquid scattering upon release from shock pressures up to 14 GPa. The transformation from the solid state to the liquid is found to occur in less than 3 ns, very much faster than previously believed. These results are the first quantitative measurements of a liquid material obtained on shock release using x-ray diffraction, and provide an upper limit for the time scale of melting of bismuth under shock loading.

Understanding antimicrobial use and prescribing behaviours by pig veterinary surgeons and farmers: a qualitative study

Increasing awareness of bacterial antimicrobial resistance in human beings and veterinary medicine has raised concerns over the issue of overprescribing and the indiscriminate use of antimicrobials. Their use in food-producing animals is under scrutiny due to the perceived risk from the zoonotic transfer of resistant pathogens from animals to human beings. This study used focus groups to explore the drivers and motivators behind antimicrobial use and prescribing by veterinary surgeons and farmers in the pig industry in the UK. Studies of two veterinary and four farmer focus groups were undertaken, each with between three and six participants, in three geographically distinct regions of low, moderate and high pig density in England. Thematic analysis of the focus group transcriptions revealed convergent themes, both within and across, the veterinary and farmer focus groups. Veterinary opinion was such that 'external pressures', such as pressure from clients, legislation and public perception, were considered to strongly influence prescribing behaviour, whereas, farmers considered issues surrounding farming systems and management to be greater drivers towards antimicrobial use. Acquiring such in-depth insight into the antimicrobial prescribing behaviours in veterinary medicine provides more detailed understanding of prescribing practice and will aid the development of interventions to promote the responsible use of antimicrobials.

Characterization and Epidemiology of Outbreaks of Impatiens necrotic spot virus on Lettuce in Coastal California

California is the leading producer of lettuce (Lactuca sativa) for the United States and grows 77% of the country's supply. Prior to 2006, coastal California lettuce was only periodically and incidentally infected by a single tospoviruses species: Tomato spotted wilt virus (TSWV). However, beginning in 2006 and continuing through 2012, severe outbreaks of disease caused by Impatiens necrotic spot virus (INSV) have affected the coastal lettuce crop, though TSWV was also present. In contrast, TSWV was the only tospovirus associated with disease outbreaks in Central Valley lettuce during this period. Disease surveys conducted over two seasons (2008 and 2009) in 10 commercial fields (acreage of 6 to 20 ha) indicated that INSV was the only tospovirus associated with economically damaging disease outbreaks in lettuce in the coastal region, with incidences of 0.5 to 27% (mean = 5.7%). Molecular characterization of INSV isolates associated with these disease outbreaks revealed little genetic diversity and indicated that lettuce-infecting INSV isolates were nearly identical to those previously characterized from ornamental or other hosts from different locations in the United States and the world. Monitoring of thrips revealed moderate to large populations in all surveyed lettuce fields, and the majority of thrips identified from these fields were western flower thrips, Frankliniella occidentalis. There was significant positive correlation (r² = 0.91, P = 0.003) between thrips populations and INSV incidence in the most commonly encountered type of commercial lettuce (romaine, direct seeded, conventional) included in this study. A reverse-transcription polymerase chain reaction assay developed for detection of INSV in thrips showed promise as a monitoring tool in the field. Surveys for INSV reservoir hosts in the coastal production area revealed that the weeds little mallow (Malva parvifolia) and shepherd's purse (Capsella bursa-pastoris) were commonly infected. M. parvifolia plants infected in the field did not show obvious symptoms, whereas plants of this species inoculated in the laboratory with INSV by sap transmission developed necrotic spots and chlorosis. Eleven other weed species growing in the lettuce production areas were found to be hosts of INSV. Coastal crops found to be infected with INSV included basil (Ocimum basilicum), bell pepper (Capsicum annuum), calla lily (Zantedeschia aethiopica), faba bean (Vicia faba), radicchio (Cichorium intybus), and spinach (Spinacia oleracea). Thus, it is likely that INSV was introduced into coastal California lettuce fields via viruliferous thrips that initially acquired the virus from other local susceptible plant species. Results of this study provide a better understanding of INSV epidemiology in coastal California and may help growers devise appropriate disease management strategies.

