Warm-season Grasses Research Articles

Biomass yield potential, feedstock quality, and nutrient removal of perennial buffer strips under continuous zero fertilizer application

Abstract. Perennial-based buffer strips have been promoted as having the potential for improving ecosystem services from riparian areas while producing biomass as livestock feed or as a bioenergy feedstock. Both biomass production and nutrient removal of buffer strips are substantially influenced by the vegetation types for the multipurpose perennial buffers. In this 2016–2019 study in western Illinois, two perennial cropping systems, including forage crops composed of cool-season grass mixtures (forage system) and bioenergy crops made up of warm-season grass mixtures (bioenergy system), were used to establish buffer strips for assessing biomass production, feedstock quality, nutrient removal, and buffer longevity. Treatments for this study reflecting agronomic practices included (1) two harvests occurring in summer (at anthesis) and fall (after complete senescence) and (2) one harvest in fall for the forage system (two-cut vs. one-cut forage) and (3) one fall harvest for the bioenergy system (one-cut bioenergy). Successively harvesting without any fertilizer input resulted in a yield decline in forage biomass over 3 years by approximately 30 % (6.3 to 4.4 Mg DM ha−1 (dry matter) with a rate of 1.0 Mg ha−1 yr−1) in the two-cut forage and by 35 % (4.9 to 3.2 Mg DM ha−1 with a rate of 0.9 Mg ha−1 yr−1) in the one-cut forage systems. The feed quality also decreased over the years by showing declined rates of 12.9 (crucial protein), 0.9 (calcium), 0.7 (copper), and 1.3 g kg−1 DM yr−1 (zinc). Empirical models predicted enteric CH4 emissions from cattle ranged from 225.7 to 242.6 g per cow per day based on the feed nutritive values. In contrast, bioenergy biomass yield increased by 27 % from 4.9 to 6.7 Mg DM ha−1 with a consistent quality (cellulose of ∼ 397.9 g kg−1; hemicellulose of ∼ 299.4 g kg−1), corresponding to the increased total theoretical ethanol yield from 1.8 × 103 to 2.4 × 103 L ha−1 (∼ 33 % increase). Annual nutrient removals of N, P, K, Ca, and Mg were significantly higher in the forage systems (e.g., two-cut: 52.6–106.9 kg N ha−1; one-cut: 44.5–84.1 kg N ha−1) than those in the bioenergy system (e.g., 25.9–34.4 kg N ha−1); however, the removal rate declined rapidly over 3 years (e.g., ∼ 49 % reduction) as the annual biomass yield declined in the forage systems. This on-farm field study demonstrated the potential of the perennial crop used as buffer strip options for biomass production and buffer sustainability at the edge of the field.

Agronomic evaluation of 15 warm season grasses grown in temporarily waterlogged soils in Northeastern Argentina

Soils with temporarily waterlogged conditions are common in Northeastern Argentina. Fifteen accessions and hybrids of cultivated and native warm season grasses (Acroceras macrum, Urochloa species, Hemarthria altissima and Paspalum species) were planted in Basail, Chaco, in a completely randomized block design in November 2019. Initial, autumn and spring forage yield were measured in February 2020, July 2021 and December 2021, respectively. Plant height and plant diameter were evaluated in February 2020. Cold tolerance was estimated after the first frost in July 2021. Initial forage yield was between 29 and 181 g/plant. Urochloa mutica exhibited the greatest initial forage yield. Autumn and spring forage yield varied from 306 to 2,183 g/m2 and from 153 to 710 g/m2, respectively. U. mutica showed the highest autumn forage yield, however, it was the most damaged by cold weather. H. altissima hybrids were the most productive during spring and were cold tolerant. There were differences in plant height (7.5–49 cm) and plant diameter (68–268 cm) among the grasses. Grasses with prostrate, intermediate and upright growth habits were identified. Results indicate all grasses tested were adapted to humid Northeastern Argentina and varied in their morphological and agronomic traits.

Evaluation of Postemergence Weed Control Programs in Cotton Without the Addition of Glyphosate

Glyphosate has played an important role in agricultural production systems, especially after the release of glyphosate resistant crops. With increased usage and an overall reliance on chemical control, weed resistance to glyphosate has occurred and is now a major issue. The objective of this research was to investigate weed control levels provided by glufosinate, 2,4-D, and clethodim as an alternative to glyphosate. Multiple POST applications generally provided superior weed control in comparison to a single early-POST application. No programs provided greater than 80% warm-season grass control beginning 21 d after mid-POST application. Applications of glufosinate or glufosinate + 2,4-D fb clethodim + glufosinate, glufosinate + 2,4-D, or clethodim + glufosinate + 2,4-D provided adequate broadleaf weed control throughout the rating period. Although POST-only programs are an option, they are not a sustainable weed control practice. It remains important to incorporate residual herbicides into a weed control program as well as alternative weed control methods.

