Grazing Wheat Research Articles

A Wheat Grazing Model for Simulating Grain and Beef Production: Part I—Model Development

It is a common practice to grow winter wheat (Triticum aestivum L.) as a dual‐purpose crop in the U.S. Southern Great Plains to decrease production risk and to increase profit margin through cattle (Bos taurus) production. Crop management of the dual‐purpose wheat is complex because of the tradeoffs between beef production and wheat grain yield. A wheat grazing model helps in making optimal decision. The objective of this study was to develop and incorporate a grazing and metabolizable energy‐based cattle growth module into the Decision Support Systems for Agrotechnology Transfer (DSSAT) to simulate beef and wheat grain production. The wheat grazing model was comprised of wheat growth, wheat–cattle interaction, and cattle growth components. Wheat growth was simulated by the cropping system model (CSM) of DSSAT. For the wheat–cattle interface, removals of canopy biomass and leaf area by grazing were estimated daily. Predicted grain yield was also reduced by 50 kg ha−1 per day for each day of grazing past the first hollow stem stage. Cattle growth rate was based on a metabolizable energy intake. Maximum voluntary daily intake was estimated based on stocker body weight and forage quality, and is further adjusted for actual forage availability, temperature, and adaptation status during the first 14 d of grazing to estimate the actual daily intake. Changes in wheat growth processes brought about by grazing, including a grazing effect on the delay of plant phenological development, are not simulated in the model. Field experiments to characterize any such effects are needed to help fine‐tune the model.

A Wheat Grazing Model for Simulating Grain and Beef Production: Part II—Model Validation

Computer models must be thoroughly evaluated before being used for decision‐making. The objective of this paper is to evaluate the ability of a newly developed wheat grazing model to predict fall–winter forage and winter wheat (Triticum aestivum L.) grain yield as well as daily weight gains of steer (Bos taurus) grazing on wheat pasture in Oklahoma. Experimental data of three independent field studies were used. The first was a variety trial in which fall–winter forage and grain yields were harvested. The second was a planting date experiment in which forage in the fall–winter period and grain yields were harvested. The third was a steer grazing experiment in which standing wheat biomass and steer weight gain were monitored. For the variety trials, the model efficiency (ME), which reflects how well model predictions match measured data (1 means a perfect match), was 0.102 for fall–winter forage prediction and 0.367 for grain yield. For the planting date experiment, the ME was 0.615 for predicting fall–winter forage yields and 0.409 for grain yields when a root downward extension rate of 20 mm d−1 was used. In the steer grazing experiment, the relationship between average daily weight gain and forage allowance was adequately represented by the model. For the total steer weight gains in a wide range of stocking rates and grazing durations, the ME was 0.616. Overall results show that the model, if well calibrated, has the potential to predict fall–winter forage and grain yields as well as mean daily weight gain per steer.

Performance, Carcass Characteristics, and Economic Analysis of Calf-Fed and Wheat Pasture Yearling Systems in the Southern Great Plains

AbstractModerate-framed Angus steers from a single cow herd were utilized in a 2-yr study that evaluated performance, carcass traits, and production economics of calf-fed vs. yearling systems. After a brief preconditioning period, weaned steer calves were placed on a high concentrate finishing diet (CF; n = 63) or grazed wheat pasture 164 d before feedlot entry (YF; n = 62). Resulting feedlot entry weight and days on feed were 228kg and 169 d, respectively, for CF and 445kg and 88 d, respectively, for YF. Final BW for YF was 87kg heavier than CF (P < 0.01). For YF, ADG and DMI was greater and G:F was less than CF steers (P < 0.05). Hot carcass weight was 55kg greater and LM area was 8cm2 larger for YF compared with CF steers (P < 0.01). Dressing percentage was not different between systems (P = 0.90). System did not affect 12th-rib fat, USDA YG, or marbling score (P > 0.27). Profitability tended (P = 0.09) to favor the CF over the YF system, although breakeven selling price was greater (P < 0.01) for CF vs. YF. Live and carcass price was greater (P = 0.02) for the CF system. Net profit for CF and YF was not different (P > 0.10) when quality or yield grid markets were applied. Inclusion of a long-term winter wheat grazing period increased hot carcass weight by 17% with no detrimental effects on carcass characteristics.