Ramp compression of diamond to five terapascals

The recent discovery of more than a thousand planets outside our Solar System, together with the significant push to achieve inertially confined fusion in the laboratory, has prompted a renewed interest in how dense matter behaves at millions to billions of atmospheres of pressure. The theoretical description of such electron-degenerate matter has matured since the early quantum statistical model of Thomas and Fermi, and now suggests that new complexities can emerge at pressures where core electrons (not only valence electrons) influence the structure and bonding of matter. Recent developments in shock-free dynamic (ramp) compression now allow laboratory access to this dense matter regime. Here we describe ramp-compression measurements for diamond, achieving 3.7-fold compression at a peak pressure of 5 terapascals (equivalent to 50 million atmospheres). These equation-of-state data can now be compared to first-principles density functional calculations and theories long used to describe matter present in the interiors of giant planets, in stars, and in inertial-confinement fusion experiments. Our data also provide new constraints on mass-radius relationships for carbon-rich planets.

Holographic and time-resolving ability of pulse-pair two-dimensional velocity interferometry

Previous velocity interferometers used at research laboratories for shock physics experiments measured target motion at a point or many points on a line on the target. Recently, a two-dimensional (2d) version (2d-velocity interferometer system for any reflector) has been demonstrated using a pair of ultrashort (3 ps) pulses for illumination, separated by 268 ps. We have discovered new abilities for this instrument, by treating the complex output image as a hologram. For data taken in an out of focus configuration, we can Fourier process to bring narrow features such as cracks into sharp focus, which are otherwise completely blurred. This solves a practical problem when using high numerical aperture optics having narrow depth of field to observe moving surface features such as cracks. Furthermore, theory predicts that the target appearance (position and reflectivity) at two separate moments in time are recorded by the main and conjugate images of the same hologram, and are partially separable during analysis for narrow features. Hence, for the cracks we bring into refocus, we can make a two-frame movie with a subnanosecond frame period. Longer and shorter frame periods are possible with different interferometer delays. Since the megapixel optical detectors we use have superior spatial resolution over electronic beam based framing cameras, this technology could be of great use in studying microscopic three-dimensional-behavior of targets at ultrafast times scales. Demonstrations on shocked silicon are shown.

Kisspeptin, c-Fos and CRFR type 2 co-expression in the hypothalamus after insulin-induced hypoglycaemia

Normal reproductive function is dependent upon availability of glucose and insulin-induced hypoglycaemia is a metabolic stressor known to disrupt the ovine oestrous cycle. We have recently shown that IIH has the ability to delay the LH surge of intact ewes. In the present study, we examined brain tissue to determine: (i) which hypothalamic regions are activated with respect to IIH and (ii) the effect of IIH on kisspeptin cell activation and CRFR type 2 immunoreactivity, all of which may be involved in disruptive mechanisms. Follicular phases were synchronized with progesterone vaginal pessaries and at 28 h after progesterone withdrawal (PW), animals received saline (n = 6) or insulin (4 IU/kg; n = 5) and were subsequently killed at 31 h after PW (i.e., 3 h after insulin administration). Peripheral hormone concentrations were evaluated, and hypothalamic sections were immunostained for either kisspeptin and c-Fos (a marker of neuronal activation) or CRFR type 2. Within 3 h of treatment, cortisol concentrations had increased whereas plasma oestradiol concentrations decreased in peripheral plasma (p < 0.05 for both). In the arcuate nucleus (ARC), insulin-treated ewes had an increased expression of c-Fos. Furthermore, the percentage of kisspeptin cells co-expressing c-Fos increased in the ARC (from 11 to 51%; p < 0.05), but there was no change in the medial pre-optic area (mPOA; 14 vs 19%). CRFR type 2 expression in the lower part of the ARC and the median eminence was not altered by insulin treatment. Thus, disruption of the LH surge after IIH in the follicular phase is not associated with decreased kisspeptin cell activation or an increase in CRFR type 2 in the ARC but may involve other cell types located in the ARC nucleus which are activated in response to IIH.

