Bermudagrass Pastures Research Articles

PSXII-6 Canopy height as a predictor of forage biomass in native rangelands and bermudagrass pastures

Abstract Accurate and less laborious estimates of forage biomass are needed for research and management decisions in grazing lands. Our objective was to develop linear regressions to estimate forage biomass using canopy height in both native rangelands and introduced bermudagrass [Cynodon dactylon (L.) Pers.] pastures in the Cross Timbers and Southern Tallgrass Prairie Ecoregion. Twelve pastures averaging 26 acres each were equally distributed in two ranches located in the Love County, Southern Oklahoma. The native rangelands comprise native tall- and mid-grasses along with forbs and some woody shrub species. Little bluestem [Schizachyrium scoparium (Michx.) Nash] is the dominant species, with brome (Bromus L.), broomsedge bluestem (Andropogon virginicus L.), ragweed (Ambrosia psilostachya DC.), purpletop tridens [Tridens flavus (L.) Hitchc.), dropseed (Sporobolus R. Br.), and Indiangrass [Sorghastrum nutans (L.) Nash] commonly found. The introduced pastures are dominated by bermudagrass with cereal rye (Secale cereale L.) and horseweed [Conyza canadensis (L.) Cronquist] commonly found as well. Samples occurred at pre- and post-grazing conditions from summer 2022 to fall 2023. Measurements included canopy height and hand-clipping all herbaceous vegetation in a 0.25-m2 frame. Forage samples were fresh weighed then dried for 72 h at 60°C and reweighed. There were 760 and 786 samples collected at native and introduced pastures, respectively. Data were analyzed using PROC GLM of SAS (SAS Inst., Cary, NC) including canopy height (cm) and forage biomass [kg of dry matter (DM)/ha] as independent and dependent variables, respectively. Only regressions including all parameters as significant (P < 0.05) were selected, and coefficient of determination (R2) and root mean square error (RMSE) were used to evaluate the predictive ability of the regressions. There was a pasture type (native or introduced) × season interaction (P < 0.001). This interaction is likely explained by the dominant species in each pasture type across seasons as well as their phenological stage. For the native rangeland, the spring linear regression including the quadratic term had the best fit with the greatest R2 (0.56) and the least RMSE (944 kg DM/ha; Table 1). Summer and fall regressions had R2 of 0.45 and 0.24 and RMSE of 1139 and 1343, respectively. No regressions were selected for winter because parameters were not significant (P = 0.53 and P = 0.18). For the introduced bermudagrass pasture, regressions presented R2 ranging from 0.24 and 0.30 except during the winter (R2 = 0.09). These results indicate that forage biomass can be acceptably estimated using canopy height only during spring in the native rangeland.

PSIV-26 Extent of use of supplemental feeding in beef cattle operations across the Southeast: A report of the regional survey

Abstract With input costs on the rise, researchers and producers, alike, are seeking alternative management strategies for profitable and sustainable beef production. Studies suggest that supplemental feed provided to grazing cattle may be used to offset some of the cost. However, there is a lack of knowledge on the extent of supplemental feeding programs in the southeastern US and which feeds may be used in these programs. Thus, the objective of this study was to better understand supplemental feeding practices and choices among beef producers in the southeastern US. To address this objective, a 24-question survey was distributed through Extension and commodity organizations to beef producers across the Southeast. This survey received 118 complete responses. The majority of respondents operated cow-calf production systems (65.6%) on either tall fescue or bermudagrass pastures (32.7 and 28.0%, respectively). Approximately 88% of these producers employed some type of supplemental feeding strategy, but there is no clear decision on whether commodity or byproduct feedstuffs were preferred. The leading commodity used was corn (61.4%), while common byproducts included whole cottonseed, corn gluten feed, and soybean hulls (17.1, 16.6, and 14.4%, respectively). At the end of the survey, the participants were asked to submit a sample of their byproduct supplements to have a nutritive analysis completed to better understand what nutritional components the products they are feeding contain and how they may vary from place to place. Some of the products that were sent in include whole cottonseed, cotton byproduct, corn gluten meal, distillers grain, chicken litter, and others. The nutritional test being run on these samples included crude protein and fiber analysis. The crude protein of the samples received ranged from 13.3% to 30.3% with an average of 21.5%. The fiber profile received ranged from 45.5% to 76.3% with an average of 59.9%. With the information recorded from these tests, recommendations can be provided on different feeding methods in both commercial settings as well as research settings.

