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Papers by David Wester
Journal of animal science, 2004
The use of power tests in the planning and design of beef cattle experiments provides critical in... more The use of power tests in the planning and design of beef cattle experiments provides critical information on sample sizes necessary to detect treatment differences at a predetermined significance (alpha) level. Retrospective power analysis provides additional information about previous experiments that may be helpful in designing subsequent investigations. However, in retrospective power analyses, power is inversely related to observed significance level. Benefits of prospective and retrospective power analyses in beef cattle experiments are similar to those for other species; however, because of differences in the methods and conditions involved, considerations for the use of power test procedures are specific for beef cattle research. Retrospective power analyses were conducted on 78 published experiments and on two unpublished experiments. Experiments were compiled into categories that represented group (or pen) feeding, individual feeding, and metabolism studies. Estimated powe...
Journal of Animal Science, 2004
The effect of supplementing diets with various levels of vitamin D 3 to provide 0, 0.5, 1, and 5 ... more The effect of supplementing diets with various levels of vitamin D 3 to provide 0, 0.5, 1, and 5 million IU/(steerؒd) for 8 d before slaughter on the mineral content and localization of Ca in LM and muscle fragments was studied during the postmortem aging process. Twelve feedlot steers of three biological types were given access to the four levels of vitamin D for 8 d before slaughter. Differential centrifugation techniques were used to determine the concentrations of minerals relative to protein in different muscle fragments on d 3 and 21 postmortem. Electron microscopy visualization of bound Ca indicated that vitamin D 3 mobilized Ca from the sarcoplasmic reticulum and transverse tubule system into the myofibrils. Bound Ca was concentrated near the Z-line at the A-band/I-band juncture within the sarcomere. Supplementing steers with 1 and 5 million IU/(steerؒd) of vitamin D 3 increased (P < 0.05) Ca, P, and Mg concentrations per unit of protein in the cytosol. Soluble cytosolic Ca concentrations were
Journal of Animal Science, 2004
Feedlot steers (n = 36) from three biological types (Bos indicus, Bos taurus-Continental, and Bos... more Feedlot steers (n = 36) from three biological types (Bos indicus, Bos taurus-Continental, and Bos taurus-English) were used to determine the Ca, P, and vitamin D 3 status of feedlot cattle. The USDA yield and quality grade traits were measured at slaughter, and the concentrations of vitamin D 3 (VITD) and the metabolites 25-hydroxyvitamin D 3 (25-OH D) and 1,25-dihydroxyvitamin D 3 (1,25-(OH) 2 D) were determined in LM, liver, kidney, and plasma. Plasma and muscle Ca and P concentrations also were determined. Biological type of cattle affected a number of carcass traits. Carcasses from Bos taurus-English cattle had more marbling, resulting in higher quality grades (P < 0.05). Carcasses from Bos taurus-Continental cattle had lower calculated yield grades (P < 0.05) than did carcasses from cattle in the other biological types. In general, differences in carcass traits resulting from biological type were consistent with other reports. Plasma and LM Ca and P concentrations were not affected (P = 0.06) by biological type of cattle, indicating that Ca and P homeostasis is a conserved trait across the different types of cattle. Plasma VITD and 25-OH D concentrations were not affected (P = 0.41) by biological type, whereas plasma 1,25-(OH) 2 D
The Professional Animal Scientist, 2010
Viral infection in newly received feedlot cattle can lead to oxidative stress. As a constituent o... more Viral infection in newly received feedlot cattle can lead to oxidative stress. As a constituent of glututhione peroxidase, Se plays a vital antioxidant role. Our objective was to evaluate effects of Se source on the performance and health of calves challenged with infectious bovine rhinotracheitis virus (IBRV; Exp. 1) or in field conditions (Exp. 2). in Exp. 1, twenty-four Holstein steers (initial B 117 = 170 0.6 kg) were given either I) no supplemental Se (control), 2) 1 mg/steer daily of Se from Se-yeast, or 8 ,) 5 mg/ 'Corresponding author: tanyacoveyphd© gmaiLcom steer daily of Se from sodium. selenite. Treatments were fed for 28 d before steers were inoculated with IBRV (d 0) and were continued 21 d after the challenge. Treatments did not affect BW or DM1 (P> 0.20) from 7 d before through 21 8 after the challenge. Supplemental Sc (P = 0.02) increased IBRV titer values on d 21. The IBRV challenge induced a febrile response; however, there were no treatment differences (P> 0.10) in rectal temperature. Total red and white blood cell counts, percentage of white blood cell types, and hemoglobin concentrations did not differ (P > 0.11) among the 3 treatments. In Exp. 2. newly received, crossbred heifers (4 pens/treatment) were fed the same treatments as in Exp. 1, except selenite was supplied at I mg/heifer daily for 28 d. No treatment differences (P > 0. It)) were observed for perforrnamice or health during Exp. 2. Results help to define the effects of Se supplementation and source on the immune response to viral infections in cattle.
Journal of Animal Science, 2001
Tall fescue (Festuca arundinacea Schreb.) infected with the endophyte Neotyphodium coenophialum (... more Tall fescue (Festuca arundinacea Schreb.) infected with the endophyte Neotyphodium coenophialum ([Morgan-Jones and Gams] Glenn, Bacon, and Hanlin) causes fescue toxicosis in cattle grazing the forage, but effects of the endophyte were considered to be abated soon after removal of the animals from pastures. Tasco-Forage, a proprietary extract from the brown seaweed Ascophyllum nodosum, is a known source of cytokinins and has increased antioxidant activity in both plants and the animals that graze the forage. Tasco was applied at 0 and 3.4 kg/ ha to infected and uninfected tall fescue pastures in Virginia and Mississippi. Forty-eight steers grazed the pastures at each location during each of 2 yr (n = 192) before being transported to Texas for feedlot finishing. On arrival at the feedlot, steers from Tasco-treated pastures had higher (P < 0.01) monocyte phagocytic activity and tended (P < 0.07) to have higher major histocompatibility complex class II expression than steers that grazed the untreated pastures. A depression (P < 0.05
Journal of Animal Science, 2002
Matua bromegrass hay (Bromus willdenowii Kunth) is a high quality forage, but its value for mares... more Matua bromegrass hay (Bromus willdenowii Kunth) is a high quality forage, but its value for mares during gestation and lactation is not well known. Intake, rate of passage, performance, and reproduction by gestating and lactating Quarter Horse mares fed the hay was investigated. In this experiment, 12, 2-to 12yr-old gravid mares (mean BW = 553 kg; SD = 36) were fed Matua hay (CP = 11.5%) or alfalfa hay (Medicago sativa L.) (CP = 15.4%) for variable days prepartum (mean 59.9 d; SD = 23.5) and for 70 d postpartum. Matua and alfalfa hay were fed as the roughage portion of the diet with a grain supplement. Mares, blocked by age, expected date of foaling, and BW, were assigned randomly within blocks to treatments (six mares per treatment). Forage type did not affect intake, gestation length, birth weight, number of foals, foal weight gain, day of first postpartum ovulation, cycles per conception, or pregnancy rate at 70 d. On d 1, milk from mares fed
Journal of Animal Science, 2001
Tasco-Forage is an Ascophyllum nodosum seaweed-based product that has increased antioxidant activ... more Tasco-Forage is an Ascophyllum nodosum seaweed-based product that has increased antioxidant activity in both plants and animals. Endophyte (Neotyphodium coenophialum ([Morgan-Jones and Gams] Glenn, Bacon, and Hanlin)-infected and uninfected tall fescue (Festuca arundinacea Schreb.) pastures in Virginia and Mississippi during 1997 were treated or not with 3.4 kg Tasco/ha in April and July. There were two replications of each treatment at each location. Forty-eight steers (6/replication) grazed pastures at each location (n = 96) from April to October prior to transportation to Texas Tech, Lubbock, for finishing during a 160-d period in the feedlot. Blood (antemortem) and liver (postmortem) samples were collected. After slaughter and chilling, the left strip loins (IMPS #180) were collected from three randomly selected steers from within each pasture replication (n = 48). Strip loins were vacuum-packaged and stored at 2°C. At postmortem d 7, 14, 21, and 28, strip loins were removed from packaging and fabricated into 2.54-cm steaks. Following each fabrication day postmortem, the strip loins were repackaged and stored at 2°C until the following postmortem time. After the prescribed
Journal of Animal Science, 2001
Effects of applying Tasco-Forage, an Ascophyllum nodosum seaweed-based product prepared by a prop... more Effects of applying Tasco-Forage, an Ascophyllum nodosum seaweed-based product prepared by a proprietary process, to endophyte (Neotyphodium coenophialum [Morgan-Jones and Gams] Glenn, Bacon, and Hanlin)-infected and endophyte-free tall fescue (Festuca arundinacea Schreb.) were studied in each of 3 yr (1995, 1996, and 1997) in Virginia and in 1996 and 1997 in Mississippi. There were 48 steers at each location in each year (n = 240) in a 2 × 2 × 2 factorial arrangement with two replications at each location. Steers in Virginia were Angus and Angus × Hereford with initial weights of 245 kg (SD = 20), 234 kg (SD = 9), and 265 kg (SD = 5) in yr 1, 2, and 3, respectively. Steers in Mississippi were 3/4 Angus and 1/4 Brahman and weighed 230 kg (SD = 8) and 250 kg (SD = 2) in yr 2 and 3, respectively. Tasco (3.4 kg/ha) was dissolved in water and applied to pastures in April before grazing was begun and again in July at the same rate. The grazing period was from mid-April to late September or mid-October.