Native Forbs Provide Pollinator Resources and Improve Forage Nutrient Composition, Animal Performance, and Pasture Productivity

Pollinator declines and expectations for more sustainable agriculture, including pasture-based enterprises, bring attention to strategies to enhance the habitat value of grazing lands. We evaluated native warm-season grass (NWSG) pastures with (FORB) and without (CONT) interseeded native forbs in 2021–2023. An analysis was conducted using R with the significance set at p ≤ 0.05. The grass appeared to be weakened predominantly by grazing management practices. Forb density and mass had an inverse relationship in seasons two and three. Total forage mass declined in response to increased grazing days and weakened stands. The forage nutritive compositions differed, with more stable, season-long crude protein and lower fiber concentrations in late-season FORB, which supported higher bodyweight gains and season-long average daily gain. Black-eyed Susan (Rudbeckia hirta; BESU), lanceleaf coreopsis (Coreopsis lanceolata; LCOR), and showy ticktrefoil (Desmodium canadensis; STTF) were the most abundant forbs, and BESU, LCOR, and purple coneflower (Echinacea purpurea; PURC) produced long flowering windows. Cattle grazed STTF, cup plant (Silphium perfoliatum; CUPP), and oxeye sunflower (Helopsis helianthoides) the most. Under continuous stocking, a blend of BESU, LCOR, PURC, STTF, and CUPP produced acceptable cattle gains and provided pollinator resources, suggesting that this model may be a viable means to enhance the sustainability of pastures.

PSXIII-3 Regrowth interval and propionic acid effects on warm-season grass silage nutritive value and fermentation characteristics

Abstract Warm-season perennial grass species are the main forages preserved as silage or haylage by livestock producers in Florida; however, the nutritive value and silage fermentation parameters are often less than desirable. The objective of this study was to investigate the effects of regrowth interval, propionic acid, and forage species on silage nutritive value and fermentation parameters. The study was conducted in Ona, FL in July and August 2021 and 2022. Treatments were the factorial combination of three forage species [Jiggs bermudagrass (Cynodon dactylon L.), ‘Camello’ brachiariagrass (Urochloa spp.), or Spain guineagrass (Megathyrsus maximus (Jacq.) B.K. Simon & S.W.L. Jacobs)], two regrowth intervals (3 or 6 wk), and propionic acid [0.5% or 0 (control)], distributed in a randomized complete block design with 4 replicates. Forage was harvested and immediately packed into a mini-silo at a density of approximately 190 kg DM/m3. Camello and Spain had less DM (24 vs. 30%; P < 0.01), CP (8.0 vs. 10.7%; P < 0.01), but greater NDF (70 vs. 68%; P < 0.01), ADF (41 vs. 38%; P < 0.01), and in vitro digestible OM concentration (57 vs. 52%; P = 0.04) than Jiggs. There were no differences in fermentation characteristics among species. Forage harvested at 3-wk regrowth interval had less DM (24 vs. 29%; P < 0.01), NDF (68 vs. 71%; P < 0.01), ADF (38 vs. 40%; P < 0.01) but greater CP (10.8 vs. 8.3%; P < 0.01) and in vitro digestible OM (56 vs. 52%; P = 0.03) than 6 wk. There was no effect (P > 0.05) of regrowth interval on fermentation characteristics. Forage treated with propionic acid had greater DM (27 vs. 25%; P < 0.01), CP (9.6 vs. 9.0%; P < 0.01), lactic acid (4.3 vs. 3.1%; P < 0.01), and propionic acid concentrations (1.8 vs 0.1%; P < 0.01) but decreased pH (4.2 vs. 4.6; P < 0.01), ammonia (12 vs. 18% CP; P < 0.01), acetic acid (1.5 vs. 2.0%; P < 0.01), and butyric acid concentrations (0.2 vs. 1.5%; P < 0.01). Propionic acid affected bacterial population abundance by decreasing Clostridium (0.6 vs. 5.3%; P < 0.01) and Enterobacteria (3.0 vs. 11.1%; P < 0.01) and increasing Lactobacillus (45.0 vs. 32.7%; P = 0.04) and Bacillus (0.35 vs. 0.15%; P < 0.01). Forage species and regrowth interval were influential on silage nutritive value while propionic acid improved fermentation characteristics.

