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Browsing by Author "Holland, Janice Lee"

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    Lecithin containing diets for the horse: acceptance, digestibility, and effects on behavior
    Holland, Janice Lee (Virginia Tech, 1994-11-05)
    Lecithins may improve the digestibility of high fat diets and the tractability of horses. Experiments were conducted to determine the acceptability, digestibility and effects on behavior of lecithin-containing diets. Seven young horses of light breeds were used for the studies. The four concentrates consisted of corn, oats, beet pulp, trace mineralized salt, dried sugar cane molasses plus 10% added fat: corn oil (CO);soy lecithin-corn oil (SL\CO); soy lecithin-soybean oil (SL\SO); or soy lecithin-corn oil-soybean oil (SL\CO\SO). Half the ration was provided by chopped hay. The CO concentrate was the most palatable (P=.OOOl). The remaining three concentrates were palatable in the following order: SL\CO, SL\CO\SO, and SL\SO, with SL\CO diet preferred (P=.OOl) to SL\SO. In the digestibility experiment, a complete mixed diet was fed containing chromic oxide as a marker. The control diet had no added fat: the others contained CO, SL\CO, or SL\SO at 10% by weight. Apparent digestibility was higher in the control diet than in the others for dry matter (P=.OOOl). Apparent digestibilities of crude protein (P=.0002) and acid detergent fiber (P=.08) decreased with any of the three fats. In contrast, apparent digestibility of ether extract was increased (P=.OOOl) in the fat containing diets. In the activity experiments, horses on the SL\CO diet were less spontaneously active (P=.0125) than horses on the control diet. Horses on the CO and SL \SO diet also had slightly lower activity levels (P=.125). Horses fed the SL\SO diet reacted less (P=.0625) than control horses to the opening umbrella. Horses fed CO and SL\CO diets showed trends towards less reactivity (P=.125 and P=.25, respectively), compared to the control horses. These studies support the practical feasibility of using lecithins in diets for horses. Especially interesting would be studies of interactivity with trainers and riders.
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    Pasture Intake, Digestibility and Fecal Kinetics in Grazing Horses
    Holland, Janice Lee (Virginia Tech, 1998-11-18)
    Pasture intake of grazing livestock needs to be estimated to allow determination of energy and nutrient intakes. It is commonly estimated by difference, subtracting intakes of other feeds from estimated needs for dry matter or energy. However, these estimates are often erroneous, because they do not take individual animal variation for growth, reproductive status or activity level into account. One method that has had success in grazing ruminants has been the use of markers, or tracers, to estimate fecal output and nutrient digestibility. External markers are dosed to the animal and can be used to determine fecal output. Internal markers are an inherent part of the diet in question and can be used to determine dry matter and nutrient digestibilities. These estimates can then be used to give estimates of intake. These studies were conducted to evaluate the effectiveness of traditional marker methods in determining fecal output, digestibility, and thus intake in grazing horses. The first trial was conducted on 8 mature mares and geldings, housed in stalls, to determine if a common external marker, Cr, could be used to determine fecal output. Horses were dosed once daily with a molasses, Cr, and hay mixture for 12 d. Feces were collected throughout the day into individual tubs so that total fecal output (TC) could be measured. Daily fecal Cr excretion values (Ct, mg/kg DM) were fit to a monoexponential equation with one rate constant (k), rising to an asymptote (Ca): Ct = Ca - Ca.e-kt. Superior fits were found when a delay (d) was incorporated into the equation, estimating the time required for Cr to enter the prefecal pool: Ct = Ca - Ca.e-k(t-d). Estimates of fecal output (FO) were calculated using the equation: FO = Cr dose-d / Ca and provided good estimates when compared to TC values. Subsequent trials evaluated to use of internal markers and more frequent dosing of Cr to improve estimates of intake. Eight mature geldings were housed in stalls and were fed 2 hays in a replicated Latin Square design. The monoexponential equation with the delay continued to fit the data well. Thrice daily dosing of Cr improved the predictions of FO, when dosing was every 8 h. The internal marker, yttrium (Y) consistently overestimated digestibility (D). The internal markers, n-alkanes, gave a better estimate of digestibility. When the digestibility estimates were combined with the FO estimates to estimate dry matter intake (DMI, kg/d): DMI = [FO / (1-D)]*100, the combination including n-alkanes gave better estimates. Further studies found that dosing Cr for 12 d did not improve the fit of the monoexponential equation compared to dosing for only 8 d. Marker methods that had been developed in stalls were applied to grazing horses, and results continued to be promising.