Evaluating the genetic consequences of population subdivision as it unfolds and how to best mitigate them: A rare story about koalas

The genetic consequences of the subdivision of populations are regarded as significant to long-term evolution, and research has shown that the scale and speed at which this is now occurring is critically reducing the adaptive potential of most species which inhabit human-impacted landscapes. Here, we provide a rare and, to our knowledge, the first analysis of this process while it is happening and demonstrate a method of evaluating the effect of mitigation measures such as fauna crossings. We did this by using an extensive genetic data set collected from a koala population which was intensely monitored during the construction of linear transport infrastructure which resulted in the subdivision of their population. First, we found that both allelic richness and effective population size decreased through the process of population subdivision. Second, we predicted the extent to which genetic drift could impact genetic diversity over time and showed that after only 10 generations the resulting two subdivided populations could experience between 12% and 69% loss in genetic diversity. Lastly, using forward simulations we estimated that a minimum of eight koalas would need to disperse from each side of the subdivision per generation to maintain genetic connectivity close to zero but that 16 koalas would ensure that both genetic connectivity and diversity remained unchanged. These results have important consequences for the genetic management of species in human-impacted landscapes by showing which genetic metrics are best to identify immediate loss in genetic diversity and how to evaluate the effectiveness of any mitigation measures.

A preliminary study of cerebral blood flow, aging and dementia in people with Down syndrome

BACKGROUND

People with Down syndrome (DS) develop Alzheimer's disease (AD) at an earlier age of onset than those with sporadic AD. AD neuropathology is typically present in DS by 40 years of age with an onset of dementia approximately 10 years later. This early onset is due to the overexpression of amyloid precursor protein from the third copy of chromosome 21. Cerebrovascular neuropathology is thought to contribute in 40-60% of cases sporadic AD. However, the vascular contribution to dementia in people with DS has been relatively unexplored. We hypothesised that vascular perfusion is compromised in older adults with DS relative to younger individuals and is further exacerbated in those with dementia.

METHOD

Cerebral blood flow (CBF) was measured using pulsed arterial spin labelling in 35 cognitively characterised adults with DS (26-65 years). DS participants were also compared with 15 control subjects without DS or dementia (26-65 years). Linear regression evaluated the difference in CBF across groups and diagnosis along with assessing the association between CBF and cognitive measures within the DS cohort.

RESULTS

Cerebral blood flow was significantly lower among DS participants with probable AD compared with controls (P = 0.02) and DS participants with no dementia (P = 0.01). Within the DS cohort, CBF was significantly associated with the Severe Impairment Battery (SIB) measure and the Dementia Questionnaire for People with Learning Disabilities (DLD) rating (F_3,25  = 5.13; P = 0.007). Both the SIB (β = 0.74; t = 2.71; P = 0.01) and DLD (β = -0.96; t = -3.87; P < 0.001) indicated greater impairment as global CBF decreased. Age was significantly associated with CBF among participants with DS. There was a non-linear effect of age, whereby CBF declined more rapidly after 45 years of age.

CONCLUSIONS

This preliminary study of CBF in DS indicates that cerebrovascular pathology may be a significant contributor to dementia in DS. CBF was associated with diagnosis, cognition and age. Notably, CBF decreases at a greater rate after age 45 and may represent a significant prodromal event in AD progression.

Detection of cardiac amyloidosis by PET/CT imaging using 124I-p5+14 peptide

Introduction

Systemic amyloidosis is characterized by the deposition of protein fibrils in abdominothoracic organs, notably the heart, leading to organ dysfunction and significant morbidity. Patients who present with light chain (AL) amyloid-associated cardiomyopathy have a poor prognosis and median survival of only ∼ 9 mos. Cardiac amyloidosis is also present in many of the other forms of the disease and may be ever present in patients with transthyretin-associated amyloidosis (ATTR). Currently, no radiotracers are approved for the quantitative imaging of cardiac amyloid load.

To address these needs, we have developed a synthetic amyloid-reactive peptide radiotracer, 124I-p5+14, suitable for PET/CT imaging. The peptide binds the three major forms of amyloid (AL, ATTR and ALECT2), as well as other, less common, types through multivalent electrostatic interactions with amyloid-associated glycosaminoglycans and fibrils. Herein we report safety, dosimetry, and efficacy data on the first 22 patients from the ongoing Phase 1, first-in-human trial of 124I-p5+14 in patients with systemic amyloidosis (NCT 03678259).

