Physiologic responses of feral horses to succinylcholine chloride immobilization

Five captive feral horses were immobilized at 72 hour intervals for 30 days by intramuscular administration of succinylcholine chloride (SCh) using a capture gun and dart system. The serum enzyme activities of creatine phosphokinase, glutamate-oxaloacetate transaminase, and lactate dehydrogenase and serum cortisol concentrations were monitored to assess the response to chemical immobilization in feral horses over time.Reference values for these parameters in feral horses were found to be in close agreement with those of normal, rested horses not in training. The results suggest that single, or infrequently repeated, use of succinylcholine-chloride by intramuscular administration to captive feral horses, or to otherwise unapproachable horses, could be efficiently and practically employed in field situations without major physiologic alterations and with minimal stress occurring in these horses.     

The effects of processing barley and maize on metabolic and digestive responses in horses

The competition for customers increases the search for new grain processing methods for equine feed, but the effect on starch digestibility and metabolic responses varies. Therefore, to evaluate the effect of the processing methods, toasting and micronizing, on starch digestion and the effect on metabolic responses, the mobile bag technique (MBT) and plasma glucose and insulin concentrations in the blood were used to estimate nutrient disappearance and metabolic responses pre-cecally. Further, cecal pH, ammonium nitrogen (N), and short-chain fatty acid (SCFA) concentrations were used to estimate the metabolic response in the cecum. Four cecally cannulated horses (body weight [BW] 565 ± 35 kg) were used in a 4 × 4 Latin square design with four periods of 8 d of diet adaptation and 2 d of data collection. Diets were formulated using hay and processed grains: micronized barley (MB), toasted barley (TB), micronized maize (MM), and toasted maize (TM) and were balanced to provide 1 g starch/kg BW in the morning meal. On day 9 in each period, blood and cecal fluid samples were taken before the morning meal and hourly thereafter for 8 h. On day 10 in each period, 15 bags of either MB, TB, MM, or TM (1 × 1 × 12 cm; 15 μm pore size; 1 g feed) were placed in the stomach, respectively. The dry matter disappearance was highest for the MM at all time points compared with the other feedstuffs (P < 0.001). Maize and micronizing had the highest starch disappearance (P = 0.048) compared with barley and toasting. No treatment effect was measured for any of the glucose and insulin parameters. No feed effect was measured for the insulin parameters. Plasma glucose peaked later (P = 0.045) for maize than for barley, and TB had a larger area under the curve for glucose than MB, MM, and TM (P = 0.015). The concentration of total SCFA increased after feeding (P < 0.001), with a higher concentration for barley than for maize (P = 0.044). No treatment or feed effects were measured for ammonium N or pH, but both were affected by time (P < 0.001). In conclusion, toasting was not as efficient as micronizing to improve pre-cecal starch digestibility; therefore, the preferred processing method for both barley and maize is micronizing. Further, the amount of starch escaping enzymatical digestion in the small intestine was higher than expected.     

Physiologic and behavioral responses to companion animals

There is a set of behavioral and physiologic responses to companion animals that can be reliably observed under both experimental and natural conditions. These responses indicate that contact with companion animals can be an effective means of reducing stress.     

Feeding practices associated with colic in horses.

OBJECTIVE: To determine whether specific feeding practices were associated with development of colic in horses. DESIGN: Prospective matched case-control study. ANIMALS: 364 horses examined by veterinarians in private practice in Texas because of colic (cases; n = 182) or any other reason (controls; 182). PROCEDURE: Participating veterinarians were sent forms at the beginning of the study to collect information on signalment, feeding management practices, farm management practices, and preventive medical treatments. Case and control horses were compared by use of conditional logistic regression to identify factors associated with colic. RESULTS: Risk factors for colic were a recent change in batch of hay, decreased exposure to pasture, a recent change in type of grain or concentrate fed, feeding > 2.7 kg (6 lb) of oats/d, feeding hay from round bales, and Thoroughbred breed. Recent anthelmintic administration decreased the risk of colic. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that certain changes in diet (eg, change in batch of hay, change in type of grain or concentrate, feeding hay from round bales) and management (eg, decreased availability of pasture) increase the risk of colic in horses.     

