Scholars

Walker, John

Agrilife Center Director

Positions:

Professor, Ecology and Conservation Biology, College of Agriculture and Life Sciences
Agrilife Center Director, San Angelo Research and Extension Center, Texas A&M AgriLIFE Extension, Texas A&M AgriLife Research

education and training

Ph.D. in Range Science, Texas A&M University - (College Station, Texas, United States) 1988

selected publications

Academic Articles67

Walker, J. W., Shoemake, B. M., Quadros, D. G., Thorne, J. W., & Cahill, N. C. (2023). Selecting goats for juniper consumption did not improve their liver Phase I detoxification.. Journal of Animal Science. 101, skad180.
Seidel, D. S., Walker, J. W., Musser, J. M., Whitney, T. R., & Callaway, T. R. (2022). Impact of camphor on the in vitro mixed ruminal microorganism fermentation from goats selected for consumption of low and high levels of Juniperus spp. 1.. Translational Animal Science. 6(3), txac097.
Seidel, D. S., Walker, J. W., Musser, J. M., Lourenco, J. M., Welch, C. B., Whitney, T. R., & Callaway, T. R. (2022). Impact of concentrations of camphor on the in vitro mixed ruminal microorganism fermentation from goats selected for consumption of low and high levels of Juniperus spp.-2.. Translational Animal Science. 6(3), txac098.
Wilcox, B. P., Fuhlendorf, S. D., Walker, J. W., Twidwell, D., Ben Wu, X., Goodman, L. E., Treadwell, M., & Birt, A. (2022). Saving imperiled grassland biomes by recoupling fire and grazing: a case study from the Great Plains. Frontiers in Ecology and the Environment. 20(3), 179-186.
Walker, J. W., & Kronberg, S. L. (2022). Nature, nurture, and vegetation management: Studies with sheep and goats.. Animal. 16(1), 100434-100434.
Leite, P., Wilcox, B. P., McInnes, K. J., & Walker, J. W. (2021). Applicability of soil moisture sensors for monitoring water dynamics in rock: A field test in weathered limestone. Vadose Zone Journal. 20(6),
Altangerel, N., Ashley, C., Hemmer, P. R., Kraemer, D., Scully, M. O., Walker, J. W., & Quadros, D. G. (2021). Raman spectroscopy of fresh feces is a practical tool for identifying animal species and estimating diet characteristics. Animal Feed Science and Technology. 281, 115081-115081.
Walker, J. W., Pope, R., & Pfeiffer, F. A. (2021). On-farm testing of FibreLux Micron Meter and OFDA2000 compared to Sirolan Laserscan in the laboratory. Small Ruminant Research. 200, 106401-106401.
Tolleson, D. R., Welsh, T. H., & Walker, J. W. (2020). Metabolic and endocrine indicators in male goats differing in genetic propensity to consume juniper.. Journal of Animal Science. 98(Supplement_2), 32-33.
Tolleson, D. R., Welsh, T. H., Garza, N., Hollingsworth, K., & Walker, J. W. (2020). Proportional tissue weights in male goats differing in genetic propensity to consume juniper.. Journal of Animal Science. 98(Supplement_2), 33-34.
Bailey, D. W., Mosley, J. C., Estell, R. E., Cibils, A. F., Horney, M., Hendrickson, J. R., ... Burritt, E. A. (2019). Synthesis Paper: Targeted Livestock Grazing: Prescription for Healthy Rangelands. Rangeland Ecology and Management. 72(6), 865-877.