Rangeland Ecology & Management, 2011
Fire is an important process in many ecosystems, especially grasslands. However, documentation of... more Fire is an important process in many ecosystems, especially grasslands. However, documentation of plant community and soil environment responses to fire is limited for semiarid grasslands relative to that for mesic grasslands. Replicated summer fire research is lacking but necessary because summer is the natural fire season and the period of most wildfires in the western United States. We evaluated summer fire effects on soil temperature, soil moisture, aboveground biomass, root biomass, and functional group composition for 2 yr in semiarid C 3-dominated northern Great Plains. Following pre-treatment measures, four 0.75-ha sites were burned during August for comparison with nonburned sites, and the experiment was repeated the next year on adjacent sites to assess weather effects. Soils were about 0.5uC cooler on burned sites in the first experiment and similar in the second. Burned sites were consistently 1% drier than nonburned sites. Litter was reduced by fire but did not account for changes in soil moisture because differences occurred before the growing season. Current-year aboveground biomass and root biomass were similar between treatments, indicating productivity was resistant to summer fire. Perennial C 3 grasses increased in dominance because of positive biomass responses to fire for all but the bunchgrass, Hesperostipa comata, and a reduction of annual grasses. Perennial C 4 grasses were unaffected by summer fire. H. comata was resilient, with biomass on burned sites equaling nonburned sites the second growing season. Biomass was more responsive to precipitation than fire, and the fireinduced changes in species composition suggest exclusion of fire may be a greater disturbance than summer fire. Resumen El fuego es un proceso importante en muchos ecosistemas, especialmente en praderas. Sin embargo, la documentación de respuestas de la comunidad vegetal y del ambiente edáfico al fuego en pastizales semiáridos es limitada comparado con praderas mesofíticas. Ensayos replicados investigando los fuegos de verano son escasos pero necesarios dado que el verano es la estación natural de ocurrencia de la mayoría de los incendios en el oeste de los Estados Unidos. Evaluamos los efectos de quemas de verano sobre la temperatura del suelo, la humedad del suelo, la biomasa ae´rea, la biomasa radicular, y la composición de grupos funcionales durante dos añ os en pastizales semiáridos dominados por especies C 3 en el norte de las Grandes Planicies de Ame´rica del Norte. Luego de mediciones pre-experimentales, cuatro sitios de 0,75 ha fueron quemados durante el mes de Agosto para compararlos con sitios que no fueron quemados y el experimento se repitió al añ o siguiente en sitios adyacentes para evaluar efectos meteorológicos. Los suelos de los sitios quemados estuvieron 0,5uC más frescos en el primer experimento y de modo similar en el segundo. Los sitios quemados estuvieron consistentemente 1% más secos que los sitios no-quemados. El fuego redujo la cantidad de broza, pero la misma no explicó las diferencias en humedad edáfica porque dichas diferencias ocurrieron antes de la estación de crecimiento. El crecimiento del añ o de biomasa aérea y la biomasa radicular fue similar entre tratamientos, indicando que la productividad resistió el fuego de verano. Los pastos perennes C 3 aumentaron en dominancia debido a respuestas positivas al fuego en producción de biomasa para todas las especies excepto el pasto Hesperostipa comata, y una reducción en las especies anuales. Los pastos perennes C 4 no fueron afectados por los fuegos de verano. H. comata demostró resiliencia con biomasas iguales en sitios quemados y no-quemados en la segunda estación de crecimiento. La biomasa respondió más a la precipitación que al fuego y los cambios en la composición de especies inducida por el fuego sugieren que la exclusión del fuego podría ser un disturbio mayor que los fuegos de verano.
Rangeland Ecology & Management, 2014
Most wildfires occur during summer in the northern hemisphere, the area burned annually is increa... more Most wildfires occur during summer in the northern hemisphere, the area burned annually is increasing, and fire effects during this season are least understood. Understanding plant response to grazing following summer fire is required to reduce ecological and financial risks associated with wildfire. Forty 0.75-ha plots were assigned to summer fire then 0, 17, 34 or 50% biomass removal by grazing the following growing season, or no fire and no grazing. Root, litter, and aboveground biomass were measured before fire, immediately after grazing, and 1 yr after grazing with the experiment repeated during 2 yr to evaluate weather effects. Fire years were followed by the second driest and fifth wettest springs in 70 yr. Biomass was more responsive to weather than fire and grazing, with a 452% increase from a dry to wet year and 31% reduction from a wet to average spring. Fire reduced litter 53% and had no first-year effect on productivity for any biomass component. Grazing after fire reduced postgrazing grass biomass along the prescribed utilization gradient. Fire and grazing had no effect on total aboveground productivity the year after grazing compared to nonburned, nongrazed sites (1 327 vs. 1 249 6 65 kg Á ha À1). Fire and grazing increased grass productivity 16%, particularly for Pascopyrum smithii. The combined disturbances reduced forbs (51%), annual grasses (49%), and litter (46%). Results indicate grazing with up to 50% biomass removal the first growing season after summer fire was not detrimental to productivity of semiarid rangeland plant communities. Livestock exclusion the year after summer fire did not increase productivity or shift species composition compared to grazed sites. Reduction of previous years' standing dead material was the only indication that fire may temporarily reduce forage availability. The consistent responses among dry, wet, and near-average years suggest plant response is species-specific rather than climatically controlled.
