Topic:Energy Metabolism
Energy metabolism in horses refers to the biochemical processes that convert nutrients into energy within the body, supporting various physiological functions. This process involves the breakdown of carbohydrates, fats, and proteins to produce adenosine triphosphate (ATP), the primary energy carrier in cells. Key metabolic pathways include glycolysis, the citric acid cycle, and oxidative phosphorylation. Energy metabolism is essential for maintaining muscle function, thermoregulation, and overall health in horses. Factors such as diet, exercise, and health status can influence these metabolic processes. This page compiles peer-reviewed research studies and scholarly articles that explore the mechanisms, regulation, and implications of energy metabolism in equine physiology.
Dietary protein and(or) energy restriction in mares: plasma glucose, insulin, nonesterified fatty acid, and urea nitrogen responses to feeding, glucose, and epinephrine. Sixteen light horse mares (8 to 9 yr of age; 457 to 579 kg BW) were fed Bermudagrass hay and a corn/cottonseed hull-based supplement formulated to contain either 100% (control) or 50% (restricted) of the protein and(or) energy requirements for maintenance in a 2 x 2 factorial arrangement of treatments. Daily measurements of intake, BW, and plasma hormones and metabolites were made for 33 d. Plasma glucose, insulin, NEFA, and urea N were measured in hourly samples drawn on d 27, and parallel with an i.v. glucose tolerance test (IVGTT) and epinephrine challenge on d 29. Energy restriction increa...
Nutrition and equine performance. Some aspects of energy, protein and vitamin E nutrition of the performance horse are discussed. The amount, dietary source and time of ingestion of energy before exercise can influence performance. In 1989 the National Research Council (NRC) increased their estimates of energy required by racehorses. Recent studies indicate that the increase was reasonable. Many factors, however, can influence energy requirements. Therefore, the best measure would be body weight and composition of the horse. A proper balance of soluble carbohydrate, fiber, fat and protein is essential. Some guidelines are pres...
Effect of increasing work rate on metabolic responses of the donkey (Equus asinus). Oxygen consumption (VO2) and concentration of venous blood metabolites were measured in donkeys trained to run and to pull loads on a treadmill. VO2 in two donkeys running at maximal speed on a 9.8% slope was 110 +/- 2 ml.min-1.kg-1, approximately 22 times preexercise VO2. Average heart rate at maximal VO2 (VO2max) was 223 +/- 2 beats/min, five times the preexercise heart rate. Blood lactate increased 14-fold, and blood glucose did not change (P > 0.05). Animals running up a 4% incline and incremental draft loading of five donkeys walking on the level were also studied. The total energy cost o...
Draught animals and welfare. In fifty developing countries, which contain half of the total human population of the world, there is a heavy dependence on draught animals as an energy source. These animals are used for agriculture operations in 52% of cultivated areas of the world, as well as for hauling 25 million carts. This situation is likely to continue for at least another fifty years. The work performed annually by these draught animals would require 20 million tons of petroleum, valued at US$6 billion, if it were performed by motorized vehicles. The poor working conditions of these animals often adversely affect th...
Nutrition of the horse. The horse was domesticated around 2500 BC and has been used for work, pleasure, and companionship since that time. However, the percentage of time devoted to these endeavors has changed greatly. The number of horses in the US peaked at more than 26 million in 1918. Thereafter, the increasing use of the internal combustion engine caused a steady decline in the number of horses. By 1960, the US Department of Agriculture (USDA) estimated that there were only about 3 million horses in the US. In the 1960s, however, the number of...
Energy metabolism, replicative ability, intracellular calcium concentration, and ionic channels of horse articular chondrocytes. Some aspects of the physiology of chondrocytes from horse articular cartilage were studied, since this animal model can be helpful in understanding arthritic processes. The replicative ability of articular chondrocytes, measured by the incorporation of [3H]thymidine, and their capacity of proteoglycan production, evaluated from the incorporation of [35S] sulfate, are very low. In addition, these cells do not differentiate in vitro as shown by the constant specific activity of alkaline phosphatase measured at different times in culture. Two types of potassium channels were identified by patch c...