Methods

Patients &gt;18 years of age with a confirmed diagnosis of systemic amyloidosis and not requiring heparin therapy are eligible. Subjects received &lt;2 mg of 124I-p5+14 (&lt;2 mCi) administered as a single IV bolus. PET/CT images for the initial cohort (n=3) were acquired from 25 min to 48h post injection. The second cohort of patients were imaged at ∼5 h and 24 h post injection. Image data were acquired using a Biograph 16 PET/CT scanner with a low dose CT. Uptake of radiotracer in the left ventricular wall was performed by automated image segmentation and standard uptake value ratios (SUVR) were calculated using blood pool as the reference tissue.

Results

To date, 22 patients (13 AL, 5 ATTR, and 4 other) patients have been evaluated. The gender-averaged mean whole body effective dose was 0.24 mSv/MBq. Cardiac uptake of the radiotracer was visually detected by a reader blinded to the patients' organ involvement in 85% and 100% of patients with AL and ATTR respectively, including patients with asymptomatic cardiac involvement - no cardiac symptoms or elevated cardiac biomarkers. The mean myocardium SUVR for visually positive AL and ATTR patients were 2.2±0.6 and 2.6±0.4. For visually negative AL patients the SUVRs were 1.0 and 0.9. In addition to cardiac amyloid, 124I-p5+14 uptake was observed in the nerves, ligaments, liver, spleen, adrenal glands, kidneys, pancreas, pituitary, and lung, with overall abdominothoracic organ-specific sensitivity of &gt;90% based on clinical presentation. Sensitivity in the heart was 100%.

Conclusions

PET/CT imaging of 124I-p5+14 provides excellent visualization of AL and ATTR cardiac amyloidosis which can be readily quantified as a means of monitoring response to therapy or disease progression. The 124I-p5+14 radiotracer was also capable of detecting amyloid in other abdominothoracic organs.

AL and ATTR cardiac amyloidosis

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): National Heart Lung and Blood Institute, National Institutes of Health; ACTP Gift Fund at the UTGSM

Concussion history associated with increased postural control deficits after subsequent injury

OBJECTIVE

Postural control deficits have been extensively reported following sport-related concussions. Concussed athletes demonstrate these deficits as early as 24 h post-concussion and may persist for up to six months. Many of these prior studies have included mixed samples with prior injury history that may affect the postural control data. The purpose of this investigation was to evaluate the effect of concussion history on postural control 24-48 h following sport-related concussion in Division I athletes.

APPROACH

Twenty-eight Division I athletes (seven athlete controls (CON), seven no history (SRC0), seven with a previous concussion (SRC1), and seven with 2-3 concussions (SRC3) participated in this study. All participants were assessed within 24-48 h post-subsequent SRC and performed three trials of quiet stance in the eyes closed (EC) conditions for 30 s each on a force platform (1000 Hz). The data were analyzed with root mean square (RMS) and mean excursion velocity (MEV) in the anteroposterior (AP) and mediolateral (ML) directions. Two 3  ×  2 MANOVAs were run by direction for group comparisons.

MAIN RESULTS

SRC2 had significantly greater RMS than CON, SRC0, and SRC1 in the AP direction and ML direction. SRC2 exhibited significantly greater AP and ML MEV than CON, SRC0, and SRC1.

SIGNIFICANCE

These results demonstrate that having 2-3 prior concussions negatively affects the postural system after a subsequent head injury. Sports medicine staff should approach the recovery process with caution with those that have a prior history of concussion, due to the negative effects that history of concussion has on postural control strategies.

A qualitative study of the processes by which carers of people with dementia derive meaning from caring

BACKGROUND

Most individuals with dementia live in the community, receiving care from family or lay carers. Carers' wellbeing, and the quality of the care they provide, partly depends on their ability to derive meaning from caring for someone with dementia. Both carers' previous relationship with their relative and the caregiving process itself contribute to this sense of meaning. However, it remains unclear why some carers derive meaning from these sources, whereas others do not.

OBJECTIVE

To further explore the processes by which carers derive a sense of meaning from caring.

METHODS

Representative case sampling was used to recruit a purposive sample of 20 carers for individuals living with dementia. In-depth semi-structured interviews were audio-recorded and transcribed, and analysed using pluralist qualitative methodology.

RESULTS

A framework of three sources from which carers derived meaning from caring was identified, encompassing: carers' perceptions of how 'right' or 'symmetrical' caring felt in light of their current and previous relationship with the person with dementia; maintenance of a 'protected' sense of self within the care relationship; and carers' perceptions of their 'social connectedness' outside the relationships.