SDG 15
Stewart, W. C., Whitney, T. R., Scholljegerdes, E. J., Waldron, D. F., Walker, J. W., Adams, R. P., & Musser, J. (2019). Ruminal fermentation characteristics of goats selectively bred to have greater consumption of juniper foliage. Animal Feed Science and Technology. 256, 114240-114240.
Toniecek, J. M., French, J. T., Walker, J. W., & Bromen, N. A. (2019). Factors influencing the movement of livestock guardian dogs in the Edwards Plateau of Texas: implications for efficacy, behavior, and territoriality. HUMAN-WILDLIFE INTERACTIONS. 13(1), 16-28.
Bromen, N. A., French, J. T., Walker, J. W., & Tomecek, J. M. (2019). Spatial relationships between livestock guardian dogs and mesocarnivores in central Texas. HUMAN-WILDLIFE INTERACTIONS. 13(1), 29-41.
Garnick, S., Barboza, P. S., & Walker, J. W. (2018). Assessment of Animal-Based Methods Used for Estimating and Monitoring Rangeland Herbivore Diet Composition. Rangeland Ecology and Management. 71(4), 449-457.
Walker, J. W., Stewart, W. C., Pope, R., Spear, S. L., Ebert, M., & Murphy, T. W. (2018). Evaluation of mean fiber diameter measurements by FibreLux micron meter and OFDA2000 in Texas and Intermountain west wool. Small Ruminant Research. 159, 31-37.
Altangerel, N., Walker, J. W., Gonzalez, P. M., Bailey, D. W., Estell, R. E., & Scully, M. O. (2017). Comparison of Near Infrared Reflectance Spectroscopy and Raman Spectroscopy for Predicting Botanical Composition of Cattle Diets. Rangeland Ecology and Management. 70(6), 781-786.
Stewart, W. C., Whitney, T. R., Scholljegerdes, E. J., Hallford, D. M., Walker, J. W., Adams, R. P., & Naumann, H. D. (2017). Effects of feeding ground redberry juniper (Juniperus pinchotii) to gestating ewes on pre- and postpartum performance, serum metabolites and hormones, milk fatty acid composition, and progeny preweaning performance.. Journal of Animal Science. 95(9), 4113-4123.
Stewart, W. C., Whitney, T. R., Scholljegerdes, E. J., Hallford, D. M., Walker, J. W., Adams, R. P., & Naumann, H. D. (2017). Effects of feeding ground redberry juniper (Juniperus pinchotii) to gestating ewes on pre- and postpartum performance, serum metabolites and hormones, milk fatty acid composition, and progeny preweaning performance. Journal of Animal Science. 95(9), 4113-4123.
Stewart, W. C., Whitney, T. R., Scholljegerdes, E. J., Naumann, H. D., Cherry, N. M., Muir, J. P., ... Estell, R. E. (2015). Effects of Juniperus species and stage of maturity on nutritional, in vitro digestibility, and plant secondary compound characteristics. Journal of Animal Science. 93(8), 4034-4047.
Stewart, W. C., Whitney, T. R., Scholljegerdes, E. J., Naumann, H. D., Cherry, N. M., Muir, J. P., ... Estell, R. E. (2015). Effects of Juniperus species and stage of maturity on nutritional, in vitro digestibility, and plant secondary compound characteristics.. Journal of Animal Science. 93(8), 4034-4047.
Walker, J. W., Waldron, D. F., Campbell, E. S., Taylor, C., Lupton, C. J., & Landau, S. (2013). Intermediate Periodicities in Juniper Consumption and Sampling Strategies to Estimate the Diet of Free-Grazing Goats. 66(2), 209-215.
Frost, R., Walker, J., Madsen, C., Holes, R., Lehfeldt, J., Cunningham, J., ... Sullivan, J. (2012). Targeted Grazing: Applying the Research to the Land. Rangelands. 34(1), 2-10.
Glasser, T. A., Landau, S. Y., Ungar, E. D., Perevolotsky, A., Dvash, L., Muklada, H., Kababya, D., & Walker, J. W. (2012). Foraging selectivity of three goat breeds in a Mediterranean shrubland. Small Ruminant Research. 102(1), 7-12.
Surber, L., Rude, M. E., Roeder, B. L., Mosley, T. K., Grove, A. V., Walker, J. W., & Kott, R. W. (2011). Percent Spotted Knapweed (Centaurea stoebe) in the Diets of Grazing Sheep. Invasive Plant Science and Management. 4(1), 95-101.
Campbell, E. J., Frost, R. A., Mosley, T. K., Mosley, J. C., Lupton, C. J., Taylor, C. A., ... Musser, J. (2010). Pharmacokinetic differences in exposure to camphor after intraruminal dosing in selectively bred lines of goats.. Journal of Animal Science. 88(8), 2620-2626.
Wilcox, B. P., Walker, J. W., & Heilman, J. L. (2010). Commentary on "Effect of brush control on evapotranspiration in the North Concho River watershed using the eddy covariance technique" by Saleh et al. (2009). Journal of Soils and Water Conservation. 65(4), 83A-84A.
Hanovice-Ziony, M., Gollop, N., Landau, S. Y., Ungar, E. D., Muklada, H., Glasser, T. A., Perevolotsky, A., & Walker, J. W. (2010). No major role for binding by salivary proteins as a defense against dietary tannins in Mediterranean goats.. Journal of Chemical Ecology. 36(7), 736-743.
Utsumi, S. A., Cibils, A. F., Estell, R. E., Baker, T. T., & Walker, J. W. (2010). One-Seed Juniper Sapling Use by Goats in Relation to Stocking Density and Mixed Grazing With Sheep. Rangeland Ecology and Management. 63(3), 373-386.