Stride length and respiratory tidal volume in exercising thoroughbred horses. The purpose of this study was to test the hypothesis that locomotor-respiratory coupling in horses may provide a basis for the appropriate matching of lung ventilation to running speed and metabolic power. This was achieved by determining the effect on respiratory frequency and tidal volume in thoroughbred horses of changing running speed while maintaining a constant metabolic demand by also varying the incline of the treadmill. This procedure was performed at three different speeds at two different levels of metabolic rate. It appears that, in response to metabolic demands which are not direc...
Nutrient intake of horses in thoroughbred and standardbred stables. Twenty-five Thoroughbred (TB) and 25 Standardbred (SB) stables were visited to determine their feeding practices. The ingredients of the main feed of the day for a mature gelding of average size in full training were weighted at each stable. Nutrient content of diets was calculated using published data for the individual ingredients. Results are expressed as mean +/- sd. The estimated body weight of TB horses was 493 +/- 34 kg and 437 +/- 32 kg for SB horses. There was considerable variation in diet composition and nutrient intake between stables. The TB trainers fed 11.0 +/- 2.4 kg and SB tra...
Study on the energy and protein metabolism in horses. The present study focused on energy and protein metabolism in pregnant and lactating mares, including the suckling and weaned growing horses, in order to determine feed availability, as also the energy and protein requirements. The authors found that the feeding diets, consisting of alfalfa hay, oats and compounds, had different availability values in terms of energy and protein, according to animal physiological conditions and age. Thus, the pregnant mares utilized the metabolizable energy (ME) and digestible crude protein (DCP) intake in average proportions of 64.5 +/- 3.2%, 54.6 +/- 3.0%, r...
Limits to maximal performance. Body size fundamentally affects maximal locomotor performance in mammals. Comparisons of performances of different-sized animals yield different results if made using relative, rather than absolute scales. Absolute speed may be a reasonable way to evaluate the locomotor performance of an animal that must escape predators in real time. However, comparisons of metabolic power in animals of different size can only be made meaningfully on a mass-specific basis. Numerous factors associated with the mechanics, energetics, and storage of elastic energy during locomotion change with body size, which r...
Voluntary intake, milk production and plasma metabolites in nursing mares fed two different diets. Voluntary food intake, milk yield and composition, and blood metabolites were measured during the first 2 mo of lactation in draft broodmares fed diets containing either 95% hay and 5% concentrates (Diet F) or 50% hay and 50% concentrates (Diet C). Voluntary food intake was higher for mares fed Diet C than for those fed Diet F (22.9 vs. 21.4 kg dry matter in wk 4). Both diets, especially Diet C, were eaten in amounts exceeding the energy requirements. Daily milk yield in wk 4 was 26.4 kg and 23.4 kg for mares fed Diets C and F, respectively. Milk fat and protein concentrations were higher (P l...
A comparative study of the metabolic effort expended by horse riders during a jumping competition. The three main Olympic horse riding disciplines are dressage, jumping, and three-day eventing (including dressage, cross country and jumping). In the jumping discipline (obstacle race), the 'team' (horse rider) is judged under the different conditions that might take place in a varied run. The horse is expected to show power and ability; the rider must show riding skill and good physical condition. However, the different conditions encountered by the rider during competition (duration of event, continuous isometric working level, especially in the inferior trunk, lead us to consider the need f...
A comparison between the nutritive value of short-cutting cycle, high temperature-dried alfalfa and timothy hay for horses. The objective was to evaluate the nutritive value of short-cutting cycle, high temperature-dried (SCCHTD) alfalfa compared to timothy hay. This was achieved by carrying out 4 x 4 Latin Square digestibility trial using 4 Thoroughbred (one three-quarter Thoroughbred) horses (mean liveweight, 531 kg). The four dietary treatments were 0AA (timothy hay only), 33AA (0.33 alfalfa: 0.67 timothy hay), 67AA (0.67 alfalfa: 0.33 timothy hay) and 100AA (alfalfa only). Digestibility data were obtained by using acid-insoluble ash to estimate apparent digestibility coefficients of nutrients. Rate of passage o...