Regional reductions in sleep electroencephalography power in obstructive sleep apnea: a high-density EEG study

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) is associated with significant alterations in neuronal integrity resulting from either hypoxemia and/or sleep loss. A large body of imaging research supports reductions in gray matter volume, alterations in white matter integrity and resting state activity, and functional abnormalities in response to cognitive challenge in various brain regions in patients with OSA. In this study, we used high-density electroencephalography (hdEEG), a functional imaging tool that could potentially be used during routine clinical care, to examine the regional distribution of neural activity in a non-clinical sample of untreated men and women with moderate/severe OSA.

DESIGN

Sleep was recorded with 256-channel EEG in relatively healthy subjects with apnea-hypopnea index (AHI) > 10, as well as age-, sex-, and body mass index-matched controls selected from a research population initially recruited for a study on sleep and meditation.

SETTING

Sleep laboratory.

PATIENTS OR PARTICIPANTS

Nine subjects with AHI > 10 and nine matched controls.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Topographic analysis of hdEEG data revealed a broadband reduction in EEG power in a circumscribed region overlying the parietal cortex in OSA subjects. This parietal reduction in neural activity was present, to some extent, across all frequency bands in all stages and episodes of nonrapid eye movement sleep.

CONCLUSION

This investigation suggests that regional deficits in electroencephalography (EEG) power generation may be a useful clinical marker for neural disruption in obstructive sleep apnea, and that high-density EEG may have the sensitivity to detect pathological cortical changes early in the disease process.

Developmental alterations in locomotor and anxiety-like behavior as a function of D1 and D2 mRNA expression

The majority of smokers start smoking in adolescence, beginning a potentially lifelong struggle with nicotine use and abuse. In rodent models of the effects of nicotine, the drug has been shown to elicit both locomotor and anxiety-like behavioral effects. Research suggests that these behavioral effects may be due in part to dopamine (DA) receptors D1 and D2 in the mesolimbic system, specifically the nucleus accumbens (NAc). We examined early adolescent (P28), late adolescent (P45), and adult (P80) male Long-Evans rats in the elevated plus maze (EPM) under normal conditions and the open field (OF) post-nicotine in order to test locomotor and anxiety-like behavior. These behavioral findings were then correlated with expression of DA D1 and D2 mRNA levels as determined via in situ hybridization. Nicotine-induced locomotor behavior was found to be significantly different between age groups. After a single injection of nicotine, early adolescents exhibited increases in locomotor behavior, whereas both late adolescents and adults responded with decreases in locomotor behavior. In addition, it was found that among, early adolescents, open arm and center time in the EPM were negatively correlated with D2 mRNA expression. In contrast, among adults, distance traveled in the center and center time in the OF were negatively correlated with D2 mRNA expression. This study suggests that DA D2 receptors play a role in anxiety-like behavior and that the relationship between observed anxiety-like behaviors and D2 receptor expression changes through the lifespan.

Identification of inadequate maternal progesterone concentrations in nulliparous dairy heifers and treatment with human chorionic gonadotrophin

