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Some horses are more prone to obesity than others. This study aimed to compare energy intake and expenditure between obese and lean horses. Ten mature, stock-type geldings (aged 11.8 ± 4.0 years; 577 ± 52 kg) maintained on the same pasture were classified as obese (n = 6, body condition score [BCS] ≥ 7) or lean (n = 4, BCS = 4–5) and adapted to free-choice grass hay over 25 days. Dry matter intake (DMI) was measured for 11 days, with body weight (BW) and blood samples (analyzed for serum leptin) collected on Days 0, 2, 4, 7, 9, and 11. Behavior was observed for 24 hours. Apparent dry matter digestibility and gross energy digestibility were measured using 48-hour total fecal collection. Digestible energy intake was calculated. Activity (distance traveled, average heart rate [HR], and maximum HR) was quantified using HR monitors with GPS tracking. Average HR was used to estimate energy expenditure. Serum leptin, DMI, and BW were analyzed as repeated measures. Other variables were analyzed using unpaired t-tests. P

Six mature stock-type geldings with maintenance only requirements were used in a randomized cross-over design to determine the effect of sward height on pasture plant nonstructural carbohydrate (NSC) concentrations and blood glucose and insulin concentrations. Horses were randomly assigned to one of two tall fescue (Lolium arundinaceum Schreb cv Max-Q, Pennington Seed, Madison, GA) grazing cells (0.37 ha) having two different sward heights for a period of 7 days: (1) short (approximately 15 cm; n = 3) or tall (between 30 and 40 cm; n = 3). After the first 7-day period, treatment groups were reversed by moving horses to ungrazed cells having similar characteristics to those used in the first 7 days, so that all horses receive all treatments resulting in six observations per treatment. Both short and tall grazing cells were mowed to a height of approximately 15 cm 32 days before the experiment starts. The short grazing cells were removed to approximately 15 cm at 11 days before the start of the first 7-day period and again 1 day before the start of each 7-day period. All horses had access to pasture for 10 h/d beginning at 8 AM and ending at 6 PM. Although not at pasture, all horses were individually housed in 3.7 × 12.2 m partially covered pens containing automatic water troughs and a crushed stone surface. Herbage mass (kg DM/ha) was determined by use of a falling plate meter for each pasture to ensure that both groups of horses had adequate dry matter to provide grazing for at least 7 days. On day 7 of each period, jugular venous blood samples were collected from each horse before being turned out to pasture, and then at 2, 4, 6, and 8 hours after turn-out. Pasture samples were also collected from each grazing cell at the same time blood samples were taken. Serum and plasma from blood samples were harvested and analyzed for insulin and glucose concentrations, respectively. Pasture samples were analyzed for water soluble carbohydrate (WSC), ethanol soluble carbohydrate (ESC), and starch. The sum of WSC and starch were used as an estimate of NSC. Area under the curve (AUC) and peak concentration were calculated for both plasma glucose (PPG) and serum insulin (PSI) concentration and were analyzed using analysis of variance for randomized cross-over designs. Pasture WSC, ESC, starch, and NSC concentrations were analyzed using analysis of variance for randomized complete block design. A P value of

Recently, there has been a renewed interest and an increase in published research on equine grazing and pasture management. The objectives of this paper are to review equine grazing research methodologies with an aim to encourage standardized research procedures. This review highlights standard methods used in equine pasture-related research, including use of climate data and soil type; seed bed preparation and grazing management; determining forage nutritive value; defining forage maturity; tracking horse health parameters; evaluating different grazing systems; and future technologies. This review covers in-depth discussions on determining forage biomass yield, forage populations, ground cover, persistence, forage intake, and grazing behavior. Specifically, mechanical harvesting, hand clipping, rising plate meter, and falling plate meter are all methods used to determine forage biomass yield. Frequency grid, point sampling, visual assessment, Natural Resources Conservation Service pasture condition score, and the double Dominant, Abundant, Frequent, Occasional, Rare (DAFOR) scale can be used to track forage populations, ground cover, and persistence of pasture species. Three primary methods have been used when estimating horse forage intake including the difference between pre- and postgrazing herbage mass, the difference in pre- and postgrazing bodyweight, and use of digestibility and fecal output markers. Equine grazing behavior has been described by investigating preference, pre- and post-sward height, and bite and mastication rate. Awareness of key methodologies should encourage movement toward research protocol standardization that will allow for scientific comparisons and application of pasture-related research results across the horse industry.