Journal of Environmental Quality, 2005
Although fire is generally becoming a readily accepted management tool, the potential of accelera... more Although fire is generally becoming a readily accepted management tool, the potential of accelerated Selective grazing of burned patches can be intense if animal distriwind erosion on sandy sites is of concern following either bution is not controlled and may compound the independent effects of fire and grazing on soil characteristics. Our objectives were to prescribed fire or wildfire. Yet, few have actually meaquantify the effects of patch burning and grazing on wind erosion, sured post-fire wind erosion (Zobeck et al., 1989; Whicker soil water content, and soil temperature in sand sagebrush (Artemisia et al., 2002). Prescribed fire is generally conducted to filifolia Torr.) mixed prairie. We selected 24, 4-ha plots near Woodminimize soil exposure by coinciding with the onset of ward, OK. Four plots were burned during autumn (mid-November) plant growth and is applied to entire pastures to prevent and four during spring (mid-April), and four served as nonburned selective grazing of burned patches. Highly preferential controls for each of two years. Cattle were given unrestricted access grazing of burned sites has been confirmed for cattle (April-September) to burned patches (Ͻ2% of pastures) and utiliza-(Vermeire et al., 2004; Mitchell and Villalobos, 1999) tion was about 78%. Wind erosion, soil water content, and soil temperand fire effects may be exacerbated by intensive herbiature were measured monthly. Wind erosion varied by burn, year, and sampling height. Wind erosion was about 2 to 48 times greater vory. Wildfires rarely respect pasture boundaries, being on autumn-burned plots than nonburned plots during the dormant of irregular shape and generally smaller than the averperiod (December-April). Growing-season (April-August) erosion age pasture in the western United States. Some estiwas greatest during spring. Erosion of spring-burned sites was double mates report the average wildfire in the western United that of nonburned sites both years. Growing-season erosion from States to cover about 13 ha (Higgins, 1984; National autumn-burned sites was similar to nonburned sites except for one Interagency Fire Center, 2004). Following wildfire, the year with a dry April-May. Soil water content was unaffected by burned area may be fenced, or the remainder of the patch burn treatments. Soils of burned plots were 1 to 3؇C warmer pasture burned to prevent concentrated herbivory on than those of nonburned plots, based on midday measurements. burned patches (Wright, 1974). However, that paradigm Lower water holding and deep percolation capacity of sandy soils probably moderated effects on soil water content and soil temperature. has recently been challenged in an effort to mimic natu-Despite poor growing conditions following fire and heavy selective ral fire-herbivore interactions and increase heterogenegrazing of burned patches, no blowouts or drifts were observed. ity (Fuhlendorf and Engle, 2001). Wind erosion is a product of the force applied to the soil and the resistance of the soil (Lee and Tchakerian,
Journal of Animal Science, 2010
Simulation methods were used to generate 1,000 experiments, each with 3 treatments and 10 experim... more Simulation methods were used to generate 1,000 experiments, each with 3 treatments and 10 experimental units/treatment, in completely randomized (CRD) and randomized complete block designs. Data were counts in 3 ordered or 4 nominal categories from multinomial distributions. For the 3-category analyses, category probabilities were 0.6, 0.3, and 0.1, respectively, for 2 of the treatments, and 0.5, 0.35, and 0.15 for the third treatment. In the 4-category analysis (CRD only), probabilities were 0.3, 0.3, 0.2, and 0.2 for treatments 1 and 2 vs. 0.4, 0.4, 0.1, and 0.1 for treatment 3. The 3-category data were analyzed with generalized linear mixed models as an ordered multinomial distribution with a cumulative logit link or by regrouping the data (e.g., counts in 1 category/ sum of counts in all categories), followed by analysis of single categories as binomial proportions. Similarly, the 4-category data were analyzed as a nominal multinomial distribution with a glogit link or by grouping data as binomial proportions. For the 3-category CRD analyses, empirically determined type I error rates based on pair-wise comparisons (F-and Wald χ 2 tests) did not differ between multinomial and individual binomial category analyses with 10 (P = 0.38 to 0.60) or 50 (P = 0.19 to 0.67) sampling units/experimental unit. When analyzed as binomial proportions, power estimates varied among categories, with analysis of the category with the greatest counts yielding power similar to the multinomial analysis. Agreement between methods (percentage of experiments with the same results for the overall test for treatment effects) varied considerably among categories analyzed and sampling unit scenarios for the 3-category CRD analyses. Power (F-test) was 24.3, 49.1, 66.9, 83.5, 86.8, and 99.7% for 10, 20, 30, 40, 50, and 100 sampling units/experimental unit for the 3-category multinomial CRD analyses. Results with randomized complete block design simulations were similar to those with the CRD; however, increasing the size of the random block effect decreased the power of the F-test for the treatment effect. Power of the binomial approach with 4-category nominal data (CRD with 50 sampling units/experimental unit) depended on the probability of the category used, but the type I error rate for individual binomial proportions did not differ (P > 0.43) from the multinomial rate. Overall, analyzing a single binomial category from the multinomial distribution did not affect the type I error rate; however, analyzing multinomial data as a series of binomial proportions increased the experiment-wise type I error rate, and power varied among categories. Within the ordered category probabilities we modeled, power decreased as the number of sampling units per experimental unit decreased. Thus, for variables with probabilities similar to those modeled, power to detect treatment differences in count data from research settings with a small number of animals per pen would be limited.
Crop Science, 2007
Information on water use effi ciency (WUE) of forage grasses is needed to select appropriate spec... more Information on water use effi ciency (WUE) of forage grasses is needed to select appropriate species for improved productivity in semiarid environments. Three old world bluestem species-[Bothriochloa bladhii (Retz) S.T. Blake 'WW-B. Dahl'], [Bothriochloa ischaemum (L.) Keng. var. ischaemum (Hack.) 'WW-Spar'], and [Bothriochloa caucasica (Trin.) C.E. Hubbard 'Caucasian']-were surface drip-irrigated with zero (dryland) and low, medium, and high levels to determine dry matter (DM) yield and WUE in 2001, 2002, and 2003 in Lubbock, TX. Water applied in the high irrigation level equaled 100% of grass reference evapotranspiration (ET o); low and medium levels were calculated as 33 and 66% of irrigation applied in the high level; the dryland treatment received no irrigation. Maximum DM yield was obtained with B. caucasica under high irrigation (18.0 Mg ha −1) vs. B. bladhii (15.2 Mg ha −1) and B. ischaemum (12.6 Mg ha −1) averaged over all years. The WUE of B. caucasica under low, medium, and high irrigation was higher than B. ischaemum in 2001 (P < 0.05), and B. ischaemum and B. bladhii in 2003. Maximum and minimum WUE of all treatment combinations and years were 24 and 6 kg DM ha −1 mm −1 in B. caucasica with low irrigation and B. bladhii under dryland, respectively. Results showed that differences exist in WUE among species of Bothriochloa under irrigation. On the basis of WUE and potential DM yield, B. caucasica may be better suited for forage production in the Texas High Plains than either B. bladhii or B. ischaemum.
