scholarly journals Evaluation of the incidence, severity and forage nutritive value of common weed species in Missouri pastures

2017 ◽  
Author(s):  
◽  
Zachary Lee Trower
Keyword(s):  
Tall Fescue ◽  
Nutritive Value ◽  
Forage Quality ◽  
Cattle Grazing ◽  
Neutral Detergent Fiber ◽  
Weed Species ◽  
Primary Parameter ◽  
Common Ragweed ◽  
Weed Density ◽  
Growing Seasons

Across the 2015-2016 growing seasons, 43 mixed tall fescue and legume pastures were surveyed to determine the effects of selected soil and forage parameters on the density of individual weed species and overall weed density. The parameters included soil phosphorus (P), potassium (K), magnesium (Mg) and calcium (Ca) concentration, soil pH, cation exchange capacity (CEC), cattle grazing density, total forage groundcover density, tall fescue density, and beneficial legume density, which was comprised of white clover, red clover and annual lespedeza densities. Sampling areas were established in each pasture at a frequency of one representative 20 m2 area per 4 ha of pasture. Once established, survey locations were sampled every 14 days during a period from April through September. Weed density was divided into categories (total, annual broadleaves, perennial broadleaves, and annual grasses) and also by the most common individual weed species encountered. These datasets were then divided into 3 timings, 05 (April-May), 07 (June-July), and 12 (August-September), and then analyzed using regression tree models. Across all weed types and species, forage groundcover density was the main parameter that affected weed density. Soil K, P, and Mg levels also impacted weed density for many life cycles and weed species. Soil K level was the primary parameter that reduced density of common ragweed in the 07 and 12 timeframes, and this is one of the most common weed species encountered in Missouri pastures. Similarly, soil P level was the primary parameter that reduced perennial broadleaf weed density in the 07 and 12 timeframes; when P was greater than 1.5 ppm, there was a 66 and 59% reduction in the density of these species in the 07 and 12 timeframes, respectively. Cattle grazing densities less than1.2 units per acre also resulted in fewer annual grass weeds in pastures. Results from this survey indicate that maximizing the groundcover of beneficial forage species is the most important factor that results in weed density reductions in mixed tall fescue and legume pastures, followed by proper maintenance of soil nutrients like P and K. Weed and representative forage samples were collected from 22 mixed tall fescue and legume pastures during the 2015 and 2016 growing seasons to investigate the seasonal variation in forage quality of 15common pasture weeds in Missouri. Sampling occurred at 14-day intervals throughout the season and began in early April or when emergence of each weed species was observed. Sampling concluded either at plant senescence or mid- to late-September. There was no significant linear relationship between increasing time and crude protein (CP) concentration or digestibility for buckhorn plantain, dandelion, sericea lespedeza, and yellow foxtail, but CP concentration and digestibility declined linearly through the growing season for all other weed species evaluated. Most weed species also had a linear decline in neutral detergent fiber digestibility (NDFD) and a linear increase in neutral detergent fiber (NDF) as the season progressed. When comparing pure weed samples to the representative forage from the same location, CP concentrations in spiny amaranth, woolly croton, annual fleabane, white snakeroot, Pennsylvania smartweed, and vervain species were not significantly different than their representative forage samples at any sampling interval throughout the season. However, CP concentration of common ragweed, lance leaf ragweed, horsenettle, and dandelion were often higher than the representative forage sample for the majority of sampling timings throughout the season while yellow foxtail and ironweed species had significantly lower CP concentration than the representative forage samples from July 26 to August 23.Additionally, digestibility of common ragweed, lanceleaf ragweed, broadleaf plantain, Pennsylvania smartweed, dandelion, and common cocklebur was greater than that of the representative forage sample for the majority of sampling periods throughout the season (P [less than] 0.05). These results can be used to understand how the nutritive value of common weed species changes throughout the season and at what times specific weed species have the potential to influence the overall forage quality in mixed tall fescueand legume pastures.

