Subchondral bone plays a critical role in the pathogenesis of osteochondral disease across veterinary species. The subchondral bone is highly adaptable, with the ability to model and remodel in response to loading stresses experienced by the joint. Repetitive stress injuries within the joint can result in primary or secondary pathologic lesions within the subchondral bone, which have been recognized to contribute to the development and progression of osteoarthritis. Recent advances in diagnostic imaging, particularly volumetric imaging modalities have facilitated earlier identification of subchondral bone disease. Despite these advancements, limitations in our knowledge about subchondral bone makes treatment and prevention of these conditions challenging. The purpose of this report is to review our current understanding of subchondral bone and its relationship to osteoarthritis across veterinary species, with a specific focus in the research that has been performed in horses. It can be concluded that our current understanding of subchondral bone is advancing, and future experimental, clinical and pathologic studies will provide additional insight about subchondral bone and its relationship to joint disease.

Changes in bacterial populations in the faecal microbiota of horses presenting for colic observed in this study concurs with previous studies in veterinary and human patients with gastrointestinal disease. Future studies focusing on different causes of colic, chronic or recurrent disease, and the association with histological changes within the intestine are needed. This article is protected by copyright. All rights reserved.

OBJECTIVE To characterize the fecal microbiota of horses and to investigate alterations in that microbiota on the basis of sample collection site (rectum vs stall floor), sample location within the fecal ball (center vs surface), and duration of environmental exposure (collection time). ANIMALS 6 healthy adult mixed-breed mares. PROCEDURES From each horse, feces were collected from the rectum and placed on a straw-bedded stall floor. A fecal ball was selected for analysis immediately after removal from the rectum and at 0 (immediately), 2, 6, 12, and 24 hours after placement on the stall floor. Approximately 250 mg of feces was extracted from the surface and center of each fecal ball, and genomic DNA was extracted, purified, amplified for the V1-V2 hypervariable region of the 16S rDNA gene, and analyzed with a bioinformatics pipeline. RESULTS The fecal microbiota was unique for each horse. Bacterial community composition varied significantly between center and surface fecal samples but was not affected by collection time. Bacterial community composition varied rapidly for surface fecal samples. Individual bacterial taxa were significantly associated with both sample location and collection time but remained fairly stable for up to 6 hours for center fecal samples. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that, for horses, fecal samples for microbiota analysis should be extracted from the center of fecal balls collected within 6 hours after defecation. Samples obtained up to 24 hours after defecation can be analyzed with the realization that some bacterial populations may deviate from those immediately after defecation.

OBJECTIVE To describe gastrointestinal histologic findings for horses with recurrent colic and evaluate possible associations between initial clinical signs, biopsy method, histologic diagnosis, and outcome 1 year after hospital discharge. DESIGN Retrospective case series. ANIMALS 66 horses with a history of recurrent colic for which gastrointestinal specimens had been submitted for histologic examination. PROCEDURES Histologic diagnosis was categorized as inflammatory, neoplastic, ischemic, other, and undiagnosed. Relationships among initial clinical features, biopsy method, histologic diagnosis, and outcome 1 year after hospital discharge (ie, alive vs dead and persistent recurrent colic [yes vs no]) and between corticosteroid treatment and outcome were investigated. Odds ratios and hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated. RESULTS Inflammatory disease (36/66 [55%]) was the most common histologic diagnosis. Horses undergoing rectal biopsy alone were significantly (OR, 14.4; 95% Cl, 2.7 to 76.1) more likely to not have a histologic diagnosis than were horses in which other biopsy methods were used. In multivariable modelling, persistence of recurrent colic (HR, 15.2; 95% Cl, 1.9 to 121.2) and a history of weight loss (HR, 4.9; 95% Cl, 1.4 to 16.5) were significantly associated with outcome (alive vs dead) 1 year after surgery. Corticosteroid treatment was not significantly associated with either outcome. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that a high proportion (36/66 [55%]) of horses with recurrent colic had inflammatory gastrointestinal disease. Use of rectal biopsy alone to obtain biopsy specimens was more likely to result in no histologic diagnosis. Use of corticosteroids in horses with inflammatory gastrointestinal disease was not associated with outcome but warrants further investigation.

Background: Previous studies have identified alterations in the faecal microbiota of horses with colic; however, further work is needed to interpret these findings.Objectives: To compare the faecal microbiota of horses presenting for colic at hospital admission, day 1 and day 3/discharge and with different colic duration and lesion locations. Study design: Prospective observational clinical study.Methods: Faecal samples were collected from 17 colic cases at hospital admission, on day 1 and on day 3 post-admission or at the time of hospital discharge if prior to 72 hours. Faecal samples were extracted for genomic DNA, PCR-amplified, sequenced and analysed using QIIME. Species richness and Shannon diversity (alpha diversity) were estimated. The extent of the relationship between bacterial communities (beta diversity) was quantified using pairwise UniFrac distances, visualised using principal coordinate analysis (PCoA) and statistically analysed using permutational multivariate analysis of variance (PERMANOVA). The relative abundance of bacterial populations at the different time points and in different types of colic was compared using ANCOM.Results: There was a decrease in species richness from admission to day 3/hospital discharge (P < .05), and a lower species richness (P = .005) and Shannon diversity (P = .02) in horses with colic ≥60 h compared to <60 h. Based on PCoA and PERMANOVA, there was a significant difference in bacterial community composition for horses with different colic duration (P = .001) and lesion location (P = .006).Several differences in bacterial phyla and genera were observed at different time points and with different types of colic. Main limitations:Relatively low numbers and a diverse population of horses. Conclusions:The microbiota change from hospital admission to day 3/discharge in horses with colic and horses with colic ≥60 h and large colon lesions have a distinct bacterial population compared to horses with colic <60 h and small intestinal lesions.