Physiologic and metabolic response of exercising horses to added dietary fat

Six mature Quarter Horse-type geldings were used in a replicated 3 × 3 Latin square experiment to determine the effects of adding 5 or 10% feed-grade rendered animal fat to the concentrate diet fed to performance horses. The experiment was conducted over a 14-day pre-trial period to acquaint horses to the experimental apparatus, a 28-day conditioning period and 3 diet treatment periods of 21 days, each conducted in a Latin square arrangement. The horses were exercised on a dirt track and diet effects were evaluated during and following a submaximal exercise test (SET) on an equine treadmill. Physiological responses to the SET were determined following each experimental period. Relative to the control, the horses required 21% and 25% less of the concentrate feed (P<.05), containing 5% and 10% added fat, respectively. There was an increase (P<.05) in muscle glycogen concentration as fat was added to the diet. There were no differences due to feeding fat in nutrient digestibility or in oxygen consumption, ventilatory capacity, respiratory quotient, heart rate blood lactate or blood pH during the SET. However, there was an overall decrease (P<.05) in blood glucose and total lipid concentration, when 10% fat was added to the concentrate diet     

Role of cholecystokinin in the gastric motor response to a meal in horses

OBJECTIVE: To measure plasma cholecystokinin (CCK) activity and the effect of a CCK-1 receptor antagonist on accommodation of the proximal portion of the stomach, and subsequent gastric emptying, in horses after ingestion of high-fat or high-carbohydrate meals. ANIMALS: 6 healthy adult horses with gastric cannulas. PROCEDURES: In the first study, horses were offered a high-fat (8% fat) or a high-carbohydrate (3% fat) pelleted meal of identical volume, caloric density, and protein content. Related plasma CCK-like activity was measured by radioimmunoassay (RIA). In a separate experiment, a horse was fed a grain meal with corn oil and phenylalanine, and plasma CCK activity was assessed by bioassay. A second study evaluated the effect of a CCK-1 receptor antagonist, devazepide (0.1 mg/kg, IV), on gastric accommodation and emptying following a meal of grain supplemented with either corn oil (12.3% fat) or an isocaloric amount of glucose (2.9% fat). Gastric tone was measured by a barostat and emptying by the (13)C-octanoic acid breath test. RESULTS: No plasma CCK-like activity was detected by RIA or bioassay before or after ingestion of meals. Preprandial devazepide did not alter the gastric accommodation response but did significantly shorten the gastric half-emptying time and time to peak breath (13)CO(2) content with the glucose-enriched meal. CONCLUSIONS AND CLINICAL RELEVANCE: In horses, CCK participates in regulating the gastric motor response to a meal. Compared with other species, horses may be more responsive to carbohydrate than fat. A vagovagal reflex most likely mediates this regulation, with CCK as a paracrine intermediary at the intestinal level.     

Physiologic responses to exercise of irradiated and nonirradiated Shetland ponies: a five-year study.

Physiologic responses of irradiated and nonirradiated Shetland Ponies to controlled exercise were measured over a period of 5 years. The 5-year test began when the ponies were 3 years old and 5 months after they were exposed to 650 R of 60-Co gamma radiation. Significant differences in heart rates, respiratory rates, and rectal temperatures were demonstrated between irradiated and nonirradiated ponies when subjected to exercise and high ambient temperatures. Inthe irradiated group, heart rates were usually slower, especially during recovery immediately after exercise, and respiratory rates and rectal temperatures were higher than these rates were in the nonirradiated group when exercising in ambient temperature of 29.5 C. Exhaustive exercise did not amplify any of the differences which were apparent with moderate exercise. From a general viewpoint, the irradiated ponies performed work as efficiently as did the nonirradiated ponies. Early changes in blood-cell concentrations after irradiation were similar to those which have been observed in other large animal species. Time required for the various types of blood cells to return to base line values ranged between 3 months and 3 years.     