Seasonal changes in forage nutritive value of common weeds encountered in Missouri pastures

2019 ◽  
Vol 34 (2) ◽  
pp. 164-171
Author(s):  
Gatlin Bunton ◽  
Zach Trower ◽  
Craig Roberts ◽  
Kevin W. Bradley
Keyword(s):  
Tall Fescue ◽  
Crude Protein ◽  
Nutritive Value ◽  
Late Summer ◽  
Growing Season ◽  
Quality Parameter ◽  
Neutral Detergent Fiber ◽  
Weed Species ◽  
Growing Seasons

AbstractDuring the 2015, 2016, and 2017 growing seasons, weed and weed-free mixed tall fescue and legume forage samples were harvested from 29 pastures throughout Missouri for investigation of the nutritive value of 20 common pasture weed species throughout the season. At certain times during the growing season, many broadleaf weed species had greater nutritive values for a given quality parameter as compared with the available weed-free, mixed tall fescue and legume forage harvested from the same location. There were no significant differences in crude protein concentration between the weed-free forage and many weeds throughout the growing season. However, crude protein content of common burdock, common cocklebur, common ragweed, dandelion, horsenettle, and lanceleaf ragweed was greater than that of the corresponding forage sample at multiple collection periods. The digestible neutral detergent fiber (dNDF) content of all broadleaf weeds except lanceleaf ragweed was significantly lower than that of the weed-free forage at all collection periods. Conversely, large crabgrass had significantly greater digestible neutral detergent fiber levels than did the mixed tall fescue forage at all sampling dates. Dandelion and spiny amaranth had greater in vitro true digestibility (IVTD) content than did the forage for the entire growing season. Three perennial weeds—horsenettle, vervains, and late boneset—did not differ in IVTD levels as compared with the mixed tall fescue and legume forage at any collection date. For most summer annual weeds, the trend was toward greater digestibility earlier in the season, with a gradual decline and often lower IVTD by the late summer or early fall. The results of this study will enable producers to make more informed management decisions about the potential benefit or detriment a weed may provide to the overall nutritive value of the pasture system.

Relationships between soil, forage, and grazing parameter effects on weed incidence in Missouri pastures

2019 ◽  
Vol 34 (3) ◽  
pp. 408-415
Author(s):  
Gatlin Bunton ◽  
Zachary Trower ◽  
Kevin W. Bradley
Keyword(s):  
Soil Ph ◽  
Tall Fescue ◽  
Perennial Grass ◽  
Weed Species ◽  
Perennial Weed ◽  
Soil P ◽  
Weed Density ◽  
Growing Seasons ◽  
Unit Increase ◽  
Grass Weed

AbstractDuring the 2015, 2016, and 2017 growing seasons, a survey of 63 pastures in Missouri was conducted to determine the effects of selected soil and forage parameters on the density of common annual, biennial, and perennial weed species. Permanent sampling areas were established in each pasture at a frequency of one representative 20-m2 area per 4 ha of pasture, and weed species and density in each area were determined at 14-d intervals for a period from mid-April until late September. The parameters evaluated included soil pH, phosphorus (P), potassium (K), magnesium (Mg), calcium (Ca), sulfur (S), zinc (Zn), manganese (Mn), and copper (Cu) concentrations, as well as tall fescue density, forage groundcover density, and stocking rate. An increase of 1 unit in soil pH was associated with 146 fewer weeds per hectare, the largest reduction in weed density in response to any soil parameter. Increased soil pH was associated with the greatest reduction in perennial grass weed density, along with an average reduction of 1,410 brush weeds per hectare for each 1-unit increase in soil pH. Common ragweed, a widespread weed of pastures, could be reduced by 3,056 weeds ha−1 when soil pH was 1 unit greater. A 1-ppm increase in soil P was correlated with a decrease of 206 biennial broadleaf weeds per hectare. Perennial broadleaf weed density was reduced in soils with greater concentrations of P, K, and Ca. Additionally, for every 1% increase of tall fescue and forage groundcover, there was a decrease of 18 and 38 perennial broadleaf weeds per hectare. The results from this research indicate that the density of many common weed species can be reduced with higher soil pH and adjustments to soil macro- and micronutrient concentrations, especially P.