Chromium propionate (Cr Prop) was recently approved by the US FDA for supplementation to horse feed at a level not to exceed 4 mg Cr/horse/day. This approval was based on the ability of Cr Prop to improve insulin sensitivity in adult horses following oral consumption of grain or intravenous administration of glucose, and also on the safety of Cr Prop when supplemented to horse diets at up to 2 times the FDA approved level. The objective of the current study was used to determine the safety of Cr Prop based on health, body weight (BW) gain, body condition score, and blood chemistry and hematological parameters when supplemented at levels of 0, 2, 4, or 8 mg Cr/day. Forty-eight registered Quarter horses were used in this study. The study was conducted as 4 trials, due to a limitation of individual stalls at the testing facility. Horses were housed individually and fed twice daily an oat-based concentrate mix at a rate of 0.2 kg/100 kg BW, and grass hay (2 kg/100 kg BW). Supplemental Cr was provided in 50 g of ground corn/day that was top dressed on the morning feeding of concentrate. In the fourth trial, 12 horses (n = 3/treatment) were bled before feeding on d 0 and 28 of the trial for blood chemistry and hematological measurements. Serum was analyzed for an Equine Chemistry panel, that consisted of calcium, phosphorus, magnesium, sodium, potassium, chloride, bicarbonate, osmolality, anion gap, glucose, urea, total protein, albumin, bilirubin, alkaline phosphatase, aspartate aminotransferase, and creatine kinase. A sample of whole blood also was obtained for a variety of hematological measurements. Each horse served as its own control, because d 28 blood data were statistically analyzed using d 0 blood values as a covariate. Feeding Cr Prop for 42 d did not affect health, body weight gain, or body condition score. Control horses had lower (P ≤ 0.05) RBC counts than those fed 8 mg Cr/day, and tended to have lower RBC counts than those receiving 2 (P = 0.07) or 4 (P = 0.06) mg Cr/day. Other hematological measurements were not affected by dietary Cr. Serum clinical chemistry parameters measured were not affected by treatment. The present study indicates that Cr Prop is safe when supplemented to horses at up to 2 times the FDA approved feeding level.

The present study was designed to determine whether a reduction in body weight (BW) and body condition score (BCS) could be achieved through 10% to 20% energy restriction in privately owned and managed horses, similar to previously published research in a controlled research setting. Twenty-four, overweight, client-owned/managed horses were identified for use in the study. At the initial (September 2012) and final evaluations (May 2013), health records, diet evaluation, estimated BW, fasting glucose and insulin (INS) concentrations, BCS, cresty neck score (CNS), and morphometric measurements were obtained from 24 client-owned horses and four control horses. At the conclusion of the trial period (26 ± 4 weeks), changes in BW, BCS, CNS, morphometric measurement, and INS were analyzed using paired t tests. Correlations between changes in BW (%initial) and ΔBCS were evaluated. Overall decreases (P

Weight loss plans in horses typically use dietary restriction, but exercise may have additional benefits. This study aimed to compare the effects of a diet or exercise protocol resulting in comparable caloric restriction in obese horses. Ten obese horses were paired according to sex, age, and breed or breed type. One horse from each pair was randomly assigned to either diet (DIET)—intake restricted to approximately 85% of digestible energy requirements or exercise (EX)—exercised to expend approximately 15% of digestible energy requirements, resulting in 85% of requirements available, for 4 weeks. Body weight (BW), heart girth (HG), girth-to-height ratio (G:H), neck circumference (NC), neck circumference-to-height ratio (NC:H), belly girth (BG), body condition score (BCS), cresty neck score (CNS), serum insulin, plasma leptin, and plasma ghrelin concentrations were measured weekly. An oral sugar test was conducted on days 0 and 28 to measure insulin to glucose ratio (Ins:glc) and 60-minute insulin sensitivity index (ISI60). Results were analyzed using repeated measures. A P ≤ .05 was considered significant, and .05

Horses' physical and digestive well-being is often enhanced when allowed to graze on pastures. Furthermore, a well-managed pasture can contribute to economic viability. Grazing can however have deleterious effects on the environment if not properly managed. Although equine grazing, defecating, and ground trampling behavior is unique from that of other livestock species, pasture management practices are often based on those derived from cattle grazing. This review summarizes the current knowledge of impacts of equine grazing on pasture quality and environment and identifies gaps where further information is needed to formulate and recommend sustainable grazing methods specific to equine.