马的饲养—中国农谚中讲如何养好马

人们在长期的生产生活中,形成了很多关于养马的农谚.这些谚语,对马的生理结构和消化特点进行了较好的归纳总结,准确地把握了马的生理特征.在马匹饲养过程中,根据马特殊的消化系统结构、生长发育特点、季节变换、马匹饲养环境以及马匹的用途等,要适应马的生理特性和需求,掌握马的饲喂原则.饲喂草料要做到定时、定量、少给多添、少吃多餐,...     

Metabolic responses to ammonium acetate infusion in exercising horses.

The relationship between elevated plasma ammonia (NH3) levels, fatigue development and muscle metabolism were examined in horses during a submaximal fatigue test. Eight Quarter Horse mares were intravenously infused prior to exercise with either sodium acetate (control) or ammonium acetate (AMINF), and exercised to fatigue on an 11% grade treadmill, carrying 27 kg of lead. Time to fatigue was not different (P greater than 0.05) between groups. Intramuscular NH3 and lactate increased (P less than 0.001) during exercise; however, the treatment did not (P greater than 0.05) affect either. A treatment by exercise interaction (P less than 0.01) occurred for plasma NH3. The reciprocal relationship between changes in plasma and intramuscular alanine (ala) and glutamate (glu) indicated activation of the glucose-alanine cycle. Plasma glutamine (gln) increased (P less than 0.001) during exercise; however intramuscular gln was not (P greater than 0.05) altered. The excretion of urea-N was depressed as a result of exercise while the orotic acid/creatinine ratio did not (P greater than 0.05) change. The amino acids and urinary metabolites were not (P greater than 0.05) affected by treatment. These results did not show any metabolic evidence for a role of increased plasma NH3 levels in fatigue development. However this study did provide insight into other aspects of nitrogen metabolism during exercise in the horse.     

Physiologic responses and plasma endothelin-1 concentrations associated with abrupt cessation of nitric oxide inhalation in isoflurane-anesthetized horses

OBJECTIVE: To assess physiologic responses and plasma endothelin (ET)-1 concentrations associated with abrupt cessation of nitric oxide (NO) inhalation in isoflurane-anesthetized horses. ANIMALS: 6 healthy adult Standardbreds. PROCEDURES: Horses were anesthetized with isoflurane in oxygen and placed in dorsal recumbency. Nitric oxide was pulsed into the respiratory tract for 2.5 hours, and then administration was abruptly discontinued. Just prior to commencement and at cessation of NO administration, and at intervals during a 30-minute period following cessation of NO inhalation, several variables including PaO(2), mean pulmonary artery pressure, venous admixture or pulmonary shunt fraction (Qs/Qt), and plasma ET-1 concentration were recorded or calculated. RESULTS: After cessation of NO inhalation, PaO(2) decreased slowly but significantly (172.7 +/- 29.8 mm Hg to 84.6 +/- 10.9 mm Hg) and Qs/Qt increased slowly but significantly (25 +/- 2% to 40 +/- 3%) over a 30-minute period. Mean pulmonary artery pressure increased slightly (14.0 +/- 1.3 mm Hg to 16.8 +/- 1 mm Hg) over the same time period. No change in serum ET-1 concentration was detected, and other variables did not change or underwent minor changes. CONCLUSIONS AND CLINICAL RELEVANCE: The improvement in arterial oxygenation during pulsed inhalation of NO to healthy isoflurane-anesthetized horses decreased only gradually during a 30-minute period following cessation of NO inhalation, and serum ET-1 concentration was not affected. Because a rapid rebound response did not develop, inhalation of NO might be clinically useful in the treatment of hypoxemia in healthy isoflurane-anesthetized horses.     

Antibody responses of horses to equine influenza viruses during a postepizootic period in Japan.