Effect of fat supplementation and wheat pasture maturity on forage intake and digestion characteristics of steers grazing wheat pasture1

Nine ruminally cannulated mixed-breed steers were used in a split-plot design to evaluate effects of fat supplementation and forage maturity on intake, digestibility, and ruminal fermentation. Treatment was the main plot, and stage of forage maturity was the subplot. Treatments were supplements containing mineral pack (M) offered at 114 g/d; M plus fiber as soybean hulls-wheat middlings (MF) offered at 0.50% BW; and MF plus tallow (MFT) offered at 0.625% BW. Stages of wheat maturity were mid-March (MAR) and early April (APR). Steers grazed in a single wheat pasture with supplements offered individually at 0700 h daily. There were supplement type x forage maturity interactions (P < 0.05) for forage OM, CP, and NDF intakes. During MAR, forage OM, CP, and NDF intakes were not affected (P > 0.05) by supplementation. During APR, forage OM, CP, and NDF intakes differed (MF = M > MFT, P < 0.05). There was also supplement type x forage maturity interaction (P = 0.04) for forage OM digestibility. The OM digestibility differed during MAR (M = MF > MFT, P < 0.05) and during APR (MF > M > MFT, P < 0.05). Crude protein digestibility was affected by supplement type (M > MF > MFT, P < 0.05) and stage of forage maturity (MAR > APR, P < 0.01). Rates of DM and NDF ruminal disappearance were not affected (P > 0.05) by supplement or forage maturity. Supplementation increased (P < 0.05) ruminal propionate concentration (19.7, 21.4, and 25.1 +/- 0.49 mol/100 mol for M, MF, and MFT, respectively). Tallow can be used in supplements for cattle grazing wheat pasture to increase energy intake without negatively affecting forage intake or ruminal fermentation, particularly if used in the early stage of wheat maturity.

Stocking Rate and Supplementation of Stocker Cattle Grazing Wheat Pasture Interseeded into Bermudagrass in Northern Arkansas

During a 2-yr study, 48 steers (24/yr, initial BW = 240 ± 2.9 kg in yr 1 and 325 ± 1.6kg in yr 2) wereplaced on 8 Bermudagrass (Cynodon dactylon [L.] Pers.) pastures (1.6 ha, n = 4; 2.4 ha, n = 4) interseeded with wheat (Triticum aestivum L.), creating stocking rates of 0.81 ha/steer (LOW) or 0.54 ha/steer (HIGH). Steers in LOW pastures were offered either no supplement or were fed soybean hulls (SBH) at a rate of 0.5% of BW. Steers in HIGH were fed SBH at either 0.5 or 0.75% of BW. Bermudagrass hay was offered ad libitum to all pastures. Data were analyzed as a completely randomized design; stocking rate and supplementation treatment combinations were the main effects, pasture was the experimental unit, and year was a random effect. Final BW, total BW gain, and ADG did not differ (P ≥ 0.14). Increasing stocking rates increased (P = 0.01) grazing-d per hectare by 50% and tended (P = 0.07) to increase hay disappearance per hectare. Body weight gain per hectare tended (P = 0.09) to increase 14kg for LOW fed 0.5% BW vs. unsup plemented LOW. Increased stocking rate increased (P < 0.01) BW gain per hectare by 63% compared with unsupple-mented LOW and by 44% compared with LOW fed 0.5% BW. Results of the study indicated that feeding moderate levels of SBH to steers grazing wheat pasture will facilitate increases in stocking rate and BW gain per hectare. Furthermore, the added cost of supplementation can be partially offset by reductions in hay requirements.

