Mineral concentration data could easily be generated by near infrared reflectance spectroscopy (NIRS) while determining quality parameters in forage samples. However, which minerals can be analyzed and why they can be determined bas not been documented adequately. Therefore, NIRS spectra were collected on 200 sainples of crested wheatgrass (Agropyron spp.), 203 tall fescue (Festuca arundinacea Scbreb.), and 59 alfalfa (Medicago satiPa L.) bays. Concentrations of Na, K, Ca, P, Mg, Fe, Mn, Cu; and Zn, as determined by atomic absorption, and calculated values of the Ca/P, K/Mg, and K/( Ca + Mg) ratios were regressed against reflectance values measured in 2-nm increments between 1100 and 2500 nm for each sample. Approximately one half of the samples in each forage set was used to develop the calibration equations, while the other half was used to validate the equations. The coefficients of variation (CV = (standard error of analysis-;-the mean) X 100) generally ranged from 10 to 20% forK, Mg, Ca, and P concentrations in each forage type. The Ca/P ratio in alfalfa was determined with a CV of 18%. The CV values of other minerals and mineral ratios generally exceeded 20%. Chlorophyll and some inorganic salts and organic-acid salts of Ca, Mg, and K were scanned with NIRS for wavelength comparisons with those wavelengths used to determine mineral concentrations in forages. Some of the wavelengths used in the equations for Ca, K, and Mg were related to peaks and changes in slope observed in chlorophyll and organic-acid salts of Ca, K, and Mg, suggesting that NIRS is indirectly measuring these minerals by their association with organic molecules. Accurate use of NIRS to determine mineral cation composition in forages appears limited to certain major minerals (Ca, P, K, and Mg).

Plants vary diurnally in concentrations of nonstructural carbohydrates. If ruminants prefer forages with higher total nonstructural carbohydrates (TNC), then the preference for hays harvested within the same 24-h period may vary. An established field of tall fescue (Festuca arundinacea Schreb.) was harvested six times in the vegetative stage. Harvests were paired such that each cutting at sundown (P M) was followed by a cutting the next morning at sunup (AM). We harvested in this manner three times, resulting in six hays. The hays were fielddried, baled, and passed through a hydraulic bale processor prior to feeding. Experiments were conducted with sheep, goats, and cattle, using six animals in each case. During an adaptation phase, hays were offered alone as meals. In the experimental phase, every possible pair of hays (15 pairs) was presented for a meal. Data were analyzed by multidimensional scaling and by traditional analyses. Multidimensional scaling indicated that selection was based on a single criterion. Preference for PM hays was greater than for AM hays (P < .01) in all experiments. Increased preference was associated with increased TNC (P < .01) and in vitro true DM disappearance (P < .01) and decreased fiber concentration (P < .01; NDF, ADF, cellulose, and ADL). Mowing hay late in the day was effective in increasing forage preference.

MATERIALS AND METHODS Grazing animals prefer some plants to others. These choices are Cultivars and Experimental Design likely related to physical and chemical factors such as energy-dense The eight endophyte-free tall fescue cultivars included in carbohydrates contained in plants. This study quantified the nonstructhis study were 'Barcel', 'Kenhy', 'Kentucky-31' (KY-31), tural carbohydrate fractions in each of eight vegetatively growing, 'Missouri-96' (MO-96), 'Mozark', 'Stargrazer', and the experiendophyte-free, tall fescue cultivars (Festuca arundinacea Schreb.) mental selections C-1 and HiMag (Mayland and Sleper, 1993). and relates their sugar concentrations to cattle grazing preferences. On 20 Sept. 1991, these grasses were seeded in rows into The experimental area consisted of eight cultivar plots replicated three an irrigated, Portneuf silt loam loess soil (Durinodic Xeric times in each of three pastures. Within each pasture, forage was Haplocalcid) near Kimberly, in south-central Idaho (42Њ30Ј sampled between 0830 and 1000 h mountain daylight time (MDT) N, 114Њ08Ј W, elevation 1200 m). The experimental design during each of four seasons and 2 yr. Freeze-dried forage samples was a randomized complete block with three pastures (blocks), were extracted with hot water and an amylase (Clarase) solution. three replications nested within blocks, eight entries (main Sugars were quantified colorimetrically using potassium-ferricyanide plots), and six rows per main plot. Rows were 0.56 m apart and glucose-oxidase methods. Cattle grazing preferences among these and main plots were 3.35 by 6.7 m. tall fescue cultivars were related to the concentrations of total nonstructural carbohydrates (TNC) (r 2 ϭ 0.49, P Ͻ 0.05). Other sugar Harvesting and Sample Preparation fractions were not significantly related to grazing preference in this study. The nonstructural carbohydrate concentrations averaged over Vegetatively growing forage was clipped at a stubble height the entire study were glucose, 14; fructose, 5; sucrose, 40; fructan, 23; of 8 cm from randomly located 0.6-m sections of Rows 3 and insoluble starch, 24; and TNC, 129 g kg Ϫ1 . A forage selection criterion 4 in each plot. The forage in Block 1 was clipped on d 131, should include measures of the TNC because of their close relationship 165, 221, and 256 of 1993 and d 129, 164, 220, and 262 of 1994. to animal grazing preference.

