This retrospective evaluation of data from a large commercial embryo transfer facility aimed to determine the extent to which age and treatment on the day of embryo transfer in recipient mares influence the likelihood of pregnancy. Embryo recovery was carried out on days 8-10 post-ovulation using transcervical uterine flushing. Recipient mares grouped according to their age were treated once on the day of embryo transfer (Day 3-8 post ovulation) and were assigned randomly to 1 of 3 groups: Mares in Group A (n=101) received antispasmodic, antimicrobial, and anti-inflammatory drugs. Mares in Group B (n=100) received gentamicin and flunixin meglumine. Group C (control) (n=103) did not receive any treatment. Detomidine (0.008 mg/kg bwt i.v.) was administered to all recipients before transfer of the embryo. The influence of treatment and recipient´s age was calculated using binary logistic regression. Day 16 post-transfer pregnancy rates were highest in Group A (74/101, 73.3a%), when compared to Group B (60/100, 60%), and Group C (57/103, 55.3b%) (a vs b, p<0.05). Pregnancy loss rates at D45 were not different between groups, A (8/74, 10.8%), B (5/60, 8.3%), and C (6/57, 10.5%), respectively (p>0.05). Pregnancy losses were increased in recipient mares 17-22 years (33.3a%) compared to younger recipient mares (2-6 years 7b%, 7-11 years 10%, 12-16 years 8b%) (a:b p<0.05). The regression model showed that the predicted probability for pregnancy after embryo transfer decreased as the age of the recipient mare increased for treated recipients in Group A (p=0.012), there was no effect of treatment and recipient´s age in Group B, and a decreased likelihood of pregnancy in recipients of advanced age (≥12 years of age) in untreated recipients (group C). Likelihood of pregnancy increased following single administration of antispasmodic, antimicrobial, and anti-inflammatory drugs at the time of embryo transfer in recipients 2-12 years of age. Likelihood of pregnancy in recipients decreased in recipients≥12 years of age. These results, obtained under the conditions of a large commercial embryo transfer program, offer an opportunity to improve pregnancy rates in recipient mares≤12 years of age.

Lateralised behavioural responses to environmental stressors have become more frequently used as indicators of social welfare in animals. These lateralised behavioural responses are under the control of asymmetrical brain functions as part of the primary functions of most vertebrates and assist in primary social and survival functions. Lateralised behavioural responses originating from the left hemisphere are responsible for processing familiar conditions, while the right hemisphere is responsible for responding to novel stimuli in the environment. The forced lateralisation and side preference tests have been used to determine the visual lateralised behavioural responses in livestock to environmental stressors. Limb preference during movement has also been used to determine motor lateralisation. Although behavioural investigations in livestock have recorded lateralised behavioural responses to environmental stressors, there are still limitations in the implication of lateralisation to other conditions, such as restraint and invasive procedures. Thus, it is important to have a non-invasive measure for these lateralised behavioural responses. Recently, lateralised behavioural responses have been correlated with the use of infrared temperature of external body surfaces, such as the eyes and coronary bands of limbs. This review summarised the different forms of the lateralised behavioural responses in livestock, especially cattle and horses, to environmental stressors, and the association between these responses and the relevant external body surfaces’ infrared temperature, with the purpose of improving the use of non-invasive measures in assessing welfare conditions in animals. The combination of the lateralised behavioural responses and infrared temperature of external body surfaces to environmental stressors could improve the assessment strategies of welfare conditions and the related additional husbandry interventions that could be applied to improve the welfare of farm animals.