In vitro bacterial growth and in vivo ruminal microbiota populations associated with bloat in steers grazing wheat forage1

The role of ruminal bacteria in the frothy bloat complex common to cattle grazing winter wheat has not been previously determined. Two experiments, one in vitro and another in vivo, were designed to elucidate the effects of fresh wheat forage on bacterial growth, biofilm complexes, rumen fermentation end products, rumen bacterial diversity, and bloat potential. In Exp. 1, 6 strains of ruminal bacteria (Streptococcus bovis strain 26, Prevotella ruminicola strain 23, Eubacterium ruminantium B1C23, Ruminococcus albus SY3, Fibrobacter succinogenes ssp. S85, and Ruminococcus flavefaciens C94) were used in vitro to determine the effect of soluble plant protein from winter wheat forage on specific bacterial growth rate, biofilm complexes, VFA, and ruminal H2 and CH4 in mono or coculture with Methanobrevibacter smithii. The specific growth rate in plant protein medium containing soluble plant protein (3.27% nitrogen) was measured during a 24-h incubation at 39 degrees C in Hungate tubes under a CO2 gas phase. A monoculture of M. smithii was grown similarly, except under H2:CO2 (1:1), in a basal methanogen growth medium supplemented likewise with soluble plant protein. In Exp. 2, 6 ruminally cannulated steers grazing wheat forage were used to evaluate the influence of bloat on the production of biofilm complexes, ruminal microbial biodiversity patterns, and ruminal fluid protein fractions. In Exp. 1, cultures of R. albus (P < 0.01) and R. flavefaciens (P < 0.05) produced the most H2 among strains and resulted in greater (P < 0.01) CH4 production when cocultured with M. smithii than other coculture combinations. Cultures of S. bovis and E. ruminantium + M. smithii produced the most biofilm mass among strains. In Exp. 2, when diets changed from bermudagrass hay to wheat forage, biofilm production increased (P < 0.01). Biofilm production, concentrations of whole ruminal content (P < 0.01), and cheesecloth filtrate protein fractions (P < 0.05) in the ruminal fluid were greater on d 50 for bloated than for nonbloated steers when grazing wheat forage. The molecular analysis of the 16S rDNA showed that 2 different ruminal microbiota populations developed between bloated and nonbloated animals grazing wheat forage. Bloat in cattle grazing wheat pastures may be caused by increased production of biofilm, resulting from a diet-influenced switch in the rumen bacterial population.

Case Study: Changes in Body Weight, Fill, and Shrink of Calves Grazing Wheat Pasture in the Winter and Spring

AbstractAlthough wheat pasture (Triticum aestivum L.) contains high concentrations of digestible CP and DM, calves may have very low or negative BW gains until they can adapt to this new nutrientrich diet. The objectives of these experiments were to determine changes in BW in stocker calves during the first 28-d period of grazing wheat pasture in the winter and spring and the impact of grazing wheat pasture on the amount of fill lost during fasting. During the spring grazing season, the adaptation period was much shorter than during the winter grazing season. During the winter grazing season, calves grazing wheat forage for the first time had negative BW gains for the first 14 d, but positive BW gains the next 14 d. By d 28 of the winter grazing season, the amount of BW lost during a 16-h fast was less (P < 0.01) for calves on wheat pasture as compared to calves in dry lot (3.99% of BW vs. 5.73% of BW), indicating that they had less GI tract fill. From these data, it is concluded that stocker calves need 14 to 20 d toadjust to the unique chemical com-position of wheat forage during the winter season and less than 14 d in the spring season. Pre-grazing management practices that reduce the duration of the adaptation period will increase overall performance of growing calves.

Comparison of Interseeding Lespedeza with Additional Nitrogen Fertilization on Forage Production and Steer Performance in a Wheat-Crabgrass Grazing System

Grazing and subsequent finishing performance of steers (Bos taurus) grazed on a wheat (Triticum aestivum L.)-crabgrass [Digitaria ciliaris (Retz) Koel.] system were evaluated in 1999, 2000, and 2001 to compare interseeding lespedeza (Lespedeza stipulacea Maxim.) with an additional application of N fertilizer. Hard red winter wheat was no-till seeded in fall 1998, 1999, and 2000 in pastures previously seeded to ‘Red River’ crabgrass. In early spring 1999, 2000, and 2001, additional crabgrass seed was broadcast over all pastures, and Korean lespedeza was no-till seeded in 4 pastures. All pastures received similar applications of fertilizer; however, 3 pastures not seeded with lespedeza received an additional 56kg of N/ha in mid July. Wheat grazing was initiated in mid to late March of each year. Following wheat graze-out, cattle remained on the pastures and grazed crabgrass from mid May until early September. Legume cover, forage DM production, grazing steer performance, and subsequent finishing performance were measured. Available forage DM and grazing BW gains were similar (P > 0.05) between pastures fertilized with additional N and those interseeded with lespedeza. Although there were no treatment differences (P > 0.05), there were significant (P < 0.05) year effects on BW gains. Overall grazing ADG for the wheat-crabgrass system were 0.74, 1.02, and 0.99 kg/d during 1999, 2000, and 2001, respectively. Forage production, BW grazing gains, and subsequent finishing gains were similar (P > 0.05) when pastures in a wheat-crab-grass grazing system were interseeded with lespedeza or fertilized with additional N. However, there were significant (P < 0.05) treatment x year interactions during the finishing phase.