No abstract

Diurnal variation in the concentration of total nonstructural carbohydrates (TNC) occurs in plants as a result of photosynthesis. Ruminants have been shown to prefer tall fescue (Festuca arundinacea Schreber) hays cut in the afternoon but the effect of morning vs. evening cutting had not been tested in legumes. To test for diurnal variation in preference for alfalfa (Medicago sativa L.), we harvested six times in the midbud stage. Harvests were paired so that each time a cutting of alfalfa was made at sundown (PM) another was made the next morning at sunup (AM). We harvested in this manner three times resulting in six hays. The hays were field dried, baled, and chopped prior to their use 3 to 6 mo after harvest. Three experiments were conducted [Exp. 1, sheep (Ovis aries); Exp. 2, goats (Capra hircus hircus); and Exp. 3, cattle (Bos taunts)] utilizing six animals in each case. During an adaptation phase, hays were offered alone as meals. In the experimental phase, every possible pair of hays (15 pairs) was presented for a meal. Data were analyzed by multidimensional scaling as well as by traditional analyses. Multidimensional scaling indicated that the animals were basing selection on at least two criteria. Variables associated with preference through multiple regression varied across experiments but significant coefficients were found between preference and nitrate, protein, carbohydrate fractions, lignin, and cellulose. Coefficients varied depending on which other variables were in the model; however, carbohydrates were associated with positive coefficients. Shifting hay mowing from early in the day to late in the day was effective in increasing forage preference as expressed by short-term dry matter intake.

The preference exhibited by animals in selecting one feed over another is important only if the preferred diet is consumed daily in larger quantities, digested to a greater extent, or both. Six alfalfa (Medicago sativa L.) hays were harvested in pairs at sunset (PM) and sunrise (AM) on consecutive days at three harvest dates. A previous study of these hays demonstrated differences in ruminant preference favoring PM harvests. This study evaluated the effects of time of cutting and harvest date on voluntary DMI and nutrient digestibility. The hays were field-cured, baled, and chopped before evaluation for intake and digestibility. Studies were conducted for sheep (Ovis aries), goats (Capra hircus), and cattle (Bos taurus). Goats, but not steers or sheep, demonstrated differences in nutrient digestibility between PM- and AM-cut hays. Goats consumed more PM than AM hay (2.97 vs. 2.83 kg/100 kg of BW; P = 0.07) and digested it to a greater extent (0.710 vs. 0.696; P = 0.03), resulting in greater digestible DMI (2.11 vs. 1.97 kg/100 kg of BW; P = 0.03). Sheep consumed (mean = 2.52 kg/100 kg of BW; P = 0.59) and digested (mean = 0.681; P = 0.25) PM- and AM-cut hays similarly. Steers consumed larger quantities of PM-than AM-cut hay (2.90 vs. 2.62 kg/100 kg of BW; P = 0.11), but digestion did not differ with cutting time (mean = 0.660; P = 0.75). Difference values (composition of fed hay minus composition of orts) indicated that sheep and goats selected from the feed offered similarly, whereas steers selected differently. Difference values for CP averaged 94 and 101 g/kg for goats and sheep and 32 g/kg for steers (P < 0.01), and difference values for NDF averaged 185 and 196 g/kg for goats and sheep and 73 g/kg for steers (P