Plasma progesterone concentrations were estimated for 381 nulliparous dairy heifers from eight farms on days 4-6 after insemination. Heifers were synchronised using two treatments of prostaglandin F2α (PGF2α) 11 days apart. Alternate heifers were treated with 1500 IU human chorionic gonadotrophin (hCG) at the time of sampling, and the pregnancy status assessed ~35 days after insemination. Heifers with no corpus luteum (CL; n-30) at the second PGF2α had lower progesterone concentrations (P<0.001) and pregnancy rates (PR; P=0.001) compared with heifers with CL (n=351, defined as cyclic). The risk of no CL increased in heifers <15 months of age (OR=7.5, P<0.001) and with body condition score <2.5 (OR=4.5, P=0.001). Those with no CL were removed from further analysis. The 20 per cent cyclic control heifers with progesterone concentrations ≤2 ng/ml on days 4-6 had lower PRs compared with those with higher concentrations (42 per cent vs 64 per cent, OR=0.3, P=0.01). There was no overall effect of hCG on PR compared with controls (51 per cent vs 60 per cent, P=0.10). However, heifers with high progesterone on days 4-6 (>2 ng/ml) had a lower PR after treatment (51 per cent vs 64 per cent, OR=0.6, P=0.02). Heifers inseminated with sexed (n=18) compared with conventional (n=333) semen had a decreased PR (33 per cent vs 57 per cent, OR=0.2, P=0.01). This study demonstrates that higher plasma progesterone concentrations as early as days 4-6 after insemination have a positive effect on first insemination PR, but there was no beneficial effect of hCG treatment on these days in dairy heifers.

Solid iron compressed up to 560 GPa

Dynamic compression by multiple shocks is used to compress iron up to 560 GPa (5.6 Mbar), the highest solid-state pressure yet attained for iron in the laboratory. Extended x-ray absorption fine structure (EXAFS) spectroscopy offers simultaneous density, temperature, and local-structure measurements for the compressed iron. The data show that the close-packed structure of iron is stable up to 560 GPa, the temperature at peak compression is significantly higher than expected from pure compressive work, and the dynamic strength of iron is many times greater than the static strength based on lower pressure data. The results provide the first constraint on the melting line of iron above 400 GPa.

Identifying host pathogenic pathways in bovine digital dermatitis by RNA-Seq analysis

Digital dermatitis is a painful foot disease compromising welfare in dairy cattle. The disease has a complex multibacterial aetiology, but little is known about its pathogenesis. In this study, gene expression in skin biopsies from five bovine digital dermatitis lesions and five healthy bovine feet was compared using RNA-Seq technology. Differential gene expression was determined after mapping transcripts to the Btau 4.0 genome. Pathway analysis identified gene networks involving differentially expressed transcripts. Bovine digital dermatitis lesions had increased expression of mRNA for α2-macroglobulin-like 1, a protein potentially involved in bacterial immune evasion and bacterial survival. There was increased expression of keratin 6A and interleukin 1β mRNA in bovine digital dermatitis lesions, but reduced expression of most other keratin and keratin-associated genes. There was little evidence of local immune reactions to the bacterial infection present in lesions.

Kisspeptin, c-Fos and CRFR type 2 expression in the preoptic area and mediobasal hypothalamus during the follicular phase of intact ewes, and alteration after LPS

Increasing estradiol concentrations during the late follicular phase stimulate sexual behavior and the GnRH/LH surge, and it is known that kisspeptin signaling is essential for the latter. Administration of LPS can block these events, but the mechanism involved is unclear. We examined brain tissue from intact ewes to determine: i) which regions are activated with respect to sexual behavior, the LH surge and LPS administration, ii) the location and activation pattern of kisspeptin cells in control and LPS treated animals, and iii) whether CRFR type 2 is involved in such disruptive mechanisms. Follicular phases were synchronized with progesterone vaginal pessaries and control animals were killed at 0 h, 16 h, 31 h or 40 h (n=4-6/group) after progesterone withdrawal (time zero). At 28 h, other animals received endotoxin (LPS; 100 ng/kg) and were subsequently killed at 31 h or 40 h (n=5/group). LH surges only occurred in control ewes, during which there was a marked increase in c-Fos expression within the ventromedial nucleus (VMN), arcuate nucleus (ARC), and medial preoptic area (mPOA), as well as an increase in the percentage of kisspeptin cells co-expressing c-Fos in the ARC and mPOA compared to animals sacrificed at all other times. Expression of c-Fos also increased in the bed nucleus of the stria terminalis (BNST) in animals just before the expected onset of sexual behavior. However, LPS treatment increased c-Fos expression within the VMN, ARC, mPOA and diagonal band of broca (dBb), along with CRFR type 2 immunoreactivity in the lower part of the ARC and median eminence (ME), compared to controls. Furthermore, the percentage of kisspeptin cells co-expressing c-Fos was lower in the ARC and mPOA. Thus, we hypothesize that in intact ewes, the BNST is involved in the initiation of sexual behavior while the VMN, ARC, and mPOA as well as kisspeptin cells located in the latter two areas are involved in estradiol positive feedback only during the LH surge. By contrast, disruption of sexual behavior and the LH surge after LPS involves cells located in the VMN, ARC, mPOA and dBb, as well as cells containing CRFR type 2 in the lower part of the ARC and ME, and is accompanied by inhibition of kisspeptin cell activation in both the ARC and mPOA.

