Forage is essential for equine health and performance, but intake of elevated pasture nonstructural carbohydrates (NSC) may exacerbate metabolic disorders. This study aimed to investigate the influence of laminitis history on metabolic and morphometric responses in grazing horses. Twelve non-pregnant mares (15 +/- 3.4 yrs) were selected based on previous diagnosis of laminitis (PRELAM; n=6) or not (NOLAM; n=6). Horses were maintained on 8.5-ha pasture. Weekly pasture samples were clipped at random for nutrient analysis. Monthly blood samples were collected and analyzed for glucose and insulin concentrations. Body weight (BW), body condition score (BCS), and cresty neck score (CNS) were evaluated monthly. Each month, a modified oral sugar test (OST) was used to assess basal (T0) and 75-minute (T75) insulin dynamics following 0.30 mL/kg BW Karo Light Corn Syrup. Data were analyzed using PROC MIXED with repeated measures (SAS Institute). PRELAM had greater CNS (P < 0.001), BW (P < 0.05), and BCS compared to NOLAM (P < 0.05). Non-fasted glucose was influenced by month (P < 0.001) while non-fasted insulin was affected by group by month (P = 0.004). Fasted insulin concentrations (T0) were affected by month and group (P < 0.001) where PRELAM had greater concentrations. T75 glucose and insulin concentrations were affected by month (P < 0.001 and P = 0.002, respectively) and were higher for PRELAM (P = 0.003). These data suggest horses with greater general and regional adiposity, and previous history of laminitis, often exhibit greater insulin concentrations on pasture and to OST.

Polyunsaturated fatty acids (PUFA) play a role in regulating the body's response to inflammation. Most grains fed to horses are high in linoleic acid (LA), a pro-inflammatory n6 PUFA, compared with α-linolenic acid (ALA), an anti-inflammatory n3 PUFA. Recent interest in hemp (Cannabis sativa) seed oil (HSO) as a PUFA source has arisen due to its unique fatty acid (FA) profile, which includes γ-linolenic acid (GLA), an n6 PUFA with anti-inflammatory properties. Dietary GLA is rapidly converted to dihomo-γ-linolenic acid (DGLA), a precursor to anti-inflammatory eicosanoids. Manipulating dietary FA may lead to alterations in tissue FA profiles in the horse which could promote a reduced inflammatory response. Thus, our objective was to determine if oral supplementation of HSO for 28 d would cause detectable changes in FA composition in synovial fluid (SF) and skeletal muscle (MUS). Six Thoroughbred geldings (11 ± 3.2 yrs, 568 ± 26 kg BW) were used in a crossover experiment with 2 consecutive 63d periods. Horses were offered a control (CON) basal diet of hay and concentrate or the basal diet with the addition of 166 mL HSO delivering 5g GLA. Diets were designed to be isocaloric. Over 7d, HSO was introduced gradually, maintained for another 28d, and then removed and horses resumed basal diets for an additional 28d. Horses were weighed, and body condition score (BCS) assessed weekly. MUS and SF samples werecollected on d0, d35, and d63 of each period. MUS biopsies were taken from the middle gluteus muscle at a depth of 8cm. SF was collected from the left carpus joint. FA were extracted from MUS and SF and analyzed by GC. Individual FA are represented as g of FA per 100g of total fatty acids. Data were analyzed using Proc MIXED in SAS (v.15.1 SAS Institute Inc., Cary, NC). No changes in BW or BCS were observed throughout the study. In SF, GLA was detected after 28d of HSO supplementation (0.32 ± 0.06g/100g) but not at any other time point. On d 28, horses supplemented with HSO also had greater SF DGLA (0.31 ± 0.04g/100g) than CON (0.19 ± 0.04g/100g; P = 0.04). MUS ALA tended (P = 0.07) to be greater in horses fed CON compared with HSO. No other differences were observed for FA in MUS or SF. These results indicate that 28d of HSO supplementation can modify FA profiles in equine skeletal muscle and synovial fluid. This could potentially influence inflammation signaling molecules and subsequently the inflammatory response, however, longer studies with more horses are needed to determine peak incorporation and the effects of varying quantities of HSO in the diet.

