Jerry W. Stuth

Fecal NIRS equations for predicting diet quality of free-ranging cattle.

The usefulness of near infrared reflectance spectroscopy (NIRS) for predicting diet quality of free-ranging cattle through fecal analysis was examined. Diet samples were obtained with esophageal fistulated steers; subsequently, study areas were grazed with nonfistulated lactating and dry cows to provide fecal samples representing differing forage diet quality. Diet samples, which were analyzed by conventional laboratory procedures for in vivo corrected digestible organic matter (DOM) and crude protein (CP), provided dependent variable reference data while fecal sample spectra provided independent variable data for development of NIRS predictive equations by stepwise regression. Equations were developed from a data set at one location with subsequent equation development using expanded data ranges obtained by adding samples from a second location. Standard errors of calibration (SEC) and validation (SEV) for the DOM equation developed from the expanded data range were 1.66 and 1.65, respectively; these values were nearly equivalent to the laboratory standard error (SEL) of 1.68. SEC and SEV for the CP equation developed from the expanded data range were 0.89 and 0.93, respectively, compared to the 0.44 SEL. Coeffkients of determination for DOM and CP equations were 0.80 and 0.92, respectively. These statistical parameters developed from fecal spectra to predict forage diet quality are equal to or better than statistics reported in the literature for NIRS equations developed using forage spectra. Furthermore, equation standard errors were within acceptable limits for NIRS calibrations. No effects of physiological stage of animals on calibration were noted in this study. Results are interpreted to This manuscript was published with the approval of the Director, Texas Agricultural Experiment Station, Texas AM Evelyn Kapes for work in the laboratory; Drs. J.E. Huston, J.W. Holloway, and C.W. HanL and the Behmann Foundation, Corpus Christi, Texas, for providing funds to support this research. Manuscnpt accepted 5 Sept. 1991.

Direct and indirect means of predicting forage quality through near infrared reflectance spectroscopy

The advent of NIRS technology for assessing quality of plant/forage/feed tissue and predicting diet quality from feces offers livestock nutritionists, researchers, farm advisors and resource consultants a rapid mechanism to acquire nutritional information. The portability and low long-term maintenance costs of this technology coupled with rapid turn around time on processing offers a mechanism for nutrition programs to address forage and dietary quality issues that were limited due to high maintenance costs of wet chemistry laboratories. The fundamentals of NIRS technology and associated development of calibration equations are discussed along with methods to validate equations. Direct methods for tissue analysis and indirect methods to predict diet quality from feces are reviewed for major constituents found in forages, including crude protein, digestibility, tannins and minerals.

Fecal NIRS equations to assess diet quality of free-ranging goats

Abstract Research was conducted to evaluate the predictability of the nutritional status of free-ranging goats through analysis of fecal material by near infrared reflectance spectroscopy (NIRS). Diet samples were collected from esophageally fistulated goats, whereas fecal samples were obtained from nonfistulated animals grazing the study areas. Percentage of crude protein (CP) and standard corrected in vitro digestible organic matter (DOM) were determined for diet samples. The resulting diet reference data and the fecal spectra were used to develop predictive equations. Standard errors of calibration (SEC) for CP and DOM were 1.12 and 2.02, being within acceptable limits for NIRS. Coefficients of determination ( R 2 ), were 0.94 and 0.93 for CP and DOM, respectively. Validation trials, performed in post oak woodlands and subtropical thornshrub regions of Texas, indicated that the selected CP and DOM equations can be useful in predicting the nutritional status of goats under different rangeland conditions.

How herbivory affects grazing tolerant and sensitive grasses in a central Texas grassland: integrating plant response across hierarchical levels

The hypothesis that herbivore selectivity, rather than plant response to defoliation, is the overriding factor in determining community level responses to grazing was tested in a Texas grassland. We monitored defoliation intensity and subsequent regrowth and reproduction of herbaceous dominants Schizachyrium scoparium and Paspalum plicatulum at the individual tiller, population, and community levels of organization. While long-term observations indicate that Schizachyrium declines and Paspalum increases in response to herbivory, individual Schizachyrium tillers exhibited little response to any level of defoliation and were able to fully compensate for lost tissue on a seasonal basis (...)

Switchgrass recruitment from broadcast seed vs. seed fed to cattle.