Influence of Increasing Common Ragweed (Ambrosia artemisiifolia) or Common Cocklebur (Xanthium strumarium) Densities on Forage Nutritive Value and Yield in Tall Fescue Pastures and Hay Fields

2011 ◽  
Vol 25 (2) ◽  
pp. 222-229 ◽  
Author(s):  
Kristin K. Rosenbaum ◽  
K. W. Bradley ◽  
Craig A. Roberts
Keyword(s):  
Tall Fescue ◽  
Nutritive Value ◽  
Plant Biomass ◽  
Total Yield ◽  
Ambrosia Artemisiifolia ◽  
Total Biomass ◽  
Weed Species ◽  
Common Ragweed ◽  
Nutritive Values ◽  
Biomass Yields

Separate field trials were conducted in 2007 and 2008 to investigate the effects of increasing densities of common ragweed or common cocklebur on total yield and forage nutritive values in tall fescue pastures. Common ragweed densities ranged from 0 to 188 plants m−2, and common cocklebur densities ranged from 0 to 134 plants m−2. Total biomass yields (weeds plus tall fescue) were determined in response to each weed density and species; pure samples of tall fescue, common ragweed, or common cocklebur were also hand collected from each plot at the time of the total biomass harvest. Near-infrared spectroscopy was used to predict crude protein (CP) concentration and in vitro true digestibility (IVTD) of the total harvested biomass, pure tall fescue, and pure weed species in each plot. Results indicate that biomass yields may increase by as much as 5 kg ha−1with each additional common ragweed plant m−2within a tall fescue stand. Additionally, CP concentration of the total harvested biomass, pure weed species, and tall fescue decreased by 0.2 to 0.4 g kg−1with each additional increase in common ragweed or common cocklebur plant per m−2. As weed densities increased, IVTD of pure tall fescue samples increased only minimally (0.04%), regardless of the weed species. An increase in common ragweed density also resulted in the CP concentration of pure samples of common ragweed to decrease by 0.2 g kg−1for each additional plant per m2and by 0.4 g kg−1for each additional common cocklebur per m2. Overall, results from these experiments indicate that plant biomass yield and nutritive values of the total harvested biomass are only marginally influenced by increasing common ragweed or common cocklebur densities.

Determining the Rate of Ergot-alkaloid Degradation in Toxic Endophyte-infected Tall Fescue Hay and Haylage During Long Term Storage

2021 ◽  
Vol 99 (Supplement_2) ◽  
pp. 22-22
Author(s):  
Charles A Zumbaugh ◽  
Susannah A Gonia ◽  
Kathryn M Payne ◽  
Thomas B Wilson
Keyword(s):  
Tall Fescue ◽  
Ergot Alkaloid ◽  
Fixed Effects ◽  
High Performance ◽  
Nutritive Value ◽  
Day Treatment ◽  
Random Effect ◽  
Storage Period ◽  
Neutral Detergent Fiber ◽  
Experimental Unit