PSXIII-6 Weed encroachment reduces soil organic carbon stock in bermudagrass pastures

Abstract Weed encroachment might reduce stocking rate and overall animal performance in grazing systems. In addition, weeds can affect soil organic carbon because of changes in primary productivity and belowground biomass compared with well managed pastures. This study assessed different levels of spiny pigweed (Amaranthus spinosus L.) encroachment on bermudagrass [Cynodon dactylon (L.) Pers.] pastures. Spiny pigweed was drilled onto bermudagrass pastures to create three levels of encroachment: weed free, medium encroachment, and high encroachment. The weed-free pastures were treated with herbicide to control weed encroachment, and the medium had strips where weeds were controlled and strips uncontrolled. The high encroachment had no weed control. Treatments (weed free, medium, and high) were allocated in a randomized complete block design. The spiny pigweed was drilled in 2020 and grazing occurred from 2021 to 2023. Soil samples were collected in October 2023 to assess soil organic carbon (C) stock by determining soil bulk density and soil C concentration in the 0- to 5- and 5- to 15-cm layers. Results indicated that weed-free and medium-encroached pastures had greater soil organic carbon stock (20.2 Mg C/ha) compared with the weed-infested pastures (17.2 Mg C/ha). Soil C concentration was similar, but soil bulk density was lower in the weed-infested pastures, affecting soil carbon stocks.

64 Effects of alternative finishing methods on performance and carcass quality of beef feeder steers

Abstract There has been an interest in directly locally marketing finished beef end products in Arkansas; however, most beef operations do not have the infrastructure to finish cattle conventionally. The objective of this study was to evaluate two non-traditional finishing methods (pasture-based with supplement) compared with a conventional finishing method on live performance and carcass quality of feeder steers. Crossbred beef steers (n = 63; 363.9 ± 28.7 kg) were blocked by body weight (BW) and assigned to pens (n = 3 steers/pen) with 7 pens randomly allocated to each treatment: conventional feedlot finishing diet with roughage included in the ration (FDLT); high starch supplement fed at 2 to 2.25% of BW with ad libitum access to bermudagrass pasture (STCH); or high by-product supplement fed at 2-2.25% of BW with ad libitum access to bermudagrass pasture (BYPD). Steers were fed their respective diets once daily and weighed on d 0, 28, 56, 84, 112, 140, and 161. Once cattle reached their targeted endpoint, they were transported to and harvested at a commercial slaughter facility in Arkansas City, Kansas. Carcass data were collected including hot carcass weight (HCW), preliminary yield grade (PYG), yield grade (YG), quality grade (QG), dressing percentage (DP), and final carcass value. Data were analyzed using PROC GLIMMIX and MIXED (SAS 9.4); pen was the experimental unit, treatment was a fixed effect, and block was considered a random effect. Cattle fed FDLT and BYPD had a greater BW on d 84, 112, and 140 (P ≤ 0.02) and greater overall carcass-adjusted BW (P = 0.03) compared with STCH. Average daily gain (ADG) was greater on d 84 (P = 0.03) for FDLT compared with STCH and BYPD. Overall carcass-adjusted ADG tended (P = 0.09) to be greater for FDLT and BYPD compared with STCH. As expected, cattle fed FDLT had greater dry matter intake (DMI) compared with STCH and BYPD for the entire study (P ≤ 0.0005). Both STCH and BYPD had a more efficient feed-only feed conversion on d 28, 56, 112, 140, and 0-161 (P ≤ 0.05) and were more economical (P < 0.0001) than FDLT. In this study, cattle fed BYPD were more profitable (P ≤ 0.04) compared with STCH and FDLT. Hot carcass weight tended (P = 0.13) to be greater and final carcass value (P = 0.01) was greater for BYPD and FDLT compared with STCH. No differences (P ≤ 0.78) were noted for PYG, YG, QG, or DP. Data from this study suggests feeding supplemental diets to beef cattle grazing pasture could successfully be used as an alternative finishing method without affecting carcass quality.