Free fatty acids in exercising Arabian horses fed two common diets. Four Arabian geldings were used in a randomized, repeated measure design to study the effect of two different diets on plasma free fatty acids at rest and during exercise. On each of four sampling days, two horses were fed one of two isoenergetic diets, either 100% corn or 100% alfalfa, at 22% of their estimated daily energy requirement. Two hours after the consumption of the diet, each horse participated in a submaximal standard exercise test consisting of three consecutive 10-min runs of increasing intensity at heart rates of 132, 140 and 147 beats/min, respectively. There were no significan...
Common horse sense. This research article corrects a common misconception about the energy metabolism in horses during short sprinting and long-distance running events, emphasizing that short sprints are primarily powered by anaerobic activity, […]
Dietary protein level and energy metabolism during treadmill exercise in horses. Six conditioned Quarter Horse mares were used in a crossover design to assess the effect of the dietary protein level on intramuscular and hepatic glycogen and lactate, oxygen uptake and blood lactate, pyruvate and free fatty acids. After a 2-wk adaptation period to either a 9.0% (control) or an 18.5% crude protein diet, each horse performed an exercise test. The horses were exercised for 15 min on an 11% grade treadmill at 4.5 m/sec. The exercise test was performed 3-4 h after a meal. Venous, arterial and mixed-venous blood samples were taken simultaneously at rest and during exercise. Muscle...
[Myopathies in a riding horse stable]. In this case report on myopathies in 6 saddle-horses, a combined dietary vitamin E and selenium deficiency is presumed. Other disorders, such as exertional myopathy ("Monday morning disease") due to excessive energy intake or ionophore intoxication could be excluded by calculating the energy supply or by a simple colour test. The selenium requirement of horses is estimated to 0.1-0.2 mg/kg dry matter (Meyer 1986). If natural feed compounds are low in selenium, adequate amounts of this trace element can be supplied by means of supplemental feeds, sodium selenite (20 mg/500 kg BW/week) or bruise...
Cold housing effects on growth and nutrient demand of young horses. Housing temperature effects on growth, feed utilization and feed digestion of 12, 7-mo-old Standardbred colts were evaluated for 22 wk beginning in late November. Colts were assigned to one of two treatments: housed in a barn heated at 10 degrees C (warm) or housed in a barn with no external heat supply (cold). All horses were allowed outdoors for 4 h daily. Mean temperatures of the warm and cold barn from November to April were 10.9 +/- .66 and -5.2 +/- 1.72 degrees C, respectively. Hair coat weight of cold-housed colts was 1.4- to twofold (P less than .05) that of warm-housed colts from Dece...
Environmental effects on thermoregulation and nutrition of horses. Horses are reared in all types of weather. Temperatures as diverse as -40 degrees C to 40 degrees C are tolerated by horses. The nutrient requirement most influenced by cold weather is energy. In cold weather, feeding good quality hays free-choice is usually sufficient for mature horses in good body condition. Grain may have to be fed when poor quality hays are used. Hot weather (greater than 30 degrees C) necessitates heat loss to maintain body core temperature. Horses sweat to reduce body heat. Heat stress can be minimized by feeding diets that reduce the heat increment. Use of grain and fat...
Nutrition and fuel utilization in the athletic horse. Substrate depletion and end product accumulation are two important factors in exercise fatigue. Fatigue during long-term exercise results from a depletion of muscle and liver glycogen and coincides with an inability to maintain blood glucose levels. During high intensity exercise, the rapid catabolism of carbohydrate and the resultant production of lactate and hydrogen ions cause a reduction in muscle pH that inhibits maximum force generation. Dietary manipulations that can influence carbohydrate status or lactate accumulation may be beneficial to performance. In human athletes, carbohydrate l...
Clinical nutrition of adult horses. Horses suffering from trauma, sepsis, and severe burns need 12% to 16% of protein (dry matter basis) in their diet. Since reduced appetite may be a problem, relatively energy dense (greater than 2 Mcal DE/kg) feeds should be offered. In hepatic failure, maintenance protein requirements (8% on a dry matter basis for adult horses) should be met with feeds that are high in short branched-chain amino acids and arginine but low in aromatic amino acids and tryptophan (for example, milo, corn, soybean, or linseed meal) in addition to grass hay. Vitamins A, C, and E should also be supplemented. In cas...
