Browsing by Author "Hoffman, Rhonda M."
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- Carbohydrate and Fat Supplementation in Grazing Mares and FoalsHoffman, Rhonda M. (Virginia Tech, 1997-06-30)The objective of these studies was to design an optimal nutritional supplement suitable for grazing horses using fat and fiber to replace the grain and molasses in the traditional sweet feed. Thoroughbred mares and foals grazing bluegrass/clover pastures were used in these studies, twenty mares and their foals in 1994 to 1995, and twenty mares and foals in 1995 to 1996. Seasonal variation in pasture was examined, and the need for supplementation of nutrients and fibers was assessed. The nutritional status of grazing mares, foals, weanlings and yearlings, fed either a starch and sugar supplement (SS) or a fat and fiber supplement (FF), was examined using growth measurements, radiographic bone evaluations, milk composition and glucose tolerance tests. These studies suggest that fiber may be an important component of an ideal supplement for improved grass/legume pastures. Seasonal variation in pasture indicated an increase in hydrolyzable and rapidly fermed carbohydrates during periods of rapid growth. The FF supplement may have buffered seasonal changes and the increased hydrolyzable carbohydrate content in rapidly growing pasture, as evidenced by smoother growth curves in the yearlings. Young horses, after weaning until the following May, had lower estimated bone mineral content when fed the FF supplement. The lower bone mineral content in the FF supplemented horses may have been due to decreased absorption of calcium or metabolic and hormonal changes associated with adaptation to the different energy sources in the supplements. Milk composition of FF supplemented mares was influenced in ways likely to improve foal health. The FF supplemented mares had enhanced linoleic acid content, which may reduce the risk of gastric ulcers in foals, and increased immunoglobulin G concentration, which may enhance passive immunity. The carbohydrate status of mares, as assessed by glucose tolerance tests, indicated a slower glucose clearance that could be a metabolic adaptation of the mares to the SS and FF supplements.
- Effects of Diet and Probiotic Supplementation on Stress during Weaning in Thoroughbred FoalsSwanson, Carrie A. (Virginia Tech, 2002-08-23)This study investigated effects of diet and probiotic supplement on stress in Thoroughbred foals at weaning. Twenty foals, whose dams were paired by age and breeding date, then randomly assigned to one of two diets prior to parturition, were used. Two groups were maintained on mixed grass pastures and fed supplements, one high in sugar and starch (SS) and one high in fat and fiber (FF) that met or exceeded NRC requirements. Half the foals on each diet were fed a commercial probiotic (Probios) containing lactic acid bacteria, while the rest were given a placebo. Plasma, fecal samples and behavioral ethograms were collected for four days pre- and post-weaning, and an ACTH response test was administered 48 h post-weaning. Cortisol, lactate, IgG, IgA and a-tocopherol were analyzed in plasma, volatile fatty acids and pH in feces. Foals fed FF had higher concentrations of IgA (P = 0.006), IgG (P = 0.012) and a-tocopherol (P = 0.005). Butyric and valeric acid concentrations were higher in feces of SS but not FF foals (P = 0.052), which may reflect better adaptation to forage in FF foals. Foals supplemented with probiotic had higher fecal lactate (P = 0.002) and lower fecal acetate (P = 0.0003) concentrations, suggesting that the lactic acid bacteria survived to the hindgut. Probiotic supplementation did not appear to benefit foals at weaning. Supplementation with FF may improve immune status and encourage a more diverse intestinal microbial population, enabling foals to better cope with the physiological stresses of weaning.