Estimating Bermudagrass Aboveground Biomass Using Stereovision and Vegetation Coverage

Accurate information about the amount of standing biomass is important in pasture management for monitoring forage growth patterns, minimizing the risk of overgrazing, and ensuring the necessary feed requirements of livestock. The morphological features of plants, like crop height and density, have been proven to be prominent predictors of crop yield. The objective of this study was to evaluate the effectiveness of stereovision-based crop height and vegetation coverage measurements in predicting the aboveground biomass yield of bermudagrass (Cynodon dactylon) in a pasture. Data were collected from 136 experimental plots within a 0.81 ha bermudagrass pasture using an RGB-depth camera mounted on a ground rover. The crop height was determined based on the disparity between images captured by two stereo cameras of the depth camera. The vegetation coverage was extracted from the RGB images using a machine learning algorithm by segmenting vegetative and non-vegetative pixels. After camera measurements, the plots were harvested and sub-sampled to measure the wet and dry biomass yields for each plot. The wet biomass yield prediction function based on crop height and vegetation coverage was generated using a linear regression analysis. The results indicated that the combination of crop height and vegetation coverage showed a promising correlation with aboveground wet biomass yield. However, the prediction function based only on the crop height showed less residuals at the extremes compared to the combined prediction function (crop height and vegetation coverage) and was thus declared the recommended approach (R2 = 0.91; SeY= 1824 kg-wet/ha). The crop height-based prediction function was used to estimate the dry biomass yield using the mean dry matter fraction.

Evaluating supplementation programs for growing calves grazing bermudagrass pastures

Evaluating supplementation programs for growing calves grazing bermudagrass pastures

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.

133 Effects of supplementing corn silage to fall-calving heifers and cows grazing bermudagrass on cow and calf performance and physiology

Abstract The objective was to test the effect of supplemental feeding of corn silage to cows grazing bermudagrass pastures on cow and calf performance and physiology. In a completely randomized design, multiparous and primiparous Angus-crossbred cows (n = 24) grazed bermudagrass pastures assigned to one of two levels of supplemental feeding (non-supplemented or supplemented at 1% of BW on a DM basis of corn silage) during the growing season. Each replicate (pasture, n = 4 per treatment) was stocked with 3 cows. Cows averaged 155 ± 14 d of gestation at trial initiation. Cows were fed corn silage (38% DM, 7.83% CP DM basis) daily in fenceline bunks, and supplementation rate was adjusted throughout the trial to maintain 1% of BW. Cows were weighed on two consecutive days at both initiation and conclusion of the trial and cows were maintained on similar diets for 4 d prior to collecting weights to minimize variation in ruminal fill. Body weight (BW), body condition score (BCS), hair score (HS), hair length (HL), and rump fat (RF) measurements were collected at initiation (the middle of the second trimester), trial mid-point (beginning of third trimester), and approximately 2 wk before estimated parturition. Cows were removed from experimental pastures upon trial conclusion and relocated to calving pastures consisting of tame grasses (>65% bermudagrass). Data were analyzed as a mixed model with pasture as experimental unit and cows within pasture as subsamples. Cows began the trial at an average BW of 549 ± 22 kg (SEM) and an average BCS of 5.2 ± 0.17 (SEM). Supplementation of second and third trimester pregnant cows on bermudagrass did not influence BW gain, BCS, HS, or HL (P > 0.27). Rump fat tended (P = 0.15) to be increased with supplemental feeding. Supplemental feeding of corn silage on warm season perennial grass during the growing season did not appear to impact late gestation cow performance at the level fed in this study.

Detection and mapping of Amaranthus spinosus L. in bermudagrass pastures using drone imagery and deep learning for a site‐specific weed management

AbstractWeed encroachment negatively affects pasture productivity by reducing herbage allowance, stocking rates, and livestock performance. Amaranthus spinosus L. is a weed species widely found in pastures worldwide and is considered challenging for ranchers due to its great potential for invasion, making it difficult to control. The high costs of chemical application and the global concern about environmental impacts restrict indiscriminate herbicide spraying in pastures. Site‐specific weed management (SSWM) is a weed management strategy based on weed spot‐spraying that has the potential to overcome these issues. Images from unmanned aerial vehicles (UAVs) can provide valuable information for weed mapping to drive the herbicide application in pastures. Deep learning techniques have been highlighted in image classification tasks. We developed a deep convolutional neural network (CNN)‐based image segmentation model based on the U‐Net architecture to detect and map Amaranthus spinosus in bermudagrass pastures using red–green–blue images acquired through UAV flying in moderate‐high altitude. The images were acquired from twelve paddocks under three treatments (weed‐free, weed‐strips, or weed‐infested) during the summer (2021‐2022). The CNN model was able to detect around 80% of the A. spinosus with an average prediction accuracy of 94%. Our weed mapping showed the potential of using the U‐Net model to generate a herbicide application map to be inserted into the sprayer system, reducing up to 76% of the amount of herbicide applied. Further studies are encouraged to increase the robustness of the model across species and development stages and develop sprayer systems to implement the spot‐spraying in field conditions.