Abstract The objectives of this experiment were to determine changes in the nutritive value and ergot alkaloid concentrations of endophyte-infected tall fescue hay and haylage during a 180-d storage period. Forage from a single field of Kentucky-31 tall fescue was cut for hay in late June and allowed to dry in the field. The dry matter (DM) of the windrow of cut forage was measured every 2 h after clipping. Forage was sampled from the windrow in 6 location blocks once forage DM reached target levels for haylage and hay treatments. Haylage and hay samples were taken when the DM of the windrow reached 50% and 80%, respectively. Seven subsamples of each treatment within block were chopped to 1.91 cm in length with a lettuce chopper and vacuum sealed in oxygen-excluding bags. Sample bags were stored indoors and opened at 30 d intervals over the 180-d storage period. Samples were analyzed for pH, nutritive value, and individual ergot alkaloid concentrations using high-performance liquid chromatography. Within each storage day, treatment within block was considered the experimental unit. Data were analyzed in SAS using the MIXED procedure with fixed effects of treatment, day, and the treatment by day interaction. Location block was considered a random effect. As expected, pH was decreased for haylage compared to hay at all time points (P < 0.01) and DM was greater (P < 0.01) for hay compared to haylage. Neutral detergent fiber values were greater (P < 0.01) for hay compared to haylage and declined during storage (P < 0.01). Total ergot alkaloid concentrations did not differ by treatment (P = 0.61), but ergovaline concentrations declined (P < 0.01) during storage. Collectively, these results indicate minimal differences in nutritive value and ergot alkaloid concentrations between hay and haylage during storage, and that ergovaline concentrations decline during storage.

scholarly journals Allometries in Plants as Drivers of Forage Nutritive Value: A Review

Agriculture ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 5 ◽  
Author(s):  
Gilles Lemaire ◽  
Gilles Belanger
Keyword(s):  
Cell Wall ◽  
Nutritive Value ◽  
Forage Quality ◽  
Functional Approach ◽  
Plant Phenology ◽  
Neutral Detergent Fiber ◽  
Forage Production ◽  
N Concentration ◽  
Long Time

The nutritive value of forage for herbivores has been for a long time determined by the concentration in protein and, hence in nitrogen (N), the concentration in different minerals (P, K, Ca, Mg, and oligo-elements), and the in vivo dry matter (DM) digestibility. Forage DM digestibility, the proportion of ingested DM being metabolized by ruminant animals has been related to different components of plant tissue composition such as Neutral Detergent Fiber (NDF) and Acid Detergent Fiber (ADF); the NDF concentration represents an estimate of cell wall content while the ADF concentration is an estimate of the more lignified cell wall content. Forage nutritive value is generally analyzed by relating the attributes of nutritive value to plant phenology, in order to predict the decline of these attributes with plant age. A more functional approach, initially developed for the analysis of N concentration dynamic analysis (Lemaire et al. 2008 and Lemaire et al. 2019), and extended for digestibility for this review, is based on the assumption that above-ground plant mass (W) is composed of two compartments: (i) the metabolic compartment (Wm), associated with plant growth process scaling with leaf area, having a high N concentration (%N), and a high Digestibility (%D); (ii) the structural compartment (Ws) associated with architectural plant development, scaling with plant height and thickness and having low %N and %D. With the postulate that Wm is allometrically related to W (Wm = c × Wα with α < 1), the ontogenetic decline of both %N and %D as the plant gets bigger and forage mass increases can be explained, and the purely empirical statistical approach of forage quality based on plant phenology can be replaced by a more mechanistic and comprehensive analysis linking forage production and forage quality dynamics within the same functional approach for a better understanding of genotype-environment-management interactions.

scholarly journals Floristic Composition Mediates Change in Forage Nutritive Quality of Atlantic Mountain Grasslands after Experimental Grazing Exclusion

Agronomy ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 25
Author(s):  
Gonzalo García-Baquero ◽  
Iñaki Odriozola ◽  
Arantza Aldezabal
Keyword(s):  
Repeated Measures ◽  
Crude Protein ◽  
Nutritive Value ◽  
Forage Quality ◽  
Floristic Composition ◽  
Neutral Detergent Fiber ◽  
Enzymatic Digestibility ◽  
Grazing Exclusion ◽  
Nutritive Quality ◽  
Mountain Grasslands

