Bothriochloa Bladhii Research Articles

83 Effects of cottonseed meal supplementation on growth performance of heifers grazing mature summer forage

Abstract As perennial warm-season grasses mature in late summer, dry matter intake (DMI) of growing heifers may be limited due to low protein (7.2 ± 2.5 %) and increased NDF content (67.5 ± 2.7%), which may compromise growth potential. Cottonseed meal (CSM) supplementation may improve forage digestibility by increasing rumen degradable protein offered, but research regarding the specific effects of CSM supplementation on gain performance and composition of gain in heifers is limited. It was hypothesized that supplementation of CSM to heifers grazing mature forage would have greater growth performance compared with heifers not receiving CSM. Objectives for this experiment were to compare the effects of two CSM supplementation strategies on the growth performance of heifers grazing mature summer forage. In two consecutive summers, commercial Angus cross heifers (n = 63) weighing 266.08 ± 32.74 kg were blocked by BW (light, medium, and heavy) and allocated to 9 paddocks (1.64 ha) of WW-B. Dahl Bluestem (Bothriochloa bladhii) for 67 to 70 d. This was a RCBD with a factorial arrangement of 3 treatments by 3 BW blocks, with paddock and year as random effects. Heifers received one of three supplementation strategies: no cottonseed meal (CON), 454 g/animal of CSM daily (CSM1), or 908 g/animal of CSM every other day (CSM2). Initial and final shrunk BW were measured; ADG and percent of BW gained were calculated. Ultrasound of initial and final longissimus muscle area (LMA), backfat (BF), and intramuscular fat (IMF) were measured; percent gained was calculated, respectively. There were no treatment by block interactions for any measured variable. Heifers receiving CSM1 and CSM2 had greater final BW than heifers receiving CON (317 and 320.8 vs 302.6 kg, respectively; (P = 0.01). Likewise, percent of BW gained was greater (P = 0.02) for CSM1 and CSM2 supplemented heifers compared with CON heifers (19.4 and 20.2 vs 14.6%, respectively). The ADG of CSM1 and CSM2 supplemented heifers was greater (P = 0.01) than CON (0.74 and 0.78 vs 0.54 kg/d, respectively). Treatment did not affect the percent of BF (P = 0.24) or IMF gained (P = 0.39). Heifers receiving CSM1 and CSM2 tended to gain proportionally more LMA than heifers receiving CON (13.58 and 13.77 % vs 7.24%, respectively; P = 0.07). As anticipated, BW block affected final BW (P < 0.001) and percent BW gained (P = 0.02), as well as percent LMA gained (P = 0.02). In conclusion, CSM supplementation significantly affected growth performance of heifers grazing late summer WW-B. Dahl Bluestem forage versus no supplementation. In addition, there was no difference in growth performance between heifers receiving 454 g/d of CSM supplementation or 908 g/animal every other day, indicating flexibility for feeding strategy.

107 Bacterial direct-fed microbial mixtures effects on beef cattle ruminal degradability kinetics

Abstract The effects of bacterial direct-fed microbial (DFM) mixtures on beef cattle ruminal degradability were evaluated. Six ruminally cannulated beef steers (BW = 520 ± 30 kg) were used in a replicated 3 × 3 Latin square design and offered a steam-flaked corn-based finishing diet to ad libitum intake during three, 28-d periods. Treatments were: 1) Control (no DFM, lactose carrier only); 2) Treat-A (L. animalis, P. freudenreichii; B. subtilis; and B. licheniformis), at 1:1:1:3 ratio, respectively; totaling 6 × 109 CFU (50 mg)/animal-daily minimum; and 3) Treat-B, the same DFM combination, but with doses at 1:1:3:1 ratio. Bacterial counts were approximately 30% greater than the minimum expected. Pre-dehydrated (55ºC for 72 h) diets and forage substrates were ground (2 mm) and placed into 10 × 20 cm (28 µm) nylon bags (8 and 5 g, as-is respectively). The diet-substrate included a mixture of (DM basis) steam-flaked corn (70%), alfalfa hay (10%), and wet corn gluten feed (20%). The forage-substrate was represented by ‘WW-B Dahl’ Old World bluestem (Bothriochloa bladhii). Substrate in-situ bags were placed within a nylon mesh (with weights) at the ruminal ventral sac, and reversely removed at 0, 2, 4, 8, 12, 20, 32, 48, 64, 72, and 96 h after feeding. Samples were removed, rinsed, and dehydrated for 72 h at 55oC. Residues were composited within period, steer, incubation-time, corrected for residual moisture and were used to fit a first-order kinetics model using the NLIN procedure of SAS (animal = experimental unit). Steers offered Treat-A tended to show an increase on the rate of degradation of NDF (P = 0.15) and ADF (P = 0.10) fractions; increased (P < 0.01) hemicellulose potentially degradable fraction (B); and increased (P = 0.02) the effective degradable fraction of NDF (tendency for ADF, P = 0.08) at pre-established rate of passages of 4, 5, and 6% of the diet-substrate compared with Control, while tending to have a reduced rate of degradation for the overall DM (P = 0.06) and OM (P = 0.08) fractions. When the in-situ bags containing the forage-substrate were incubated, steers offered Treat-A showed an increased (P < 0.01) lag time (T0) for hemicellulose compared with Control, while those offered Treat-B had a decreased (P = 0.02) hemicellulose potentially degradable fraction (B) compared with Control. The effective degradable fraction for hemicellulose at pre-established rate of passages of 4, 5, and 6% tended (P = 0.09) to numerically increase for steers offered Treat-A compared with Control. The combination of bacteria in Treat-A enhanced the ruminal degradation of high-quality fiber components, as indicated by the improvements observed within the more degradable fractions from ingredients used in the diet and the forage substrates. Further assessment is warranted to investigate post-ruminal nutrient disappearance.