Economic assessment of using Bermudagrass stockpiling and annual cereal pasture to extend grazing in cow-calf operations.

Bermudagrass (Cynodon dactylon L.) stockpiling and cool-season annual pastures can extend grazing seasons in cow-calf operations and reduce winter feeding costs, but less is known about how these practices interact and their effect on producer profitability. Data from a completely randomized-design experiment in South-Central Oklahoma were collected on three grazing systems for cows and calves: bermudagrass pasture (CONTROL), stockpiled bermudagrass and interseeded cool-season pasture (SPINT), and stockpiled bermudagrass plus cropland no-till seeded with a summer cover-crop followed by cool-season annuals (SPCROP). A mixed model was used to estimate the effects of grazing system on weaning weights, total hay, and total range cubes (crude protein [CP] = 30%) fed in each system. Enterprise budgeting was used to calculate the expected net return of each system. Weaning weight did not vary between systems (P = 0.6940), resulting in similar revenues. Relative to other treatments, the quantity of cubes fed in the CONTROL system were significantly higher (P < 0.0001) while hay fed was significantly higher in the SPCROP system (P = 0.0036). Increased machinery costs, seed costs, and fertilization requirements in bermudagrass stockpiling, interseeding, and cropland production outweighed the cost savings associated with less feeding. Total costs were $446 ha-1 ($722 hd-1), $451 ha-1 ($732 hd-1), and $553 ha-1 ($895 ha-1) for the CONTROL, SPINT, and SPCROP systems, respectively. Overall, the CONTROL system was $3.13 ha-1 ($5.08 hd-1) and $98.91 ha-1 ($160.10 hd-1) more profitable than the SPINT and SPCROP systems.

Farm-Scale Effectiveness of Feed Additives Supplied through a Mineral Mix for Beef Cattle Grazing Tropical Pastures

The effectiveness of feed additives delivered through free-choice mineral mixtures (MMs) to grazing cattle remains unclear. Two farm-scale and one in vitro experiment (Exp.) were conducted to investigate the effects of salinomycin and virginiamycin, delivered through an MM, on growing bulls grazing tropical pastures. In Exp. 1, 316 zebu (Bos indicus) Nellore bulls (225 ± 26.7 kg liveweight (LW)) were randomly allocated to four treatments: (1) MM no additives (CON), (2) MM with salinomycin at 1950 mg/kg (SLI), (3) MM with salinomycin at 780 mg/kg (SHI), and (4) MM with virginiamycin at 1950 mg/kg (VGN). Over 123 days, these bulls grazed tropical grasses on pastures of guinea grass, palisade grass, or Bermuda grass. No significant treatment effects were observed for oocyst eggs or ruminal parameters. Bulls fed VGN had higher average daily gain (ADG) compared to CON (p = 0.02) and SLI (p = 0.03) but similar compared to SHI (p = 0.07). In Exp. 2, 308 zebu cross bulls (237 ± 23.0 kg LW) grazed Bermuda grass paddocks and were allocated into two treatments: (1) MM with no additives (CON) and (2) MM containing virginiamycin at 2522 mg/kg (VGN). Cattle fed VGN had a significantly higher ADG (p = 0.007). Exp. 3 tested salinomycin’s effectiveness in vitro at different exposure times to MM, revealing no impact of exposure time on short-chain fatty acid production. In conclusion, virginiamycin delivered through free-choice MM can increase grazing beef bulls’ ADG by 12% compared with CON, with no clear link to rumen fermentation or coccidiostat effects.

