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6 The effect of fat supplementation on behavior and glycemic response in horses
Abstracts / Journal of Equine Veterinary Science 35 (2015) 383e391
diagnosed to have metabolic syndrome through various parameters such as body weight, regional adiposity, body condition score (BCS), and glucose and insulin response tests. These mares remained on pasture for the duration of the study but no intake measurements were done. Frequent sampling intra venous glucose tolerance tests (FSIGT) were performed once in April, May, and June for a total of 3 times. Blood was analyzed for glucose, insulin, cholesterol, nonesterified fatty acids (NEFA), triglycerides (TG), tumor necrosis factor a (TNFa), and interleukin 1 b (IL-1b). Pasture samples were taken biweekly, in dates between FSGITS, and analyzed for nutritional content. Data were analyzed by ANOVA for time effect and all significant results had a P-value of < 0.05. Body weight, BCS, and TNFa increased progressively from April to June. These results corroborate previous studies which have shown that an increase in inflammatory factors is associated with obesity. Insulin sensitivity (SI) and b pancreatic response measured as acute insulin response to glucose (AIRg) increased from April to May despite weight increase and returned to April levels in June, perhaps due to increased activity of horses. Basal glucose decreased progressively from April to June. Basal insulin and IL-1b did not vary with time. Cholesterol did not change from April to May but decreased from May to June. NEFA decreased from April to June and TG decreased in May and returned to previous levels in June. Pasture watersoluble (WSC) and ethanol-soluble carbohydrates (ESC) increased from April to May and did not significantly change from May to June. Increased ESC and WSC in pasture may have caused NEFA to decrease, indicating less fat mobilization and higher carbohydrate metabolism. Beta pancreatic response increased to high levels (>338 mU/L per minute) in June and also could have been an effect of the increased amount of ESC and WSC in the pasture which induced a higher pancreatic response to maintain euglycemia. These results confirm a relationship between season and pasture content, and current results could serve to manage horses with metabolic syndrome. Owners should be proactive changing management before spring weight gain to avoid problems associated with insulin resistance.
Key Words: equine, season, insulin dynamics
6 The effect of fat supplementation on behavior and glycemic response in horses K.E. Martin*, R.M. Hoffman, and H.S. Spooner Middle Tennessee State University, Murfreesboro, TN, USA Previous research indicates horses are less reactive to novel stimuli when fed a high fat diet, but no research documents the mechanism for this phenomenon. The purpose of this study was to evaluate glycemic response as a mechanism for decreased reactivity in horses fed a high fat diet. Six Quarter horse geldings aged 8 to 15 yrs were randomly assigned to 2 groups and fed grass hay plus a control diet of Purina Strategy vs. Purina Strategy plus fat, as 324 mg soybean oil per kg BW, in a crossover design for 2 21-d periods, so each horse served as its own control. Glycemic response was tested on d 19 and reactivity on d 21. For reactivity tests, each horse was fitted with a heart rate monitor and turned loose in an 18 m round pen. Startle reactivity was measured over 4 min with a fog machine used as a novel stimulus for the first 30 s, and heart rate recorded every 30 s from 0 to 4 min. Catch score was assigned when the horse was caught and removed from the round pen. Pressure reactivity was measured using a soil penetrometer with a 2.5 cm diameter adapter foot as the pressure point surface. Pressure was applied at the girth and lateral forearm until the horse shifted weight or
385
moved away, and pressure required to elicit a response was recorded. For glycemic response tests, blood samples were collected 15 min before, and 30, 60, 90, 120, 180, 240, and 300 min after feeding. Plasma glucose concentrations were analyzed using a colorimetric assay, and incremental area under the curve (AUC) of postprandial glucose response was calculated using graphical approximation. A mixed model with repeated measures was used to test effects of diet, period and time on postprandial blood glucose concentrations during the glycemic index test, heart rates and catch scores during the novel stimulus test, and responsiveness to pressure during the penetrometer test. There was no effect of diet on glycemic response or AUC (P > 0.16), catch score (P ¼ 0.20), or pressure reactivity at the girth or lateral forearm (P > 0.15). Heart rate responses to the novel stimulus during the reactivity test were lower when horses were fed high fat compared with the control diet (P < 0.0001). These results agree with previous reports, indicating that high fat diets decrease startle reactivity in horses. This project was supported by an MTSU Undergraduate Research Experience and Creative Activity grant.