Crop Science, 2005
Investigations by Sanderson et al. (1999), Dewald et al. (1995), and Niemann (unpublished data, 2... more Investigations by Sanderson et al. (1999), Dewald et al. (1995), and Niemann (unpublished data, 2000, Texas Introduced forages offer alternatives to traditional cropping sys-Tech University) suggested that nutritive value of old tems in the semiarid Texas High Plains, but effects of irrigation on nutritive value are not well known. Three old world bluestem (Bothri-world bluestems (OWB) was influenced by species, enochloa) species [B. bladhii (Retz) S.T. Blake 'WW-B. Dahl', B. vironmental conditions, management, and physiographic ischaemum (L.) Keng. var. ischaemum (Hack.) 'WW-Spar', and B. location. Morphological characteristics of forages influcaucasica (Trin.) C.E. Hubbard 'Caucasian'] were surface drip-irrience and can help in predicting nutritive value (Mitchell gated with zero (dryland) and low, medium, and high irrigation levels, et al., 2001). to determine nutritive value and morphological development in 2001 Available moisture as precipitation and irrigation is to 2003 under a completely randomized block design, a split-plot directly related to growth and total productivity of these treatment arrangement, and three replicates. Water applied in the OWB species (Philipp, 2004). In the Texas High Plains, high treatment was 100% replacement of potential evapotranspiration water for irrigation is declining and additional land will minus precipitation. Medium and low treatments were 66 and 33% likely be converted from cropland to grassland. While of the high treatment. Dry matter digestibility (DMD) of all species was higher (P Ͻ 0.05) at low irrigation than at other levels (580, 560, Bothriochloa species have been widely adopted, little 550, and 570 g kg Ϫ1 for low, medium, high, and dryland, respectively; information is available regarding their nutritive value SE ϭ 4.0). Dahl was higher (P Ͻ 0.05) in crude protein (87 g kg Ϫ1) and morphological responses to a variety of water rethan Spar (76 g kg Ϫ1) and Caucasian (75 g kg Ϫ1 ; SE ϭ 2.0) during the gimes when grown in the climatic conditions of Texas growing season. In all species, total nonstructural carbohydrates and High Plains. Thus, our objectives were to determine DMD declined while neutral detergent fiber and acid detergent fiber nutritive value and growth characteristics of B. caucasincreased with increasing irrigation. Before hay harvest, leaf blade: ica, B. ischaemum, and B. bladhii under the semiarid stem-plus-sheath ratio declined also, but after hay harvest, effects of environmental conditions of the southern High Plains irrigation were less consistent. Results suggested that irrigation likely of Texas as influenced by amount of irrigation water. affected nutritive value through effects on plant morphology and physiological age. Thus, irrigation strategies and species selection may aid in optimizing forage quality. MATERIALS AND METHODS Three old world bluestem species (B. caucasica, ischaemum, and bladhii) and four water treatments (dryland, low, medium, I n the semiarid environment of the Texas High Plains, and high) were compared to determine effects on forage nutritive value and morphology. The research was conducted dur-old world bluestems (Bothriochloa spp.) have been ing 2001 to 2003 in northeast Lubbock County (101Њ 47Ј west among the more successfully introduced grasses for livelongitude; 33Њ 45Ј north latitude; 993 m elevation). Mean anstock grazing. The B. ischaemum varieties were planted nual precipitation was 337 mm during the 3 yr. The area has widely on Conservation Reserve Program areas in this a semiarid climate with annual mean long-term (1911-2002) region. More recently, B. bladhii was introduced (Deprecipitation of 470 mm and average air temperature of 15.5ЊC. wald et al., 1995) and is becoming adopted quickly there. Existing stands of 'Caucasian' (B. caucasica), 'WW Spar' Bothriochloa caucasica has not been grown extensively (B. ischaemum), and 'WW-B. Dahl' (B. bladhii) old world in this area. bluestems were used. There were three replicates of each Nutritive value of forages is influenced by many facforage (0.07 ha per replicate) in a complete randomized block tors including soil fertility, growth stage, species, and design. Forages, established in 1996, were used in a grazing experiment with lambs (Ovis aris) during 3 yr (1998-2000; photosynthetic pathway (Hodges and Bidwell, 1993).
Crop Science, 2013
ABSTRACT Benefits of legume–grass mixtures are well known but water required for legume growth li... more ABSTRACT Benefits of legume–grass mixtures are well known but water required for legume growth limits use in semiarid, irrigation-dependent environments. Research conducted over 4 yr (2007 to 2010) in the semiarid Texas High Plains compared alfalfa (Medicago sativa L.), yellow sweetclover [Melilotus officinalis (L.) Lam.], and sainfoin (Onobrychis viciifolia Scop.) interseeded into three old world bluestems (Bothriochloa spp.). No fertilizer N (control) and 60 kg N ha-1 treatments were applied to grasses alone. The five treatments imposed on each grass were replicated three times in a randomized complete block design with the legume and N treatments in a split-plot arrangement. Irrigation water applied through subsurface drip was limited to 250 mm annually. Annual dry matter yield of grass monocultures exceeded grass– legume mixtures in year 1 but yield of grass– legume mixtures was similar to N fertilizer in subsequent years. Crude protein (CP) and dry matter digestibility (DMD) were higher while cell wall was lower in the mean of grass–legume mixtures than grass monocultures. Nitrogen fertilization increased CP but had little effect on cell wall or DMD (g kg-1). Nutritive value benefits from yellow sweetclover occurred in year 1 and then declined while benefits from alfalfa increased over 4 yr. Lower sainfoin stands limited nutritive value. With limited irrigation, benefits of including legumes can exceed 60 kg N ha-1 in this semiarid environment.
Journal of Range Management, 2001
Little information is available about seasonal application and carry-over effects of biosolids ap... more Little information is available about seasonal application and carry-over effects of biosolids application to semi-arid grasslands. Biosolids rates of 0 (control), 7, 18, or 34 Mg ha-1 were topically applied to tobosagrass (Hilaria mutica (Buckl.) Benth.) experimental plots in a Chihuahuan desert grassland in western Texas. Biosolids were applied twice in 1994, for one-year-only, either in winter-and-summer (WS), or spring-and-summer (SS) seasons. Half of the plots were irrigated every summer for 4 years (1994-1997). Tobosagrass standing crop (herbage yield) and total Kjeldahl nitrogen concentration (plant %TKN) were measured every year during the 4 years of the study (1994-1997). An increase in biosolids rate increased tobosagrass herbage yield linearly during the 4 growing seasons. Linear and quadratic responses to biosolids rates were observed in %TKN during the experiment. Irrigation increased tobosagrass herbage yield. Irrigation decreased %TKN in 1995 and 1996 and had no influence during the other years. Winter-and-summer applications increased herbage yield more than spring and summer applications in 3 out of 4 years. Spring-and-summer applications increased %TKN more than winter and summer applications only in 1996. Carry-over effects on tobosagrass herbage yield and %TKN were observed in the second, third, and fourth growing seasons after biosolids application. Twice-a-year application of biosolids for 1-year-only offers an excellent means to improve tobosagrass productivity and forage quality.
Southwestern Entomologist, 2000
Remote Sensing, 2020
The application of unmanned aerial vehicles (UAVs) in the monitoring and management of rangelands... more The application of unmanned aerial vehicles (UAVs) in the monitoring and management of rangelands has exponentially increased in recent years due to the miniaturization of sensors, ability to capture imagery with high spatial resolution, lower altitude platforms, and the ease of flying UAVs in remote environments. The aim of this research was to develop a method to estimate forage mass in rangelands using high-resolution imagery derived from the UAV using a South Texas pasture as a pilot site. The specific objectives of this research were to (1) evaluate the feasibility of quantifying forage mass in semi-arid rangelands using a double sampling technique with high-resolution imagery and (2) to compare the effect of altitude on forage mass estimation. Orthoimagery and digital surface models (DSM) with a resolution <1.5 cm were acquired with an UAV at altitudes of 30, 40, and 50 m above ground level (AGL) in Duval County, Texas. Field forage mass data were regressed on volumes obtai...