Developing the herbage allowance-nutritive value- based pasture factor for estimating daily herbage intake of stocker cattle grazing bermudagrass pasture

Developing the herbage allowance-nutritive value- based pasture factor for estimating daily herbage intake of stocker cattle grazing bermudagrass pasture

Relationships of residual feed intake and residual average daily gain with carcass traits and growth of Brahman steers

The objectives of this study were (a) to quantify residual feed intake (RFI), residual average daily gain (RADG), and G:F efficiencies for yearling Brahman bulls; and (b) to ascertain the relationships of these ef- ficiency groupings with subsequent growth, feedlot per- formance, and carcass characteristics of Brahman steers. For each of 3 years, yearling (380 d of age) Brahman bulls (n = 56, 47, and 34 head) were fed for 70 d using Calan gates (American Calan Inc.), with 5 to 6 head per pen. After feeding, efficiency mea- sures of RFI, RADG, and G:F were calculated for each bull. For each efficiency measure, bulls were classified into 4 efficiency groups based on 0.5 standard deviation from the means. In early July after Calan gates, bulls were stocked on bermudagrass pastures. At completion of stocking (19 mo, 400 kg) steers were shipped 700 km to a South Texas feedlot. After feeding, steers were transported 65 km to a commercial abattoir. In year 3, steaks from the 13th rib were dissected, vacuum-packed, and frozen for Warner–Bratzler (WB) shear force measurement. During the 70-d period, 3-yr means for daily feed intake, ADG, and G:F were simi- lar for RFI groups. For RADG and G:F groups, feed in- take was similar, but ADG and G:F differed (P < 0.0001) among groupings. Feedlot ADG was similar for all efficien-cy groupings, at approximately 1.5 kg/d. From yearling through feedlot, the most efficient RADG group (group 1) reached harvest earlier than the least efficient RADG group (group 4). Hot carcass weights were greater for the most efficient compared with the least efficient RADG grouping. Internal fat (KPH) was greater (P = 0.04) for the RFI efficiency group 1 compared with group 4. The WB measurement showed that the most tender steaks were from the most efficient groupings and the least ten- der from the least efficient groupings of RADG and G:F. Growth rate from yearling to harvest of the most efficient RADG group has significant economic implications for Brahman bulls– steers. Steak tenderness in the 4 RADG groupings showed the most direct alignment for most efficient compared with the least efficient Brahman steers.

110 Improving Southern Bermudagrass Pastures with Alfalfa: An Evaluation of the Impacts of Alfalfa Establishment Timing and Crabgrass Competition

Abstract Inclusion of alfalfa (Medicago sativa) in bermudagrass (Cynodon dactylon) pastures improves nutritive value, increases grazing days, and reduces the need for synthetic nitrogen fertilizer. Crabgrass (Digitaria sanguinalis) is a very palatable warm-season annual grass with high nutritive value, prolific reseeding ability, and proclivity to volunteer in many southeastern pastures. Crabgrass is a common pest that requires pre-emergent herbicide technologies to control in alfalfa hayfields used to produce stored forage. However, in a grazing system, crabgrass could serve as a key component to a mixture aimed at increasing nutritive value and filling gaps in the grazing season. The purpose of this study is to evaluate the impact of alfalfa establishment timing (fall vs. spring) in bermudagrass pastures in the Coastal Plains, and the resultant impact of crabgrass inclusion rather than removal in alfalfa bermudagrass mixed pastures on nutritive value, botanical composition, forage accumulation, alfalfa stand density and persistence. This on-going two-year study is being conducted in Tifton, GA using a randomized complete block design with 4 replications of the following 6 treatments: Fall Alfalfa + Summer Crabgrass, Fall Alfalfa, Spring Alfalfa + Summer Crabgrass, Spring Alfalfa, Bermudagrass + Synthetic Nitrogen, and Untreated Bermudagrass Control. Data were collected from plots on a 28 to 35-day interval to determine botanical composition, forage availability, and nutritive value. The projected impact of this research is three-fold; first, to identify how differing management strategies for restoring bermudagrass pastures are improved with inclusion of alfalfa. Second, it aims to quantify and support a recommended timing for planting alfalfa in the coastal plains, and third to estimate the impact of crabgrass inclusion in alfalfa bermudagrass systems. Data evaluation and statistical analysis is ongoing for this research and will be finalized in winter 2022.