PSX-12 Effects of Cottonseed Meal Supplementation on Calf Performance and Forage Utilization Grazing Late Season Summer Forage

Abstract Nutritive quality of perennial warm-season grasses during summer may limit the DMI of growing calves due to low protein and increased NDF content. Cottonseed meal (CSM) supplementation may improve forage utilization by increasing rumen degradable protein, but research in calves is limited. It was hypothesized that supplementation of CSM to heifers grazing mature forage would have improved performance due to greater forage DMI and fiber digestibility. Objectives were to compare the effects of CSM supplementation on calf gain performance, estimated forage intake, and in vitro true digestibility (IVTD) and neutral detergent digestibility (IVNDFD) of low-quality, warm-season forage. Angus heifers (n = 18) weighing 232.7 ± 12.6 kg were blocked by BW (light, medium, and heavy) and allocated to 6 paddocks (1.64 ha) of W.W. B-Dahl Bluestem (Bothriochloa bladhii) for 67 d. Heifers were supplemented daily with a mineral mix and either no cottonseed meal (CON) or 454 g/animal of CSM (CSM1) in a RCBD with a 2×3 factorial arrangement of treatments and BW blocks, respectively. Initial and final shrunk BW was measured to calculate total gain, ADG, and percent of BW gained. Forage samples were collected weekly and composited into 3 periods for chemical analysis and in vitro incubations. Forage DMI was estimated using a double sampling technique for each paddock within period. Forage IVTD and IVNDFD were analyzed using batch fermentation with and without CSM in a CRD (2 treatments by 3 periods). Mean forage CP during periods 1 and 2 were 5.75% and increased to 10.3% in period 3 (P < 0.01). Forage NDF content increased over time (64.1 vs. 69.3%; P < 0.01) and estimated forage DMI of heifers tended (P = 0.07) to decrease from 2.9 to 2.1% of BW. Treatment did not affect estimated forage DMI (P = 0.40). Heifers receiving CSM1 gained 28.3% more BW than heifers receiving CON (47.27 vs. 36.82 kg, respectively; P = 0.02). Percent of BW gained was greater for heifers receiving CSM1 than CON (16.9 vs. 13.8% of initial BW, respectively, P = 0.029). There were no treatment by period interactions on IVTD or IVNDFD. The IVTD of forage from period 1 was greater than periods 2 and 3 (49.9 vs. 47.1 and 46.6%, respectively; P = 0.005). The IVTD of forage incubated with CSM tended (P = 0.06) to be greater than forage without CSM (52.1% vs. 47.8%, respectively). The IVNDFD was not affected by period but tended to be greater with CSM inclusion (P = 0.09) relative to CON (24.83% vs. 18.95%, respectively). In conclusion, 454 g/d of CSM supplemented to heifers grazing late-summer W.W. B-Dahl Bluestem forage likely provided sufficient protein to alter ruminal fiber digestibility, without affecting forage intake, and had measurable effects on gain.