143 Short- and long-term effects of heat stress in cow-calf pairs adapted to tropical and subtropical regions

Abstract Chronic exposure to high temperatures and humidity can limit beef cattle performance in tropical/subtropical environments, regardless of breed. Despite better heat adaptability compared with Bos taurus cattle, heat-stressed Bos indicus cattle also experience an increase in body temperature above the physiological limit. As body temperature increases, cascades of behavioral and physiological events are triggered to lessen heat load but often at the expense of productive outcomes. Contrary to other species and feedlot beef cattle, the effects of heat stress on physiology and performance of grazing cow-calf pairs have not been evaluated in detail, particularly for Bos indicus cattle. Preliminary data showed opposite outcomes to heat stress in Bos indicus vs. Bos taurus cattle, limiting the implications of the existing data generated from studies using beef and dairy Bos taurus cattle. This presentation will share some nutritional and management practices to mitigate heat stress in grazing beef cattle. Practices mentioned herein include altering the timing of body weight (BW) growth pattern (stair-step, SST) and immunomodulatory feed ingredient (IFI) supplementation for replacement beef heifers, and maternal access to shade to reduce heat load. For 100 d before the breeding season, Bos indicus-influenced beef heifers grazing warm-season grasses received a constant supplementation amount or SST strategy (50 d of low then 50 d of high supplementation), with or without IFI. Under severe heat stress conditions, IFI supplementation reduced heifer vaginal temperature but did not increase their growth and reproduction, whereas the SST strategy lowered internal body temperature, enhanced growth performance and pregnancy success compared with a conventional constant supplementation practice. Our group is also focused on the critical need to determine the specific effects of heat stress mitigation during pre- and postnatal phases on physiology and performance of Bos indicus-influenced cow-calf pairs. Study 1 evaluated the impacts of maternal access to artificial shade from 83 d prepartum until 50 d postpartum on body thermoregulation, performance, and physiology of beef heifers and their first offspring. Removing maternal access to shade led to greater maternal respiration rate, vaginal and body surface temperatures and reduced maternal body condition score and calf BW at birth. Nonetheless, offspring born from cows with no access to shade were remarkably heavier during a 60-d post-weaning period and had decreased plasma indicators of inflammation and positive effects to humoral immune response. Study 2 is a multi-year, USDA/NIFA-funded study designed to capitalize on the ability of cattle to reprogram physiological/immunological systems following exposure to stress during gestation. Study 2 combined gestational and postnatal heat abatement to enhance the overall growth/immune/reproductive performance of grazing Bos indicus-influenced cow-calf pairs. Partial data on long-term growth and reproductive performance, physiology, metabolome, and microbiome of both cows and their female offspring will be shared in this presentation.

157 Microbial inoculant effects on limpograss silage

Abstract Warm-season perennial grasses are the main forage sources preserved as silage or haylage by livestock producers in subtropical and tropical regions; however, the nutritive value and silage fermentation parameters are often less than desirable. Microbial inoculants have been used to improve grass silage nutritive value and fermentation characteristics with inconsistent results. The objective of this study was to investigate the effects of a microbial inoculant on nutritive value and fermentation parameters of ‘Gibtuck’ limpograss (Hemarthria altissima) silage. Treatments were silage treated with SiloSolve FC (68.1 billion CFU/g, Lactobacillus lactis and Lactobacillus buchneri) or control (no microbial inoculant) distributed in a complete randomized design with 10 replicates. The inoculant level used was 0.5 g/Mg of forage. The experiment was conducted in Ona, FL in May 2023. Twenty 4 × 4 m plots of established limpograss were harvested at 15-cm stubble height with 58-d regrowth interval. The forage was chopped to a particle size ranging from 10 to 18 mm, placed into mini-silos (PVC pipes with rubber), and sealed immediately. The inoculant was applied with a hand sprayer before ensiling. The silos were opened after 60 d for analysis. There was no difference (P > 0.05) between the inoculant and control treatments on DM concentration (25%), DM recovery (96%), NDF (67%), and NFC concentrations (14%); however, silage treated with inoculant had greater CP (8.5 vs. 8.0%; P = 0.03), IVTD (56 vs. 54%; P = 0.01), and NDFD (53 vs. 51%, P = 0.02) and lesser ADF concentrations (38 vs. 40%; P = 0.02) than control. The inoculant did not affect (P > 0.05) silage pH (4.2) and lactic acid concentrations (1.5%) but resulted in greater acetic acid (2.5 vs. 2.0%; P = 0.01), propionic acid (1.6 vs. 1.0%, P < 0.01), and total acid concentrations (5.6 vs. 5.0%; P = 0.04), and decreased butyric acid (0 vs. 0.2%; P < 0.01), isobutyric acid (0.1 vs. 0.4%; P < 0.01), and NH3-N concentrations (4.4 vs. 5.3% N; P < 0.01). Aerobic stability (140 h), mold (1.1 log cfu/g) and yeast (2.2 log cfu/g) count were not affected (P > 0.05) by the inoculant treatment. At the genus level, there was no difference (P > 0.05) in relative abundance of Lactobacillus (85%), Enterobacter (4.0%), Enterococcus (1.8%), and Weissella (0.2%) between inoculant and control, but silage treated with inoculant had less Clostridium (1.0 vs. 2.3%, P = 0.04), Pediococcus (0.2 vs. 0.3%, P = 0.03) and greater relative abundance of Lactococcus (2.8 vs. 0.5%, P < 0.01) and Bacillus (0.2 vs. 0.1%, P = 0.01). At the species level, the inoculant was effective to increase the relative abundance of Lactococcus lactis (from 0.02 to 0.48, P = 0.002) and Lactobacillus buchneri (from 1.4 to 1.9, P = 0.03). SiloSolve FC is a promising microbial inoculant to be used in warm-season grass silage in subtropical and tropical regions.

