To test the hypothesis that complexed trace mineral supplementation would increase antioxidant capacity and decrease muscle oxidative stress and damage in young horses entering an exercise training program, Quarter Horses (mean $$\pm$$ ± SD; 9.7 ± 0.7 mo) balanced by age, sex, and BW were assigned to receive complexed (CTM; n = 8) or inorganic (INORG; n = 8) trace minerals at -12 week relative to this study. Blood and muscle samples were collected before (week 0) and after 12 week of light exercise training surrounding a 1.5-h trailer stressor. Muscle glutathione peroxidase (GPx) activity was higher for CTM than INORG horses (P ≤ 0.0003) throughout the study. Following both trailer stressors, serum creatine kinase increased (P < 0.0001) and remained elevated through 24 h post-trailering (P < 0.0001). At week 0, muscle malondialdehyde, expression of superoxide dismutase 2, and whole blood GPx activity increased (P$$\le$$ ≤ 0.003) following trailering but trailering did not affect these measures at week 12. Young horses supplemented with CTM had higher muscle GPx activity than horses receiving INORG, but CTM did not affect damage markers following a stressor. Dietary CTM may be useful for improving antioxidant capacity during exercise training in young equine athletes.

Conjugated linoleic acid (CLA) improves oxidative stress and mitochondrial biogenesis in various species but has not been thoroughly investigated in horses. We collected blood and muscle samples from lightly exercising horses before and 6 and 12 wk after receiving either soybean oil (CON; n = 5) or CLA (CLA; n = 5) supplementation. Samples were analyzed for markers of mitochondrial characteristics, antioxidant status, oxidative stress, and muscle damage. Data were analyzed using a linear model with repeated measures. In the triceps brachii (TB), citrate synthase (CS) activity was higher in CON than CLA horses (P = 0.003) but was unaffected by diet in the gluteus medius (GM). Integrative (relative to mg protein) cytochrome c oxidase (CCO) activity was higher in TB than the GM (P &lt; 0.0001), while intrinsic (relative to CS) CCO was lower in the TB than the GM (P = 0.02) and tended to be lower in CON than CLA horses (P = 0.06). Neither CS nor integrative CCO activities were affected by time. In the GM, superoxide dismutase activity tended to increase in CON through wk 12 (P = 0.10). Over both muscle groups, glutathione peroxidase activity tended to be higher in CON compared to CLA at wk 12 (P = 0.06). Malondialdehyde was higher in the TB than the GM (P = 0.0004) but was unaffected by diet, while serum creatine kinase activity tended to be lower in CLA than CON horses (P = 0.07). These results suggest that CLA supplementation may lead to mitochondrial adaptations and prevent myofiber perturbation in skeletal muscle of young, lighlty exercised horses.

In aged humans, low-intensity exercise increases mitochondrial density, function and oxidative capacity, decreases the prevalence of hybrid fibers, and increases lean muscle mass, but these adaptations have not been studied in aged horses. Effects of age and exercise training on muscle fiber type and size, satellite cell abundance, and mitochondrial volume density (citrate synthase activity; CS), function (cytochrome c oxidase activity; CCO), and integrative (per mg tissue) and intrinsic (per unit CS) oxidative capacities were evaluated in skeletal muscle from aged (n = 9; 22 ± 5 yr) and yearling (n = 8; 9.7 ± 0.7 mo) horses. Muscle was collected from the gluteus medius (GM) and triceps brachii at wk 0, 8, and 12 of exercise training. Data were analyzed using linear models with age, training, muscle, and all interactions as fixed effects. At wk 0, aged horses exhibited a lower percentage of type IIx (p = 0.0006) and greater percentage of hybrid IIa/x fibers (p = 0.002) in the GM, less satellite cells per type II fiber (p = 0.03), lesser integrative and intrinsic (p≤ 0.04) CCO activities, lesser integrative oxidative phosphorylation capacity with complex I (PCI; p = 0.02) and maximal electron transfer system capacity (ECI+II; p = 0.06), and greater intrinsic PCI, ECI+II, and electron transfer system capacity with complex II (ECII; p≤ 0.05) than young horses. The percentage of type IIx fibers increased (p &lt; 0.0001) and of type IIa/x fibers decreased (p = 0.001) in the GM, and the number of satellite cells per type II fiber increased (p = 0.0006) in aged horses following exercise training. Conversely, the percentage of type IIa/x fibers increased (p ≤ 0.01) and of type IIx fibers decreased (p ≤ 0.002) in young horses. Integrative maximal oxidative capacity (p ≤ 0.02), ECI+II (p ≤ 0.07), and ECII (p = 0.0003) increased for both age groups from wk 0 to 12. Following exercise training, aged horses had a greater percentage of IIx (p ≤ 0.002) and lesser percentage of IIa/x fibers (p ≤ 0.07), and more satellite cells per type II fiber (p = 0.08) than young horses, but sustained lesser integrative and intrinsic CCO activities (p≤ 0.04) and greater intrinsic PCI, ECI+II, and ECII (p≤ 0.05). Exercise improved mitochondrial measures in young and aged horses; however, aged horses showed impaired mitochondrial function and differences in adaptation to exercise training.