128 Effects of Cottonseed Meal Supplementation Strategy to Stocker Calves Grazing Late Season Summer Forage

Abstract Summer stocker calves grazing perennial warm-season grasses may benefit from protein supplementation due to the low protein content typically observed in these forages. Cottonseed meal (CSM) is an excellent protein supplement that is readily available in the south and is competitively priced per unit of protein in early summer. However, research regarding the effects of CSM supplementation level and frequency on calf gain and composition of gain is limited. It was hypothesized that supplementing CSM to grazing heifers would improve ADG and perhaps alter composition of gain when compared with non-supplemented heifers. Objectives for this experiment were to 1) compare gain and composition of gain between calves supplemented with CSM to non-supplemented calves, and 2) compare the effect of daily vs. alternating days of CSM supplementation. A total of 27 commercial Angus beef heifers weighing 234.1 ± 4.18 kg were blocked by BW (light, medium, and heavy) and allocated to 9 paddocks of W.W. B-Dahl Bluestem (Bothriochloa bladhii) for 67 d. The experimental was designed as a RCBD with 3×3 factorial arrangement of 3 treatments and 3 weight blocks. Heifers were supplemented daily with a mineral mix and either no cottonseed meal (CON), 454 g/animal of CSM daily (CSM1), or 909 g/animal of CSM every other day (CSM2). Initial and final shrunk BW was measured, and total gain, ADG, and percent of BW gained were calculated. Ultrasound of initial and final longissimus muscle area (LMA), backfat (BF), and intramuscular fat (IMF) were measured. There were no treatment by block interactions for any measured variable. Treatment significantly affected total gain and ADG (P = 0.0156), as well as percent of BW gain (P = 0.029). Heifers receiving CSM1 treatment gained 28.3% more total BW than heifers receiving CON (47.27 vs. 36.82 kg, respectively) and CSM2 was intermediate (42.73 kg). Likewise, percent of BW gained was greatest for CSM1 and least for CON (16.9 vs.3.8% of initial BW), with CSM2 not differing (15.5% of initial BW). Treatment did not affect the composition of gain (P ≥ 0.190); however, block tended (P = 0.0812) to affect LMA % gain, with light heifers being greater than medium and heavy heifers (12.00% vs. 7.35% and 5.09% increase, respectively). As expected, heifers grazing late summer W.W. B-Dahl Bluestem forage who received 454 g of CSM daily had significantly greater ADG than heifers not receiving CSM. Heifers receiving 909 g of CSM every other day tended to gain more than heifers not receiving CSM, but replication of this experiment is needed for validation of this specific supplementation strategy. In conclusion, supplementation of CSM to calves grazing low protein summer forage within a limited period may have positive measurable effects on gain.

Effect of Long-Term Semiarid Pasture Management on Soil Hydraulic and Thermal Properties

Semiarid pasture management strategies can affect soil hydraulic and thermal properties that determine water fluxes and storage, and heat flow in unsaturated soils. We evaluated long-term (>10 years) perennial and annual semiarid pasture system effects on saturated hydraulic conductivity (ks), soil water retention curves (SWRCs), soil water thresholds (i.e., volumetric water content (θv) at saturation, field capacity (FC), and permanent wilting point (PWP); plant available water (PAW)), thermal conductivity (λ), and diffusivity (Dt) within the 0-20 cm soil depth. Forage systems included: Old World bluestem (Bothriochloa bladhii) + legumes (predominantly alfalfa (Medicago sativa)) (OWB-legume), native grass-mix (native), alfalfa + tall wheatgrass (Thinopyrum ponticum) (alfalfa-TW), and annual grass-mix (annual) pastures on a clay loam soil; and native, teff (Eragrostis tef), OWB-grazed, and OWB-ungrazed pastures on a sandy clay loam soil. The perennial OWB-legume and native pastures had increased soil organic matter (SOM) and reduced bulk density (ρb), improving ks, soil water thresholds, λ, and Dt, compared to annual teff and alfalfa-TW (P < 0.05). Soil λ, but not Dt, increased with increasing θv. Grazed pastures decreased ks and water retention compared to other treatments (P < 0.05), yet did not affect λ and Dt (P > 0.05), likely due to higher ρb and contact between particles. Greater λ and Dt at saturation and PWP in perennial versus annual pastures may be attributed to differing SOM and ρb, and some a priori differences in soil texture. Overall, our results suggest that perennial pasture systems are more beneficial than annual systems for soil water storage and heat movement in semiarid regions.

Effects of Late-Summer Prescribed Fire on Botanical Composition, Soil Cover, and Forage Production in Caucasian Bluestem-Infested Rangeland in the Kansas Smoky Hills: Year 4 of 5

Objective: Our objective was to determine effects of late-summer prescribed fire on frequency of Caucasian bluestem (Bothriochloa bladhii) in the Kansas Smoky Hills as well as changes in soil cover, botanical composition, and forage production associated with fire treatment. Study Description: The study was in Ellsworth County, KS. Eighteen one-acre plots were randomly assigned to one of three treatments: no burn, one burn (August 14, 2019), and two burns (August 14, 2019, and August 11, 2021). Soil cover, botanical composition, forage production, and Caucasian bluestem frequency were measured annually beginning in 2019. The Bottom Line: These data suggest that regular application of late-summer prescribed fire may be an effective method to reduce Caucasian bluestem frequency while improving overall grass-species richness.