Horses are transported in the United States more than any other livestock species and co-mingle at various events; therefore, they are considered to be at an increased risk for infectious disease transmission. The fragmented movement of horses combined with numerous sites of co-mingling makes tracing the potential spread of a disease outbreak a necessary part of an infection control plan, both locally and nationally. The cross-movement of personnel with horses and the persistence of endemic diseases make biosecurity implementation an ongoing challenge. Although many of the risks for infection are known, there is limited documentation about the usefulness of prospective control measures. The objective of this survey was to determine horse owners' understanding and knowledge of biosecurity practices for preventing infectious diseases in the United States. Questions covered owner demographic information, including horse use which was divided into 10 categories as follows: Pleasure/Trail Riding, Lessons/School, Western Show, English Show, Breeding, Farm/Ranch, Retired, Racing, Driving and Other. The survey was distributed by sending requests to a list of horse owner organizations, which then sent emails to their members. The email request described the survey and provided a website link to start the survey. A total of 2413 responses were collected. Analysis of the results included cross-tabulation to identify significant differences in biosecurity knowledge and awareness by horse use. Significant differences by horse use were identified for vaccination, biosecurity planning, use of isolation, disease risk, monitoring for diseases, co-mingling of horses, sanitation, medical decision making and health record requirements for horse events. In summary, the results suggest that most owners are not highly concerned about the risk of disease or the use of biosecurity. There are several biosecurity applications and techniques which can be increased and will benefit horse health and welfare. These include reliance on temperature monitoring, isolation of new horses at facilities, risks of horse mingling, entry requirements such as vaccination and health certificates at events, and an emphasis on having biosecurity plans for facilities and events where horses co-mingle. The information from this study will be used to create tools and information that horse owners and veterinarians can use to implement appropriate biosecurity practices for different types of horse uses and events.

SummaryThe paranasal sinuses of horses can be exposed through an osteoplastic flap to determine the cause of clinical signs of disease referable to the paranasal sinuses, such as facial deformity or abnormal chronic, unilateral nasal charge, or to remove abnormal contents within it, such as a progressive ethmoidal haematoma, an osteoma, a neoplasm, a cyst, inspissated exudate, a fungal granuloma or feed. The two types of osteoplastic flaps are the frontonasal flap and the maxillary flap. The frontonasal flap is the easier of the two to create and is the most commonly created flap because it provides direct or indirect access to all compartments of the ipsilateral paranasal sinuses. The maxillary flap provides good access to the rostral and caudal maxillary sinuses and is created most commonly to provide access to an orosinus fistula or the alveolus of a diseased maxillary molar to remove dental or osseous fragments.

To investigate pseudohyperkalemia occurring in horses experiencing rhabdomyolysis when serum chemistry profiles are run on an VetScan VS2 analyzer (Abaxis). 18 horses with rhabdomyolysis (creatine kinase [CK] > 1,000 U/L). In 3 horses with serum CK activities > 5,800 U/L and persistent serum potassium concentrations of > 8.5 mmol/L (VetScan VS2), potassium concentrations were reevaluated with either i-STAT Alinity Base Station (Abbott), Catalyst (Idexx), or Cobas c501 (Roche) ion-specific analyzers. Paired serum samples from 15 additional horses (median serum CK activity, 7,601 U/L; range, 1,134 to 192,447 U/L) were analyzed on both VetScan VS2 and Cobas c501 machines. Serum potassium concentrations were compared between the VetScan VS2 and ion-specific analyzers by Bland-Altman and Wilcoxon ranked tests and correlated to log10 CK activity via Pearson correlation. Serum potassium concentrations were significantly higher on the VetScan VS2 (6.7 ± 1.6 mmol/L) versus the ion-specific analyzers (4.0 ± 1.1 mmol/L; P < .0001), with high bias shown in Bland-Altman analysis (43.1 ± 27.9). Potassium concentrations positively correlated with log10 CK activity with the VetScan VS2 (R2 = 0.51; P = .003) but not the Cobas (R2 = 0.09; P = .3) analyzer. An alternate analyzer to the VetScan VS2 should be used to evaluate serum potassium concentrations in horses with rhabdomyolysis because the VetScan VS2 methodology uses lactate dehydrogenase, which increases in serum with rhabdomyolysis and falsely elevates potassium concentrations.