CONCLUSION

Holistic assessment based on this framework could help to tailor individualised provision of support, foster resilience and safeguard carers' well-being.

Indoles derived from intestinal microbiota act via type I interferon signaling to limit graft-versus-host disease

The intestinal microbiota in allogeneic bone marrow transplant (allo-BMT) recipients modulates graft-versus-host disease (GVHD), a systemic inflammatory state initiated by donor T cells that leads to colitis, a key determinant of GVHD severity. Indole or indole derivatives produced by tryptophan metabolism in the intestinal microbiota limit intestinal inflammation caused by diverse stressors, so we tested their capacity to protect against GVHD in murine major histocompatibility complex-mismatched models of allo-BMT. Indole effects were assessed by colonization of allo-BMT recipient mice with tryptophanase positive or negative strains of Escherichia coli, or, alternatively, by exogenous administration of indole-3-carboxaldehyde (ICA), an indole derivative. Treatment with ICA limited gut epithelial damage, reduced transepithelial bacterial translocation, and decreased inflammatory cytokine production, reducing GVHD pathology and GVHD mortality, but did not compromise donor T-cell-mediated graft-versus-leukemia responses. ICA treatment also led to recipient-strain-specific tolerance of engrafted T cells. Transcriptional profiling and gene ontology analysis indicated that ICA administration upregulated genes associated with the type I interferon (IFN1) response, which has been shown to protect against radiation-induced intestinal damage and reduce subsequent GVHD pathology. Accordingly, protective effects of ICA following radiation exposure were abrogated in mice lacking IFN1 signaling. Taken together, these data indicate that indole metabolites produced by the intestinal microbiota act via type I IFNs to limit intestinal inflammation and damage associated with myeloablative chemotherapy or radiation exposure and acute GVHD, but preserve antitumor responses, and may provide a therapeutic option for BMT patients at risk for GVHD.

Putative chemosensory receptors are differentially expressed in the sensory organs of male and female crown-of-thorns starfish, Acanthaster planci

BACKGROUND

Chemosensation is a critical signalling process for all organisms and is achieved through the interaction between chemosensory receptors and their ligands. The Crown-of-thorns starfish, Acanthaster planci species complex (COTS), is a predator of coral polyps and Acanthaster cf. solaris is currently considered to be one of the main drivers of coral loss on the Great Barrier Reef in Queensland, Australia.

RESULTS

This study reveals the presence of putative variant Ionotropic Receptors (IRs) which are differentially expressed in the olfactory organs of COTS. Several other types of G protein-coupled receptors such as adrenergic, metabotropic glutamate, cholecystokinin, trace-amine associated, GRL101 and GPCR52 receptors have also been identified. Several receptors display male-biased expression within the sensory tentacles, indicating possible reproductive significance.

CONCLUSIONS

Many of the receptors identified in this study may have a role in reproduction and are therefore key targets for further investigation. Based on their differential expression within the olfactory organs and presence in multiple tissues, it is possible that several of these receptor types have expanded within the Echinoderm lineage. Many are likely to be species-specific with novel ligand-binding affinity and a diverse range of functions. This study is the first to describe the presence of variant Ionotropic Glutamate Receptors in any Echinoderm, and is only the second study to investigate chemosensory receptors in any starfish or marine pest. These results represent a significant step forward in understanding the chemosensory abilities of COTS.

Circulating immunoreactive substance P in man

Immunoreactive substance P (iSP) has been measured in plasma in 77 normal subjects and in 125 hospital patients. Factors affectingin-vitro degradation of iSP were studied.In vivo, iSP is degraded in the liver and its level in the circulation is independent of kidney excretory function.During insulin-induced hypoglycaemic stress and also during glucose-tolerance test, iSP in plasma decreased transiently. No circadian rhythm of iSP was observed, but in a study in sleeping volunteers episodic secretory bursts were seen, separated by one- to two-hour intervals, the first peak appearing about 90 minutes after the subjects fell asleep.In a patient with carcinoid metastases in the liver, an elevated level of iSP was found in the general circulation with a marked gradient at the hepatic venous effluent.