Inoculation with native soil improves seedling survival and reduces non‐native reinvasion in a grassland restoration

Losses of grasslands have been largely attributed to widespread land‐use changes, such as conversion to row‐crop agriculture. The remaining tallgrass prairie faces further losses due to biological invasions by non‐native plant species, often with resultant ecosystem degradation. Of critical concern for conservation, restoration of native grasslands has been met with little success following eradication of non‐native plants. In addition to the direct and indirect effects of non‐native invasive plants on beneficial soil microbes, management practices targeting invasive species may also negatively affect subsequent restoration efforts. To assess mechanisms limiting germination and survival of native species and to improve native species establishment, we established six replicate plots of each of the following four treatments: (1) inoculated with freshly collected prairie soil with native seeds; (2) inoculated with steam‐pasteurized soil with native seeds; (3) noninoculated with native seeds; or (4) noninoculated/nonseeded control. Inoculation with whole soil did not improve seed germination; however, addition of whole soil significantly improved native species survival, compared to pasteurized soil or noninoculated treatments. Inoculation with whole soil significantly decreased reestablishment of non‐native invasive Bothriochloa bladhii (Caucasian bluestem); at the end of the growing season, plots receiving whole soil consisted of approximately 30% B. bladhii cover, compared to approximately 80% in plots receiving no soil inoculum. Our results suggest invasion and eradication efforts negatively affect arbuscular mycorrhizal hyphal and spore abundances and soil aggregate stability, and inoculation with locally adapted soil microbial communities can improve metrics of restoration success, including plant species richness and diversity, while decreasing reinvasion by non‐native species.

Effects of Late Summer Prescribed Fire on Botanical Composition, Soil Cover, and Forage Production in Caucasian Bluestem-Infested Rangeland in the Kansas Smoky Hills: Year 3 of 4

Objective: The objective was to document the effects of late-summer prescribed fire on soil cover, botanical composition, and forage production in the Kansas Smoky Hills and associated effects on dense Caucasian bluestem (Bothriochloa bladhii) stands therein.

Herbicide Activity on Old World Bluestems

Two main species of old world bluestems (OWB), yellow bluestem (Bothriochloa ischaemum) and Caucasian bluestem (Bothriochloa bladhii), have encroached on rangelands, pastures, and road right-of-ways in Kansas. Patches of these OWB have been shown to reduce species diversity and abundance at multiple trophic levels, and pose a long-term threat to native plant, insect, rodent, and grassland bird populations. These OWB species are utilized by cattle early in the growing season, directly following prescribed burns, and during droughts when other forages lack water uptake and may go dormant. However, these OWB species mature more quickly than native grass species and quickly form stem tissue, thus losing palatability to grazing animals rather rapidly compared to native grass species. In native pastures where OWB has invaded, native species may become overutilized because animals avoid the OWB. This weakens the native grasses and allows OWB to have a competitive advantage for moisture and nutrient resources. Over time, patches of OWB have expanded from 2.5 to 3.5 times their original patch size in 9 years, or a 15% annually compounded patch growth rate, when left uncontrolled. Several herbicides have been analyzed for OWB control, but glyphosate and imazapyr are the two herbicides that in the past have been shown to reduce OWB abundance most effectively in pastures. However, other herbicides with new label information for use in different forms of grassland or recreation areas may also have some activity on OWB and provide control. This study was performed to test several alternative herbicides with no known prior history of evaluation for control of OWB.

Reclaiming Old World Bluestem Pasture with Imazapyr Application and Native Grass Overseeding

Old world bluestems (OWB), mainly Caucasian bluestem (Bothriochloa bladhii) and yellow bluestem (Bothriochloa ischaemum) introduced from parts of eastern Europe, Asia, Africa, and Australia, have been shown to reduce abundance and diversity of some insect and wildlife species compared to native grasses when these OWB grasses form dense stands. These OWBs have been invading native pastures in the southern Great Plains and are rapidly increasing in the amount of area occupied in Kansas. Two landowners purchased pasture property in Ellsworth County, KS, and observed that Caucasian old world bluestem had increased in the pasture significantly over the course of several years. They developed a plan with local partners to reclaim the pasture back to native grass and forb dominance in an effort to improve wildlife habitat and cattle grazing on the property.