131 Evaluating Supplementation Programs for Growing Calves Grazing Bermudagrass Pastures

Abstract Due to factors such as, high delivery costs, supplement availability, and labor; producers are interested in supplement delivery alternatives. Our objective was to determine gain in response to hand-fed (HF) or self-fed (SF) summer supplementation programs at the University of Arkansas Livestock and Forestry Research Station, on 20, 0.81-ha common bermudagrass pastures at a stocking rate of 5 growing calves per pasture (BW ± SD = 247 ± 24.6) over three years. This was a 2 x 2 + factorial arrangement of treatments, which included: Control (CON) – only free choice mineral; HF 1.13 kg/d by-product-based supplement offered only late summer (LS) or all summer (AS); SF tub supplement (PVM Cattle Tub, Positive Feed Ltd., Sealy, TX) either LS or AS. The HF supplement in year was a 50:50 blend of soybean hulls and corn gluten feed, in year 2 an extruded dried distillers grains cube (MasterHand Milling, Lexington NE) was used for HF, while in year 3 corn gluten feed was the HF supplement. Data were analyzed as a generalized randomized complete block design using the mixed procedure of SAS (SAS Inst. Inc., Cary, NC). Fixed effects in the model included supplementation treatment, year, and year by treatment interaction. Even though different HF supplements were used each year there was no year X treatment interactions (P ≥ 0.10); therefore, results are presented pooled across years. Early summer ADG was greater for HFAS (P &amp;lt; 0.01) than CON and SFAS, while supplemental efficiency (SE, kg added gain/kg supplement) in early summer was less (P = 0.05) SFAS than HFAS. Late summer ADG was greater for HF than SF and CON; while SE did not differ (P = 0.52) among treatments. Total supplement costs, in US dollars per steer for SF, were $67.50 when fed AS and $49.36 when fed in late summer only. Supplement costs for HF were much lower, $33.54 and $15.72/steer for AS and LS, respectively. Cost of added gain for SF was $28.33 and $16.14/kg for SFAS and SFLS, respectively. When providing supplement by HF, cost of added gain was $3.32 and $1.68/kg for HFAS and HFLS, respectively. With these results, we determined the most cost-effective way to add gain with supplement to growing calves grazing bermudagrass pasture is to hand-feed. When calves were HFAS, total supplement costs were higher, but considering the greater ADG, ending bodyweight, and supplemental efficiency ratio, HF supplements should provide a positive net return. Calves on this experiment did not respond as expected to the SF supplement, likely because the bermudagrass pastures in this experiment averaged over3% CP and were in excess of 10% even in the LS sampling periods.

18 Influence of Pregnant Cattle Grazing Endophyte-Infected Tall Fescue on Innate Immune Response of Male Offspring

Abstract The objective was to evaluate the influence of dams grazing endophyte-infected tall, toxic, fescue (E+) during gestation on innate immune response of male offspring to an endotoxin challenge. Crossbred pregnant multiparous cows (n = 36) bred to Red Angus sires were housed in replicated E+ or novel endophyte-infected, non-toxic, fescue (NE+) pastures before breeding and through the length of gestation. After parturition, cows and calves were moved to a common bermudagrass pasture until calves were weaned. From this calf-crop, a subset of post-weaned steers (E+ n = 8; NE+ n = 8) were selected for a lipopolysaccharide (LPS) challenge. Steers (302 ± 36 d of age; 261 ± 62 kg body weight) were fitted with jugular vein catheters &amp;gt;7 h before sampling. Blood was collected every 30 min starting 2 h before (Pre-LPS) and 9 h following (Post-LPS) LPS administration (0.5 µg/kg body weight). Sickness behavior score (SBS), cortisol, and glucose were analyzed every 30 min. Complete blood count (CBC) and rectal temperature (RT) were analyzed hourly. Peak concentration, time at peak concentration, baseline, return to baseline, and area under the curve (AUC) were evaluated for cortisol and glucose. Cortisol and glucose were determined by radioimmunoassay and hexokinase colorimetric assay, respectively. The CBC data were analyzed using a Hemavet hemocytology analyzer. Pre-LPS and Post-LPS cortisol, glucose, SBS, RT, and CBC were analyzed using the MIXED procedure of SAS specific for repeated measures with treatment, time, and the interaction as fixed effects and dam sire breed as a random effect. Peak concentration, time at peak concentration, baseline, return to baseline, and AUC for cortisol and glucose were analyzed using the MIXED procedure of SAS with treatment as a fixed effect and dam sire breed as a random effect. There was a Pre-LPS treatment by time interaction for RT (P &amp;lt; 0.05). Pre-LPS monocyte count was lower in offspring of dams grazing E+ relative to NE+ during gestation (P &amp;lt; 0.05). Pre-LPS hematocrit was increased in offspring of dams grazing E+ relative to NE+ during gestation (P &amp;lt; 0.05). There was a Pre-LPS effect of time on SBS (P &amp;lt; 0.05). As expected, Post-LPS cortisol, glucose, RT, WBC, neutrophil count, lymphocyte count, lymphocyte percentage, eosinophils count, eosinophils percentage, hematocrit percentage, RBC, and platelets changed over time in response to LPS (P &amp;lt; 0.05). Post-LPS lymphocyte count and monocyte percentage were decreased in offspring of dams grazing E+ relative to NE+ during gestation (P &amp;lt; 0.05). Post-LPS eosinophils count, eosinophil percentage, and hematocrit were increased in offspring of dams grazing E+ relative to NE+ during gestation (P &amp;lt; 0.05). There was a Post-LPS treatment by time interaction for monocyte count and neutrophil percentage (P &amp;lt; 0.05). Preliminary results suggest an altered innate immune response of male offspring of dams grazing toxic relative to novel fescue during gestation.