Simultaneous reduction of biodiversity and forage nutritive value after grazing abandonment represents a critical agroecological problem observed in temperate mountain grasslands. However, how both processes affect each other after the exclusion of large grazers is not well understood. To address this knowledge gap, we used four Atlantic grassland sites in the Aralar masif (northern Iberian Peninsula) to ask whether floristic composition mediates change in forage nutritive quality after grazing exclusion, and, if so, how much of the effect on forage quality is mediated. To examine the effects of grazing exclusion on forage quality and floristic composition a repeated-measures (2005–10) randomized complete block experiment was used. Then, the direct effects of grazing exclusion on forage quality were disentangled from the indirect effects mediated by concurrent change in floristic composition. Grazing exclusion deteriorated forage mineral content, phosphorus content, neutral detergent fiber and, especially, crude protein and enzymatic digestibility. Concurrent floristic change mediated change in crude protein (80%), enzymatic digestibility (55%) and forage content in calcium (31%). Our study shows that plant diversity and forage quality are intimately linked features of Atlantic mountain grasslands and highlights the importance of preserving leguminous and dicotyledonous species to maintain the nutritive value of these grasslands.

scholarly journals 261 Prescribed burning of endophyte-infected tall fescue pastures: Effects on forage production, ergot alkaloid concentrations, and stand composition

2019 ◽  
Vol 97 (Supplement_3) ◽  
pp. 89-90
Author(s):  
Kevin Meng ◽  
Eric Bailey ◽  
Hannah Allen ◽  
Derek Brake
Keyword(s):  
Prescribed Fire ◽  
Tall Fescue ◽  
Ergot Alkaloid ◽  
Prescribed Burning ◽  
Forage Quality ◽  
Warm Season ◽  
Neutral Detergent Fiber ◽  
Prescribed Burn ◽  
Forage Production ◽  
Seed Head

Abstract Prescribed fire may be a non-chemical alternative for seedhead suppression in endophyte-infected tall fescue forage systems. A study was conducted to observe the effects of a single prescribed burn on seed head production, ergot alkaloid concentration, forage production, forage quality, and stand composition in K31 tall fescue plots (endophyte infection=96%). Treatments of an undisturbed control (CON), March mow (MOW), March burn (EARLY), and April burn (LATE) were randomly applied to 56 square meter plots with ten replicates per treatment. Plots were sampled for forage quality and ergot alkaloid concentrations monthly from May to October. Forage production and species composition was recorded in June and October. Fescue seedhead count was conducted in May. After June sampling, plots were clipped to a height of 10 cm and litter was removed to simulate spring grazing. CON had greater (P &lt; 0.01) total forage production in June than other treatments. MOW had greater (P &lt; 0.01) forage production (≤107 kg/ha) than EARLY and LATE in June. There was no effect (P = 0.30) of treatments on forage production in October. LATE burn reduced (month × trt; P = 0.02) ergovaline concentration in June but all treatments were above the established threshold (150 ppb) for fescue toxicosis. Fescue seed head frequency was decreased (P &lt; 0.01) by 50% in LATE plots. There was no treatment effect (P ≥ 0.22) on forb and non-fescue grass frequency in May, but warm season grass frequency was greater (P &lt; 0.01) in LATE plots in October. Crude protein in LATE was greater than other treatments in May and both LATE and CON were greater than other treatments in June (P &lt; 0.01). Neutral detergent fiber for LATE was less than other treatments in May and June (P &lt; 0.01). Under conditions of this experiment, prescribed fire decreased seed head count and ergot alkaloid concentration, with a modest reduction in forage production.