Effect of feed additives on in vitro and in vivo rumen characteristics and frothy bloat dynamics in steers grazing wheat pasture

Research was conducted to determine the potential efficacy of feed additives (FA) to mitigate frothy bloat in yearling cattle grazing wheat pasture. Two experiments were conducted to: (1) quantify in vitro effect of FA on total rumen and methane gas production and foam potential and (2) quantify the influence of FA on rumen protein characteristics, bloat potential and weight gain of steers grazing wheat pasture. In Exp 1, duplicated analyses of in vitro gas production were measured as sequential plunger displacement (cc) at 0, 1, 2, 3, 4, 5, and 6 h incubation periods. In vitro rumen foam production and strength was measured at 0, 2, and 6 h incubation of minced wheat forage. In Exp 2, eight ruminally cannulated steers (386 ± 35.8 kg/steer) were randomly allocated to one of four FA treatments that included control, monensin, poloxalene, and condensed tannins (CT). Treatments were administered daily through rumen cannulla as pre-mixes with a mixed ration (300 mg/steer/day; as-fed basis). Steers grazed on wheat during a 2-week adaptation period prior to data collection from 05 March to 12 April, 2004. Rumen contents were collected 2 h post-FA infusion (1030 to 1130 h) on day −5, 0, 5, 15, and 22. Cattle were weighed at 28-days intervals. Bloat was visually scored weekly. In Exp 1, in vitro ruminal gas and methane gas production per gram of forage were similar between control and poloxalene, but were lower for monensin ( P<0.01) and CT ( P<0.05) treatments. The lowest ( P<0.01) in vitro foam strength occurred with the addition of poloxalene and the highest occurred in control and monensin treatments. CT was intermediate in rumen foam strength. Mean bloat score was lower in poloxalene and CT than that in monensin and control treatments. Among six-rumen protein components assayed, steers receiving CT after 10, 15, and 22 day had greater protein concentrations in whole rumen content, particulate matter, cheese-cloth filtrate, and protozoa and plant particle fractions than steers fed other treatments. Bacterial and cell-free supernatant protein fractions were comparable among treatments. Ruminal dry matter (DM) content, cell-free supernatant, protozoal and bacterial fractions were similar between the bloated and non-bloated steers. In bloated animals, ruminal pH was lower, and whole rumen content and cheese-cloth filtrate protein fractions tended to be greater ( P=0.08) than in non-bloated animals. Animal average daily gain (ADG) was not affected by FA during experimental period. The results of this trial suggest that wheat pasture bloat was associated with dietary protein and low ruminal pH. Feeding FA can be used to decrease either ruminal gas or foam production or both, and it may protect against the incidence of frothy bloat.