- Exercise and Immunodeficiency Affect Immunoglobulins in Endurance HorsesKrick, Kari Elizabeth (Virginia Tech, 2002-07-16)Two studies were conducted on endurance horses predominantly of Arabian breeding participating in an 80 km ride dedicated to research in April 2001 (Trial 1) and April 2002 (Trial 2). Objectives were to determine effects of endurance exercise, antioxidant supplementation, and a feed rich in fiber and fat vs. a high fat sweet feed on immunoglobulin A and G concentrations as well as identify selective IgA deficiency in endurance horses of Arabian breeding. There were no effects of distance in Trial 1 on IgA (P = 0.73) or IgG (P = 0.18) concentrations. In Trial 2, IgA concentrations increased (P = 0.05) and IgG concentrations increased (P = 0.006) after the start of the race. There were no effects of antioxidant supplementation on IgA (P = 0.16), IgG (P = 0.16), and IgM (P = 0.70) concentrations. There were no diet effects on IgA (P = 0.80), IgG (P = 0.59), and IgM (P = 0.54) concentrations. There were horses in both trials that were deficient in IgA only. Concentrations of IgG and IgM were within normal ranges, and there were no differences in training, performance and transportation variables, IgG concentrations, antioxidant supplementation, and feed supplementation compared to the horses with normal IgA concentrations. The concentration of IgM was higher in IgA deficient horses in Trial 1 (P = 0.035) and Trial 2 (P = 0.017). Horses with deficient IgA tended to be associated with health problems commonly found in humans and dogs affected with selective IgA deficiency.
- Folate Status and Supplementation in the HorseOrdakowski, Amy L. (Virginia Tech, 2001-07-10)A series of studies were conducted to evaluate effects of lactation, exercise, and anti-folate drugs on folate status in the horse, and the bioavailability of supplement and feed folate in the horse. In the first study, mares and foals had adequate plasma folate, RBC folate, and plasma homocysteine concentrations during 6 mo of lactation and growth. Therefore, mares and foals maintained on quality grass/legume pastures and offered a pasture supplement did not require additional folate supplementation to maintain folate status during lactation and growth. In the second study, 25 mg of oral folic acid (FA) supplemented 5 times/wk to 11 mature horses engaged in routine submaximal exercise did not improve folate status, submaximal athletic performance, or combat the increase in oxidative stress during the 12 wk supplementation period compared to 11 horses not given supplemental folate. The common practice of supplementing horses with oral FA in vitamin supplements appears to be of little benefit to horses engaged in routine submaximal exercise. In the third study, daily oral administration of pyrimethamine (PYR) and sulfadiazine (SDZ) for 9 wk followed by 6 wk of coadministration of either Peptidoglycan or FA was associated with a decline in folate status resulting in moderate hyperhomocysteinemia, but not clinical signs of anemia. Peptidoglycan as a source of formylated folate and FA were not effective in improving folate status in horses coadministered PYR and SDZ, two anti-folate drugs commonly administered in equine veterinary practice. The last study assessed the bioavailability of oral and i.v. 5-methyltetrahydrofolate (5-mTHF), 5-formyltetrahydrofolate (5-fTHF), or FA, and the bioavailability of folate from concentrates fed to horses. The minimum efficiency of absorption for supplemental FA was 11 %. The low bioavailability of FA indicates a need for further research on the potential benefits of alternative sources of folate, including 5-fTHF, on increasing folate status in the horse.