Fecal seeding by livestock may be an effective, low-cost means of rangeland restoration. We compared recruitment of switchgrass (Panicum virgatum L.) from seed fed to cattle and deposited in dung to that of broadcast-seeded plots receiving a comparable number of unfed seed. Although germinability of seed passed through livestock (52 to 62%) was reduced relative to that of broadcast seed (85 to 91%), recruitment of switchgrass from seed in cattle feces was equal to or superior to that of broadcast seed in terms of establishment (frequency of occurrence and density), plant growth and final plant sire. The frequency of plots with emerging switchgrass plants ranged from 62 to 100% when seeds were delivered in feces, but only 2 to 40% when seeds were broadcast. After 1 year, the frequency of occurrence of switchgrass plants in fecal vs. broadcast-seeded plots was comparable for autumn trials. However, evaluations 1 year after the spring trials continue to result in higher frequency of plots with switchgrass plants from seed delivered in feces than of broadcast seedings (56 vs. 4% for May 1990, PcO.05; and 90 vs. 51% for May 1991, PI 0.01). Enhanced plant recruitment on fecal-seeded plots occurred even though broadcast-seeded plots received 1.5 to 1.7 times more pure five seed (PLS). Plants on fecal-seeded plots had a greater plant size score (based on visual ratings of height, cuhn density, and biomass) than plants on broadcast-seeded plots (P O.lO for October 1991). Results suggest significant advantages of fecal seeding over conventional broadcast seeding in terms of seedling emergence, establishment and growth

Influence of range site on diet selection and nutrient intake of cattle.

It is common in range science to base stocking rate estimates on range sites as units of forage production. However, little is known about how diet composition, quality, and intake may differ by range site. This study examines the influence of 2 range sites on the diet selection and nutrient intake of cattle. A sandy loam (SL) and a clay loam (CL) range site were compared in 4 seasonal, trials on an Acacia dominated, mixed-brush savanna on the Texas Rio Grande Plains. Diet composition and quality, and nutrient intake of cattle were determined throughout each 16-21 day trial using esophageally fistulated cattle and daily dosing with ytterbium acetate. The range sites differed widely in proportions of grass, forb, and browse biomass. Cattle generally selected similar diets and adjusted diets to increasing grazing pressure and decreasing forage availability in a similar manner regardless of site, except in fall when cattle selected more browse on the SL site where herbaceous forage was severely limited. Fecal output of cattle differed between sites only in fall when cattle on the SL site had lower fecal output than cattle on the CL site. Cattle on the site of lower herbaceous mass (SL site) generally achieved higher diet quality and nutrient intake during the growing season, when herbaceous forage was readily available because of greater access to green forage. Therefore, the SL site yielded higher diet quality at low grazing pressure during the growing season. Conversely, the CL site, because of its greater herbaceous mass, yielded higher nutrient intake in the fall and at high levels of grazing pressure.

Improving Estimates of Rangeland Carbon Sequestration Potential in the US Southwest

Abstract Rangelands make an important contribution to carbon dynamics of terrestrial ecosystems. We used a readily accessible interface (COMET VR) to a simulation model (CENTURY) to predict changes in soil carbon in response to management changes commonly associated with conservation programs. We also used a subroutine of the model to calculate an estimate of uncertainty of the model output based on the similarity between climate, soil, and management history inputs and those used previously to parameterize the model for common land use (cropland to perennial grassland) and management (stocking rate reductions and legume addition) changes to test the validity of the approach across the southwestern United States. The conversion of small grain cropland to perennial cover was simulated acceptably (< 20% uncertainty) by the model for soil, climate, and management history attributes representative of 32% of land area currently in small grain production, while the simulation of small grain cropland to perennial cover + legumes was acceptable on 73% of current small grain production area. The model performed poorly on arid and semiarid rangelands for both management (reduced stocking) and restoration (legume addition) practices. Only 66% of land area currently used as rangeland had climate, soil, and management attributes that resulted in acceptable uncertainty. Based on our results, it will be difficult to credibly predict changes to soil carbon resulting from common land use and management practices, both at fine and coarse scales. To overcome these limitations, we propose an integrated system of spatially explicit direct measurement of soil carbon at locations with well-documented management histories and climatic records to better parameterize the model for rangeland applications. Further, because the drivers of soil carbon fluxes on rangelands are dominated by climate rather than management, the interface should be redesigned to simulate soil carbon changes based on ecological state rather than practice application.

Value of multiple fecal indices for predicting diet quality and intake of steers.