Designing supplements for stocker cattle grazing wheat pasture,

Abstract Supplementation of cattle grazing wheat pasture is of interest to 1) provide a more balanced nutrient supply and feed additives such as ionophores or bloat preventive compounds, 2) substitute supplement for forage where it is desirable to increase stocking rate in relation to grazing management and/or marketing decisions, and 3) substitute supplement for forage under conditions of low forage standing crops. Two different strategies for providing energy supplements to growing cattle on wheat pasture are presented. One was to develop a “small package” (i.e., target intake of 0.91 to 1.36 kg/d on an as-fed basis), self-limited monensin-containing energy supplement to provide additional degradable OM relative to rumen degradable N and increase nonammonia N supply per unit of ME. The supplement very consistently increased ADG by approximately 0.22 kg and increased profit by $15 to 31/steer depending on supplement cost and profit potential of the cattle. The sorghum grain-based supplement contained (as-fed basis) 4% fine mixing salt, 165 mg/kg of monensin, and 0.75% magnesium oxide. Monensin limited intake, but MgO at concentrations up to 1.75% did not limit intake. Modification of the formula for every-other-day hand-feeding resulted in similar improvements in ADG as achieved with the self-limited supplement. An additional study using small numbers of ruminally cannulated steers in a completely randomized design compared the effects of monensin or lasalocid vs. no ionophore on wheat pasture bloat. Monensin decreased (P &amp;lt; 0.05) both the incidence and severity of bloat and was more efficacious than lasalocid for prevention of bloat. A second strategy was to feed two types of energy supplements (i.e., high-starch, corn-based supplement vs. high-fiber by-product feed-based supplement) at a level of 0.75% of BW. Over the 3-yr study, mean daily supplement consumption was 0.65% of BW. This energy supplementation program increased ADG by 0.15 kg and allowed stocking rate to be increased by one-third. Type of supplement did not influence ADG, supplement conversion, or the substitution ratio of supplement for forage. Supplement conversion was approximately 5 kg of as-fed supplement•kg of increased gain−1•ha−1 and was substantially less than conversions of 9 to 10 that have traditionally been used in evaluating the economics of energy supplementation programs for wheat pasture stocker cattle.

Long-term fertilization effects on soil organic matter quality and dynamics under different production systems in semiarid Pampean soils

Soil quality can be determined by monitoring, over time, specific chemical, physical or biological properties. Agronomists have long recognized the benefits of maintaining and increasing soil organic carbon (SOC), as well as its labile or particulate (POC) and humic acid (HA) fractions. This research was aimed at the evaluation of continuous wheat (WW) and wheat-grazing (WG), non-fertilized (nf) and annually fertilized with N + P (f), effects on the quantity, quality and dynamics of the organic fractions. The soil (0–0.15 m) was sampled during 1991, 1992, 1993, 1994, 1995 and 1997. Fertilizer application increased labile organic fraction contents compared with the recalcitrant ones. Fertilization increased POC from 0.11 to 0.19% in WW and from 0.15 to 0.20% in WG, while fulvic acid carbon was increased from 0.083 to 0.167% and from 0.101 to 0.140% in WW and WG, respectively. The humified fraction quantity and quality were modified by fertilization. Quantity differences depended on production system, mainly, animal grazing activity. Changes in HA quality were related to higher labile OC content. The HA extracted from fertilized soils showed higher aliphatic and phenolic OH groups contents than unfertilized ones, associated to high labile organic fractions contents. The POC dynamics suggested a strong dependence to annual precipitation, mainly water availability during the fallow period. These results confirm the important effect of the long-term fertilization on POC content and HA quality. They could be utilized as soil quality indicators, however, soil physical and climatic conditions must be considered.

Effects of diet quality and age of meat goat wethers on early subsequent growth while grazing wheat forage

Thirty six meat goat wethers (3/4 Spanish and 1/4 Boer), born in the previous Spring (initial age and BW of 8.5 months and 17±0.6 kg) or Fall (initial age of 2.5 months and 13±0.8 kg), were used to determine effects of ad libitum consumption of different quality diets and age on early subsequent growth while grazing wheat forage. The experiment was 14 weeks long, with 9 weeks in the winter consuming prairie hay (5% CP and 71% NDF) supplemented with 0.125% BW of soybean meal (PH), alfalfa pellets (AP) or a 70% concentrate diet (CD), and 5 weeks in the spring grazing wheat forage. ADG in Period 1 (28, 54 and 81 g per day; S.E.=14.0) and Period 2 (123, 137 and 100 g per day for PH, AP and CD, respectively; S.E.=13.8) was similar among dietary treatments and greater for Spring vs. Fall wethers (Period 1: 72 vs. 37 g per day, P<0.05; Period 2: 131 vs. 108 g per day, P<0.09). There was not a discernible pattern of change in ADG as week of grazing wheat forage advanced (week 1: 65 and 22 g per day; week 2: 236 and 188 g per day; week 3: 65 and 105 g per day; week 4: 49 and 23 g per day; week 5: 249 and 215 g per day for Spring and Fall, respectively). Body composition (estimated from shrunk BW and urea space) on days 42 and 98 and composition of gain were similar among dietary treatments. Differences between ages ( P<0.05) in protein mass on day 42 (2.92 and 2.65 kg for Spring and Fall, respectively) and 98 (3.72 and 3.36 kg for Spring and Fall, respectively) were similar in magnitude, although that in fat mass on day 98 (4.60 and 3.31 kg) was considerably greater than on day 42 (2.39 and 1.96 kg for Spring and Fall, respectively). In accordance, protein accretion from day 42 to 98 was similar between ages (14.3 and 12.6 g per day for Spring and Fall, respectively; S.E.=0.86), whereas rate of fat accretion was greater ( P<0.05) for Spring vs. Fall wethers (39.6 vs. 24.1 g per day). In conclusion, the nature of the diet consumed ad libitum did not impact subsequent growth by 3/4 Spanish wethers, regardless of age, when grazing wheat forage.