- Insulin-like Growth Factor Binding Proteins in the Plasma of Growing HorsesBurk, John Robert (Virginia Tech, 2002-12-13)Insulin-like growth factor binding proteins (IGFBP) are modulators of insulin-like growth factor I (IGF-I), which functions as a regulator of cartilage and bone development. Rapid growth and high starch diets have been associated with increased circulating concentrations of IGF-I, which lead to developmental orthopedic disorders in foals. The objective of this study was to assess the effects of age, diet, growth and season on plasma IGFBP and IGF-I concentrations from birth to 16 mo of age in Thoroughbred foals. Twenty-two mares maintained on mixed grass/legume pasture were randomly divided into two dietary groups and fed either a high starch and sugar supplement (SS) or a starch-restricted fiber and fat supplement (FF) for 3 mo prior to and after foaling. Monthly blood samples were obtained from SS and FF foals up to 16 mo of age and analyzed for IGF-I using an RIA and IGFBP using western ligand blot analysis. Auxilogical measurements of foals were also obtained each month. The effect of diet, month, and diet*month interactions upon the subject horse (diet) were analyzed using a mixed model with repeated measures, and correlations of normally distributed data were calculated using Pearson's correlation. Six IGFBP bands of molecular weights 109, 39, 36, 35, 34, and 33 kDa were identified in foal plasma. Doublet bands were recognized at 109, 39, and 35 kDa, however they were not all believed to be singular pure IGFBP. A band with a molecular weight of 213 kDa was observed and presumed to be a ternary complex of IGFBP-3, IGF-I, and an acid labile subunit. The IGFBP 109 kDa has been previously recognized as a band unique to the equine, it was not a singular pure IGFBP because of its high molecular weight. No effect of diet on plasma IGFBP was found in individual sampling of yearlings, but an effect of month was noted when testing May - August 2001 against May - August 2002 in pooled plasma samples with concentrations of the IGFBP 39 kDa increasing (P < 0.0003). In contrast, concentrations of the IGFBP's 33, 34 and 36 kDa decreased (P < 0.003, P < 0.0002, and P < 0.0003 respectively). Environmental effects were noted upon IGFBP's 33, 36, 39, and 109 kDa (P < 0.003, P < 0.001, P < 0.04, and P < 0.01) with a temperature*daylength interaction. Correlations existed between ADG and IGFBP 33 (r = 0.64; P < 0.0001), 34 (r = 0.40; P < 0.0001), 35 (r = 0.33; P < 0.0006), 36 (r = 0.47; P < 0.0001), and 39 kDa (r = - 0.18, P < 0.02). A correlation was also found between IGF-I and ADG (r = 0.11; P < 0.04), confirming the previously reported relationship of IGF-I in growth rate of foals. These results underline the importance of characterizing the activity of IGFBP's in relation to growth, age and season when interpreting changes of the somatotropic axis. Further, the increase in certain IGFBP's and simultaneous decrease in others stress the need for further research on the tissue specific modulating effects that IGFBP's have on IGF-I.
- Oxidative Stress and Antioxidant Supplementation During Endurance Exercise in the HorseWilliams, 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.
- Pre-weaning diet and stall weaning method influences on stress response in foalsHoffman, Rhonda M. (Virginia Tech, 1994-09-15)The response of foals to the stress of weaning was examined in terms of a behavioral protocol and the responses of plasma ascorbate, serun1 cortisol, and the serum cortisol response to an ACTH challenge. Behavior scores (1 to 10) as an index of stress were assigned to each foal daily, with high scores indicating less stress and better adjustment. The experimental plan was a 2 X 2 factorial of pre-weaning diet and stall weaning method. Foals were raised on pasture supplemented with hay and a pelleted concentrate (PHC) or pasture supplemented with hay only (PH). Foals were placed in stalls singly or in pairs for weaning. Gender influences were also examined. The foals exhibited characteristic behavioral and physiological responses to the social dislocative stress of weaning. Behavior scores were lower in paired than in single foals (p = .008) and tended to be lower in PH than PHC foals (p = .15). No differences in post-weaning plasma ascorbate concentrations were found among treatments. Responses of serum cortisol to an ACTH challenge were lower in PH than PHC foals (p = .001) and in paired than single foals (p = .058), and lower responses were taken to represent adrenal depletion arising from stress. Behavior scores were positively correlated with the response of serum cortisol to ACTH. Both behavioral data and the serum cortisol response to ACTH indicate that foals were better able to cope with weaning stress when supplemented with concentrate prior to weaning and when weaned singly.
- Virginia's Horse Pastures: Forage Species for Horse PasturesTeutsch, Christopher D.; Hoffman, Rhonda M. (Virginia Cooperative Extension, 2009)Provides information on which forages should be used in Virginia's horse pastures to ensure successful pasture management.
- Virginia's Horse Pastures: Grazing ManagementTeutsch, Christopher D.; Hoffman, Rhonda M. (Virginia Cooperative Extension, 2009)Presents sound grazing management practices for Virginia's horse pastures.