151 Microbial inoculant effects on cool- and warm-season grass silage

151 Microbial inoculant effects on cool- and warm-season grass silage

Flowering Periods, Seed Yield Components, Seed Quality, and Patterns of Seed Shattering in Paspalum: Effect of Taxonomy and Nitrogen Fertilization.

Perennial warm-season grasses typically have reduced seed yield, making it essential to identify the critical seed yield components. An induced increase in nitrogen could help determine which components are most limiting. This research aimed to estimate seed yield components in Paspalum; evaluate N fertilization effects on the reproductive phase, seed yield components, and seed quality; and establish the pattern of seed shattering over time. Nine genotypes covering different reproductive periods were used. The experimental design was a randomized complete block design in a split-plot arrangement with three replications. The main plots had two nitrogen levels (0 and 150 Kg N ha-1), and the sub-plots contained different genotypes. Seed yield variation was mainly related to reproductive tiller density among germplasm with different flowering periods. Early-flowering germplasm showed an extended flowering period (159%), greater tiller density (27.7%), greater reproductive tiller density (157%), and higher yield (302%) in response to nitrogen fertilization. Seed-quality traits and seed retention were not affected by nitrogen fertilization. Seed retention over time followed an inverted sigmoid pattern, though there was considerable variation among taxonomic groups. Early-flowering germplasm exhibited superior seed retention. Seed yield in Paspalum is mainly influenced by the density of reproductive tillers and seed retention.

Performance of heifers grazing native or introduced mixed warm-season grasses during summer months in south-central United States

Performance of heifers grazing native or introduced mixed warm-season grasses during summer months in south-central United States

Botanical composition gradients in silvopastoral systems on temperate native grasslands of Uruguay

AbstractSilvopastoral systems may provide important production and environmental benefits. The loss of cool-season (C3) grasses from temperate grazed native grasslands is associated with selective grazing and excessive solar radiation that limit their survival. Silvopastoral systems integrate trees with grasslands that provide shade to both cattle and herbaceous plants, potentially favoring C3 species. There is limited information about the effect of trees on the species and functional composition of native grasslands in the Campos biome in South America. The objective of this study was to detect gradients in the botanical composition of grasslands as affected by changes in the shade associated with distance to the trees and cardinal orientation in three situations defined by the combination of soil and tree species (Prosopis on Solonetz, Acacia on Brunisols, and Eucalyptus on Brunisols). Soil cover of the herbaceous species under trees was recorded in double transects located in the four cardinal directions. In all situations there were changes in pasture composition in the different shaded regions (total shade, partial shade, or full sun). Under the canopy, there was an increase of cool-season grasses such as Bromus catharticus Vahl, Lolium multiflorum Lam., Stipa hyalina (Nees) Barkworth, and S. setigera J.Presl. At greater distances from trees, cover of warm-season grasses, such as Axonopus affinis Chase and Paspalum notatum Flueggé increased. These gradients suggest that trees in silvopastoral systems can increase the abundance of cool-season species and potentially improve the forage nutritive value of the native pasture.

First Report of a 'Candidatus Phytoplasma sacchari'-Related Strain Associated with Yellowing and Decline of Silver Bluestem in Texas, U.S.A.