Management factors associated with colic, particularly related to stall confinement and nutrition, have been linked to alterations in gastrointestinal mucosal transport, motility, and microbiome, which in turn creates conditions that induce colic. In particular, meal feeding creates large changes in water movement in and out of the colon and alters the microbiome. These conditions may in turn result in colic conditions such as large colon impaction or large colon volvulus. In addition, a range of management and nutritional factors have been found to place horses at risk of select colic conditions such as ileal impaction. Other specific colic conditions, such as strangulating lipomas, may be related to fat metabolism in geldings and ponies, although the association with nutrition and the endocrine system are less well defined. It has long been understood that parasites are associated with colic, and with the advent of highly effective anthelmintics, parasite-induced colic has been markedly reduced. Nonetheless, equine mangers and veterinarians have to be aware of changes in parasite resistance or patterns of activity, such as the resurgence of large strongyles with surveillance-based management of parasites. Overall, understanding management risk factors can lead to recommendations that prevent colic in horses. Additional study of these factors may ultimately lead to reductions in the prevalence of colic by suggesting optimal management practices.

This study aimed to evaluate the effects of processing method and meal time of day on certain metabolic responses in horses. Both factors influence postprandial glycemic and insulinemic response, but any interaction is unknown. Nine thoroughbred geldings (9.9 ± 2.2 yrs) were used in a randomized 3x3 crossover design. Treatments consisted of three diets: hay only (control), hay plus the same compound feed either pelleted (P), or extruded (E). Horses were fed a daily total dry matter intake (DMI) of 2.5% BW (P and E diets were offered at 0.75% BW, with hay at 1.75% BW), evenly split into two meals and given at 0800 (AM) and 1600 (PM) h daily. Horses were gradually adapted to their respective diets over the first 7 d of each 25 d period. Blood samples were collected (via intravenous jugular catheters) 30 and 0 min pre- and 15, 30, 45, 60, 75, 90, 105, 120, 135, 150, 180, 210, and 240 min post-prandially both AM and PM on d 25, and plasma analyzed for glucose and insulin concentrations. Areas under the curve (AUC) were determined and evaluated using two-tailed paired t-tests (GraphPad Prism6) with statistical significance set at P ≤ 0.05. Horses fed P and E had increased AM AUC compared to PM for both glucose (P = 0.0005 and P = 0.0037; respectively) and insulin (P = 0.0042 and P = 0.0419; respectively). There were no differences in AM AUC between the two diets. However, there was a trend for increased PM AUC for glucose and insulin when diet E was fed compared to P (P = 0.08 and P = 0.09; respectively). Processing method did not alter metabolic response in horses during the AM meal but may influence PM response. Further research is needed to explain these differences.

High intakes of pasture non-structural carbohydrates (pNSC) can cause digestive and metabolic disturbances. This study aimed to investigate the influence of seasonal patterns of pNSC content on grazing horses. Twelve sporthorse mares (15 ± 3.4 yrs) were maintained together on 8.5-ha mixed-grass pasture (free-choice mineral supplementation) for 12 mo beginning October 2016. Horses were grouped according to their baseline cresty neck score (CNS); CNS≥2.5 (C; n=5) or CNS<2.5 (NC; n=7). Weekly pasture samples (200g wet weight) were clipped at random, 2.5 cm from plant base. Samples were weighed, dried at 70ºC and analyzed to determine monthly pNSC content (Equi-analytical, Ithaca, NY). Monthly fecal grab samples were collected from the rectum to measure pH and D-lactate concentrations. Monthly body weight (BW), body condition score (BCS), and CNS were evaluated. Blood glucose and insulin dynamics (%∆ change) were assessed using an oral sugar test (pre and 75min post 0.3ml/kgBW Karo syrup). All sample analyses were performed in duplicate. Data were analyzed using PROC Corr and ANOVA in PROC Mixed (SAS v9.4) with P≤0.05 considered statistically significant. pNSC was highest in April (17.13 ± 3.18 %DM) and varied by mo (P<0.0001). Fecal pH and D-lactate differed by mo (both P<0.0001) with pH lowest in April (6.65 ± 0.05) and D-lactate highest in April (4177.51 ± 190.59 µM); however, there were no differences between C and NC. pNSC was associated with D-lactate (r=0.36, P=0.008) and there was a trend with pH (r=-0.26, P=0.07). Throughout, C had higher BW and BCS than NC (P<0.0001 and P=0.0009, respectively) with no effect of mo. Mo influenced glucose (P<0.0001), but there was no treatment effect. Insulin differed by mo in both groups (P=0.01), but C had higher insulin compared to NC across all mo (P<0.0002). These results highlight seasonal changes in pNSC and its potential effect on grazing horses which will help direct grazing management strategies.