Eight mature horses were used in a 4 × 4 Latin square design to determine the effect of restricted pasture access on dry matter intake rate (DMIR), energy intake, and fecal pH. Horses were randomly assigned to one of four groups (HGRPs), each containing two horses. HGRPs were randomly assigned to one of four treatments consisting of 3, 6, 9, or 24 hours of pasture access, for a period of 7 days. Treatments were switched every 7 days. The 3- and 6-hour groups were fed free choice mature grass hay while not grazing. Daily pasture dry matter intake (DMI) for each HGRP was estimated by calculating the difference between initial herbage mass of the grazing cell before grazing and residual herbage mass after 7 days of grazing. Total dry matter intake was the sum of pasture and hay DMI for the 3- and 6-hour treatments. Fecal pH was measured on day 7 of each period. Response variables were analyzed using analysis of variance for Latin square design. Restricting pasture access decreased mean pasture DMI (P = .02), pasture dietary energy (DE) (P = .02), and fecal pH (P

Eight mature horses weighing 576 ± 32 kg (mean ± SD) were used to compare differences in pasture dry matter (DM) intake rate in October (period 1), February (period 2), and May (period 3). Horses were randomly assigned to a pair of adjacent 5 m × 5 m grazing cells containing nontoxic, endophyte-infected tall fescue. Horses had access to each cell for 4 hours. Pasture DM intake rate was estimated over the entire 8-hour period by measuring the pre- and postgrazing herbage mass within each cell and was expressed as kg DM/100 kg body weight (BW)/hr. Mean 8-hour DM intake rate in period 1 (0.17 ± 0.01 kg DM/100 kg BW/hr) was greater (P

The current study was conducted to evaluate daily within-horse variation of plasma alpha-tocopherol concentration (TOC) (Experiment 1 [EXPT1]) and to determine the effect of a single meal on plasma TOC (Experiment 2 [EXPT2]). In EXPT1, venous jugular blood samples were collected from four pregnant (6–7 months of gestation), light horse mares (8.8 ± 2.9 years of age, mean ± SD; range, 5–11 years of age) between 7:30 AM and 8:30 AM, followed by eight hourly samples, and analyzed for plasma TOC. All horses were fed 5 kg dry matter (DM) grass hay 18 hours before sample collection and received no additional feed during the sampling period. Mean within-horse coefficient of variation for TOC was 3.5% ± 0.01%. In EXPT2, seven mature light horses, four mares and three geldings (4.9 ± 4.4 years of age, mean ± SD; range, 2–14 years of age), were randomly assigned to one of two treatments (fasted [FST; n = 7] or fed [FD; n = 7]), followed by reversal of treatments 24 hours later. At 7:30 AM, FD horses were fed 2.1 kg DM grain-mix concentrate (187 IU vitamin E/kg DM) plus 3.3 kg DM mixed-grass hay, whereas FST horses received no feed. Neither group received any feed for 18 hours before 7:30 AM. Venous jugular blood samples were collected at 10:30 AM from all horses and analyzed for plasma TOC. The mean (±SD) within-horse paired-treatment difference was not significant (0.05 ± 0.12 μg/mL). The results suggest that variation in within-horse plasma TOC is relatively small over an 8-hour period in fasting horses and is unaffected 3 hours after a hay grain meal.