Silver bluestem [Bothriochloa laguroides (DC.) Herter] is a warm-season grass native to Texas. This perennial grass plays a crucial role in maintaining ecological balance and supporting wildlife in the region. In September 2022, while investigating the ecological impact of invasive grass species on a grassland located near Pipe Creek (TX), B. laguroides plants were observed showing symptoms that included yellowing of the blades and occasionally brown discoloration of the midveins and stems (Fig. S1). Disease incidence was estimated as 2% of silver bluestem plants in the 2 hectares surveyed. To investigate the possibility of a phytoplasma association with the symptoms, four symptomatic and four asymptomatic leaf samples were collected for further study. Total DNA was extracted from leaf midribs using a DNeasy Plant Mini Kit (Qiagen). The DNA extracts were tested using a phytoplasma-specific quantitative PCR assay (Hodgetts et al. 2009), which identified two out of the four symptomatic B. laguroides samples as positive for phytoplasmas. A semi-nested PCR assay for amplification of the 16S rRNA gene fragment was then performed on these samples with primers P1/16S-SR followed by P1A/16S-SR (Deng, and Hiruki 1991; Lee et al. 2004), and two additional housekeeping genes (tuf and secA) were amplified as previously described (Makarova et al. 2012; Hodgetts et al. 2008; Bekele et al. 2011). All amplicons of the expected size, 1.5 kb (16S rRNA), 0.4 kb (tuf) and 0.6 kb (secA), were purified and bi-directionally sequenced using primers from each gene second round PCR amplification. Analysis of the sequences derived from the three gene fragments revealed no variation between the two plant samples and confirmed they originated from a phytoplasma, termed strain TXSB-2 (Texas Silver Bluestem). Sequences from a single B. laguroides plant DNA extract were deposited in GenBank with accession numbers OR711913 (16S rRNA), OR709687 (tuf) and OR709688 (secA). A BLAST search of the 16S rRNA gene sequence from TXSB-2 against the NCBI nucleotide database, showed 99.58% sequence identity with an unclassified phytoplasma clone 139-1 from a leafhopper collected in Australia (MW281491) (Fig. S2). The partial nucleotide sequence of the tuf and secA genes showed 90.60% and 89.78% similarity, respectively, to the corresponding genes in 'Ca. P. sacchari' strain SCWL1 (CP115156) associated with sugarcane in China. The iPhyClassifier, an interactive online tool for phytoplasma identification and classification (Zhao et al. 2009), was used to determine the 'Candidatus Phytoplasma' species affiliation and group/subgroup classification status of this phytoplasma strain. The result showed that the TXSB-2 16S rDNA shared 98.94% sequence identity with that of the 'Ca. P. sacchari' reference strain (GenBank accession: MN889545), indicating TXSB-2 is a 'Ca. P. sacchari'-related strain. The result from virtual restriction fragment length polymorphism (RFLP) analysis of the 16S rDNA F2nR2 fragment revealed that TXSB-2 possessed a collective RFLP pattern that is distinct from the reference patterns of all established phytoplasma ribosomal subgroups and is proposed as the representative strain of a new subgroup designated as 16SrXI-H. 'Candidatus Phytoplasma sacchari' has been reported associated with sugarcane grassy shoot disease, which is considered among the most damaging diseases of sugarcane across parts of Southeast Asia and India (Kirdat et al. 2021). The same phytoplasma was recently confirmed infecting sorghum in India (Nithya et al. 2024). To our knowledge, this is the first report of a 'Ca. P. sacchari'-related strain infecting B. laguroides in the United States. Moreover, B. laguroides is a new host for strains related to 'Ca. P. sacchari'. Further investigation is required to elucidate the prevalence of this disease in the area, its natural vectors, and the potential consequences arising from this novel phytoplasma strain within its ecosystem in Texas.

Surface Resistance Controls Differences in Evapotranspiration Between Croplands and Prairies in U.S. Corn Belt Sites

AbstractWater returned to the atmosphere as evapotranspiration (ET) is approximately 1.6x global river discharge and has wide‐reaching impacts on groundwater and streamflow. In the U.S. Midwest, widespread land conversion from prairie to pasture to cropland has altered spatiotemporal patterns of ET, yet there is not consensus on the direction of change or the mechanisms controlling changes. We measured ET at three locations within the Long‐Term Agroecosystem Research network along a latitudinal gradient with paired rainfed cropland and prairie sites at each location. At the northern locations, the Upper Mississippi River Basin (UMRB) and Kellogg Biological Station (KBS), the cropland has annual ET that is 84 and 29 mm/year (22% and 5%) higher, respectively, caused primarily by higher ET during springtime when fields are fallow. At the southern location, the Central Mississippi River Basin (CMRB), the prairie has 69 mm/year (11%) higher ET, primarily due to a longer growing season. Differences in climate and that the CMRB prairie is remnant native prairie, while the UMRB and KBS prairies are restored, make it challenging to attribute differences to specific mechanisms. To accomplish this, we examine the energy balance using the Two‐Resistance Method (TRM). Results from the TRM demonstrate that higher surface conductance in croplands is the primary factor leading to higher springtime ET from croplands, relative to prairies. Results from this study provide insight into impacts of warm season grasses on the hydrology of the U.S. Corn Belt by providing a mechanistic understanding of how land use change affects the water budget.