Salt and water movement was measured in unsaturated frozen soil columns incubated under a thermal gradient for 3, 6, or 9 weeks. Both water and salt moved from the warmer to cooler areas in the soil, creating a twofold concentration difference over a 24-cm distance. Movement of CaC12, LiI, and K2SO4 was studied in detail Cation exchange reactions and salt solubilities at high concentrations affected the movement. Although the results suggested that mass flow of dissolved salts in a liquid film of water was the principal transfer mechanism, both vapor and salt diffusion were sometimes significant. Thermal diffusion and salt sieving did not appear to be important.Since the vapor pressure of ice controls the water potential in frozen soil, the amount of unfrozen water and matric suction could be calculated from a water release curve and data from ice suspensions in salt solutions. These results led to the conclusion that mass flow in the liquid phase is described by Darcy's law. Thus, salt flow as well as net water transfer can probably be predicted in unsaturated frozen soil using information available from unfrozen systems.Additional Index Words: salinity, salt diffusion, thermal diffusion, salt separation, frost heaving. M OIST UNSATURATED SOIL freezes downward from the surface in the fall and is subject to varied thermal gradients throughout the winter (Benz et al., 1968). As the soil water freezes, small ice crystals form in the pore spaces. Not all of the water freezes under temperatures commonly experienced in the field. A liquid-like film 10 to 40A thick remains at the ice-air interface. Liquid films of varying thicknesses also remain in the soil particleice interfaces and in the soil particle-air interfaces (Anderson, 1970).Since ice crystals freeze out of a solution in a pure state, all soluble salts are forced into the unfrozen water films and may form relatively concentrated brines. The vapor pressure of ice is less than that of pure liquid water. Consequently, water will continue to crystallize from the soil solution until the combined osmotic and matric forces reduce the solution's vapor pressure to that of the ice (Hoeckstra, 1966;Low et al., 1968). Under natural conditions in the field, temperature gradients always exist, and liquid water tends to move from warmer to cooler areas (Fergusen et al., 1964). A spontaneous vapor pressure gradient in this same direction is fixed by the temperature of the ice phase. While some movement is in the vapor phase, most of the flow is in the unfrozen liquid films (Hoeckstra, 1966;Benz et al., 1968 apparent that salt will also move from warmer to cooler areas in the unsaturated frozen soil.Most of the liquid phase movement occurs along the water films adsorbed to the soil particles. While there are liquid films in the ice crystal air interfaces, they comprise a small fraction of the total unfrozen water in unsaturated soil because of the relatively small surface area of the ice crystals compared to that of the soil particles (Anderson, 1970). As the water ...

Highlight: Soil ingestion was determined for cattle grazing a Bromus tectorum range in southern Idaho by measuring titanium concentrations in animal feces collected at 2-week intervals during the droughty 1973 grazing season. The experiment was based on the premise that titanium, which is abundant in soils, is contained only in small quantities (less than 1 ppm) in plants not contaminated with soil. Fecal-soil values averaged 14%, with values ranging from 3 to 30% of fecal dry matter, increasing as forage availability decreased. Soil ingestion levels were estimated to range from 0.1 to 1.5 kg with a median of 0.5 kgsoillanimal-day. This soil was ingested primarily with the roots of Bromus tectorum, which were often pulled up and consumed with the aboveground plant parts. Dust on leaves and stems accounted for only a small portion of the ingested soil. Measurements of acid-insoluble residue concentration in feces overestimated soil ingestion because of the probable presence of SiOZ of plant origin. Large changes in forage SiOZ concentrations of the diet reduce the effectiveness of this method compared to the Ti method. Ingested soil may be a possible source of trace minerals, pesticides, heavy metals, and radionucleides that may be sorbed to surface soil particles.