PSI-4 Animal and agronomic performance while grazing winter stockpiled novel endophyte tall fescue established with three pasture renovation strategies

2021 ◽  
Vol 99 (Supplement_3) ◽  
pp. 276-276
Author(s):  
Charlotte L Talbott ◽  
Deidre D Harmon ◽  
Matt H Poore ◽  
Alan J Franluebbers ◽  
Carolyn A Young ◽  
...  
Keyword(s):  
Tall Fescue ◽  
Cover Crop ◽  
Nutritive Value ◽  
Block Design ◽  
Average Daily Gain ◽  
Forage Yield ◽  
Neutral Detergent Fiber ◽  
Agronomic Performance ◽  
Economic Returns ◽  
Grazing Period

Abstract Comparing animal and agronomic performance following renovation of toxic-infected tall fescue (TF) to novel endophyte tall fescue (NE) is fundamental to evaluating economic returns and increasing adoption of NE. In 2018, three NE renovation strategies were implemented in a randomized complete block design in Bahama, NC. Strategies included: 1) control (C), 2) renovation to NE after one season of a single specie cover crop (1-SM), 3) renovation to NE after three seasons of a single specie cover crop (3-SM), and 4) renovation to NE after three seasons of a multi-specie cover crop (3-CM). Sixty-four Angus heifers (initial BW 290 kg ± 88) were randomly assigned to treatments and strip-grazed stockpiled fescue for 56-d, two years after NE establishment. Forage yield and nutritive value was measured every 14-d. Data were analyzed using proc GLIMMIX of SAS v9.4. Average daily gain was greatest (P = 0.0024) for cattle grazing 1-SM (0.67 kg/d), and least for 3-CM (0.54 kg/d) and C (0.44 kg/d), which did not differ. 3-SM (0.57 kg/d) did not differ from other treatments. Within the grazing period, forage yield was greatest (P = 0.0001) in 3-CM, 3-SM, and C compared to 1-SM (3053, 2941, 2856 and 2465 kg/ha, respectively). Prior to the initiation of grazing, crude protein concentration was greater (P = 0.0089) for 3-CM (17.5%) compared to C, 1-SM, and 3-SM (15.8%, 15.8% and 15.3%, respectively). Neutral detergent fiber was greater (P = 0.0135) for 3-SM (57%) than C (55.1%) and 3-CM (54.5%), but did not differ from 1-SM (54.6%). Concentration of total digestible nutrients was greater (P = 0.0187) for 3-CM (73.2%) compared to 1-SM (72.1%) and 3-SM (71.9%), but did not differ from C (72.5%). Data suggest animal and agronomic performance for NE was improved compared to TF during winter stockpile grazing in years following renovation.

scholarly journals 111 Metsulfuron and variable nitrogen application rates on infected tall fescue: effects on stocker performance, forage yield, nutritive value, ergovaline concentration and botanical composition

2020 ◽  
Vol 98 (Supplement_2) ◽  
pp. 31-31
Author(s):  
Kevin R Meng ◽  
Eric Bailey ◽  
Josh Zeltwanger ◽  
Hannah Allen ◽  
Mikaela Adams ◽  
...  
Keyword(s):  
Species Composition ◽  
Tall Fescue ◽  
Nutritive Value ◽  
Ergot Alkaloids ◽  
Fertilization Rate ◽  
Forage Yield ◽  
Nitrogen Application ◽  
Forage Production ◽  
Seed Head ◽  
Application Rates