312 Effects of Bismuth Subsalicylate and Different Sulfate Concentrations on in vitro Ruminal Fermentation Using a Warm-season Perennial Hay Substrate

Abstract A randomized complete block design was used to evaluate the effects of bismuth subsalicylate (BSS) on in vitro ruminal fermentation with differing concentrations of sulfate. In vitro fermentation consisted of 50 mL of a 4:1 buffer:ruminal fluid inoculum and 0.7 g (pre-dehydrated) of substrate [WW-B Dahl bluestem hay (Bothriochloa bladhii)] incubated for 48 h (39oC). Treatments were arranged as a 3 × 4 factorial with concentration of sulfate (0.2, 2.9, or 5.6 g sulfate/L buffer) and BSS (0.0, 0.165, 0.330, or 0.495% substrate DM) as the main factors. In vitro organic matter digestibility (IVOMD), and CH4, H2S, and total gas production (TGP) were measured. Data were analyzed using the MIXED procedure of SAS with the fixed effects of BSS, sulfate, and their interaction. Incubation day (block) was considered a random effect. The average of 2 bottles within day was considered experimental unit. A BSS × sulfate interaction was observed for TGP (P = 0.040) and H2S production (P &amp;lt; 0.001), where BSS had a larger negative impact on TGP and production of H2S with greater concentrations of sulfate. A linear effect (P &amp;lt; 0.001) of sulfate was observed for CH4 production per gram of incubated OM, where CH4 was decreased as sulfate concentration increased. A quadratic effect of sulfate was observed for IVOMD (P = 0.010) and pH (P = 0.009). Production of H2S linearly decreased (P = 0.001) as BSS concentration increased. The addition of BSS to in vitro incubations did not affect (P &amp;gt; 0.10) any other variables measured. Bismuth subsalicylate does not appear to have negative effects on in vitro fermentation parameters while decreasing H2S production; however, elevated concentrations of sulfate in the buffer appears to have negative impacts on fermentation. Further in vivo research is warranted to support BSS supplementation to cattle with high dietary sulfate.

Ruminal degradation kinetics, intake, digestibility, and feeding behavior of beef steers offered annual or perennial grass-hay with or without supplementation.

Effects of dried distillers grains plus solubles (DDGS) on ruminal fermentation, degradation kinetics, and feeding behavior of steers offered annual (Eragrostis tef; TEFF) or perennial (Bothriochloa bladhii; OWB) grass hay were evaluated. Ruminally cannulated Angus crossbred steers (n = 6; body weight [BW] = 304 ± 11 kg) were assigned to a 4 × 6 unbalanced Latin square design with four treatments arranged as a 2 × 2 factorial: hay type (OWB or TEFF) and DDGS supplementation (0% or 0.5% BW [dry matter {DM} basis]). Steers had ad libitum access to hay. Periods consisted of a 14-d adaptation followed by 7 d of collection. Residues from the in situ incubations (0, 3, 6, 12, 24, 36, 48, 72, and 96 h post-feeding) were fitted to a first-order kinetics model using the NLIN procedure of SAS. The DDGS decreased (P < 0.01) TEFF DM intake (DMI) by 11.3%, while not affecting DMI of OWB. The greatest DMI was observed for steers supplemented with DDGS, regardless of forage, and least in steers consuming OWB without DDGS (hay type × DDGS; P = 0.03). Non-supplemented steers spent more (P < 0.01) time eating hay. Digestibility of DM tended (P = 0.06) to increase with DDGS supplementation. A hay type × DDGS interaction was observed (P ≤ 0.05) on ruminal effective degradable fractions. The rate of degradation, soluble fraction, and the potentially degradable fraction of organic matter (OM), neutral detergent fiber, and acid detergent fiber (ADF) increased (P ≤ 0.05), while the undegradable fraction of all components decreased (P ≤ 0.01) when steers were offered TEFF compared to OWB. Ruminal DM, OM, and ADF degradation lag-time increased (P ≤ 0.02) in steers offered OWB. Ruminal degradation kinetics were not (P ≥ 0.17) independently affected by DDGS supplementation. Average ruminal pH of steers offered TEFF (P < 0.01) and those offered DDGS (P < 0.01) were lower than OWB and non-supplemented steers. Total concentration of VFA tended (P = 0.09) to increase when DDGS was provided with OWB, while decreasing when TEFF was offered. The acetate:propionate increased (P < 0.01) with DDGS supplementation due to a decrease (P = 0.03) in propionate. Ruminal NH3-N was greater (P = 0.03) in steers offered TEFF compared to OWB, and those supplemented with DDGS (P = 0.03). An annual, in place of a conventional, perennial hay improved intake and digestion of nutrients, without affecting feeding behavior. The supplementation with DDGS appears to affect forage intake, ruminal degradation, and feeding behavior, although not independent of forage quality.