SummaryBackgroundEquine odontoclastic tooth resorption and hypercementosis (EOTRH) is being increasingly recognised as a painful and debilitating condition in some affected horses, that can produce pain on prehension or result in infected, fractured and loose incisors. The only known way to completely alleviate the pain and secondary infection associated in many horses affected with EOTRH is by extraction of the diseased incisors. Currently, few large‐scale clinical outcome studies have been performed.ObjectivesThe purpose of this study was to determine if horses that are diagnosed with clinical EOTRH experience a statistically significant improvement in the quality of their lives after surgical extraction of all incisors and to determine if owners were satisfied with the results of the surgery.Study designA retrospective web‐based survey was sent out to owners of horses diagnosed with EOTRH who had undergone extraction of all incisors in the previous 3 years.MethodsForty‐eight surveys were completed, and the answers examined for statistical significance.ResultsStatistically significant differences were found in the horses' body condition, dropping of hay, speed of eating, general behaviour, resistance to bridling and headshaking. In addition, owners reported that horses were ‘happier’ after surgery and that total extraction improved quality and extended the life of their horse. Over 90% of owners would also elect to have the procedure performed on another horse in the future.Main limitationsRetrospective surveys are prone to selection, recall and misclassification bias.ConclusionsOwners were highly satisfied with the total extraction of all incisors as a treatment for horses affected by EOTRH. Survey results showed that post‐extraction horses had improved body condition and exhibited better bridling and eating behaviours which are consistent with a decrease in dental pain. Owners felt that their horse was happier and that the surgery had improved the horse's quality of life.

Equine protozoal myeloencephalitis (EPM) caused by Sarcocystis neurona remains an antemortem diagnostic challenge in some horses. Recent work suggested the use of real-time PCR (rtPCR) on cerebrospinal fluid (CSF) as a promising diagnostic tool. To evaluate the sensitivity and specificity of S. neurona rtPCR on CSF for EPM diagnosis using horses with EPM and S. neurona-seropositive horses with other neurologic conditions. Ninety-nine horses with neurologic disease that underwent complete neurologic examination, CSF collection, and, if euthanized, necropsy including the central nervous system (CNS). Retrospective case-control study using banked CSF samples. Samples from horses with neurologic abnormalities and necropsy-confirmed EPM diagnosis, presumptive EPM diagnosis using strict criteria (SnSAG2/4/3 ELISA serum:CSF titer ratios <50) and horses diagnosed with other neurologic diseases were used. Fifty-two horses had EPM; 23 were confirmed on necropsy, and 29 were presumptive clinical diagnoses. The other 47 horses all had necropsy-confirmed diagnoses. Four of the 47 horses had normal neurologic findings on necropsy and the remaining 43 horses had neurologic diseases including equine degenerative myeloencephalopathy (EDM), cervical vertebral stenotic myelopathy, trauma, and other miscellaneous conditions. One CSF sample was weakly positive for S. neurona by rtPCR, this sample was obtained from a horse with confirmed EDM. Samples from the other 98 horses were negative for S. neurona by rtPCR. Our study contradicts previous conclusions that S. neurona rtPCR is potentially useful for EPM diagnosis, because our results indicate that the assay has a low sensitivity (0%) for EPM.

There is a paucity of data relating to the vitamin D status of racehorses. We hypothesised that the management of racehorses in Hong Kong (HK) predisposes to low vitamin D status unless they receive dietary supplementation. Serum concentrations of 25-hydroxyvitamin D2 (25OHD2), 25-hydroxyvitamin D3 (25OHD3) and total 25-hydroxyvitamin D (total 25OHD) for 79 non-grazing HK racehorses were compared with those for 22 racehorses training in the United Kingdom (UK) that grazed for ≥1 h/d, and for which published data exists. A nested group of 41 HK horses was sampled twice to determine the effect of the duration in HK on vitamin D status. The HK horses had significantly lower serum concentrations of total 25OHD and 25OHD2 than the UK horses; 25OHD2 was undetectable in 15/79 HK sera and serum concentrations of 25OHD2 declined with the duration in HK. The main determinants of vitamin D status were assessed using linear regression; the retained variables were the 25OHD3 concentration and the duration in HK. The inverse relationship between the serum concentrations of 25OHD2 and 25OHD3, previously identified in humans, was observed for the first time in horses. In conclusion, HK racehorses have low serum 25OHD2 and total 25OHD concentrations and rely on D3 supplementation to maintain adequate vitamin D status. Further study is required to determine the optimal form of dietary vitamin D supplementation for Thoroughbred racehorses.

