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Browsing by Author "Ordakowski, Amy L."

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    Alkanes as Internal Markers to Estimate Digestibility in Horses
    Ordakowski, Amy L. (Virginia Tech, 1998-08-10)
    Fecal recoveries of n-alkanes were determined in three digestion balance experiments consisting of two periods each. Each experiment compared two diets in a switch-back design using eight mature Thoroughbred geldings. Horses were randomly assigned to two groups of four and offered one of two mixed grass/legume hays (Diets 1 and 2) in Exp. 1, mixed grass/legume hay and one of two concentrates (Diets 3 and 4) in Exp. 2, and mixed grass/legume pasture (Diets 5 and 6) in Exp. 3. In Exp. 1 and 2, horses were housed in stalls and in Exp. 3, two horses from each diet were housed in stalls and two horses remained on pasture. Balance periods lasted 11 days with d 1 to d 7 consisting of a dietary accommodation period, followed by 4 days of total collection. Results indicated that fecal recoveries of odd-chain alkanes (C25 to C33) were less than 100 % and similar between chain lengths. Estimates of DMD (DE) were similar to the total collection DMD (DTC) for Diet 1 in Exp. 1, but underestimated DTC for Diet 2 in Exp. 1 (P < .05) and Diets 3 and 4 in Exp. 2 (P < .05). For Diet 5 in Exp. 3, the DE for stall-fed horses using C25 and C33 was similar to DTC, whereas C27, C29, and C31 underestimated DTC (P < .05). For pastured horses, the DE using C29 and C31 were similar to DTC, whereas C25, C27, and C33 underestimated DTC (P < .05). For Diet 6 in Exp. 3, the DE for stalled horses calculated using C25 was similar to the DTC, whereas use of C27, C29, C31, and C33 underestimated DTC (P < .05). For pastured horses, the DE using C29 was similar to DTC, whereas all other alkanes underestimated DTC (P < .05). When DE was adjusted (DA1) using the mean recovery of each odd-chain alkane, DA1 was similar to DTC for Diet 2 in Exp. 1, Diets 3 and 4 in Exp. 2, and stalled horses offered Diets 5 and 6 in Exp. 3. The DA1 using C25 underestimated DTC for Diet 1 in Exp. 1 (P < .05). For pastured horses offered Diet 5, DA1 for C33 was not different from the DTC estimate, whereas all other DA1 for n-alkanes overestimated DTC (P < .05). For pastured horses offered Diet 6, DA1 for C29 and C31 overestimated, but were similar to the DTC, whereas the DA1 for C33 underestimated DTC and was similar to the DTC. The DA1 for C25 and C27 overestimated DTC (P < .05). When DE was adjusted for the mean recovery of all n-alkanes (DA2), all DA2 estimates for stalled horses in Exp. 1, 2, and 3 were similar. In pastured horses offered Diets 5 and 6 in Exp. 3, the DA2 overestimated DTC (P < .05). These results suggest that accurate mean estimates of DMD can be obtained by adjusting for mean recovery of each odd-chain alkane in a specific diet.
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    Folate Status and Supplementation in the Horse
    Ordakowski, 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.