In the horse, resting insulin concentration (INS), the glucose-to-insulin ratio (G:I), and the reciprocal of the square root of insulin (RISQI = 1/√INS) are commonly used to estimate insulin sensitivity, whereas the modified insulin-to-glucose ratio (MIRG = [800 – 0.30 × (INS -50) 2 ]/(GLU – 30) is used to estimate pancreatic beta-cell responsiveness. Because no estimates of their within-horse variability and repeatability have been reported, the objective of this study was to evaluate the within-horse variation of these estimates. Resting blood samples were obtained from six healthy equids (three geldings, two mares; mean ± SD body weight, 525.0 ± 43.36 kg; mean age, 9.8 ± 8.2 years; and one pony gelding: 293 kg; 12 years) on three consecutive days in week 1 and again in week 2. Samples were collected at 12:00 noon, approximately 6 hours postprandially. Serum insulin and plasma glucose (GLU) concentrations were analyzed and used to calculate G:I, RISQI, and MIRG, as well as the insulin to glucose ratio (I:G). The coefficient of variation was used to determine within-horse variation, and repeatability was determined using the repeatability coefficient (RC; measurements from a single horse should differ less than the RC for 95% of the pairs). The mean coefficients of variation (CVs) for resting GLU, INS, G:I, I:G, MIRG, and RISQI were 5.5%, 33.7%, 36.0%, 31.6%, 22.3%, and 18.6%, respectively. All variables had values that differed more than the RC in at least one horse. These data suggest that care should be taken when interpreting insulin sensitivity estimates from a single blood sample.

The U.S. Department of Agriculture supports agricultural research by encouraging the formation of multidisciplinary and multi-institutional teams. Project teams focus on agricultural issues related to profitability and economic and environmental sustainability. Recently, a U.S. Department of Agriculture project to study the impact of equine management and feeding practices on the environment was approved. The project, “NE-1041: Environmental Impacts of Equine Operations,” is a Northeast regional project but includes research and extension faculty from across the country. The project team includes representatives from Alabama, Connecticut, Kentucky, Louisiana, Maryland, Michigan, Minnesota, New Jersey, North Carolina, Pennsylvania, South Dakota, and Vermont. The goal of this project is to incorporate the best available data on horse management and feeding practices, manure storage and disposal, pasture and cropping management, soil and environmental quality, erosion control, and farm management practices to minimize negative impacts of equine operations on the environment. The specific objectives of the project are to assess existing data on environmental impacts of equine operations, identify gaps in current knowledge, conduct research when data are lacking or nonexistent, and incorporate existing and newly generated data into a systematic description of nutrient flow in soil, water, and air occurring on horse farms. Estimates will be made of pathogen transports and nitrogen (N)-, phosphorus (P)-, potassium (K)-, and energy (carbon)-loss potentials. In addition to identifying system-wide losses on equine farms, another goal of the project is to assist farmers and agricultural professionals in determining the value of equine management practices and other accepted best management practices.

Summary Serum samples from 15 suckling foals, 119 days of age, of Quarter Horse and Thoroughbred breeding, that were weaned at either 140 days of age (EW) or 182 days of age (LW) were used to measure changes in vitamin K status over time and to assess the effect of age at weaning on vitamin K status. Jugular venous blood samples were collected from each foal at the start of the experiment and 21-day intervals thereafter, with the exception of a one-week interval post-weaning in both groups. The study continued for 84 days post-weaning in both groups. Serum was analyzed for total osteocalcin and hydroxyapatite binding capacity of serum osteocalcin (HABOC) which was calculated as follows: HABOC = [(total serum osteocalcin — serum osteocalcin following extraction of serum with hydroxyapatite)/total serum osteocalcin]x100. Osteocalcin's capacity to bind hydroxyapatite is vitamin K-dependant and, therefore, is used as a marker of vitamin K status. Hydroxyapatite binding capacity of serum osteocalcin increased (quadratic; P

Summary Eight ponies were used in a two-period, crossover design experiment to determine if the physical form of a concentrate feed affected selected gastric fluid and blood variables. Each pony had been surgically fitted with a gastric cannula 2 years prior to the study. In each 29-day period, four ponies received hay and a pelleted concentrate and four ponies received hay and a textured (sweet feed) concentrate. The concentrate portions of the diets were identical except for physical form and contained 57.5% corn, 25% oat, 8.5% soybean meal, 7% molasses and 2% minerals and vitamins. On day 15 of each period, the ponies received a concentrate meal (.4% of body weight) and blood and gastric fluid samples were obtained for 9 h after feeding. Feeding a concentrate meal resulted in increased plasma glucose, serum insulin, gastric fluid glucose and gastric fluid L-lactate concentrations. The pH of gastric fluids before feeding ranged from 1.4 to 8.36, but gastric fluid pH was at least 5.0 within 30 min of eating in all ponies. Few effects of concentrate form were observed, but plasma glucose concentrations at 150 and 180 min after feeding were higher (P