(1)H-MRS metabolites in adults with Down syndrome: Effects of dementia

To determine if proton magnetic resonance spectroscopy (¹H-MRS) detect differences in dementia status in adults with Down syndrome (DS), we used ¹H-MRS to measure neuronal and glial metabolites in the posterior cingulate cortex in 22 adults with DS and in 15 age- and gender-matched healthy controls. We evaluated associations between ¹H-MRS results and cognition among DS participants. Neuronal biomarkers, including N-acetylaspartate (NAA) and glutamate-glutamine complex (Glx), were significantly lower in DS patients with Alzheimer's should probably be changed to Alzheimer (without ' or s) through ms as per the new naming standard disease (DSAD) when compared to non-demented DS (DS) and healthy controls (CTL). Neuronal biomarkers therefore appear to reflect dementia status in DS. In contrast, all DS participants had significantly higher myo-inositol (MI), a putative glial biomarker, compared to CTL. Our data indicate that there may be an overall higher glial inflammatory component in DS compared to CTL prior to and possibly independent of developing dementia. When computing the NAA to MI ratio, we found that presence or absence of dementia could be distinguished in DS. NAA, Glx, and NAA/MI in all DS participants were correlated with scores from the Brief Praxis Test and the Severe Impairment Battery. ¹H-MRS may be a useful diagnostic tool in future longitudinal studies to measure AD progression in persons with DS. In particular, NAA and the NAA/MI ratio is sensitive to the functional status of adults with DS, including prior to dementia.

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¹H-MRS was used to compare demented and nondemented adults with Down syndrome.

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Neuronal biomarkers were lowest in demented adults with Down syndrome.

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Glial biomarkers including myoinositol were higher in demented adults with DS.

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Neuronal and glial biomarkers were correlated with cognition in Down syndrome.

Low expression of pro-apoptotic Bcl-2 family proteins sets the apoptotic threshold in Waldenström macroglobulinemia

Waldenström macroglobulinemia (WM) is a proliferative disorder of IgM-secreting, lymphoplasmacytoid cells that inhabit the lymph nodes and bone marrow. The disease carries a high prevalence of activating mutations in MyD88 (91%) and CXCR4 (28%). Because signaling through these pathways leads to Bcl-xL induction, we examined Bcl-2 family expression in WM patients and cell lines. Unlike other B-lymphocyte-derived malignancies, which become dependent on expression of anti-apoptotic proteins to counter expression of pro-apoptotic proteins, WM samples expressed both pro- and anti-apoptotic Bcl-2 proteins at low levels similar to their normal B-cell and plasma cell counterparts. Three WM cell lines expressed pro-apoptotic Bcl-2 family members Bim or Bax and Bak at low levels, which determined their sensitivity to inducers of intrinsic apoptosis. In two cell lines, miR-155 upregulation, which is common in WM, was responsible for the inhibition of FOXO3a and Bim expression. Both antagonizing miR-155 to induce Bim and proteasome inhibition increased the sensitivity to ABT-737 in these lines indicating a lowering of the apoptotic threshold. In this manner, treatments that increase pro-apoptotic protein expression increase the efficacy of agents treated in combination in addition to direct killing.

Elastic and vibrational properties of group IV semiconductors in empirical potential modelling

We have developed an interatomic potential that with a single set of parameters is able to accurately describe at the same time the elastic, vibrational and thermodynamics properties of semiconductors. The simultaneous inclusion of radial and angular forces of the interacting atom pairs (short range) together with the influence of the broken crystal symmetry when the atomic arrangement is out of equilibrium (long range) results in correct predictions of all of the phonon dispersion spectrum and mode-Grüneisen parameters of silicon and germanium. The long range interactions are taken into account up to the second nearest neighbours, to correctly influence the elastic and vibrational properties, and therefore represent only a marginal computational cost compared to the full treatment of other proposed potentials.Results of molecular dynamics simulations are compared with those of ab initio calculations, showing that when our proposed potential is used to perform the initial stages of the structural relaxation, a significant reduction of the computational time needed during the geometry optimization of density functional theory simulations is observed.

Incidence of serious side effects with intravenous bisphosphonate: a clinical audit

BACKGROUND

Bisphosphonates (BP) have been associated with osteonecrosis of the jaw (ONJ) and atypical femoral fractures (AFF). The prevalence of these side effects in intravenous (IV) BP-treated subjects is not well understood.

AIM

This audit aimed to delineate the prevalence of ONJ, thigh pain and AFF in patients having regular IV BP and its effect on bone mineral density (BMD). Design and

METHODS

Patients attending for IV BP over a 3-month period completed a questionnaire about thigh pain and dental health. Data concerning BMD, treatment indication and treatment history were obtained from medical records.