165 Does supplementation of beef cattle impact the agronomy performance of tall fescue and bermudagrass pastures?

Abstract In forage-based beef cattle systems, bermudagrass [Cynodon dactylon (L.) Pers.] and tall fescue (Festuca arundinacea Schreb.) stand as widely used forage species. The strategic supplementation of animals may reduce forage intake, thereby potentially affecting the agronomic performance of these grasses. Our objective was to evaluate the impact of beef cattle supplemental feeding on forage accumulation, forage mass, and nutritive value in tall fescue and bermudagrass pastures. Two studies were conducted where pregnant beef cows were supplemental fed 1% of BW on DM basis of corn silage daily (SUP) or received no supplemental feeding (free-choice mineral; NON). Trial 1: conducted on bermudagrass pastures (BERM) grazed from late May to early October. Experimental design for BERM was completely randomized design with 4 pastures per treatment (n = 3 cows/pasture; average 5 years of age; 550 ± 72 kg initial BW). Trial 2: conducted on fescue pastures (FES) with an experimental design of a 2 x 2 factorial arrangement. The two factors evaluated were fescue type [TOXIC (507 ppm ± 0.82 SEM ergot alkaloids; 92.5% endophyte infection)] or non-toxin-producing (NT; 5 ppm ± 2.50 SEM ergot alkaloids; 38.6% endophyte infection) and two levels of supplemental feeding (NON or SUP). There were 3 or 4 replications per fescue x supplemental feeding treatment (n = 15 pastures), stocked with 3 cows/pasture (average age 4.75 years; 558 ± 73 kg initial BW) and grazed from early May through November. Forage accumulation (FA) was estimated every 28 d using the paired-cage method (4 exclosure cages/pasture). On each exclusion period, the forage mass (FM) was estimated both inside and outside the cages through destructive sampling method and samples analyzed for forage quality. Pasture was experimental unit and repeated measures were included in analysis. Bermudagrass FM tended to be increased by 31% with SUP (P = 0.09; 774 kg/ha greater). Forage accumulation tended (P = 0.07) to be affected by feeding method x month. There was greater FA in June for SUP; however, there was greater FA for NON in July. SUP pastures had greater ADF (1% more; P = 0.01) and reduced TDN (1.5%; P < 0.01) than NON. Forage mass tended to be 10% greater for TOXIC pastures (P = 0.09; 409 kg/ha more forage mass). Supplemental feeding on fescue did not impact FM (P = 0.74). Forage accumulation was not impacted by fescue type, feeding method, nor the interaction (P > 0.30). Cows generally do not consume as much toxic fescue, thus more forage is available in pastures and supplemental feeding did not alter forage parameters. However, on a warm-season grass that is growing while supplemental feeding, forage availability was increased and maybe useful as method to increase stocking rates or as mitigation tool during drought.

145 The effect of a plant secondary metabolite blend on energy metabolism and nutrient balance of beef cattle consuming low-quality warm season grass hay

Abstract Plant secondary metabolites (PSM) such as condensed tannins, hydrolysable tannins, saponins and essential oils purportedly impact rumen fermentation at low inclusion rates in beef cattle diets. Twelve steers (347 ± 23 kg BW) of British and continental influence were allocated to 1 of 4 replicated 3 x 3 Latin squares. Latin squares each had 14 d periods (10 d adaptation and 4 d for sample collection). All cattle were fed ground warm-season hay (89.5% DM, 92.8% OM, 65.9% NDF, 43.6% ADF, 6.70% CP) at 1.5% of BW (DM-basis) and supplemented with soybean meal at 0.18% of BW (DM-basis) once daily. Treatments consisted of a blend of tannins, saponins and essential oils provided at 0% (Control), 0.1% (Low) and 0.3% (High) of hay offering. Treatments were mixed with daily soybean meal allotment and provided before feeding of hay. Urine and feces were completely collected from d 11 through 14 at 0730 h and daily amounts of urine and feces produced were measured gravimetrically. Measures of gaseous exchange were determined via indirect calorimetry on d 13 and 14. Open-circuit respiration calorimeters (91.4 × 91.4 × 191.2 cm) were used to collect respired gas and ruminal methane production. Total oxygen consumption and production of carbon dioxide and methane were calculated from the difference in concentration of oxygen, carbon dioxide, and methane from air exhausted from each calorimeter and concentration of oxygen, carbon dioxide, and methane in ambient air and multiplied by amounts of air flowing from each calorimeter standardized for temperature, pressure, and humidity. Data were analyzed for a Latin square using the MIXED procedure of SAS with fixed effect of treatment, period and square and random effect of steer. Linear and quadratic contrast coefficients were assigned using PROC IML for uneven spacing of treatments. Significance was declared when P ≤ 0.05. Per experimental design, forage N and OM intake did not differ (P ≥ 0.77). Apparent total tract digestion of OM, NDF and ADF did not differ (P ≥ 0.66) among treatments. Fecal nitrogen excretion, and the percentage of N excreted in feces increased linearly (P = 0.01). N balance tended (P = 0.08) to decrease linearly with increasing PSM supplemented. Methane (L/kg DMI) was not affected (P = 0.28) by treatments. Methane, GE, DE, and ME (mcal/kg DMI) was unaffected (P = 0.19) by treatment. Under the conditions of this experiment, a blend of PSM had little effect on rumen fermentation or energy metabolism in beef steers.