The relationship of fecal nitrogen fractions and condensed tannins dietary crude protein, in vitro organic matter digestibility, and intake of steers was assessed to determine the suitability of these multiple fecal indices for predicting quality of animal diets under free-roaming conditions. Research was conducted on the Texas A&M Native Plant and Animal Conservancy near College Station, located in the Post Oak Savannah region of Texas. Regression equations were used to evaluate relationships between dietary intake and quality to fecal variables. Dietary crude protein, digestible organic matter, organic matter intake, crude protein intake, and digestible energy intake were determined from previous studies. Corresponding fecal samples were analyzed for absolute output, proportions, and concentrations of nitrogen and selected fractions of fecal organic matter, as well as fecal condensed tannins, proportions of fecal monocot and dicot fragments, and fecal organic matter. In general, no fecal parameter by itself had a high correlation with dietary variables when expressed on a proportion or concentration basis. A combination of fecal indexes accounted for more variation in dietary parameters than fecal nitrogen. Fecal nitrogen fractions did not improve the predictive power of multiple variable models. Equations predicting dietary crude protein (%) and crude protein intake yielded the highest coefficients of determination (R2 = .57 and .51, respectively). Multiple fecal indices used in this study were of limited value in predicting diet quality and intake.

Nutrient intake of cattle on rotational and continuous grazing treatments.

Many benefits have been obtained from rotational grazing, including management flexibility and livestock distribution, but long-term positive effects on plant and animal production have been inconsistent. The purpose of this cast study was to investigate nutrient intake of animals in 2 production scale grazing, treatments. The study site was the Texas Experimental Ranch located in Throckmorton County, in the eastern portion of the Rolling Plains of Texas. Treatments were a 465-ha, 16-paddock, 1-herd, cell designed rotational grazing system (RG) stocked at a heavy rate (3.7 ha . cow-1 . yr-1) and a 248-ha continuously grazed (CG) treatment stocked at a moderate rate (6.2 ha . cow-1 . yr-1). Size of RG paddocks was varied to create different livestock densities to simulate rotational grazing at a 14 and 42 paddock level. Comparisons were made to determine the effect of type of grazing system (RG vs. CG) and the effect of livestock density within the RG system on nutrient intake. Nutrient intake of esophageally fistulated steers was determined by daily dosing them with ytterbium nitrate-labeled forage and collection of fecal samples plus collection of fistula extrusa samples for crude protein and in vitro organic matter digestibility determinations. The only difference caused by different livestock densities was a higher (P < 0.001) intake of forage crude protein in the simulated 42 paddock system. Nutrient intake of steers in the CG treatment was greater (P < 0.001) than those in the RG treatment. Differences between treatment were attributed primarily to differences in stocking rate rather than grazing system.

Insights in development and deployment of the GLA and NUTBAL decision support systems for grazinglands

Abstract The evolution of two decision support systems are traced from their roots in academia to deployment to technical advisors in USDA Natural Resource Conservation Service. The Grazing Lands Application (GLA) decision support system (DSS) was designed to provide forage inventories for grazing management of ranches. The other tool, NUTBAL, evolved as a stand alone DSS, emerging as a component of GLA when a supporting monitoring technology for nutritional profiling of free-ranging animals provided the user rapid estimates of diet quality from fecal scans with near infrared reflectance spectroscopy (NIRS). The adoption pattern of GLA and NUTBAL were quite different, with GLA experiencing less widespread adoption in USDA NRCS. The primary causes were (1) limited adoption rate of GLA within NRCS associated with changing culture in the information technology development group, (2) time overloading and staff reassignments for new programs, (3) changing software/hardware development environments imposed by the client disrupting development and system design and (4) large up front conversion of a largely paper-based system to a digital form. GLA was transformed to web-based delivery and streamlined to gain greater acceptance by users and ease time constraints on use of spatial tools. The NUTBAL system experienced more of a user driven evolution since it emerged from the GLA suite of tools and was supported by on-ranch monitoring systems capability of directly linking the livestock producers animals with the software. NUTBALs linkage to animal monitoring systems seems to have accelerated adoption rates. Ease of access to supporting input data coupled with early involvement of the target user and extensive analysis of the decision environment were critical to future success of these systems. Targeting technical advisors instead of livestock producers appears to be a more viable development track unless new innovations in DSS delivery systems can emerge using the internet.