Journal of animal science, 2004
The use of power tests in the planning and design of beef cattle experiments provides critical in... more The use of power tests in the planning and design of beef cattle experiments provides critical information on sample sizes necessary to detect treatment differences at a predetermined significance (alpha) level. Retrospective power analysis provides additional information about previous experiments that may be helpful in designing subsequent investigations. However, in retrospective power analyses, power is inversely related to observed significance level. Benefits of prospective and retrospective power analyses in beef cattle experiments are similar to those for other species; however, because of differences in the methods and conditions involved, considerations for the use of power test procedures are specific for beef cattle research. Retrospective power analyses were conducted on 78 published experiments and on two unpublished experiments. Experiments were compiled into categories that represented group (or pen) feeding, individual feeding, and metabolism studies. Estimated powe...
Journal of Animal Science, 2004
The effect of supplementing diets with various levels of vitamin D 3 to provide 0, 0.5, 1, and 5 ... more The effect of supplementing diets with various levels of vitamin D 3 to provide 0, 0.5, 1, and 5 million IU/(steerؒd) for 8 d before slaughter on the mineral content and localization of Ca in LM and muscle fragments was studied during the postmortem aging process. Twelve feedlot steers of three biological types were given access to the four levels of vitamin D for 8 d before slaughter. Differential centrifugation techniques were used to determine the concentrations of minerals relative to protein in different muscle fragments on d 3 and 21 postmortem. Electron microscopy visualization of bound Ca indicated that vitamin D 3 mobilized Ca from the sarcoplasmic reticulum and transverse tubule system into the myofibrils. Bound Ca was concentrated near the Z-line at the A-band/I-band juncture within the sarcomere. Supplementing steers with 1 and 5 million IU/(steerؒd) of vitamin D 3 increased (P < 0.05) Ca, P, and Mg concentrations per unit of protein in the cytosol. Soluble cytosolic Ca concentrations were
Journal of Animal Science, 2004
Feedlot steers (n = 36) from three biological types (Bos indicus, Bos taurus-Continental, and Bos... more Feedlot steers (n = 36) from three biological types (Bos indicus, Bos taurus-Continental, and Bos taurus-English) were used to determine the Ca, P, and vitamin D 3 status of feedlot cattle. The USDA yield and quality grade traits were measured at slaughter, and the concentrations of vitamin D 3 (VITD) and the metabolites 25-hydroxyvitamin D 3 (25-OH D) and 1,25-dihydroxyvitamin D 3 (1,25-(OH) 2 D) were determined in LM, liver, kidney, and plasma. Plasma and muscle Ca and P concentrations also were determined. Biological type of cattle affected a number of carcass traits. Carcasses from Bos taurus-English cattle had more marbling, resulting in higher quality grades (P < 0.05). Carcasses from Bos taurus-Continental cattle had lower calculated yield grades (P < 0.05) than did carcasses from cattle in the other biological types. In general, differences in carcass traits resulting from biological type were consistent with other reports. Plasma and LM Ca and P concentrations were not affected (P = 0.06) by biological type of cattle, indicating that Ca and P homeostasis is a conserved trait across the different types of cattle. Plasma VITD and 25-OH D concentrations were not affected (P = 0.41) by biological type, whereas plasma 1,25-(OH) 2 D
The Professional Animal Scientist, 2010
Viral infection in newly received feedlot cattle can lead to oxidative stress. As a constituent o... more Viral infection in newly received feedlot cattle can lead to oxidative stress. As a constituent of glututhione peroxidase, Se plays a vital antioxidant role. Our objective was to evaluate effects of Se source on the performance and health of calves challenged with infectious bovine rhinotracheitis virus (IBRV; Exp. 1) or in field conditions (Exp. 2). in Exp. 1, twenty-four Holstein steers (initial B 117 = 170 0.6 kg) were given either I) no supplemental Se (control), 2) 1 mg/steer daily of Se from Se-yeast, or 8 ,) 5 mg/ 'Corresponding author: tanyacoveyphd© gmaiLcom steer daily of Se from sodium. selenite. Treatments were fed for 28 d before steers were inoculated with IBRV (d 0) and were continued 21 d after the challenge. Treatments did not affect BW or DM1 (P> 0.20) from 7 d before through 21 8 after the challenge. Supplemental Sc (P = 0.02) increased IBRV titer values on d 21. The IBRV challenge induced a febrile response; however, there were no treatment differences (P> 0.10) in rectal temperature. Total red and white blood cell counts, percentage of white blood cell types, and hemoglobin concentrations did not differ (P > 0.11) among the 3 treatments. In Exp. 2. newly received, crossbred heifers (4 pens/treatment) were fed the same treatments as in Exp. 1, except selenite was supplied at I mg/heifer daily for 28 d. No treatment differences (P > 0. It)) were observed for perforrnamice or health during Exp. 2. Results help to define the effects of Se supplementation and source on the immune response to viral infections in cattle.
Journal of Animal Science, 2001
Tall fescue (Festuca arundinacea Schreb.) infected with the endophyte Neotyphodium coenophialum (... more Tall fescue (Festuca arundinacea Schreb.) infected with the endophyte Neotyphodium coenophialum ([Morgan-Jones and Gams] Glenn, Bacon, and Hanlin) causes fescue toxicosis in cattle grazing the forage, but effects of the endophyte were considered to be abated soon after removal of the animals from pastures. Tasco-Forage, a proprietary extract from the brown seaweed Ascophyllum nodosum, is a known source of cytokinins and has increased antioxidant activity in both plants and the animals that graze the forage. Tasco was applied at 0 and 3.4 kg/ ha to infected and uninfected tall fescue pastures in Virginia and Mississippi. Forty-eight steers grazed the pastures at each location during each of 2 yr (n = 192) before being transported to Texas for feedlot finishing. On arrival at the feedlot, steers from Tasco-treated pastures had higher (P < 0.01) monocyte phagocytic activity and tended (P < 0.07) to have higher major histocompatibility complex class II expression than steers that grazed the untreated pastures. A depression (P < 0.05
Journal of Animal Science, 2002
Matua bromegrass hay (Bromus willdenowii Kunth) is a high quality forage, but its value for mares... more Matua bromegrass hay (Bromus willdenowii Kunth) is a high quality forage, but its value for mares during gestation and lactation is not well known. Intake, rate of passage, performance, and reproduction by gestating and lactating Quarter Horse mares fed the hay was investigated. In this experiment, 12, 2-to 12yr-old gravid mares (mean BW = 553 kg; SD = 36) were fed Matua hay (CP = 11.5%) or alfalfa hay (Medicago sativa L.) (CP = 15.4%) for variable days prepartum (mean 59.9 d; SD = 23.5) and for 70 d postpartum. Matua and alfalfa hay were fed as the roughage portion of the diet with a grain supplement. Mares, blocked by age, expected date of foaling, and BW, were assigned randomly within blocks to treatments (six mares per treatment). Forage type did not affect intake, gestation length, birth weight, number of foals, foal weight gain, day of first postpartum ovulation, cycles per conception, or pregnancy rate at 70 d. On d 1, milk from mares fed
Journal of Animal Science, 2001
Tasco-Forage is an Ascophyllum nodosum seaweed-based product that has increased antioxidant activ... more Tasco-Forage is an Ascophyllum nodosum seaweed-based product that has increased antioxidant activity in both plants and animals. Endophyte (Neotyphodium coenophialum ([Morgan-Jones and Gams] Glenn, Bacon, and Hanlin)-infected and uninfected tall fescue (Festuca arundinacea Schreb.) pastures in Virginia and Mississippi during 1997 were treated or not with 3.4 kg Tasco/ha in April and July. There were two replications of each treatment at each location. Forty-eight steers (6/replication) grazed pastures at each location (n = 96) from April to October prior to transportation to Texas Tech, Lubbock, for finishing during a 160-d period in the feedlot. Blood (antemortem) and liver (postmortem) samples were collected. After slaughter and chilling, the left strip loins (IMPS #180) were collected from three randomly selected steers from within each pasture replication (n = 48). Strip loins were vacuum-packaged and stored at 2°C. At postmortem d 7, 14, 21, and 28, strip loins were removed from packaging and fabricated into 2.54-cm steaks. Following each fabrication day postmortem, the strip loins were repackaged and stored at 2°C until the following postmortem time. After the prescribed
Journal of Animal Science, 2001
Effects of applying Tasco-Forage, an Ascophyllum nodosum seaweed-based product prepared by a prop... more Effects of applying Tasco-Forage, an Ascophyllum nodosum seaweed-based product prepared by a proprietary process, to endophyte (Neotyphodium coenophialum [Morgan-Jones and Gams] Glenn, Bacon, and Hanlin)-infected and endophyte-free tall fescue (Festuca arundinacea Schreb.) were studied in each of 3 yr (1995, 1996, and 1997) in Virginia and in 1996 and 1997 in Mississippi. There were 48 steers at each location in each year (n = 240) in a 2 × 2 × 2 factorial arrangement with two replications at each location. Steers in Virginia were Angus and Angus × Hereford with initial weights of 245 kg (SD = 20), 234 kg (SD = 9), and 265 kg (SD = 5) in yr 1, 2, and 3, respectively. Steers in Mississippi were 3/4 Angus and 1/4 Brahman and weighed 230 kg (SD = 8) and 250 kg (SD = 2) in yr 2 and 3, respectively. Tasco (3.4 kg/ha) was dissolved in water and applied to pastures in April before grazing was begun and again in July at the same rate. The grazing period was from mid-April to late September or mid-October.