SDG 3
Bailey, D. W., Thomas, M. G., Walker, J. W., Witmore, B. K., & Tolleson, D. (2010). Effect of Previous Experience on Grazing Patterns and Diet Selection of Brangus Cows in the Chihuahuan Desert. Rangeland Ecology and Management. 63(2), 223-232.
Glasser, T. A., Ungar, E. D., Landau, S. Y., Perevolotsky, A., Muklada, H., & Walker, J. W. (2009). Breed and maternal effects on the intake of tannin-rich browse by juvenile domestic goats (Capra hircus). Applied Animal Behaviour Science. 119(1-2), 71-77.
Waldron, D. F., Taylor, C. A., Walker, J. W., Campbell, E. S., Lupton, C. J., Willingham, T. D., & Landau, S. Y. (2009). Heritability of juniper consumption in goats.. Journal of Animal Science. 87(2), 491-495.
Musser, J., Taylor, C. A., Guo, J., Tizard, I. R., & Walker, J. W. (2008). Development of a contagious ecthyma vaccine for goats.. American Journal of Veterinary Research. 69(10), 1366-1370.

SDG 3
Wilcox, B. P., Huang, Y., & Walker, J. W. (2008). Long-term trends in streamflow from semiarid rangelands: uncovering drivers of change. 14(7), 1676-1689.