The antibody responses to equine influenza viruses were investigated during a postepizootic period of the disease. Serum samples were collected from a total of 128 horses on three occasions during the years 1967-77. No significant increase of hemagglutination-inhibition antibody titers to subtypes 1 and 2 of equine influenza virus were detected in any of the sera tested. The maternal hemagglutination-inhibition antibody titers of foals decreased over a four month interval. A marked increase of the titers was recognized in only the equine influenza virus vaccinated horses. These findings suggest that equine influenza virus was not prevalent in the horse populations during the observation period. In such conditions, the dissemination of equine influenza viruses in the horses is discussed in relation to introduction of the disease from abroad. We also examined whether the doctrine of original antigenic sin, an immunological phenomenon recognized in human influenza, was applicable for equine influenza. However, no marked increase of hemagglutination-inhibition antibody titer to the primary infecting subtype in the 44 horses was observed after administration of the heterologous subtype vaccine.     

Behavioral and physiological responses to stabling in naive horses

The purpose of this study was to investigate the response of horses to confinement and isolation in a stable (indoor individual housing) for the first time using behavioral indices, heart rate, and salivary cortisol concentration. Six naive 2-year-old Australian Stock Horse fillies were examined at 4-hour intervals over 24 hours in an outdoor group paddock followed by 24 hours in indoor individual housing. Behavioral observations and scores and heart rates were recorded and saliva samples were taken at each interval. During stabling, all horses became agitated and demonstrated increased vocalization and movement. Behavioral scores were significantly higher in the indoor individual housing (P < .001). No significant difference in heart rates between the two environments was detected. Mean salivary cortisol did not increase significantly (2 ng/mL ± 1.4 ng/mL in outdoor group paddock vs 2.5 mL ± 1.2 ng/mL in indoor individual housing). No diurnal rhythm in salivary cortisol was evident in either the outdoor group paddock or indoor individual housing. The results of this study highlight that a combination of behavioral and physiological measures allow better understanding of stress, where one measurement may be misleading. First time stabling of horses elicited marked behavioral responses indicative of stress that were not reflected in increased heart rates or salivary cortisol concentrations. The lack of a diurnal cortisol rhythm and the comparatively high basal cortisol concentrations found in the outdoor group paddock environment may imply that the fillies were already stressed; therefore, stabling did not cause further aberrations detectable by salivary cortisol analysis.     

Physiologic effects of succinylcholine chloride in mechanically ventilated horses anesthetized with halothane in oxygen.

Succinylcholine chloride, administered to horses anesthetized with halothane in oxygen and mechanically ventilated, caused slight but significant (P less than 0.01) increases in heart rate. Significant alteration in mean arterial blood pressure did not occur, and there were clinically insignificant increases in serum K+ and C1- concentration. Cardiac dysrhythmia and myoglobinuria did not occur. Thus, effects of halothane anesthesia and mechanical ventilation prevented cardiac dysrhythmia and hypertension and greatly reduced the tachycardia generally associated with siccinylcholine administration.     

Endocrinal responses in exercising horses

The intensity and duration of exercise exert a major influence on energy expenditure and physiological changes in the horse. Stressful environmental conditions, acclimation, and training status may further modify these responses. To maintain functional homeostasis during exercise, changes in autonomic nervous activity and hormone secretion are coupled to both the feedforward and the feedback mechanisms that control substrate mobilisation and utilisation.During exercise, both the sympathetic nervous system and the hypothalamic-pituitary-adrenal axis are activated, which increases the circulating levels of adrenocorticotropin (ACTH), cortisol, adrenaline and noradrenaline. Furthermore, adrenaline inhibits the release of insulin from the pancreas. Catecholamines, adrenaline, and noradrenaline increase glycogen breakdown in the muscles. In the liver, catecholamines, together with cortisol, increase blood glucose by activating glycogen breakdown and gluconeogenesis. Cortisol and catecholamines also enhance the mobilisation of free fatty acids from fat stores.In addition to efficient energy metabolism, the ability to exercise is highly dependent on the well-coordinated neuroendocrine control of cardiovascular function. Catecholamines increase oxygen delivery during exercise by enhancing cardiac output, splenic erythrocyte release, and skeletal muscle flow. Furthermore, cardiovascular homeostasis is maintained by changes in plasma renin activity and in plasma concentrations of atrial natriuretic peptide (ANP), arginine vasopressin, and aldosterone.