Dilation x-ray imager a new∕faster gated x-ray imager for the NIF

As the yield on implosion shots increases it is expected that the peak x-ray emission reduces to a duration with a FWHM as short as 20 ps for ∼7 × 10(18) neutron yield. However, the temporal resolution of currently used gated x-ray imagers on the NIF is 40-100 ps. We discuss the benefits of the higher temporal resolution for the NIF and present performance measurements for dilation x-ray imager, which utilizes pulse-dilation technology [T. J. Hilsabeck et al., Rev. Sci. Instrum. 81, 10E317 (2010)] to achieve x-ray imaging with temporal gate times below 10 ps. The measurements were conducted using the COMET laser, which is part of the Jupiter Laser Facility at the Lawrence Livermore National Laboratory.

Plasma-accelerated flyer-plates for equation of state studies

We report on a new technique to accelerate flyer-plates to high velocities (∼5 km/s). In this work, a strong shock is created through direct laser ablation of a thin polyimide foil. Subsequent shock breakout of that foil results in the generation of a plasma characterized by a smoothly increasing density gradient and a strong forward momentum. Stagnation of this plasma onto an aluminum foil and the resultant momentum transfer accelerates a thin aluminum flyer-plate. The aluminum flyer-plate is then accelerated to a peak velocity of ∼5 km/s before impact with a transparent lithium fluoride (LiF) window. Simulations of the stagnating plasma ramp compression and wave reverberations within the flyer-plate suggest that the temperature at the flyer-plate impact surface is elevated by less than 50 °C. Optical velocimetry is used to measure the flyer-plate velocity and impact conditions enabling the shocked refractive index of LiF to be determined. The results presented here are in agreement with conventional flyer-plate measurements validating the use of plasma-accelerated flyer-plates for equation of state and impact studies.

Two-dimensional imaging velocity interferometry: data analysis techniques

We describe data analysis procedures for an emerging interferometric technique for measuring target motion across a two-dimensional image at a moment in time, i.e., a snapshot 2D-VISAR. Conventional VISARs (velocity interferometer system for any reflector) are commonly used in shock physics to measure velocity history at a single point or many points across a line on target. These however are not recorded in two-dimensions and cannot be used with ultrashort pulsed illumination because the coherence length is smaller than the interferometer delay, preventing fringe formation. In our scheme, dual matched interferometers allow use of low- or incoherent illumination such as ultrashort laser pulses to freeze motion of target, allowing use of slow CCD imaging detectors. Quadrature phase recording and push-pull data analysis simultaneously produces an ordinary nonfringing reflectivity image and a fringing image. The latter is converted into a 2D-phase map which is proportional to target velocity. Example data on shocked crystalline [111] Si shows incipient features of ~50 μm scale.

Evidence for a phase transition in silicate melt at extreme pressure and temperature conditions

Laser-driven shock compression experiments reveal the presence of a phase transition in MgSiO(3) over the pressure-temperature range 300-400 GPa and 10 000-16 000 K, with a positive Clapeyron slope and a volume change of ∼6.3 (±2.0) percent. The observations are most readily interpreted as an abrupt liquid-liquid transition in a silicate composition representative of terrestrial planetary mantles, implying potentially significant consequences for the thermal-chemical evolution of extrasolar planetary interiors. In addition, the present results extend the Hugoniot equation of state of MgSiO(3) single crystal and glass to 950 GPa.