SDG 15
Glasser, T., Landau, S., Ungar, E. D., Perevolotsky, A., Dvash, L., Muklada, H., Kababya, D., & Walker, J. W. (2008). A fecal near-infrared reflectance spectroscopy-aided methodology to determine goat dietary composition in a Mediterranean shrubland.. Journal of Animal Science. 86(6), 1345-1356.
Campbell, E. S., Taylor, C. A., Walker, J. W., Lupton, C. J., Waldron, D. F., & Landau, S. Y. (2007). Effects of supplementation on juniper intake by goats. Rangeland Ecology and Management. 60(6), 588-595.
Fraker-Marble, M. J., Launchbaugh, K. L., & Walker, J. W. (2007). Differences in Food Ingestion and Digestion Among Sheep Classified as High or Low Sagebrush Consumers. Rangeland Ecology and Management. 60(2), 191-194.
Kronberg, S. L., & Walker, J. W. (2007). Learning through foraging consequences: A mechanism of feeding niche separation in sympatric ruminants. Rangeland Ecology and Management. 60(2), 195-198.
Walker, J. W., Campbell, E. S., Lupton, C. J., Taylor, C. A., Waldron, D. F., & Landau, S. Y. (2007). Effects of breed, sex, and age on the variation and ability of fecal near-infrared reflectance spectra to predict the composition of goat diets.. Journal of Animal Science. 85(2), 518-526.
Landau, S., Glasser, T., Muklada, H., Dvash, L., Perevolotsky, A., Ungar, E. D., & Walker, J. W. (2005). Fecal NIRS prediction of dietary protein percentage and in vitro dry matter digestibility in diets ingested by goats in Mediterranean scrubland. Small Ruminant Research. 59(2-3), 251-263.
Ellis, C. R., Jones, R. E., Scott, C. B., Taylor, C. A., Walker, J. W., & Waldron, D. F. (2005). Sire Influence on Juniper Consumption by Goats. Rangeland Ecology and Management. 67(3), 324-328.
Frost, R. A., Scott, C. B., Walker, J. W., & Hartmann, F. S. (2003). Effects of origin, experiences early in life, and genetics on bitterweed consumption by sheep. Applied Animal Behaviour Science. 84(4), 251-264.
Johnson, D. A., Saliendra, N. Z., Walker, J. W., & Hendrickson, J. R. (2003). Bowen Ratio versus Canopy Chamber CO 2 Fluxes on Sagebrush Rangeland. Journal of Range Management. 56(5), 517-517.
Walker, J. W., McCoy, S. D., Launchbaugh, K. L., Fraker, M. J., & Powell, J. (2002). Calibrating Fecal NIRS Equations for Predicting Botanical Composition of Diets. Journal of Range Management. 55(4), 374-374.
Stellflug, J. N., Hatfield, P. G., Wulster-Radcliffe, M. C., & Walker, J. W. (2001). Reproductive performance of ewe lambs from ewes from different selection practices with or without induced estrus.. Animal Reproduction Science. 66(3-4), 185-193.
Snowder, G. D., Walker, J. W., Launchbaugh, K. L., & Van Vleck, L. D. (2001). Genetic and phenotypic parameters for dietary selection of mountain big sagebrush (Artemisia tridentata Nutt. ssp. vaseyana.. Journal of Animal Science. 79(2), 486-492.
Bork, E. W., West, N. E., Price, K. P., & Walker, J. W. (1999). Rangeland Cover Component Quantification Using Broad (TM) and Narrow-Band (1.4 NM) Spectrometry. Journal of Range Management. 52(3), 249-249.
Kronberg, S. L., & Walker, J. W. (1999). Sheep preference for leafy spurge from Idaho and North Dakota. Journal of Range Management. 52(1), 39-44.
Walker, J. W., Clark, D. H., & McCoy, S. D. (1998). Fecal NIRS for Predicting Percent Leafy Spurge in Diets. Journal of Range Management. 51(4), 450-450.
Bork, E. W., West, N. E., & Walker, J. W. (1998). Cover Components on Long-Term Seasonal Sheep Grazing Treatments in Three-Tip Sagebrush Steppe. Journal of Range Management. 51(3), 293-293.