Interseeding lespedeza into crabgrass pasture versus additional nitrogen fertilization on forage production and cattle performance (2003)

A total of 160 steers grazed "˜Red River' crabgrass pastures that were either fertilized with additional nitrogen (N) or interseeded with lespedeza during the summers of 1998, 1999, 2000, and 2001. Wheat was also grazed in 1999, 2000, and 2001 prior to crabgrass emergence. Legume cover, forage dry matter production, grazing steer performance, and subsequent feedlot performance were measured. Available forage dry matter and grazing steer performance were similar between pastures of crabgrass fertilized with additional N and those interseeded with lespedeza in 1998, 1999, and 2000. In 1999, finishing feed intake, finishing gain and ribeye area were higher (P<0.05) for steers that grazed pastures with lespedeza. In 2001, wheat grazing gain, overall grazing performance, finishing gain, and overall performance (grazing + finishing) were higher (P<0.05) for steers that grazed pastures fertilized with additional N. Total grazing gain per acre (wheat + crabgrass) was similar between pastures fertilized with additional N and those interseeded with lespedeza and averaged 304, 452, and 406 lb/acre in 1999, 2000, and 2001, respectively. In conclusion, the crabgrass wheat double-crop system produced satisfactory cattle performance with grazing gains being similar (P>0.05) between pastures fertilized with additional N and those interseeded with lespedeza. Therefore, economics rather than cattle performance would likely determine which option a producer might select. This study will be continued for three additional grazing seasons with no additional crabgrass being seeded to determine whether crabgrass will voluntarily re-seed itself sufficiently to sustain the system.

Irrigated Wheat Grazing and Tillage Effects on Subsequent Dryland Grain Sorghum Production

Use of conservation tillage has improved sorghum [Sorghum bicolor (L.) Moench] grain yield 10 to 20% in ungrazed wheat (Triticum aestivum L.)–fallow–sorghum production systems. Our objective in this 2‐yr field study was to develop tillage guidelines for systems where the wheat was grazed. Grazing duration on winter wheat and tillage during the fallow period preceding dryland grain sorghum were treatments on Pullman clay loam (Torrertic Paleustoll). Grazing increased surface soil compaction and reduced wheat residues. Surface soil (0–5 cm) penetration resistance was 0.36, 0.52, 0.75, and 0.92 Mpa, and wheat residue in 1996 was 6.0, 4.8, 3.5, and 1.2 Mg ha for ungrazed and early, normal, and late cattle removal dates, respectively. As a result, sorghum grain yield in 1996, an exceptionally wet season, was 7.9, 7.5, 7.0, and 3.8 Mg ha−1, respectively, with no tillage (NT). In 1997, a dry season with low runoff, only the late cattle removal with NT had reduced yield (3.4 Mg ha−1 compared with 3.9 Mg ha−1 for ungrazed NT). Use of one‐time sweep tillage early in fallow resulted in an increase in sorghum grain yield of 1.9 Mg ha−1 in 1996 for the late cattle removal treatment compared with NT, but it had no effect on yield with the normal cattle removal treatment. In 1997, one‐time sweep tillage increased yield by 0.3 Mg ha−1 with late removal. When wheat residue was ≤2.4 Mg ha−1 following grazing, sweep tillage reduced surface compaction, increased soil water at planting an average of 26 mm over 2 yr, and improved grain yield of sorghum compared with NT. If wheat residues were ≥3.5 Mg ha−1 after grazing, NT was as effective as any tillage treatment. Results agree with conservation tillage guidelines developed on ungrazed wheat.