Ruminal Degradation Kinetics of Beef Steers Fed Annual or Perennial Grass-hay with or Without Supplementation

Abstract The effects of dried distillers grains plus solubles (DDGS) supplementation on ruminal degradation kinetics of steers fed annual [‘Tiffany’Eragrostis tef (Zucc.) Trotter; TEFF] or perennial [‘WW-B Dahl’ Old World bluestem, Bothriochloa bladhii (Retz).T. Blake; OWB] grass hay were evaluated. Ruminally cannulated crossbred-Angus steers (n = 6; BW = 304 ± 11 kg) were assigned to a 4 × 6 unbalanced Latin square design with 4 treatments. Treatments were arranged as a 2 × 2 factorial, with factors being hay type (OWB or TEFF) and DDGS supplementation [0 or 0.5% BW (DM basis)]. Steers had ad libitum access to hay and received 110 g of a mineral/vitamin packet daily. Periods consisted of a 14-d adaptation followed by 7 d of collection. Hay types were reverse-incubated at 0, 3, 6, 12, 24, 36, 48, 72, and 96 h post-feeding. Residues from the in situ incubations were fitted to a first-order kinetics model using the non-linear procedure of SAS. The GLIMMIX procedures of SAS were used for the statistical analysis. A hay type × DDGS interaction was observed (P ≤ 0.05) for the estimation of substrate effective degradable fraction of OM, NDF, ADF, and hemicellulose; however, after adjusting with Tukey’s, there were no treatment mean differences (P ≥ 0.08). The rate of digestion, soluble fraction, and the potentially degradable fraction of OM, NDF, ADF, and hemicellulose increased (P ≤ 0.05), while the undegradable fraction decreased (P ≤ 0.01) when steers were fed TEFF, regardless of DDGS supplementation. Ruminal degradation lag-time increased (P ≤ 0.02) by 1.5, 1.45, and 2.6 h for DM, OM, and ADF, respectively in steers fed OWB, regardless of DDGS supplementation. Ruminal degradation kinetics were not (P ≥ 0.17) independently affected by DDGS supplementation. Future investigations should elucidate the interaction between supplementation and forage quality.

Compost and legume management differently alter soil microbial abundance and soil carbon in semiarid pastures

AbstractEstablishment of improved perennial pasture systems for livestock production has been demonstrated to improve soil health in the semiarid Texas Southern High Plains (SHP). Use of waste products from other components of the animal production chain, such as applying composted manure from feedlot operations to grazed pastures, may provide an additional means of improving soil health and sustainability of these systems. However, few studies have examined the impact of composted animal manure on the changes in soil microbial communities, although they are important indicators of soil health. We investigated the effects of a one‐time composted cattle manure application at 3.36 Mg ha−1 on soil microbial community size and structure, soil organic C (SOC), total N (TN), and soil organic matter (SOM) up to 1.5 yr after application. We compared pastures consisting of either WW‐B. Dahl Old World bluestem grass [Bothriochloa bladhii (Retz.) S.T. Blake] alone or in mix with alfalfa (Medicago sativa L.). Results showed that compost application significantly increased SOC by about 4.4 g kg−1 soil within 1.5 yr after application. In N‐fertilized grass‐only pastures, compost addition increased microbial phospholipid fatty acid abundance, SOC, TN, and SOM, but no significant differences were observed between compost treatments in unfertilized pastures containing legumes. Our results show that even a one‐time compost addition at a relatively low rate can augment SOC in this semiarid pasture system after 1.5 yr, and that stimulation of soil microbial abundance and soil C and N from compost is more pronounced in fertilized grass‐only pastures compared with those with legume establishment.

Managing an Invasive Weed Species, Parthenium hysterophorus, with Suppressive Plant Species in Australian Grasslands.

Parthenium weed has been invading native and managed Australian grasslands for almost 40 years. This study quantified the potential of selected plant mixtures to suppress the growth of parthenium weed and followed their response to grazing and their impact upon plant community diversity. The first mixture consisted of predominantly introduced species including Rhodes grass, Bisset bluegrass, butterfly pea and green panic. This mixture produced biomass rapidly and showed tolerance to weed species other than parthenium weed. However, the mixture was unable to suppress the growth of parthenium weed. The second mixture of predominantly native pasture species (including forest bluegrass, Queensland bluegrass, Buffel grass and siratro) produced biomass relatively slowly, but eventually reached the same biomass production as the first mixture 12 weeks after planting. This mixture suppressed parthenium weed re-establishment by 78% compared to the control treatment. Its tolerance to the invasion of other weed species and the maintenance of forage species evenness was also superior. The total diversity was five times higher for the mixture communities as compared to the plant community in the control treatment. Therefore, using the suppressive pasture mixtures may provide an improved sustainable management approach for parthenium weed in grasslands.