Kronberg, S. L., Lynch, W. C., Cheney, C. D., & Walker, J. W. (1995). Potential aversive compounds in leafy spurge for ruminants and rats.. Journal of Chemical Ecology. 21(10), 1387-1399.
Walker, J. W. (1995). Viewpoint: Grazing Management and Research Now and in the Next Millennium. Journal of Range Management. 48(4), 350-350.
Walker, J. W., Kronberg, S. L., Al-Rowaily, S. L., & West, N. E. (1994). Comparison of Sheep and Goat Preferences for Leafy Spurge. Journal of Range Management. 47(6), 429-429.
Kronberg, S. L., Walker, J. W., & Fitzgerald, J. A. (1993). Feeding behavior of grazing ruminants experiencing stress.. Physiology and Behavior. 54(6), 1191-1194.
Kronberg, S. L., & Walker, J. W. (1993). Ruminal metabolism of leafy spurge in sheep and goats: A potential explanation for differential foraging on spurge by sheep, goats, and cattle.. 19(9), 2007-2017.
Hatfield, P. G., Walker, J. W., Fitzgerald, J. A., Glimp, H. A., & Hemenway, K. J. (1993). The effects of different methods of estimating fecal output on plasma cortisol, fecal output, forage intake, and weight change in free-ranging and confined wethers.. Journal of Animal Science. 71(3), 618-624.
Walker, J. W., Hemenway, K. G., Hatfield, P. G., & Glimp, H. A. (1992). Training Lambs to Be Weed Eaters: Studies with Leafy Spurge. Journal of Range Management. 45(3), 245-245.
MCKOWN, C. D., WALKER, J. W., STUTH, J. W., & HEITSCHMIDT, R. K. (1991). NUTRIENT INTAKE OF CATTLE ON ROTATIONAL AND CONTINUOUS GRAZING TREATMENTS. Journal of Range Management. 44(6), 596-601.
Hatfield, P. G., Walker, J. W., Glimp, H. A., & Adams, D. C. (1991). Effect of level of intake and supplemental barley on marker estimates of fecal output using an intraruminal continuous-release chromic oxide bolus.. Journal of Animal Science. 69(4), 1788-1794.
BAILEY, D. W., WALKER, J. W., & RITTENHOUSE, L. R. (1990). SEQUENTIAL-ANALYSIS OF CATTLE LOCATION - DAY-TO-DAY MOVEMENT PATTERNS. Applied Animal Behaviour Science. 25(1-2), 137-148.
WALKER, J. W., & HEITSCHMIDT, R. K. (1989). SOME EFFECTS OF A ROTATIONAL GRAZING TREATMENT ON CATTLE GRAZING BEHAVIOR. Journal of Range Management. 42(4), 337-342.
WALKER, J. W., HEITSCHMIDT, R. K., DEMORAES, E. A., KOTHMANN, M. M., & DOWHOWER, S. L. (1989). QUALITY AND BOTANICAL COMPOSITION OF CATTLE DIETS UNDER ROTATIONAL AND CONTINUOUS GRAZING TREATMENTS. Journal of Range Management. 42(3), 239-242.
WALKER, J. W., HEITSCHMIDT, R. K., & DOWHOWER, S. L. (1989). SOME EFFECTS OF A ROTATIONAL GRAZING TREATMENT ON CATTLE PREFERENCE FOR PLANT-COMMUNITIES. Journal of Range Management. 42(2), 143-148.
WALKER, J. W., STUTH, J. W., & HEITSCHMIDT, R. K. (1989). A SIMULATION APPROACH FOR EVALUATING FIELD DATA FROM GRAZING TRIALS. Agricultural Systems. 30(4), 301-316.
WALKER, J. W., & HEITSCHMIDT, R. K. (1986). EFFECT OF VARIOUS GRAZING SYSTEMS ON TYPE AND DENSITY OF CATTLE TRAILS. Journal of Range Management. 39(5), 428-431.
WALKER, J. W., STUTH, J. W., HEITSCHMIDT, R. K., & DOWHOWER, S. L. (1985). A NEW ESOPHAGEAL PLUG. Journal of Range Management. 38(2), 185-187.
WALKER, J. W., HEITSCHMIDT, R. K., & DOWHOWER, S. L. (1985). EVALUATION OF PEDOMETERS FOR MEASURING DISTANCE TRAVELED BY CATTLE ON 2 GRAZING SYSTEMS. Journal of Range Management. 38(1), 90-93.

Chapters1

Muir, J. P., Butler, T. J., & Ocumpaugh, W. R. (2005). Pastoral systems in marginal environments, Proceedings of a satellite workshop of the XXth International Grassland Congress, July 2005, Glasgow, Scotland. Milne, J. A. (Eds.), Pastoral Systems in Marginal Environments: Proceedings of a Satellite Workshop of the XXth International Grassland Congress, July 2005, Glasgow, Scotland. 107-79. Wageningen Academic Publishers.