Spatially Located Platform and Aerial Photography for Documentation of Grazing Impacts on Wheat

Goose populations that winter in Oregon's Lower Willamette Valley have increased from 25 000 to more than 250 000 birds in the last 25 years, resulting in heavy grazing of wheat and other crops. To map and document the extent and intensity of goose impacts on wheat fields, we combined rectified aerial photography with both globally positioned ground observations and vertical platform photographs. Aerial photos revealed areas of fields with sparse wheat cover while platform photos documented the cause. We estimated wheat cover in ground level photographs by ratioing red, green and blue digital numbers. From platform photographs we recorded occurrence of grazing (from grazed leaf tips), intensity of grazing (from residual plant cover and leaf length), and other indicators of goose use (footprints and droppings). Because the ground photographs were spatially positioned, we could use this information to verify the cause of “thin” wheat. Crop damage from grazing/trampling, water submergence, and other factors was evident. Our results illustrate practical ways to combine aerial and ground‐level image analysis, spectral observations, and global positioning systems to quantify field conditions in wheat.

Growth Performance and Serum Mineral Concentrations of Stocker Calves Grazing Wheat Pastures and Fed Different Sources of Magnesium1,21Published with the approval of the director, Arkansas Agricultural Experiment Station, Manuscript No. 99028.2Partial financial assistance was provided by Micro-Lite, LLC, 3731S. Santa Fe Ave., Chanute, KS 66720.

<h2>Abstract</h2> Magnesium supplementation has been shown to benefit feedlot cattle and is typically added at high concentrations to mineral supplements for calves grazing wheat pasture. Two experiments were conducted to determine the effects of Mg-mica supplementation on performance and serum mineral concentrations of stocker calves grazing wheat pasture. Supplemental Mg was provided at 6.1 g/d of supplemental Mg/ animal, Monday through Friday. In Exp. 1, 36 mixed-breed stocker calves (243±3.9kg BW) were stratified by BW and gender and allocated randomly to one of nine groups of four animals for a 112-d grazing study. Weight gain, shrink percentage, and serum Mg, Ca, K, Cu, and Zn concentrations did not differ (P>0.10) among calves fed either weathered Mg-mica (WMM), unweathered Mg-mica (UMM), or MgO. All serum mineral concentrations were within normal physiological ranges. In Exp. 2, 64 mixed-breed stocker steers (275±1.7kg BW) were stratified by BW and allocated randomly to one of 16 groups of four animals. Weight gain during a 50-d grazing study and subsequent feedlot period did not differ (P>0.10) among calves fed either no added Mg source or WMM, UMM, or MgO. Serum Cu was higher (P<0.05), and serum Mg was lower (P<0.05), from steers fed MgO, but all serum mineral concentrations were within normal physiological ranges. Although Mg-mica is relatively high in Fe (4%), using it as a supplemental Mg source appeared to have no negative impact on growth performance or serum mineral concentrations of calves grazing wheat pasture.

Effects of Grazing System on Performance of Cow-Calf Pairs Grazing Bermudagrass Pastures Interseeded with Wheat and Legumes11Contribution No. 00-310-J from the Kansas Agricultural Experiment Station.

Abstract A total of 96 fall-calving cows and 64 calves grazed Hardie bermudagrass [Cynodon dactylon (L.) Pers.] interseeded with wheat (Triticum aestivum L.), red clover (Trifolium pratense L.), ladino white clover (Trifolium repens L.), and lespedeza (Lespedeza stipulacea Maxim.) during 1996, 1997, and 1998 in either a continuous or a rotational system stocked at equal rates. Grazing of wheat was initiated in early spring with cows and calves and terminated in late summer with cows grazing bermudagrass. Rotationally grazed units were subdivided into eight paddocks that were grazed for 3.5-d (1996 and 1997) or 2-d intervals (1998). Residual forage was removed as hay in late July each year and credited to the corresponding grazing system. Legume cover, available forage DM, residual hay production, gains of cows and calves grazing wheat, and gains of cows grazing bermudagrass interseeded with legumes were measured. Grazing system had no effect (P>0.05) on legume cover, available forage DM, BW gains of cows and calves grazing wheat, or BW gains of cows grazing bermudagrass interseeded with legumes. However, rotationally grazed pastures produced more (P