Long-term pasture management impacts on eolian sand soils in the southern mixed-grass prairie

Mixed grass pastures which occupy the eolian sand dunes of the southern Great Plains provide stabilizing soil cover, soil carbon (C) storage, and are a critical resource for livestock production. Large areas of dunes cover the American Great Plains, were active 700–1000 years ago during periods of frequent drought and have the potential to reactivate under forecasted climate scenarios and poor management. This study determined the soil age and development of eolian sandy soils and evaluated long-term grazing of native and improved pasture on root carbon, soil organic C (SOC), stable isotopes of soil fractions, and other soil properties. Pasture treatments included grazed and ungrazed (50 + yrs), improved pastures (28–50 yrs), and winter wheat (Triticum aestivum) or go-back grass (for 28–30yrs). Improved pasture grass species included both native (switchgrass (Panicum virgatum L.), and sand bluestem (Andropogon hallii Hack.) and non-native (weeping lovegrass (Eragrostis curvula (Schrad.) Nees)), and caucasian bluestem (Bothriochloa bladhii (Retz.) S.T. Blake) species. The Eda soil age was very recent and ranged from present at the surface to <1200 to <1600 yr BP (by luminescent or 14C dating, respectively) at the bottom of the soil profile (~130 cm). Long-term moderate grazing had relatively little impact on soil properties compared to ungrazed pastures. Soil C was dependent on grass root biomass across all improved pasture treatments, but with few differences among individual grasses or long-term pastures. Most improved pasture treatments either increased or maintained indicators of soil health (SOC, soil organic nitrogen (SON), mineral-associated carbon (Cmin-C), particulate organic matter carbon (POM-C), and silt and clay content). However, soils under winter wheat and sand bluestem had a third the SOC and SON of pasture, indicating soil degradation. Long-term grazing is a resilient practice that can stabilize these sandy soils and increase soil health. Soil protection is necessary should global warming result in drought and/or high winds and increase the potential for reactivation of eolian sand movement.

PSXIV-41 Warm-season annual or perennial hay fed to growing beef steers with or without dried distillers grains supplementation: ruminal fermentation characteristics, digestion, and feeding behavior

Abstract The effects of hay type and protein supplementation on intake, feeding behavior, nutrient digestion, and ruminal digestion characteristics were evaluated. Ruminally cannulated Angus beef steers (n = 6; BW = 304 kg ± 11 kg) were randomly assigned within a sequence of treatments using a 4 × 6 unbalanced Latin square design (6 steers; and 4 diets; fed once-daily). A 2 x 2 factorial treatment arrangement was used as follows: 1) ‘WW-B. Dahl’ Old World bluestem [Bothriochloa bladhii (Retz) S.T. Blake; WWBD or Eragrostis tef (Zucc.) Trotter; TEFF); and 2) dried distillers grain (DDGS) at 0 or 0.5% BW. Each period consisted of a 14-d of adaptation and 7-d collection. Steers were observed (5-min intervals, 24 h) for behavioral assessment; while ruminal pH was continuously measured (wireless pH probe), and ruminal fluid collected at 0, 2, 4, 8, and 16 h after-feeding. Steers fed TEFF hay and those fed DDGS (both, P = 0.04) had greater DMI compared to WWBD and not supplemented. Chewing activity did not differ (P ≥ 0.54). Non-supplemented steers spent more time eating hay (P &amp;lt; 0.01) than supplemented steers. Average ruminal pH of TEFF (6.32) was lower (P &amp;gt; 0.01) than WWBD (6.56). Non-supplemented steers produced less in vitro total gas and methane (both, P = 0.02) per g rumen fluid DM. The VFA profile was not affected (P ≥ 0.45) by treatments. Apparent total-tract digestibility and ruminal degradation (P ≤ 0.01) were greater with TEFF fed steers than WWBD. Hemicellulose digestion was reduced by 6.95% (P = 0.03) with DDGS supplementation. An annual hay in place of a conventional perennial hay improved intake, ruminal digestion of nutrients, without affecting feeding behavior, while supplementation with DDGS reduced forage intake time and quantity, without negatively affecting ruminal fiber digestion.

Understanding the effects of pasture type and stocking rate on the hydrology of the Southern Great Plains