RESULTS

There were 201 patients between 28 and 94 years (74.1% female) mostly on zoledronate (ZOL) (102) or pamidronate (PAM) (97). Osteoporosis (75.6%) and Paget's disease (16.5%) were the main indications for treatment; median length of IV BP was 4 years (range 0.25-25). One patient had ONJ (0.5%) while oral pain was reported by 6.5% and 12.7% noted tooth loosening. Twenty-seven subjects (13.4%) complained of current thigh pain. AFF occurred in four patients (2%), none of whom had idiopathic osteoporosis. At time of AFF, only one patient had a femoral neck T-score less than -2.5. All four had received pamidronate treatment; median 12.5 years (range 7-22). IV BP treatment significantly increased lumbar spine BMD but not femoral neck BMD.

CONCLUSION

Classical ONJ was rare (0.5%), although tooth loss was more frequent. Thigh pain was frequent while AFF occurred in 2.0% of subjects and was associated with long treatment periods and non-osteoporotic bone.

Observation of public health risk behaviours, risk communication and hand hygiene at Kansas and Missouri petting zoos--2010-2011

Outbreaks of human illness have been linked to visiting settings with animal contact throughout developed countries. This study details an observational study of hand hygiene tool availability and recommendations; frequency of risky behaviour; and handwashing attempts by visitors in Kansas (9) and Missouri (4), USA, petting zoos. Handwashing signs and hand hygiene stations were available at the exit of animal-contact areas in 10/13 and 8/13 petting zoos, respectively. Risky behaviours were observed being performed at all petting zoos by at least one visitor. Frequently observed behaviours were as follows: children (10/13 petting zoos) and adults (9/13 petting zoos) touching hands to face within animal-contact areas; animals licking children's and adults' hands (7/13 and 4/13 petting zoos, respectively); and children and adults drinking within animal-contact areas (5/13 petting zoos each). Of 574 visitors observed for hand hygiene when exiting animal-contact areas, 37% (n = 214) of individuals attempted some type of hand hygiene, with male adults, female adults and children attempting at similar rates (32%, 40% and 37%, respectively). Visitors were 4.8× more likely to wash their hands when a staff member was present within or at the exit to the animal-contact area (136/231, 59%) than when no staff member was present (78/343, 23%; P < 0.001, OR = 4.863, 95% CI = 3.380-6.998). Visitors at zoos with a fence as a partial barrier to human-animal contact were 2.3× more likely to wash their hands (188/460, 40.9%) than visitors allowed to enter the animals' yard for contact (26/114, 22.8%; P < 0.001, OR = 2.339, 95% CI = 1.454-3.763). Inconsistencies existed in tool availability, signage and supervision of animal contact. Risk communication was poor, with few petting zoos outlining risks associated with animal contact, or providing recommendations for precautions to be taken to reduce these risks.

A critical role of dendritic cells in CD8 T cell IL-10 expression during inflammatory response triggered by CD40-activated B cells (159.16)

CD40LBTg mice, expressing a CD40 ligand (CD40L) transgene on B cells, represent a model for human diseases where B cells aberrantly express CD40L or receive excess CD40/CD40L signaling under inflammatory conditions. Here, we show that B cells expressing transgenic CD40L are capable of priming CD8 T cells and generate strong antigen-specific cytotoxicity. Adoptively transferred SIINFEKL peptide-loaded B cells from CD40LBTg but not wild type mice were able to activate self-reactive OT-I CD8 T cells upon immunization with OVA plus alum and trigger diabetes in RIP-OVA mice by enhancing the help of endogenous self-reactive CD4 T cells. CD40L expressing B cells also trigger spontaneous activation of splenic CD8 T cells, which rapidly up-regulate PD-1, Blimp-1 and LAG-3 and lose cytotoxicity along with IL-10 expression via interaction with PDL-1hi CD11c+ dendritic cells in T cell zones. Thus, CD11c+ dendritic cells from CD40LBTg mice exhibit regulatory phenotype, which block granzyme B expression and preferentially induce IL-10 expression in activated CD8 T cells. These results demonstrate that constitutive CD40 signaling on B cells under inflammation increases the risk of breaking peripheral CD8 T cell tolerance. However, the presence of CD40-activated B cells results in PDL-1hi CD11c+ dendritic cells, which exhibit a regulatory role to dampen harmful self-reactive cytotoxicity by promoting IL-10 expression in CD8 T cells.