Abstract Chemical seed-head suppression of endophyte infected tall fescue (Lolium arundinaceum) improves stocker cattle performance but may decrease forage yield. Spring nitrogen application increases tall fescue growth with a concomitant increase in ergot alkaloids, produced by the symbiotic endophyte Epichloë coenophiala. We hypothesized that greater amounts of nitrogen applied to tall fescue would increase forage yield and offset losses in forage production from chemical suppression of seed-heads with metsulfuron without effect on alkaloid concentration. Ninety-six steers (270 ± 20 kg) were randomly assigned to one of sixteen paddocks (1.8 ha) on April 18 and continuously grazed for 57 d. Paddocks were blocked by previous use (n = 4) and randomly assigned to one of four treatments; no metsulfuron, no nitrogen (NEGCON), metsulfuron with 0 (MET0), 67 (MET67), or 134 (MET134) kg/ha of ammonium nitrate, applied March 11. Steers grazing MET0 paddocks were removed 17 d early due to insufficient forage availability. Steer weight, forage yield, forage nutritive value and ergot alkaloids in forage samples were measured monthly. Seed-head frequency and species composition were determined in June. Metsulfuron application reduced (P &lt; 0.01) tall fescue seed-heads by 80%. Metsulfuron decreased (P = 0.03) ergovaline but ergovaline increased (P &lt; 0.01) at each monthly sampling across treatments. Nitrogen had no impact on ergovaline concentration (P = 0.50). Forage yield tended to be least (P = 0.07) for MET0, intermediate for NEGCON and MET67, and tended to be greatest for MET134 (P = 0.08). Steer ADG was not affected by treatment (P &lt; 0.80). Metsulfuron decreased NDF (P=0.02) regardless of fertilization rate. Forage CP increased with fertilization (P &lt; 0.01) and no differences were detected between NEGCON and MET0 (P = 0.45). Species composition was not impacted (P &gt;0.07) by treatment. Metsulfuron decreased seed-head growth and ergovaline concentration in tall fescue. Additional nitrogen fertilizer ameliorated forage yield lost to metsulfuron application but did not impact steer gain.

scholarly journals 57 Effects of Diploid and Tetraploid Annual Ryegrass Cultivars on Cattle Performance, Herbage Mass, and Nutritive Value

2020 ◽  
Vol 98 (Supplement_2) ◽  
pp. 20-20
Author(s):  
Sarah M Montgomery ◽  
Brandi Karisch ◽  
Jane A Parish ◽  
Jesse Morrison ◽  
Brian Baldwin
Keyword(s):  
Weight Gain ◽  
Nutritive Value ◽  
Lolium Multiflorum ◽  
Average Daily Gain ◽  
Cattle Grazing ◽  
Annual Ryegrass ◽  
Significance Level ◽  
Body Weights ◽  
Grazing Period ◽  
Daily Gain

Abstract Annual ryegrass (Lolium multiflorum Lam.) can be divided into two cytotypes: diploid (2n = 2x) and tetraploid (2n = 4x). Polyploid versions of a given plant species result in increased seedling vigor, more robust growth and, potentially, greater yield. While most data suggest no difference in yield between diploid and tetraploid cultivars, there is still potential for weight gain advantages thanks to increased non-structural carbohydrates in tetraploid cells. The objectives of this study were to compare weight gain of cattle grazing either diploid or tetraploid cultivars of annual ryegrass. Two diploid annual ryegrass cultivars (Marshall and Tam 90) and two tetraploid cultivars (Jumbo and Nelson) were planted in 0.81-ha pastures, each replicated four times. Four steers (mean initial BW = 214 kg) were randomly assigned to each pasture for an 82-d grazing period. Body weights were recorded starting at d0 then every 28 days throughout the season. Data were analyzed in the GLM procedure of SAS using a significance level of α = 0.05. There were significant differences between cytotypes with respect to seasonal yield with diploids (9547.90 kg/ha) yielding greater than tetraploids (7762.00 kg/ha). As expected, ADF and NDF fractions were significantly less for tetraploids (ADF; 31.39%, NDF; 31.39%) compared to diploids (ADF; 33.75%, NDF; 53.25%). Tetraploids also contained significantly greater crude protein (13.50%) than diploids (12.90%). Cytotype had no effect on final average daily gain (ADG) (P = 0.9427). However, final ADG was significantly impacted by cultivar (P = 0.0134). Final ADG for Tam 90 (1.10 kg/d) was greater than Marshall (0.92 kg/d). Cattle grazing Nelson (1.04 kg/d) and Jumbo (0.99 kg/d) did not differ. Results show that regardless of differences in seasonal yield and nutritive value between cytotypes, there were no advantages in ADG for cattle grazing either cytotype.

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