Grassland is one of the major biomes in the United States (US) and the world. In the US, the majority of grasslands are concentrated in the Great Plains and has undergone through significant interventions or management changes over the last few decades. A key economy-driven intervention in the Southern Great Plains (SGP) include the introduction of new forage species and conversion of native grassland to introduced pasture to increase productivity and its nutritive value for improved cattle production. Since water is one of the fundamental resources needed to sustain grassland productivity, it is important to understand how such pasture conversion and prevailing cattle grazing practices affect water balance and biomass production in a given pasture system. In this study, the Nutrient Tracking Tool (NTT) with its core APEX (Agricultural Policy Environmental eXtender) model was used to assess the hydrological impacts of the pasture introduction, i.e., native pasture (little bluestem, Schizachyrium halapense) vs. introduced pasture (old world bluestem, Bothriochloa caucasica), and the stocking rate in the SGP. Monthly evapotranspiration (ET) and biomass estimates from NTT compared well with observed data at two USDA-ARS experimental pastures (native and introduced) near El Reno, Oklahoma, for the years 2015 and 2016. Simulated long-term average annual hydrologic fluxes (i.e., ET, runoff, and groundwater recharge) from the introduced pasture were slightly lower than the observed data but not significantly different than those from the native pasture under the current management conditions. NTT predicted higher water yield (runoff and recharge) and significantly lower ET for the introduced pasture than the native pasture. Results suggest that grazing has the potential to alter the hydrological balance in the SGP. For example, the increase in stocking rate within the carrying capacity of the farm decreases ET and increases runoff and groundwater recharge for both pastures. Comparison of estimated biomass production between native and introduced pastures indicated that introduced pastures are more efficient in using the available water and thus produce a higher forage biomass per unit of water in the SGP. This study highlighted the potential significance of considering hydrological and other biophysical impacts of new forage introduction and stocking rate changes for the sustainable management of grazing and pasture systems in the SGP.

Assessing the role of interseeding alfalfa into grass on improving pasture soil health in semi-arid Texas High Plains

The rapid decline in water supply for irrigation in the Texas High Plains is encouraging some growers to convert their irrigated cropland to production of drought-tolerant forages such as ‘WW-B.Dahl’ cultivar of Old World bluestem [OWB, Bothriochloa bladhii (Retz) S.T. Blake]. This perennial, warm-season pasture grass protects the soil surface from erosion; however, it needs nitrogenous fertilizer from an external source or by interseeding a nitrogen (N)-fixing legume to maximize productivity and quality of the pasture. Alfalfa (Medicago sativa L.) is a relatively drought-tolerant and high quality forage legume which is compatible with perennial grasses and enhances dietary protein supply for grazing cattle and improves pasture soil health. The aim of this study was to assess the value of interseeding alfalfa into established OWB grass on improving pasture soil health in relation to OWB grown in a monoculture stand. We investigated the microbial and chemical properties of soil taken at 0–10 cm in March of 2019 from OWB and OWB-alfalfa as a preliminary information for understanding the potential role of alfalfa on improving soil health. At this early assessment of the introduction of alfalfa into OWB, soil microbial biomass carbon (MBC) and nitrogen (MBN) were greater (P < 0.05) in OWB-alfalfa than in OWB. There were no forage treatment effects on soil organic carbon (SOC), total N, and the potential combined enzyme activity associated with C, N, P, and S transformations. The analysis of soil microbial community structure showed that forage treatments were not significant for total fatty acid methyl esters (FAMEs), arbuscular mycorrhiza fungi (AMF), and protozoa, but OWB-alfalfa had greater abundances. Saprophytic fungi were greater in the soil under OWB-alfalfa (P = 0.048) compared to that of under OWB. The bacterial markers for Gram+, Gram‒, and actinobacteria were not significantly different. It is not clear whether the elevated soil microbial community in OWB-alfalfa in the current study was solely because of alfalfa, but enhanced soil microbial biomass and saprophytic fungal populations in OWB-alfalfa are at least partially caused by alfalfa. Results indicated that the OWB-alfalfa is a promising forage species combination for stimulating pasture soil health through enhanced soil microbial biomass and fungal populations.

Essential oil composition of ‘WW-B.Dahl’ old world bluestem (Bothriochloa bladhii) grown in the Texas High Plains

Bothriochloa spp. include aromatic grasses that produce essential oils. Some of these grasses are reported to repel economically important insects. Leaves, stems, and seedheads of ‘WW-B.Dahl’ old world bluestem [Bothriochloa bladhii (Retz) S.T. Blake] were sampled during 3 years. Quantitative analysis by GC and GC–MS methods revealed a total of 172 compounds from methylation method, and 105 compounds from steam distillation method. Acorenone-B [spiro[4.5]dec-6-en-8-one, 1,7-dimethyl-4-(1-methylethyl)-] was in greatest concentration in both methods; however, this compound was detected on only one date (12 August) out of three collection dates extracted by steam distillation. Twenty-two compounds were detected by simple solvent extraction, in which acorenone-B was in greatest concentration in seedheads and least in stems. Diethylhexyl adipate was in highest concentration in stems and least in seedheads among the oils extracted by simple solvent. Camphene and limonene were present in the samples that contained seedheads. Naphthalene, a known insect deterrent, was detected in oils extracted from all methods and in all plant parts. Old world bluestem grass contained measurable amounts of essential oils that may be associated with previously observed repellency of red imported fire ants (Solenopsis invicta Buren).