The Task-Dependent Efficacy of Shared-Control Haptic Guidance Paradigms

Shared-control haptic guidance is a common form of robot-mediated training used to teach novice subjects to perform dynamic tasks. Shared-control guidance is distinct from more traditional guidance controllers, such as virtual fixtures, in that it provides novices with real-time visual and haptic feedback from a real or virtual expert. Previous studies have shown varying levels of training efficacy using shared-control guidance paradigms; it is hypothesized that these mixed results are due to interactions between specific guidance implementations ("paradigms") and tasks. This work proposes a novel guidance paradigm taxonomy intended to help classify and compare the multitude of implementations in the literature, as well as a revised proxy rendering model to allow for the implementation of more complex guidance paradigms. The efficacies of four common paradigms are compared in a controlled study with 50 healthy subjects and two dynamic tasks. The results show that guidance paradigms must be matched to a task's dynamic characteristics to elicit effective training and low workload. Based on these results, we provide suggestions for the future development of improved haptic guidance paradigms.

Parathyroid Hormone in Human Plasma: IMMUNOCHEMICAL CHARACTERIZATION AND BIOLOGICAL IMPLICATIONS

Antigenic recognition of four anti-bovine parathyroid hormone antisera was characterized by their reactivity with bovine hormonal fragments (1-34, 1-13, 14-34, 19-34, 53-84) and human hormone extracted from parathyroid adenomas. All antisera were found to have antibody populations which recognized more than one antigenic determinant and all antisera differed in their specificity and reactivity for the fragments of bovine hormone. By modification of two antisera, GP-1 and GP-133, by preincubation with excess concentrations of 1-34 or 53-84 fragments, antigenic recognition was restricted to defined regions of the hormonal sequence.When assays using these modified antisera were applied to the study of hormones extracted from glands, greater immunochemical similarities were seen between bovine and human parathyroid hormone using assays that were specific for the measurement of amino-terminal portions of the hormones than of the carboxy-terminal portions.When assays using these antisera were applied to the study of endogenous parathyroid hormone in human plasma, the immunoreactive hormone in the general circulation was shown to substantially lack an amino-terminal portion of the sequence of the intact hormone, including an antigenic determinant requiring all or some of the 14-19 region. This deletion accounts, at least in part, for the immunochemical heterogeneity of plasma parathyroid hormone in man. Radioimmunoassay of fractions of peripheral plasma subjected to gel filtration confirms that the dominant form of the immunoreactive hormone in the general circulation of man is a hormonal fragment that is totally devoid of amino-terminal reactivity. Because of this deletion, it can be concluded that most of the immunoreactive parathyroid hormone in the general circulation of man must be biologically inactive.

Reproductive performance measures among Thoroughbred mares in central Kentucky, during the 2004 mating season

REASON FOR PERFORMING STUDY

To improve efficiency at the farm level, a better understanding of how farm management factors impact reproductive performance is important.

OBJECTIVE

To assess reproductive efficiency and effectiveness among Thoroughbred mares in central Kentucky.

METHODS

A cohort of 1011 mares on 13 farms in central Kentucky was followed during the 2004 mating and 2005 foaling season. Information on farm level practices was collected via interviews with farm managers. Reproductive records were collected for each mare mated to obtain information on mare characteristics. The influence of mare age and status (maiden, foaling, barren) on Days 15 and 40 post mating pregnancy rates, foaling rates and total effective length of the mating season were assessed. The influence of stallion book size on reproductive performance measures was also examined.

RESULTS

Per season pregnancy rates on Days 15 and 40 post mating and live foal rate were 92.1, 89.3 and 783%, respectively. Per cycle rates for the same time periods were 64.0, 583 and 50.8%. There were no significant associations between stallion book size and reproductive performance outcomes. The mean +/- s.d. interval from the beginning of the mating season to the last mating of the mare was 36.5 +/- 26.1 days.

CONCLUSIONS

Mare age had a significant impact on efficiency of becoming pregnant, maintaining pregnancy and producing a live foal. Overall, fertility did not decrease among stallions with the largest book sizes. Total interval length of the mating season can be reduced if managers ensure maiden and barren mares are mated at the beginning of the season and foaling mares are mated at the earliest oestrus after acceptable uterine involution has been achieved.

POTENTIAL RELEVANCE

Measures identified in the study can be used by owners, farm managers and veterinarians to improve mare reproductive performance and identify parameters to assist with the implementation of effective culling practices.