Rangeland Ecology & Management, 2011
Fire is an important process in many ecosystems, especially grasslands. However, documentation of... more Fire is an important process in many ecosystems, especially grasslands. However, documentation of plant community and soil environment responses to fire is limited for semiarid grasslands relative to that for mesic grasslands. Replicated summer fire research is lacking but necessary because summer is the natural fire season and the period of most wildfires in the western United States. We evaluated summer fire effects on soil temperature, soil moisture, aboveground biomass, root biomass, and functional group composition for 2 yr in semiarid C 3-dominated northern Great Plains. Following pre-treatment measures, four 0.75-ha sites were burned during August for comparison with nonburned sites, and the experiment was repeated the next year on adjacent sites to assess weather effects. Soils were about 0.5uC cooler on burned sites in the first experiment and similar in the second. Burned sites were consistently 1% drier than nonburned sites. Litter was reduced by fire but did not account for changes in soil moisture because differences occurred before the growing season. Current-year aboveground biomass and root biomass were similar between treatments, indicating productivity was resistant to summer fire. Perennial C 3 grasses increased in dominance because of positive biomass responses to fire for all but the bunchgrass, Hesperostipa comata, and a reduction of annual grasses. Perennial C 4 grasses were unaffected by summer fire. H. comata was resilient, with biomass on burned sites equaling nonburned sites the second growing season. Biomass was more responsive to precipitation than fire, and the fireinduced changes in species composition suggest exclusion of fire may be a greater disturbance than summer fire. Resumen El fuego es un proceso importante en muchos ecosistemas, especialmente en praderas. Sin embargo, la documentación de respuestas de la comunidad vegetal y del ambiente edáfico al fuego en pastizales semiáridos es limitada comparado con praderas mesofíticas. Ensayos replicados investigando los fuegos de verano son escasos pero necesarios dado que el verano es la estación natural de ocurrencia de la mayoría de los incendios en el oeste de los Estados Unidos. Evaluamos los efectos de quemas de verano sobre la temperatura del suelo, la humedad del suelo, la biomasa ae´rea, la biomasa radicular, y la composición de grupos funcionales durante dos añ os en pastizales semiáridos dominados por especies C 3 en el norte de las Grandes Planicies de Ame´rica del Norte. Luego de mediciones pre-experimentales, cuatro sitios de 0,75 ha fueron quemados durante el mes de Agosto para compararlos con sitios que no fueron quemados y el experimento se repitió al añ o siguiente en sitios adyacentes para evaluar efectos meteorológicos. Los suelos de los sitios quemados estuvieron 0,5uC más frescos en el primer experimento y de modo similar en el segundo. Los sitios quemados estuvieron consistentemente 1% más secos que los sitios no-quemados. El fuego redujo la cantidad de broza, pero la misma no explicó las diferencias en humedad edáfica porque dichas diferencias ocurrieron antes de la estación de crecimiento. El crecimiento del añ o de biomasa aérea y la biomasa radicular fue similar entre tratamientos, indicando que la productividad resistió el fuego de verano. Los pastos perennes C 3 aumentaron en dominancia debido a respuestas positivas al fuego en producción de biomasa para todas las especies excepto el pasto Hesperostipa comata, y una reducción en las especies anuales. Los pastos perennes C 4 no fueron afectados por los fuegos de verano. H. comata demostró resiliencia con biomasas iguales en sitios quemados y no-quemados en la segunda estación de crecimiento. La biomasa respondió más a la precipitación que al fuego y los cambios en la composición de especies inducida por el fuego sugieren que la exclusión del fuego podría ser un disturbio mayor que los fuegos de verano.
Rangeland Ecology & Management, 2014
Most wildfires occur during summer in the northern hemisphere, the area burned annually is increa... more Most wildfires occur during summer in the northern hemisphere, the area burned annually is increasing, and fire effects during this season are least understood. Understanding plant response to grazing following summer fire is required to reduce ecological and financial risks associated with wildfire. Forty 0.75-ha plots were assigned to summer fire then 0, 17, 34 or 50% biomass removal by grazing the following growing season, or no fire and no grazing. Root, litter, and aboveground biomass were measured before fire, immediately after grazing, and 1 yr after grazing with the experiment repeated during 2 yr to evaluate weather effects. Fire years were followed by the second driest and fifth wettest springs in 70 yr. Biomass was more responsive to weather than fire and grazing, with a 452% increase from a dry to wet year and 31% reduction from a wet to average spring. Fire reduced litter 53% and had no first-year effect on productivity for any biomass component. Grazing after fire reduced postgrazing grass biomass along the prescribed utilization gradient. Fire and grazing had no effect on total aboveground productivity the year after grazing compared to nonburned, nongrazed sites (1 327 vs. 1 249 6 65 kg Á ha À1). Fire and grazing increased grass productivity 16%, particularly for Pascopyrum smithii. The combined disturbances reduced forbs (51%), annual grasses (49%), and litter (46%). Results indicate grazing with up to 50% biomass removal the first growing season after summer fire was not detrimental to productivity of semiarid rangeland plant communities. Livestock exclusion the year after summer fire did not increase productivity or shift species composition compared to grazed sites. Reduction of previous years' standing dead material was the only indication that fire may temporarily reduce forage availability. The consistent responses among dry, wet, and near-average years suggest plant response is species-specific rather than climatically controlled.