80 Effect of copper bolus administration on circulating copper concentration, blood metabolites and parasite load

Abstract In Texas and Southeastern United States Cu concentration in the soil is in the lower 50th percentile, this leads low bioavailability of copper for livestock. Therefore, a 70-d completely randomized block design study was conducted to determine the effects of Cu and fecal egg count in grazing beef cows (n = 40). Cows were blocked by parity and body weight (BW) then randomly assigned to 1 of 2 treatments: standard offering of copper via free choice mineral (CON; Ragland Sweet Mag Mineral Mix, 425 ppm Cu) and those receiving a 25 mg Cu rumen bolus in addition to the standard offering (Santa Cruz Animal Health, Dallas, TX). Cattle were managed as a single herd at the with equal access to water, a grain supplement, and a warm season grass pasture. Fecal samples via rectal grab, blood via coccygeal venipuncture, BW, BCS, hair coat (1 being the healthiest) and shedding (1 being the most slick) scores were all collected on d 0, 10, 24, 38, and 66 relative to treatment initiation. Sera were analyzed to determine circulating Cu, macrominerals, urea, creatinine, and various blood proteins. Fecal egg counts were conducted to determine Coccidial, Moniezia, and Trichostrongyle egg content. Data were analyzed using the GLIMMIX procedure of SAS 9.4 (SAS inst. Inc, Cary, NC). No treatment × day interaction (P = 0.988) was observed for circulating Cu; however, Cu decreased (P < 0.001) in all cattle over time, and TRT tended (P = 0.090) to have increased Cu compared with CON. No interactions or main effects occurred (P > 0.509) for BW. No interaction (P = 0.4389) occurred for BCS, hair, or shedding scores. Hair scores (P < 0.001), shedding scores (P < 0.041), and BCS(P < 0.001) decreased in all cattle over time. Body condition for TRT (5.2 ± 0.056) was greater (P =.0024) than CON (4.9 ± 0.057). Hair score by day decreased (P < 0.001) in TRT, while the shedding had a tendency of increasing (P = 0.0411) by TRT. There were no interactions or main effects on Coccidial (P < 0.220) or Trichostrongyle (P < 0.274) egg content. While no interaction (P = 0.673) for Moniezia was observed, TRT tended (P = 0.095) to have fewer Moniezia eggsthan CON. No interactions (P > 0.100) were observed for any of the blood metabolites, and while they differed (P < 0.05) day to day for all cows, no treatment effects occurred (P > 0.10). Although Cu bolus administration at this concentration did tend to change Cu copper in the animal, effects resulting from it were minimal.

74 Effect of grazing native warm season grasses on parasitism and growth in weaned Katahdin lambs

Abstract Parasitism in lambs during the post-weaning period has effects on growth, survival, and sheep enterprise profitability. Opportunities to minimize exposure to infective larvae during this period may reduce clinical effects and improve lamb performance. Native warm season grasses (NWSG) offer increased growth during summer months and taller plants that allow grazing at greater heights. The objective here was to evaluate NWSG as a forage for post-weaning development of lambs in spring lambing, forage-based systems. Over 2 yr, Katahdin lambs (Yr 1, n = 30; Yr 2, n = 31) were managed at a producer farm in the piedmont region of North Carolina. Beginning 2 wk post-weaning, lambs were randomly assigned to graze on either NWSG (Big Bluestem and Indiangrass) or cool season grass (CSG, Kentucky 31 Tall Fescue base) pasture. Lambs were continuously grazed for 70 d in Yr 1 and 55 d in Yr 2. Fecal egg count (FEC), FAMACHA score, and body weight (BW) were measured every two weeks. Lambs were dewormed at FAMACHA ≥ 3. Forage analysis was conducted at the start and end of the grazing period. Statistical analysis were performance using the PROC Mixed procedure of SAS. Lambs in each group were raised in similar litter sizes and sire and sex were evenly distributed between groups. Fecal egg count and growth estimated breeding values (EBV) were similar between NWSG and CSG groups. In Yr 1 and 2, no differences were observed in FEC between grazing groups (P > 0.05). However, FEC did increase in both groups throughout the grazing period (P < 0.05). In Yr 1, no differences were observed in total BW gain (P = 0.74). However, in Yr 2, lambs grazing CSG had greater total BW gain than the NWSG group (P < 0.05). In both years, there were no differences in the percentage of lambs requiring deworming (Yr 1, P = 0.36; Yr 2, P = 0.47) but lambs requiring treatment had greater FEC EBVs (P < 0.05). Nutrient quality of NWSG pasture was reduced compared with CSG pastures. Total digestible nutrients and crude protein were less in NWSG compared with CSG pastures (Yr 2: 61.5% vs. 63.9% and 8.9% vs. 13.6%, respectively) and neutral detergent fiber was greater (Yr 2: 74.1% vs. 65.2%, respectively) resulting in decreased nutrient availability for NWSG group. While NWSG may provide additional biomass for summer grazing, rapid maturity rates may limit nutrient availability for lambs resulting in decreased growth performance despite similar levels of parasitism. Lamb FEC EBV may have a role in parasite resistance and deworming requirements regardless of forage type. Thus, genetics must be considered along with grazing management as part of an integrated parasite management plan.

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.