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Equine research and management is limited to single-housing systems if individual animal intake is to be precisely recorded. Even then, dry forage intake is difficult to quantify accurately due to stomping or mixing hay with fecal matter and bedding. In cattle management, GrowSafe Systems (GrowSafe) is a commonly used tool to closely monitor individual animal feeding data using radio frequency identification (RFID) tag technology. Animals are equipped with a unique RFID tag that is read by the feed bunks each time the animal lowers its head into the bunk to consume feed. The objectives of this pilot study were 1) to test the feasibility of use of the GrowSafe system with horses by measuring intake of dry hay and 2) to characterize feeding behaviors of horses in an individually housed (without competition) or group-housed (with competition) setting. To test the hypothesis that horses would consume more hay when individually (NOCOMP) compared to group-housed (COMP), 10 mature Quarter Horses (14 ± 1.5 yr) were placed in one of four pens containing GrowSafe feed bunks in a 4-wk crossover design consisting of two 2-wk treatment periods. Pen 1 contained five horses with access to two GrowSafe bunks (Period 1: n = 4 mares, n = 1 gelding; Period 2: n = 5 geldings); pens 2, 3, and 4 contained one horse each with access to one bunk. Horses were individually fed 0.25% body weight (BW; dry matter [DM] basis) of a commercial concentrate once per day and were allowed Coastal bermudagrass hay in the GrowSafe bunks ad libitum. Although five horses were used in the group-housed (COMP) pen to more closely mimic a true group environment, only data from horses that experienced both housing systems (n = 3 mares and n = 3 geldings) were used for statistical analyses. Hourly (P = 0.008) and daily (P = 0.003) durations of hay feeding were higher for NOCOMP compared to COMP horses, and total daily intake (g DM/kg BW) of NOCOMP horses tended to be greater (P = 0.09) than COMP horses. Conversely, eating rate (g DM/kg BW/min) was greater (P = 0.04) for COMP compared to NOCOMP mares but was unaffected by housing in geldings. The GrowSafe system may provide an opportunity for efficient and effective monitoring of individual horse feed intake and feeding behavior in group-housing situations in horses.

Sixteen Quarter Horse mares (mean±SEM; 12±5 yr; 5.1±1.0 BCS; 579±9 kg BW) were used to evaluate the time course of the nutrient profile of colostrum and milk following parturition. Mares received a commercial concentrate designed to meet NRC (2007) requirements for gestating mares and were fed to maintain a BCS between 5 and 7. Horses were group housed in dry lots with ad libitium access to coastal Bermudagrass hay and water. As soon as parturition was observed, colostrum was collected by hand pre-suckle (0 h post-parturition), and at 6, 12, 24, and 36 h post-parturition. Samples were evaluated for concentrations of protein, fat, lactose, somatic cell count (SCC), urea nitrogen, and non-fat solids (NFS) by a commercial laboratory. Differences between means were determined using PROC MIXED in SAS (v9.4) with time as a repeated measure. Following parturition, colostrum protein and NFS decreased from h 0 to 6 (protein: 13.1±0.7 to 9.7±0.8%; NFS: 20.9±0.8 to 16.8±0.9%) and from h 6 to 12 (P0.04). Protein continued to show a trend for a decrease from h 12 to 24 (P = 0.08), plateauing around 3%. NFS remained around 10% from h 12 to 36. Conversely, lactose did not change from h 0 to 6 (3.6±0.2 to 3.9±0.2%) but increased from 6 to 12 h (5.5±0.2%) post-parturition (P &lt; 0.0001). Fat, SCC, and urea nitrogen remained unchanged through 36 h post-parturition. These results indicate colostrum protein concentration decreases as early as 6 h post-parturition, and the non-fat solid portion of milk shifts from primarily proteins to lactose. However, the impact of these changes on foal health should be more clearly defined.

Sixteen Quarter Horses (mean±SEM; 12±5 yr; 5.1±1.0 BCS; 579±9 kg BW) were used to test the hypothesis that mare body fat was related to colostrum composition. Mares received a commercial concentrate to meet NRC (2007) requirements and to maintain a BCS between 5 and 7. Horses were group-housed in dry lots with ad libitium access to coastal Bermudagrass hay. Within 1 wk of expected foaling date, ultrasound images were obtained to determine rump fat, intramuscular fat (IMF), and longissimus dorsi area and fat thickness (LDF) at the 13th/14th and 17th/18th ribs. At parturition, colostrum was collected by hand and evaluated for Brix%, immunoglobulin (Ig) concentrations by commercial ELISA, and concentrations of protein, fat, lactose, somatic cell count, urea nitrogen, and non-fat solids (NFS) by a commercial laboratory. Correlations were determined using PROC CORR in SAS (v9.4). Significant correlations are presented in Table 1. Overall, mare LDF was correlated with protein, lactose, and NFS but was not related to Ig concentrations. Further, the common on-farm test for colostrum quality (Brix%) positively correlated with Ig, protein, and NFS levels.

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