Improving bermudagrass in the Southeastern United States with alfalfa as an alternative nitrogen source in grazing systems

AbstractBackgroundBermudagrass (Cynodon spp.) is one of the most common perennial warm‐season forages grown in the Southeastern United States. The incorporation of alfalfa (Medicago sativa) into bermudagrass pastures could serve as an alternative source of nitrogen (N) while also improving the nutritive value of the forage base.MethodsA 2‐year grazing evaluation arranged in a randomized complete block design was conducted from May to September 2018 (Year 1) and May–August 2019 (Year 2) in Tifton, GA, USA. The objective was to compare the production of alfalfa–bermudagrass mixed pastures (BGA) with bermudagrass monoculture pastures with (BGN) or without (BG) the application of synthetic nitrogen on forage production and stocker cattle performance.ResultsDifferences were observed for average daily gain (p = 0.10), gain per hectare (p = 0.02) and stocking rate (p = 0.01), in that BGA was greatest compared to BGN and BG, which did not differ from each other. Furthermore, BGA had increased forage crude protein (p = 0.01) and total digestible nutrients (p = 0.01) compared to BGN and BG. Finally, BGA provided the greatest economic return per hectare compared to BG or BGN.ConclusionsThese data illustrate improved animal performance and forage nutritive value using alfalfa–bermudagrass systems and offer a viable option for producers seeking alternatives to synthetic N sources for bermudagrass pastures in the Southeastern United States.

Grazing cotton crop residue to reduce winter supplementation cost in late-gestation beef cows and assessment of the negative effects of gossypol on fermentation of mixed ruminal microorganisms

This research aimed to evaluate the use of standing cotton crop residue as a winter supplementation source for gestating beef cows and the effects of gossypol, a naturally occurring pigment with potential anti-quality characteristics, on in vitro mixed ruminal microorganism fermentations. Experiment 1 used a 3-yr completely randomized study with 108 Angus cross cows (BW 559 ± 7.9 kg) enrolled in a 30-d grazing trial. Cows were weighed, stratified by weight, and randomly assigned to 1 of 2 treatments: dormant bermudagrass ( Cynodon dactylon ) pasture + bermudagrass hay (GR) or cotton ( Gossypium ) crop residue + bermudagrass hay (CT). Experiment 2 used a completely randomized in vitro mixed ruminal microorganism fermentation with 3 × 5 factorial arrangements of treatments. This included 3 substrates: corn ( Zea mays ; CC), average relative forage quality (RFQ 100) coastal bermudagrass (ABG), and high relative forage quality (RFQ 120) coastal bermudagrass (HBG), along with 5 concentrations of gossypol: 0, 0.0615, 0.123, 0.1845, or 0.246 mg of gossypol/mL. Total hay offered and hay per head per day were greater ( P ≤ 0.02) in the GR group compared with the CT group. Economic analysis indicated that total hay cost, cost per head per day, and cost of gain were all significantly decreased for cows in the CT treatment compared with cows in the GR treatment ( P < 0.002). In vitro DM digestibility and total VFA production were lower ( P < 0.002) as gossypol concentration reached the highest concentration. Results suggest that grazing cotton crop residue is a partial replacement for hay supplementation during the winter months. Increased levels of gossypol have negative effects on DM disappearance and VFA production. The gossypol amount found in crop residue is approximately the same as the lowest concentration evaluated in the in vitro experiment. These results indicate that grazing cotton crop residue should not influence ruminal fermentation.