Key Words: fat, behavior, glycemic response
7 Effects of rotational grazing on water-soluble carbohydrate and energy content of horse pastures A.D. Daniel*1, B.J. McIntosh 2, J.D. Plunk 1, M. Webb 1, D. McIntosh 1, and A.G. Parks 1 1 University of Tennessee, Knoxville, TN, USA; 2 Virginia Tech, Blacksburg, VA, USA Rotational grazing is a recommended strategy to reduce overgrazing and improve pasture health. A study at the University of Tennessee was conducted to evaluate the effects of rotationally grazing horse pastures on the forage water-soluble carbohydrate and digestible energy content. A 2.02 ha rotational grazing system (RG) and a 2.02 ha continuous grazing system (CG) composed of primarily Tall Fescue (Festuca arundinacea) and Bermuda Grass (Cynodon dactylon) were each grazed by 3 adult horses at a stocking rate of 0.6 ha/horse over a 2 year period. The RG system was divided into 4 0.40 ha paddocks and a heavy use area. Pastures were maintained at uniform maximum height of 15 to 20 cm by mowing. Horses were rotated between the RG paddocks every 14 d, or when forage was grazed to a height of approximately 8 cm. Forage samples (n ¼ 520) were collected and composited monthly (n ¼ 14) during the growing season (April to November) by clipping forage from randomly placed 0.25 m2 quadrates from RG and CG, as well as before and after grazing each RG paddock. Forage samples were oven-dried at 60 C in a forced air oven for 72 h to determine DM. Digestible energy (DE, Mcal/kg), sugar (%, DM), fructan (%, DM) and total water soluble carbohydrates (WSC, %, DM) were measured using a FOSS 6500 near-infrared spectrometer. Data were analyzed using paired t-tests and differences were determined significant at P < 0.05. Data are reported as means ± SEM as a percent of DM. Digestible energy was higher in RG compared with CG (2.42 ± 0.039 Mcal/kg vs. 2.31 ± 0.064 Mcal/kg, respectively) (P < 0.05). Total WSC and sugar content were higher in RG compared with CG (WSC: 6.72 ± 0.71 vs. 4.95 ± 0.60, respectively, P < 0.01; sugar: 4.86 ± 0.55 vs. 3.33 ± 0.50, respectively, P < 0.01). The RG paddocks were higher in DE before grazing compared with after grazing (2.34 ± 0.025 vs. 2.22 ± 0.021, respectively) (P < 0.001). Sugar and WSC were higher before grazing compared with after grazing (WSC: 6.05 ± 0.47 vs. 4.85 ± 0.39, respectively, P < 0.01; sugar: 4.40 ± 0.38 vs. 3.22 ± 0.30,
diagnosed to have metabolic syndrome through various parameters such as body weight, regional adiposity, body condition score (BCS), and glucose and insulin response tests. These mares remained on pasture for the duration of the study but no intake measurements were done. Frequent sampling intra venous glucose tolerance tests (FSIGT) were performed once in April, May, and June for a total of 3 times. Blood was analyzed for glucose, insulin, cholesterol, nonesterified fatty acids (NEFA), triglycerides (TG), tumor necrosis factor a (TNFa), and interleukin 1 b (IL-1b). Pasture samples were taken biweekly, in dates between FSGITS, and analyzed for nutritional content. Data were analyzed by ANOVA for time effect and all significant results had a P-value of < 0.05. Body weight, BCS, and TNFa increased progressively from April to June. These results corroborate previous studies which have shown that an increase in inflammatory factors is associated with obesity. Insulin sensitivity (SI) and b pancreatic response measured as acute insulin response to glucose (AIRg) increased from April to May despite weight increase and returned to April levels in June, perhaps due to increased activity of horses. Basal glucose decreased progressively from April to June. Basal insulin and IL-1b did not vary with time. Cholesterol did not change from April to May but decreased from May to June. NEFA decreased from April to June and TG decreased in May and returned to previous levels in June. Pasture watersoluble (WSC) and ethanol-soluble carbohydrates (ESC) increased from April to May and did not significantly change from May to June. Increased ESC and WSC in pasture may have caused NEFA to decrease, indicating less fat mobilization and higher carbohydrate metabolism. Beta pancreatic response increased to high levels (>338 mU/L per minute) in June and also could have been an effect of the increased amount of ESC and WSC in the pasture which induced a higher pancreatic response to maintain euglycemia. These results confirm a relationship between season and pasture content, and current results could serve to manage horses with metabolic syndrome. Owners should be proactive changing management before spring weight gain to avoid problems associated with insulin resistance.
