Browsing by Author "Williams, Carey Ann"

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    Glycemic Response in Thoroughbred Mares
    Williams, Carey Ann (Virginia Tech, 2000-08-09)
    The objective of this study is to determine if fat as an energy source, and fiber in a pasture supplement will be beneficial when compared to a concentrate high in sugar and starch. In the first experiment, 12 pregnant and lactating mares were used in three different glycemic response tests to determine the effect of feeds on pregnant mares. The mares were fed a pelleted concentrate (PC) three months before foaling; after foaling they were divided into two groups and fed a feed high in sugar and starch (SS), or a feed high in fat and fiber (FF). The second experiment, used the same 12 mares (R mares) and 10 barren mares (B mares) in three different tests to determine the effects of the feeds, season and reproductive stage. A series of blood samples was collected via a jugular catheter from 0 to 390 min after consuming a meal. Glucose and insulin baseline and peak values, increments and areas under curves (AUC) were compared by ANOVA. For the first experiment, responses to PC did not differ between the two groups. Peak plasma glucose and insulin concentrations were higher in SS group than in FF during both early and late lactation. Glucose and insulin AUCs were higher in SS than in FF during both early and late lactation. In the second experiment, peak glucose increments had differences for the main effects feed, pregnancy and season, and interactions feed by pregnancy and feed by season. The glucose AUC values showed similar differences for the main effects and the interaction feed by pregnancy. Peak insulin increments had a difference for feed and pregnancy, but not the interactions. Insulin AUCs also revealed a difference between feed and pregnancy, and also for season, and the interaction feed by pregnancy. These results indicate that metabolic fluctuations are moderated by the replacement of sugar and starch with fat and fiber. This replacement may reduce the risk of certain digestive and metabolic disorders.
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    Oxidative Stress and Antioxidant Supplementation During Endurance Exercise in the Horse
    Williams, Carey Ann (Virginia Tech, 2003-06-12)
    In these studies antioxidant supplementation and oxidative stress measures were the basis for determining the health and welfare of the equine endurance athlete. The first study determined that lipoic acid (LA) orally administered to horses is effective in diminishing the levels of lipid peroxidation in the plasma, and is non-toxic at a dose of 10-mg/kg body weight. The second study showed muscle leakage measured by plasma creatine kinase (CK) and aspartate aminotransferase (AST) positively correlated to oxidative stress (measured by lipid hydroperoxides) during an endurance race (Research Ride 2001; R1). Also higher plasma ascorbate (ASC) status was found in the vitamin E plus C supplemented group versus the group receiving vitamin E alone. In the third study, the Research Ride 2002 (R2) determined that horses that did not finish the ride had higher CK and AST before, during and after (P < 0.05) the ride compared to horses that finished. These results were compared to the finishers of the Old Dominion 2000 (OD) and R1 and found that oxidative stress and muscle enzymes were greater during R2 due to the difficulty of terrain and ambient temperature. A higher level of horses' fitness in OD also could have explained the diminished oxidative stress. The fourth study calculated that horses at R2 were receiving 2265 ± 114 IU/d of vitamin E in the total diet prior to the race. These levels negatively correlated to plasma CK and AST and positively correlated to plasma a-tocopherol (TOC; r = 0.21; P = 0.005) throughout the 80-km race. In the final study the LA supplemented group had similar increases in antioxidant status (TOC, ASC, and total glutathione) as the vitamin E supplemented group of horses exercising for 55 km on a treadmill to simulate an endurance race. Both groups also had lower (P < 0.050) white blood cell apoptosis throughout exercise then the control group. These studies prove the need for antioxidant supplementation, specifically vitamin E or LA, during heavy endurance exercise to improve the health and welfare of our equine athlete.