Effects of stress on reproduction in ewes

Stressors, such as poor body condition, adverse temperatures or even common management procedures (e.g., transport or shearing) suppress normal oestrus behaviour and reduce ewe fertility. All these events are co-ordinated by endocrine interactions, which are disrupted in stressful situations. This disruption is usually temporary in adult ewes, so that, when prevailing conditions improve, normal fertility would resume. Imposition of an experimental stressor (shearing, transport, isolation from other sheep, injection of endotoxin or insulin or cortisol infusion) suppresses GnRH/LH pulse frequency and amplitude. Part of the cause is at the pituitary, but effects on GnRH/LH pulse frequency and the GnRH/LH surge are mediated via the hypothalamus. It is not yet clear whether delays in the surge are caused by interruption of the oestradiol signal-reading phase, the signal transmission phase or GnRH surge release. Stressors also delay the onset of behaviour, sometimes distancing this from the onset of the pre-ovulatory LH surge. This could have deleterious consequences for fertility.

Comparison of oestrus detection methods in dairy cattle

Sixty-seven Holstein-Friesian cows, from 20 days postpartum, were recruited into the study and fitted with both a pedometer (SAE Afikim) and a Heatime neck collar (SCR Engineers) and allocated a heat mount detector (either scratchcard [Dairymac] or KaMaR [KaMaR]) or left with none, relying only on farm staff observation. Common production stressors and other factors were assessed to determine their impact on the ability of each method to accurately detect oestrus and to investigate effects on the frequency of false-positive detections. Only 74 per cent of all potential oestrus periods (episodes of low progesterone) were identified by combining information from all methods. There was no difference between the methods in terms of sensitivity for detecting 'true oestrus events' (approximately 60 per cent), with the exception of scratchcards, which were less efficient (36 per cent). Pedometers and KaMaRs had higher numbers of false-positive identifications. No production stressors had any consequence on false-positives. The positive predictive values for neck collars or observation by farm staff were higher than those of other methods, and combining these two methods yielded the best results. Neck collars did not detect any of the nine oestrus events occurring in three cows with a body condition score (BCS) of less than 2, and the efficiency of correctly identifying oestrus was also reduced by high milk yield (odds ratio [OR]=0.34). Pedometer efficiency was reduced by lameness, low BCS or high milk yield (OR=0.42, 0.15 or 0.30, respectively).

Influence of lameness on follicular growth, ovulation, reproductive hormone concentrations and estrus behavior in dairy cows

The objective of this study was to examine the effect of a chronic stressor, lameness, on reproductive parameters. Seventy cows 30–80 days post-partum were scored for lameness and follicular phases synchronized with GnRH followed seven days later by prostaglandin (PG). Fifteen Lame animals did not respond to GnRH ovarian stimulation. Milk progesterone for 5 days prior to PG was lower in the remaining Lame cows than Healthy herdmates. Fewer Lame cows ovulated (26/37 versus 17/18; P = 0.04) and the interval from PG to ovulation was shorter in Lame cows. In Subset 1 (20 animals), the LH pulse frequency was similar in ovulating animals (Lame and Healthy) but lower in Lame non-ovulators. An LH surge always preceded ovulation but lameness did not affect the interval from PG to LH surge onset or LH surge concentrations. Before the LH surge, estradiol was lower in non-ovulating cows compared to those that ovulated and estradiol concentrations were positively correlated with LH pulse frequency. In Subset 2 (45 cows), Lame ovulating cows had a less intense estrus than Healthy cows, although Lame cows began estrus and stood-to-be-mounted earlier than Healthy cows. In conclusion, we have identified several parameters to explain poor fertility in some chronically stressed animals. From 30 to 80 days post-partum, there was a graded effect that ranged from 29% Lame cows with absence of ovarian activity, whereas another 21% Lame cows failed to express estrus or ovulate a low estrogenic follicle; in 50% cows, many reproductive parameters were unaffected by lameness.