Key Words: equine, season, insulin dynamics
6 The effect of fat supplementation on behavior and glycemic response in horses K.E. Martin*, R.M. Hoffman, and H.S. Spooner Middle Tennessee State University, Murfreesboro, TN, USA Previous research indicates horses are less reactive to novel stimuli when fed a high fat diet, but no research documents the mechanism for this phenomenon. The purpose of this study was to evaluate glycemic response as a mechanism for decreased reactivity in horses fed a high fat diet. Six Quarter horse geldings aged 8 to 15 yrs were randomly assigned to 2 groups and fed grass hay plus a control diet of Purina Strategy vs. Purina Strategy plus fat, as 324 mg soybean oil per kg BW, in a crossover design for 2 21-d periods, so each horse served as its own control. Glycemic response was tested on d 19 and reactivity on d 21. For reactivity tests, each horse was fitted with a heart rate monitor and turned loose in an 18 m round pen. Startle reactivity was measured over 4 min with a fog machine used as a novel stimulus for the first 30 s, and heart rate recorded every 30 s from 0 to 4 min. Catch score was assigned when the horse was caught and removed from the round pen. Pressure reactivity was measured using a soil penetrometer with a 2.5 cm diameter adapter foot as the pressure point surface. Pressure was applied at the girth and lateral forearm until the horse shifted weight or
385
moved away, and pressure required to elicit a response was recorded. For glycemic response tests, blood samples were collected 15 min before, and 30, 60, 90, 120, 180, 240, and 300 min after feeding. Plasma glucose concentrations were analyzed using a colorimetric assay, and incremental area under the curve (AUC) of postprandial glucose response was calculated using graphical approximation. A mixed model with repeated measures was used to test effects of diet, period and time on postprandial blood glucose concentrations during the glycemic index test, heart rates and catch scores during the novel stimulus test, and responsiveness to pressure during the penetrometer test. There was no effect of diet on glycemic response or AUC (P > 0.16), catch score (P ¼ 0.20), or pressure reactivity at the girth or lateral forearm (P > 0.15). Heart rate responses to the novel stimulus during the reactivity test were lower when horses were fed high fat compared with the control diet (P < 0.0001). These results agree with previous reports, indicating that high fat diets decrease startle reactivity in horses. This project was supported by an MTSU Undergraduate Research Experience and Creative Activity grant.
Key Words: fat, behavior, glycemic response
7 Effects of rotational grazing on water-soluble carbohydrate and energy content of horse pastures A.D. Daniel*1, B.J. McIntosh 2, J.D. Plunk 1, M. Webb 1, D. McIntosh 1, and A.G. Parks 1 1 University of Tennessee, Knoxville, TN, USA; 2 Virginia Tech, Blacksburg, VA, USA Rotational grazing is a recommended strategy to reduce overgrazing and improve pasture health. A study at the University of Tennessee was conducted to evaluate the effects of rotationally grazing horse pastures on the forage water-soluble carbohydrate and digestible energy content. A 2.02 ha rotational grazing system (RG) and a 2.02 ha continuous grazing system (CG) composed of primarily Tall Fescue (Festuca arundinacea) and Bermuda Grass (Cynodon dactylon) were each grazed by 3 adult horses at a stocking rate of 0.6 ha/horse over a 2 year period. The RG system was divided into 4 0.40 ha paddocks and a heavy use area. Pastures were maintained at uniform maximum height of 15 to 20 cm by mowing. Horses were rotated between the RG paddocks every 14 d, or when forage was grazed to a height of approximately 8 cm. Forage samples (n ¼ 520) were collected and composited monthly (n ¼ 14) during the growing season (April to November) by clipping forage from randomly placed 0.25 m2 quadrates from RG and CG, as well as before and after grazing each RG paddock. Forage samples were oven-dried at 60 C in a forced air oven for 72 h to determine DM. Digestible energy (DE, Mcal/kg), sugar (%, DM), fructan (%, DM) and total water soluble carbohydrates (WSC, %, DM) were measured using a FOSS 6500 near-infrared spectrometer. Data were analyzed using paired t-tests and differences were determined significant at P < 0.05. Data are reported as means ± SEM as a percent of DM. Digestible energy was higher in RG compared with CG (2.42 ± 0.039 Mcal/kg vs. 2.31 ± 0.064 Mcal/kg, respectively) (P < 0.05). Total WSC and sugar content were higher in RG compared with CG (WSC: 6.72 ± 0.71 vs. 4.95 ± 0.60, respectively, P < 0.01; sugar: 4.86 ± 0.55 vs. 3.33 ± 0.50, respectively, P < 0.01). The RG paddocks were higher in DE before grazing compared with after grazing (2.34 ± 0.025 vs. 2.22 ± 0.021, respectively) (P < 0.001). Sugar and WSC were higher before grazing compared with after grazing (WSC: 6.05 ± 0.47 vs. 4.85 ± 0.39, respectively, P < 0.01; sugar: 4.40 ± 0.38 vs. 3.22 ± 0.30,