Journal of Environmental Quality, 2005
Although fire is generally becoming a readily accepted management tool, the potential of accelera... more Although fire is generally becoming a readily accepted management tool, the potential of accelerated Selective grazing of burned patches can be intense if animal distriwind erosion on sandy sites is of concern following either bution is not controlled and may compound the independent effects of fire and grazing on soil characteristics. Our objectives were to prescribed fire or wildfire. Yet, few have actually meaquantify the effects of patch burning and grazing on wind erosion, sured post-fire wind erosion (Zobeck et al., 1989; Whicker soil water content, and soil temperature in sand sagebrush (Artemisia et al., 2002). Prescribed fire is generally conducted to filifolia Torr.) mixed prairie. We selected 24, 4-ha plots near Woodminimize soil exposure by coinciding with the onset of ward, OK. Four plots were burned during autumn (mid-November) plant growth and is applied to entire pastures to prevent and four during spring (mid-April), and four served as nonburned selective grazing of burned patches. Highly preferential controls for each of two years. Cattle were given unrestricted access grazing of burned sites has been confirmed for cattle (April-September) to burned patches (Ͻ2% of pastures) and utiliza-(Vermeire et al., 2004; Mitchell and Villalobos, 1999) tion was about 78%. Wind erosion, soil water content, and soil temperand fire effects may be exacerbated by intensive herbiature were measured monthly. Wind erosion varied by burn, year, and sampling height. Wind erosion was about 2 to 48 times greater vory. Wildfires rarely respect pasture boundaries, being on autumn-burned plots than nonburned plots during the dormant of irregular shape and generally smaller than the averperiod (December-April). Growing-season (April-August) erosion age pasture in the western United States. Some estiwas greatest during spring. Erosion of spring-burned sites was double mates report the average wildfire in the western United that of nonburned sites both years. Growing-season erosion from States to cover about 13 ha (Higgins, 1984; National autumn-burned sites was similar to nonburned sites except for one Interagency Fire Center, 2004). Following wildfire, the year with a dry April-May. Soil water content was unaffected by burned area may be fenced, or the remainder of the patch burn treatments. Soils of burned plots were 1 to 3؇C warmer pasture burned to prevent concentrated herbivory on than those of nonburned plots, based on midday measurements. burned patches (Wright, 1974). However, that paradigm Lower water holding and deep percolation capacity of sandy soils probably moderated effects on soil water content and soil temperature. has recently been challenged in an effort to mimic natu-Despite poor growing conditions following fire and heavy selective ral fire-herbivore interactions and increase heterogenegrazing of burned patches, no blowouts or drifts were observed. ity (Fuhlendorf and Engle, 2001). Wind erosion is a product of the force applied to the soil and the resistance of the soil (Lee and Tchakerian,
Journal of Animal Science, 2010
Simulation methods were used to generate 1,000 experiments, each with 3 treatments and 10 experim... more Simulation methods were used to generate 1,000 experiments, each with 3 treatments and 10 experimental units/treatment, in completely randomized (CRD) and randomized complete block designs. Data were counts in 3 ordered or 4 nominal categories from multinomial distributions. For the 3-category analyses, category probabilities were 0.6, 0.3, and 0.1, respectively, for 2 of the treatments, and 0.5, 0.35, and 0.15 for the third treatment. In the 4-category analysis (CRD only), probabilities were 0.3, 0.3, 0.2, and 0.2 for treatments 1 and 2 vs. 0.4, 0.4, 0.1, and 0.1 for treatment 3. The 3-category data were analyzed with generalized linear mixed models as an ordered multinomial distribution with a cumulative logit link or by regrouping the data (e.g., counts in 1 category/ sum of counts in all categories), followed by analysis of single categories as binomial proportions. Similarly, the 4-category data were analyzed as a nominal multinomial distribution with a glogit link or by grouping data as binomial proportions. For the 3-category CRD analyses, empirically determined type I error rates based on pair-wise comparisons (F-and Wald χ 2 tests) did not differ between multinomial and individual binomial category analyses with 10 (P = 0.38 to 0.60) or 50 (P = 0.19 to 0.67) sampling units/experimental unit. When analyzed as binomial proportions, power estimates varied among categories, with analysis of the category with the greatest counts yielding power similar to the multinomial analysis. Agreement between methods (percentage of experiments with the same results for the overall test for treatment effects) varied considerably among categories analyzed and sampling unit scenarios for the 3-category CRD analyses. Power (F-test) was 24.3, 49.1, 66.9, 83.5, 86.8, and 99.7% for 10, 20, 30, 40, 50, and 100 sampling units/experimental unit for the 3-category multinomial CRD analyses. Results with randomized complete block design simulations were similar to those with the CRD; however, increasing the size of the random block effect decreased the power of the F-test for the treatment effect. Power of the binomial approach with 4-category nominal data (CRD with 50 sampling units/experimental unit) depended on the probability of the category used, but the type I error rate for individual binomial proportions did not differ (P > 0.43) from the multinomial rate. Overall, analyzing a single binomial category from the multinomial distribution did not affect the type I error rate; however, analyzing multinomial data as a series of binomial proportions increased the experiment-wise type I error rate, and power varied among categories. Within the ordered category probabilities we modeled, power decreased as the number of sampling units per experimental unit decreased. Thus, for variables with probabilities similar to those modeled, power to detect treatment differences in count data from research settings with a small number of animals per pen would be limited.
Crop Science, 2007
Information on water use effi ciency (WUE) of forage grasses is needed to select appropriate spec... more Information on water use effi ciency (WUE) of forage grasses is needed to select appropriate species for improved productivity in semiarid environments. Three old world bluestem species-[Bothriochloa bladhii (Retz) S.T. Blake 'WW-B. Dahl'], [Bothriochloa ischaemum (L.) Keng. var. ischaemum (Hack.) 'WW-Spar'], and [Bothriochloa caucasica (Trin.) C.E. Hubbard 'Caucasian']-were surface drip-irrigated with zero (dryland) and low, medium, and high levels to determine dry matter (DM) yield and WUE in 2001, 2002, and 2003 in Lubbock, TX. Water applied in the high irrigation level equaled 100% of grass reference evapotranspiration (ET o); low and medium levels were calculated as 33 and 66% of irrigation applied in the high level; the dryland treatment received no irrigation. Maximum DM yield was obtained with B. caucasica under high irrigation (18.0 Mg ha −1) vs. B. bladhii (15.2 Mg ha −1) and B. ischaemum (12.6 Mg ha −1) averaged over all years. The WUE of B. caucasica under low, medium, and high irrigation was higher than B. ischaemum in 2001 (P < 0.05), and B. ischaemum and B. bladhii in 2003. Maximum and minimum WUE of all treatment combinations and years were 24 and 6 kg DM ha −1 mm −1 in B. caucasica with low irrigation and B. bladhii under dryland, respectively. Results showed that differences exist in WUE among species of Bothriochloa under irrigation. On the basis of WUE and potential DM yield, B. caucasica may be better suited for forage production in the Texas High Plains than either B. bladhii or B. ischaemum.
