Summary In the first study, 5 mature, unconditioned, Thoroughbred geldings performed an initial submaximal exercise test (UC) prior to any conditioning and a final test (C) following 8 weeks conditioning. Serum creatine kinase (CK) and aspartate aminotransferase (AST) activity were measured before and for 72 h after exercise. Plasma lactate concentration [La−] was used as an indicator of exercise conditioning. Serum CK and AST activity remained increased above pre‐exercise levels from 0–24 h and 0–8 h post exercise, respectively. There was a time by conditioning interaction for AST, CK and plasma [La−] resulting in an attenuated response of each variable following exercise test C as compared to following exercise test UC. These results indicate that submaximal exercise can elevate serum AST and CK and that conditioning can attenuate these changes. A second study using 8 mature Thoroughbred horses was conducted to evaluate the effect of 2 different types of exercise, short term high intensity (STHI) and repeated submaximal exercise (RS) on serum AST and CK activities. Serum AST and CK activities during the post exercise period were higher in response to the RS test compared to the STHI test.
Summary The purpose of this study was to determine whether a difference in roughage intake could affect electrolyte and water balance in horses during endurance type exercise. In each of 2 experiments, 2 treatments (a high hay or limited hay diet) were assigned in a crossover design so that each horse performed 2 exercise tests, 1 on each treatment. In experiment 1, diet was controlled only the night before the exercise test. Water intake was lower (P<0.001) when horses received the limited hay diet. Exercise caused a decrease in plasma chloride and potassium concentration and an increase in plasma total protein concentration, but there were no diet differences (P>0.05). Weight loss was 2.8% of body weight for both treatments. In experiment 2, horses were adapted to the diets for 7 days prior to the exercise test. Again, water intake was lower when the horses received the limited hay diet (P<0.01). During exercise, both groups lost about 4% of bodyweight, but total protein concentration was lower (P<0.05) in the horses receiving the high hay diet. Plasma potassium concentration initially increased and then decreased during exercise (P<0.05), but the horses receiving the high hay diet maintained a higher potassium concentration during exercise (P<0.05). Sodium was not affected by diet or exercise (P>0.05). Plasma chloride concentration decreased during exercise (P<0.05). The increased water intake and lower plasma protein concentration associated with the hay diet may be beneficial for horses involved in endurance type exercise.
The metabolic effects of short-term feed restriction and dietary calorie source were studied in horses receiving high-roughage or high-concentrate diets. Four Thoroughbred geldings were assigned to four treatment groups in a 4 x 4 Latin square experiment. The four treatments were 1) a nutritionally adequate high-roughage ration (70% roughage, 30% concentrate; AHR), 2) a nutritionally adequate high-concentrate ration (40% roughage, 60% concentrate; AHC), 3) 70% of the intake of the AHR diet (RHR), and 4) 70% of the intake of the AHC diet (RHC). Diets AHR and AHC were designed to meet the caloric need of horses undergoing moderately intense work. Blood samples were taken on the first 7 d of each period for analysis of serum T4 and T3 concentrations. On d 9 of each feeding period, each horse was fed 1.0 kg of oats as the morning meal. Jugular blood was sampled before and immediately after, as well as at 30 min after, completion of the meal and subsequently every hour for 7 h. Daily serum T4 and T3 concentrations were not affected by day, feeding level, or diet composition. Meal feeding produced an increase (P < 0.01) in T4 and T3 concentrations when horses were adapted to the AHR and AHC diets but not the RHR or RHC diets. Thyroxine concentrations were lowest (P < 0.05) when horses were adapted to the AHC diet. Glucose (P < 0.05), insulin (P < 0.01), and NEFA (P < 0.01) concentrations were higher in response to the meal when horses received RHR than for the other diets. These results indicate that nutrient restriction alters responses to meal feeding in horses and that this response may also be affected by the dietary roughage:concentrate ratio.
In order to determine the allergenic activity of five purified horse allergens, 22 children allergic to horses according to history, skin test, and leukocyte histamine release were evaluated. Washed leukocytes from all patients were tested for allergen-induced histamine release utilizing four epidermal horse allergens (Ags 6, 9, 11, and 15) and horse serum albumin. Crossed radioimmunoelectrophoresis was carried out with a standard horse dander extract and serum from each patient. The results showed considerable variation in the individual allergoprints. Ag 11 had the highest mean allergenic activity. Sensitivity to horse serum albumin was demonstrated three times. Our data show that the amount of serum IgE antibodies bound by horse allergens correlates significantly with the capacity of the allergens to induce histamine release from washed leukocytes.
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