Changes in muscle free carnitine and acetylcarnitine with increasing work intensity in the Thoroughbred horse. Treadmill exercise in Thoroughbred horses of 2 min duration and increasing intensity resulted in increased formation and accumulation of acetylcarnitine in the working middle gluteal muscle. At high work intensities a plateau in acetylcarnitine formation was reached corresponding to approximately 70% of the total carnitine pool (approx. 30 mmol.kg-1 dry muscle). Formation of acetylcarnitine was mirrored by an equal fall in the free carnitine content, which stabilised, at the highest work intensities, at around 8 mmol.kg-1 dry muscle. Acetylcarnitine and carnitine reached their point of maximum...
Blood and muscle metabolic responses to draught work of varying intensity and duration in horses. Three standardbred trotters performed treadmill exercise at a velocity of 2 m s-1 with a draught load of both 34 kiloponds (kp) (test 1) and 80 kp (test 2), and also at 7 m s-1 with 34 kp (test 3). The heart rate increased to average values of 111 (+/- 5), 157 (+/- 10) and 197 (+/- 7) beats min-1 in tests 1, 2, and 3, respectively. Plasma free fatty acids increased only during tests 1 and 2. Blood lactate and muscle glucose-6-phosphate and lactate concentrations were low after tests 1 and 2, but high after test 3, where also muscle glycogen utilisation was greatest. Muscle creatine phosphate a...
Comparative ventilation and gas exchange in the horse and the cow. Ventilation and gas exchange were studied in healthy, adult horses and cows, two large species with different lung structures and different breathing patterns. The oxygen uptake (VO2), carbon dioxide output (VCO2), respiratory rate (fR), minute ventilation (VE), alveolar ventilation (VA), alveolar oxygen pressure (PAO2), and VE/VO2 ratio were higher in the cows, while the tidal volume (VT) and physiological dead space (VD) were larger in the horses. The arterial blood gases, alveolar-arterial oxygen pressure difference (PAO2-PaO2) and VD/VT ratio did not differ between the two species. The hig...
Energy uptake and utilization by limit- and ad libitum-fed growing horses. Eighteen weanling horses were assigned to two treatments: limited or ad libitum feed intake. Growth and feed utilization were evaluated over a 78-wk period. Ad libitum-fed horses gained 24% more (P less than .05) weight than limit-fed horses. Total BW was distributed into 57% fore and 43% hind weight and did not differ between groups regardless of dietary treatment or age. Net gain and ADG in wither height of ad libitum-fed horses exceeded (P less than .05) that of limit-fed horses over 78 wk. Ad libitum-fed horses consumed 19, 44 and 34% more digestible energy (DE) than indicated in 1978 NRC ...
Nutrient utilization by limit- and ad libitum-fed growing horses. Eighteen Quarter Horse and Paint weanling colts were assigned to two treatments, either limit or ad libitum feeding. Nutrient digestibilities of diets were evaluated between 6 and 12 mo, 12 and 18 mo and 18 and 24 mo of age. From 6 to 12 mo, energy digestibility (64 to 68%) was unaffected by feed intake level. Ad libitum-fed horses had energy digestibilities 9 to 10% greater (P less than .05) than limit-fed horses between 12 and 24 mo of age, but adjustment for DM intake removed these differences. Limit-fed, mature ponies used dietary energy similarly to growing horses from 6 to 18 mo of age, ...
Effects of diet and climate on growing horses. The effects of diet and climate were assessed in 42 light horse weanlings over 30 wk. Horses were fed diets varying in energy and phosphorus content. Diets were predominantly forage (73 to 77.5%) or concentrate (62 to 62.25%) and had 2.65 or 3.09 Mcal DE/kg DM, respectively. Horses were weighed every 14 d. Group feed intakes and climatic variables were recorded daily. Dietary phosphorus content did not affect intake or gain. Horses fed forage diets ate 18% more (P less than .001) DM than horses fed concentrate, but DE intakes did not differ. Average DE intakes, 21.5 Mcal daily, were 33% more t...