160 Comparison of native to introduced mixed warm-season grass pastures on heifer weight gain and fecal egg count

Abstract The objective of this study was to compare summer body weight gain and fecal egg count change of spring weaned heifers grazing either native grass (NG; predominately big bluestem [Andropogon gerardii)) or mixed warm-season grass (MWS; predominately bermudagrass (Cynodon dactylon) and crabgrass (Digitaria sanguinalis)]. Pastures (n = 3 per treatment and 2.02 ha each) were continuously stocked with 10 heifers each in yr 1 and 2, respectively. All pastures received 56 kg/ha N mid-May. Grazing began at the end of May and all pastures were grazed for 84 d. Heifers were previously treated with an anthelmintic at weaning (benzimidazole in yr 1 and macrocyclic lactone plus benzimidazole in yr 2). Dependent responses were analyzed for the fixed effect of treatment, year, and their interaction and random effect of pasture. Pasture was the experimental unit. Fecal egg counts as eggs per gram were transformed to a log base 10 value (log10:epg). Average daily gain differed between treatments by year (P = 0.05). In yr 1, NG gained 0.22 kg/d more than MWS; whereas, in yr 2, NG gained 0.11 kg/d more than MWS. Heifers grazing NG were 15.9 ± 3.52 kg heavier than MWS by d 84 (P = 0.01). Change in fecal egg count differed by year (P < 0.001) and tended to be less for NG compared with MWS (P = 0.11). Native grass fecal egg count change was 45% of MWS. Impact of forage system on internal parasite load may be attributed to canopy structure. Native grasses averaged 67 and 81 ± 2.3 cm at the beginning of grazing in yr 1 and 2, respectively (P = 0.01). Native grass height in yr 1 and yr 2 was similar (P = 0.68) by wk 12 and averaged 41 ± 3.2 cm. By comparison, grazing in the MWS system would be much closer to the soil surface. Initial forage mass and forage mass change was greater in NG than MWS and differed by year (treatment × year P = 0.02 and 0.05, respectively). While this study demonstrated beneficial responses to grazing NG over MWS during summer months, further information regarding how these summer forage options compare under varied stocking rate and grazing duration is warranted.

134 A 12-year summary of effects of body weight at breeding and synchronization protocols on reproductive success of Bos indicus-influenced beef heifers grazing warm-season grasses

Abstract A retrospective analysis of 5 studies (2011 to 2022) evaluated the effects of body weight and synchronization protocols before the start of breeding season on reproduction of Bos indicus-influenced beef heifers. Data were collected from 594 Brangus crossbred heifers weaned on average at 280 ± 26 d of age, allocated to bahiagrass pastures (4 to 5 heifers and 0.8 to 1.0 ha/pasture), and supplemented with soybean hulls-based concentrate (0.5 to 1.8% of body weight, (BW); dry matter basis] from 2 weeks post-weaning until the end of the breeding season (189 ± 24 days of supplementation). Heifers were initially sorted into those that were supplement (S) and were not supplemented (NS) assigned to an estrous synchronization protocol before the start of the breeding season. Then, within each synchronization group, heifers were sorted into those that were below (BE) or above (AB) the average BW of all heifers (300 kg) at the start of the breeding season (n = 130, 126, 146, and 192 for BE+NS, BE+S, AB+NS, and AB+S heifers, respectively). Data were analyzed using GLIMMIX procedure of SAS using synchronization, BW at breeding, and resulting interaction as fixed effects, and heifer (synchronization × BW), study, and pasture(study) as random effects. Effects of synchronization × BW at breeding and synchronization were not detected for heifer BW and overall average daily gain (ADG). However, AB heifers were always (P < 0.0001) heavier from post-weaning until the end of the breeding season and had (P < 0.0001) greater overall ADG than BE heifers. Effects of synchronization × BW at breeding tended (P = 0.07) to detected for puberty attainment at the start of the breeding season, which was least (P < 0.01) for BE+NS, did not differ between BE+S vs. AB+NS (P = 0.37), and was greatest for AB+S heifers (31, 66, 60, and 81 ± 7.4%, respectively). However, final pregnancy and calving percentages differed (P < 0.01) only for BE vs. AB heifers (68 vs. 81 ± 4.4% and 63 vs. 75 ± 5.2%, respectively). Effects of synchronization × BW at breeding tended (P = 0.10) to detected for percent of heifers calving within the first 30 days of the calving season, which was least (P < 0.03) for BE+NS and did not differ (P = 0.20) among BE+S, AB+NS, and AB+S heifers (48, 69, 61, and 64 ± 5.9%, respectively). Hence, in Bos indicus-influenced beef heifers, BW above 300 kg at the start of the breeding season led to improved overall reproductive performance compared to BW < 300 kg, whereas estrous synchronization protocols had positive effects to puberty attainment (regardless of heifer BW) and improved early calving distribution only when heifers were below 300 kg at the start of the breeding season.