Crop Science, 2005
Investigations by Sanderson et al. (1999), Dewald et al. (1995), and Niemann (unpublished data, 2... more Investigations by Sanderson et al. (1999), Dewald et al. (1995), and Niemann (unpublished data, 2000, Texas Introduced forages offer alternatives to traditional cropping sys-Tech University) suggested that nutritive value of old tems in the semiarid Texas High Plains, but effects of irrigation on nutritive value are not well known. Three old world bluestem (Bothri-world bluestems (OWB) was influenced by species, enochloa) species [B. bladhii (Retz) S.T. Blake 'WW-B. Dahl', B. vironmental conditions, management, and physiographic ischaemum (L.) Keng. var. ischaemum (Hack.) 'WW-Spar', and B. location. Morphological characteristics of forages influcaucasica (Trin.) C.E. Hubbard 'Caucasian'] were surface drip-irrience and can help in predicting nutritive value (Mitchell gated with zero (dryland) and low, medium, and high irrigation levels, et al., 2001). to determine nutritive value and morphological development in 2001 Available moisture as precipitation and irrigation is to 2003 under a completely randomized block design, a split-plot directly related to growth and total productivity of these treatment arrangement, and three replicates. Water applied in the OWB species (Philipp, 2004). In the Texas High Plains, high treatment was 100% replacement of potential evapotranspiration water for irrigation is declining and additional land will minus precipitation. Medium and low treatments were 66 and 33% likely be converted from cropland to grassland. While of the high treatment. Dry matter digestibility (DMD) of all species was higher (P Ͻ 0.05) at low irrigation than at other levels (580, 560, Bothriochloa species have been widely adopted, little 550, and 570 g kg Ϫ1 for low, medium, high, and dryland, respectively; information is available regarding their nutritive value SE ϭ 4.0). Dahl was higher (P Ͻ 0.05) in crude protein (87 g kg Ϫ1) and morphological responses to a variety of water rethan Spar (76 g kg Ϫ1) and Caucasian (75 g kg Ϫ1 ; SE ϭ 2.0) during the gimes when grown in the climatic conditions of Texas growing season. In all species, total nonstructural carbohydrates and High Plains. Thus, our objectives were to determine DMD declined while neutral detergent fiber and acid detergent fiber nutritive value and growth characteristics of B. caucasincreased with increasing irrigation. Before hay harvest, leaf blade: ica, B. ischaemum, and B. bladhii under the semiarid stem-plus-sheath ratio declined also, but after hay harvest, effects of environmental conditions of the southern High Plains irrigation were less consistent. Results suggested that irrigation likely of Texas as influenced by amount of irrigation water. affected nutritive value through effects on plant morphology and physiological age. Thus, irrigation strategies and species selection may aid in optimizing forage quality. MATERIALS AND METHODS Three old world bluestem species (B. caucasica, ischaemum, and bladhii) and four water treatments (dryland, low, medium, I n the semiarid environment of the Texas High Plains, and high) were compared to determine effects on forage nutritive value and morphology. The research was conducted dur-old world bluestems (Bothriochloa spp.) have been ing 2001 to 2003 in northeast Lubbock County (101Њ 47Ј west among the more successfully introduced grasses for livelongitude; 33Њ 45Ј north latitude; 993 m elevation). Mean anstock grazing. The B. ischaemum varieties were planted nual precipitation was 337 mm during the 3 yr. The area has widely on Conservation Reserve Program areas in this a semiarid climate with annual mean long-term (1911-2002) region. More recently, B. bladhii was introduced (Deprecipitation of 470 mm and average air temperature of 15.5ЊC. wald et al., 1995) and is becoming adopted quickly there. Existing stands of 'Caucasian' (B. caucasica), 'WW Spar' Bothriochloa caucasica has not been grown extensively (B. ischaemum), and 'WW-B. Dahl' (B. bladhii) old world in this area. bluestems were used. There were three replicates of each Nutritive value of forages is influenced by many facforage (0.07 ha per replicate) in a complete randomized block tors including soil fertility, growth stage, species, and design. Forages, established in 1996, were used in a grazing experiment with lambs (Ovis aris) during 3 yr (1998-2000; photosynthetic pathway (Hodges and Bidwell, 1993).
Crop Science, 2013
ABSTRACT Benefits of legume–grass mixtures are well known but water required for legume growth li... more ABSTRACT Benefits of legume–grass mixtures are well known but water required for legume growth limits use in semiarid, irrigation-dependent environments. Research conducted over 4 yr (2007 to 2010) in the semiarid Texas High Plains compared alfalfa (Medicago sativa L.), yellow sweetclover [Melilotus officinalis (L.) Lam.], and sainfoin (Onobrychis viciifolia Scop.) interseeded into three old world bluestems (Bothriochloa spp.). No fertilizer N (control) and 60 kg N ha-1 treatments were applied to grasses alone. The five treatments imposed on each grass were replicated three times in a randomized complete block design with the legume and N treatments in a split-plot arrangement. Irrigation water applied through subsurface drip was limited to 250 mm annually. Annual dry matter yield of grass monocultures exceeded grass– legume mixtures in year 1 but yield of grass– legume mixtures was similar to N fertilizer in subsequent years. Crude protein (CP) and dry matter digestibility (DMD) were higher while cell wall was lower in the mean of grass–legume mixtures than grass monocultures. Nitrogen fertilization increased CP but had little effect on cell wall or DMD (g kg-1). Nutritive value benefits from yellow sweetclover occurred in year 1 and then declined while benefits from alfalfa increased over 4 yr. Lower sainfoin stands limited nutritive value. With limited irrigation, benefits of including legumes can exceed 60 kg N ha-1 in this semiarid environment.
Journal of Range Management, 2001
Little information is available about seasonal application and carry-over effects of biosolids ap... more Little information is available about seasonal application and carry-over effects of biosolids application to semi-arid grasslands. Biosolids rates of 0 (control), 7, 18, or 34 Mg ha-1 were topically applied to tobosagrass (Hilaria mutica (Buckl.) Benth.) experimental plots in a Chihuahuan desert grassland in western Texas. Biosolids were applied twice in 1994, for one-year-only, either in winter-and-summer (WS), or spring-and-summer (SS) seasons. Half of the plots were irrigated every summer for 4 years (1994-1997). Tobosagrass standing crop (herbage yield) and total Kjeldahl nitrogen concentration (plant %TKN) were measured every year during the 4 years of the study (1994-1997). An increase in biosolids rate increased tobosagrass herbage yield linearly during the 4 growing seasons. Linear and quadratic responses to biosolids rates were observed in %TKN during the experiment. Irrigation increased tobosagrass herbage yield. Irrigation decreased %TKN in 1995 and 1996 and had no influence during the other years. Winter-and-summer applications increased herbage yield more than spring and summer applications in 3 out of 4 years. Spring-and-summer applications increased %TKN more than winter and summer applications only in 1996. Carry-over effects on tobosagrass herbage yield and %TKN were observed in the second, third, and fourth growing seasons after biosolids application. Twice-a-year application of biosolids for 1-year-only offers an excellent means to improve tobosagrass productivity and forage quality.
Southwestern Entomologist, 2000
Remote Sensing, 2020
The application of unmanned aerial vehicles (UAVs) in the monitoring and management of rangelands... more The application of unmanned aerial vehicles (UAVs) in the monitoring and management of rangelands has exponentially increased in recent years due to the miniaturization of sensors, ability to capture imagery with high spatial resolution, lower altitude platforms, and the ease of flying UAVs in remote environments. The aim of this research was to develop a method to estimate forage mass in rangelands using high-resolution imagery derived from the UAV using a South Texas pasture as a pilot site. The specific objectives of this research were to (1) evaluate the feasibility of quantifying forage mass in semi-arid rangelands using a double sampling technique with high-resolution imagery and (2) to compare the effect of altitude on forage mass estimation. Orthoimagery and digital surface models (DSM) with a resolution <1.5 cm were acquired with an UAV at altitudes of 30, 40, and 50 m above ground level (AGL) in Duval County, Texas. Field forage mass data were regressed on volumes obtai...