The effects of crop rotation and fertilization on wheat productivity in the Pampean semiarid region of Argentina. 1. Soil physical and chemical properties

Wheat in the semiarid region of Argentina has often been grown as a low-input crop. Rainfall scarcity and distribution are the main characteristics of this region. The knowledge of the combined effects of crop rotation and fertilization on soil physical and chemical properties are the key for a sustainable crop production. Soil properties for an Entic Haplustoll in the semiarid region of Argentina were evaluated, where different crop rotations were used for 15 years. Wheat–wheat ( Triticum aestivum L.) (WW), wheat–grazing natural grasses (WG) and wheat–legume [vetch ( Vicia sativa L.) plus oat ( Avena sativa L.) or Triticale ( Triticum aestivum L. × Secale cereale L.)] (WL) rotations with and without fertilizer (64 kg N and 16 kg P ha −1) were studied. The annual wheat cropping system (WW) resulted in the lowest soil organic carbon (SOC) and total nitrogen (N t) levels. Extractable phosphorus (P ext) values were sufficient for wheat growth with all treatments and decreased with depth. Fertilizer applications significantly increased the proportion of large pores (>8.81 μm) in the 0–0.07 m depth of the WW and WG system plots. A decrease in the proportion of medium size pores (0.19–8.81 μm) and in the water holding capacity was observed in the WG rotation plots. The fertilized treatments resulted in the following sequence of available water: WL > WW > WG. Bulk density was similar with all treatments for each depth, except with the fertilized WG treatment that had the lowest value in the 0–0.07 m depth. These results showed the positive influence of legume inclusion (WL) and alternate cattle grazing (WG) on SOC and N t contents.

Cool‐Season annual legume effects on wheat forage nutritive value

Hard red winter wheat (Triticum aestivum L. emend. Thell.) is an important cool‐season winter forage used primarily for increasing weight gain on growing beef cattle in the southern Great Plains. ‘Karl’ hard red winter wheat grown alone or grown with either hairy vetch (Vicia villosa Roth) or pea [(Pisum sativum L. subsp. arvense) var. ‘Austrian winter'] was sampled for forage nutritive value. The interplanted legume forage was also sampled for forage nutritive value. Ruminally degradable nitrogen (RDN):ruminally degradable organic matter (RDOM) ratios were highest for legume forage and exceeded the National Research Council (NRC) recommendation of 26.13 g RDN: 1 kg RDOM for peak ruminai microbial efficiency during March, April, and May sample periods over the 2‐year study. Wheat grown alone met the NRC requirement only during March. Wheat grown with either hairy vetch or pea had higher (P<0.05) RDN:RDOM ratios and crude protein (CP) values when compared to wheat grown alone during May. There were no differences (P>0.05) in dry matter (DM) yield between wheat grown alone or grown with the legumes except when analyzed by individual date, and then only for 1 of 6 sample dates. Undegraded intake protein (UIP) was generally higher (PO.05) for wheat compared to the legumes and higher (PO.05) for wheat grown alone during May compared to wheat grown with the legumes during May. The decline of the RDN:RDOM values to 40% below the NRC recommendation of wheat grown alone during May indicates a possible need for protein supplementation for growing beef cattle grazing wheat during this period. These data also indicate that interplanting legumes with wheat may enhance animal performance by providing forage of higher nutritive value. More information regarding grazing tolerance of these selected cool‐season annual legumes and subsequent animal performance is required.

Effects of Early Treatment with Micotil on Animal Health and Performance of Stocker Cattle During Preconditioning and Winter Wheat Grazing

Two studies were conducted to evaluate the effects of early treatment with Micotil on animal health and performance of calves at high risk of contracting Bovine Respiratory Disease (BRD) during the preconditioning period and also while grazing winter wheat pasture.