PSIV-A-11 Effects of Supplementing Extruded Dried Distillers' Grains Cubes to Stocker Cattle Grazing Introduced Pastures on Subsequent Feedlot Performance and Carcass Characteristics

Abstract This research evaluated the effects of supplementing extruded dried distillers’ grains (DDG) cubes to grazing steers on subsequent finishing performance and carcass characteristics. Steers (n = 140) grazed tall fescue (Festuca arundinacea)/bermudagrass (Cynodon dactylon) pastures from 14 April to 17 September 2020 with supplementation treatments (n = 3 pastures/treatment) that included: 1) Fertilized Control (FC), no supplementation on N fertilized pastures (112 kg N/ha); 2) Fertilized Supplement (FS), supplemented DDG cubes at 2.9 kg/d prorated for 3-d/wk feeding on N fertilized pastures; and 3) Supplement (S), supplemented DDG cubes at 0.75% of BW/d prorated for 5-d/wk feeding on unfertilized pastures. All animals were followed through the finishing phase in a commercial feedyard to investigate carryover effects on feedlot performance in 2 pens comingled across supplemental treatment. Carcass characteristics were evaluated via ultrasonography on d0 and d84 of finishing, and measurements were obtained at harvest. Feed DMI were segregated to individual animals according to Guiroy et al. (2001) and Tedeschi and Fox (2020b). Supplemented animals were heavier (P &amp;lt; 0.01) at feedlot entry than FC, but harvest BW did not differ (P = 0.23). However, S and FS required 37 fewer days on feed (P = 0.01) than FC. Supplementation on pasture reduced total feed required (P = 0.02) and feed costs (P = 0.01) relative to FC. Gains were greater (P = 0.02) for FC and FS than S from d0 to d84, but did not differ thereafter (P ≥ 0.15). At harvest, FC had the greatest dressing percent (P &amp;lt; 0.01) and lower yielding carcasses than FS (P = 0.01), but did not differ (P = 0.11) from S. Overall, extruded DDG cube supplementation during grazing did not negatively affect subsequent feedlot performance or carcass characteristics, but reduced the total feed required for finishing.

PSXII-16 Intercropped Sorghum Sudan Grass and Cowpea for Improved Summer Pasture

Abstract Pastures in the southeastern United States are dominated primarily by warm season perennials such as bermudagrass which can be low in energy. Assessment of stocker cattle performance on bermudagrass pastures overseeded with alternative warm-season forages, such as sorghum Sudan grass and cowpea, are scarce. A study was conducted during the summer of 2021 with crossbred steers (n = 72; 305 ± 2.8 kg initial BW) to investigate growth performance when grazing sorghum Sudan grass and sorghum Sudan grass intercropped with cowpea as alternatives to bermudagrass. The experiment was a randomized complete block design with 3 treatments and 3 replicates (2 ha each) per treatment. Treatments were bermudagrass (Cynodon dactylon (L.) Pers) (CON), CON overseeded with brown mid-rib sorghum Sudan grass (Sorghum bicolor L.) (SS), and SS with cowpeas (Vigna unguiculata (L.) Walp) (SSCP) planted in alternate planting passes. Forage samples were collected from 3, 0.25m2 quadrats placed randomly in the next available paddock just prior to grazing. The SSCP pastures had 3 additional randomly placed quadrats, 3 in SS and 3 in CP. Forage crude protein and neutral detergent fiber (NDF) did not differ (P &amp;gt;0.96 and 0.19, respectively) among treatments and averaged 9.1% and 65.6%. Pre-grazing forage mass was greater in SS and SSCP (P&amp;lt; 0.01) averaging 4,925, 3,460, and 1,590, in SS, SSCP, and CON, respectively. Animal gains were 1.04 in SSCP and 0.96 in SS, greater than 0.78 in CON (P&amp;lt; 0.01). Grazing days were greatest (P&amp;lt; 0.01) in CON (91 d) followed by SS (68 d), with the fewest grazing days in SSCP (60 d). Despite differences in grazing days, gain per ha, did not differ (P=0.39) among treatments, and averaged 261 kg/ha. Although SSCP and SS had fewer grazing days, gain per ha were similar among treatments due to greater ADG on SS and SSCP pastures.