Objective: To report clinical characteristics, surgical management, and medium-term outcomes of 3 Arabian neonatal foals with meniscal disruption associated with septic arthritis of the lateral femorotibial joint. Methods: Three neonatal Arabian foals with septic arthritis of the lateral femorotibial joint (LFTJ), were diagnosed with lateral meniscal (LM) tears, based on persistent lameness despite improving synovial parameters, ultrasound (US) findings (protrusion of meniscal tissue beyond the level of the condyles, with hypoechoic regions), contrast Computed Tomography findings, and confirmed on arthroscopy. Treatment included arthroscopic debridement and lavage of the joint with debridement of the meniscal tear. Postoperative care included systemic and intra-articular antimicrobials, based on culture and sensitivity results. Two of the foals received intra-articular injections of autologous mesenchymal stem cells. Results: Grade III meniscal tears were observed in the LFTJ of the affected joints of all foals, involving the meniscal body (n=3) and caudal horn (n=1). Purulent material within the torn tissue, was debrided with a synovial resector. Foal 1 was lame-free as a yearling. Foal 2 was lame at walk at 7.5 months and euthanatized due to poor prognosis. Foal 3 showed mild lameness at trot in a straight line at 6 months. Disruption of the LM continued to be visible on US in both foals at these time-points. Conclusion: Meniscal disruption and infection should be considered a differential in neonatal foals with persistent femorotibial septic arthritis. In such cases, the LM could be the primary nidus of infection.

Historically, nocardioform placentitis (NP), has been associated with the presence of Amycolatopsis spp., Crossiella equi, and Streptomyces spp. However, these organisms have not been detected or isolated in all NP cases, suggesting alternative causative agents. Additionally, a previous attempt to experimentally induce NP using Crossiella equi was not successful (Canisso et al. EVJ. 2014; 47(1)). Recent studies suggest the existence of a placental microbiome and suggest that a shift in the relative abundance of community members may alter the outcome of gestation. Here, we investigated the placental microbial population in normal (n=11) and NP cases (n=31). Total RNA was extracted, ribosomal depletion was performed, and sequencing libraries were constructed followed by deep sequencing (>160 million reads/sample, 150bp PE). Host RNA was mapped to the equine reference genome (EquCab3.0) using STAR-2.5.3a, annotated and quantified by featureCount. Microbial RNA was separated from host RNA and mapped to the NCBI prokaryotic database (Kraken2). Additionally, these data were analysed using Phyloseq, vegan, amplicon, microbiome, and WGCNA for compositional analysis. The phylum Actinomycetota, containing the nocardioform bacteria, was more abundant in NP samples than in controls (p<0.01). Even though Amycolatopsis spp., Crossiella equi, and Streptomyces spp. had a high abundancy in NP cases, these microbes were also present in the healthy placentas at a 60-fold (p<0.01), 100-fold (p<0.05) and 2-fold (p>0.05) lower abundancy, respectively. Alpha diversity(inverse Simpson) was similar between the groups, but beta diversity was higher in NPs than in the controls (Bray Curtis and Aitchison distances, p<0.05), suggesting no difference in richness within groups, but a change in diversity between groups that may be linked to disease outcome. Microbial gene expression analysis revealed several genes solely expressed in NP cases, associated with microbial responses to hyperosmotic shocks, protein synthesis during stress, and ATP-dependent zinc metalloproteases and were associated with expression from Actinomycetota and Mycobacteriaceae. In the NP samples, 30 virulence factors (VF) were expressed, while no VF expression was detected in the controls. Interestingly, 70% (21/30) of VFs were expressed by Mycobacterium spp. An abundance of Amycolatopsis (r=0.56) and Mycobacterium (r=0.64) was positively correlated with genes associated with inflammation and immune cells in the placenta (p<0.01). Overall, these results suggest that the shift in the microbial composition during NP was associated with the disease. Additionally, the results suggest involvement of Mycobacterium spp. in NP cases. These bacteria have not been previously linked to NP, however, Mycobacterium avium has been previously linked to equine abortions with similar placental lesions as NP (Kinoshita et al. Vet Med Sci. 2021; 7:621-625). Funding: Special Research Fund (BOF) at UGent, The Foundation for The Horse, Grayson Jockey Club Foundation, Clay Endowment at UKY, and the Center for Equine Health at UCDavis.