Grass-legume Pastures Research Articles

Impact of a forage legume or nitrogen fertilizer application on ammonia volatilization and nitrous oxide emissions in Brachiaria pastures

ABSTRACT The largest proportion of greenhouse gas (GHG) emissions in the Agriculture sector of the Brazilian national GHG inventory is derived from the large (>200 million head) herd of cattle. The greatest contribution to these emissions comes from the enteric methane from cattle, but the direct and indirect emissions of nitrous oxide (N 2 O) from cattle excreta and N fertilizer are responsible for approximately 9 % of all national anthropogenic GHG emissions. Ammonia (NH 3 ) can be volatilized from N fertilizer and cattle excreta and deposited in sites remote from the source, constituting an indirect source of N 2 O. This study aimed to determine whether direct N 2 O emissions and NH 3 volatilization from N-fertilized pastures were greater than those derived from a mixed grass-legume pasture without N fertilizer addition. Emissions of N 2 O and NH 3 from excreta and N fertilizer from a Palisade grass (Urochloa brizantha cv. Marandu) monoculture fertilized with 2 × 60 kg N ha -1 yr -1 urea were compared to those from a mixed Palisade grass-forage peanut (Arachis pintoi) pasture. Dung and urine were collected from these cattle, and NH 3 losses and N 2 O emissions from the excreta and from N fertilizer were monitored using static chamber techniques. Volatilization of NH 3 and N 2 O emissions were found to be greater from urine than from dung. Ammonia losses from excreta and urea fertilizer were low, not exceeding 6.8, 1.1, and 4.7 % of the N applied as urine, dung, and fertilizer, respectively. The N 2 O emissions showed a tendency to be greater for the urine from the N-fertilized compared to the mixed grass-legume pasture, and the N 2 O emissions from the urine of the N-fertilized pasture ranged from 0.08 to 0.94 % of applied urine N. The N 2 O emission from the N fertilizer was at maximum 0.46 % of the applied N. The direct N 2 O emissions and the loss of NH 3 by volatilization (indirect N 2 O emission) from the excreta of cattle grazing the mixed grass-legume pasture were similar to, or lower than, the grazed grass monoculture fertilized with 120 kg N ha -1 yr -1 . As the mixed pasture received no N fertilizer and hence no GHG emission from its manufacture or application, introducing forage peanut to the Urochloa brizantha pastures shows potential to be responsible for lower GHG emissions than the N fertilized grass pasture.

Effects of Seed Proportion on Forage Yield of Greenleaf Desmodium (<i>Desmodium intortum)</i> and Guinea Grass (<i>Panicum maximum)</i> Mixture at Adami Tulu Agricultural Research Center

Establishing of grass-legume pastures is one of the recognized strategies for enhancing both quantity and quality of feed resources. Therefore, determining the impact of seed proportion on the nutritional qualities and forage yield of combinations of guinea grass and green leaf desmodium is the goal of this study. A Randomized Complete Block Design (RCBD) with three replications was used to arrange five seed proportions of desmodium and guinea grass. Analysis of variance revealed that variations in treatments have significant differences (p<0.05) on panicum heights, desmodium tillers, and Desmodium height. In addition, the effects of years showed significant (p<0.05) effects on panicum tiller, desmodium height, and percentage of coverages. Interaction of treatments with years showed a significant effect on tiller per plant and plant heights while the other parameters weren’t influenced. The combined mean of dry matter and percentage of coverage have showed significant differences (p<0.05) between the treatments. This result reveals that the seed proportion have effect on the dry matter and percentage of plant coverages. The aggressivity index also has significant mean differences (P<0.05) between the treatments. Legumes with the lowest proportion (25%) performed less competently than those with the highest proportions (75%) and 50% D. intortum. The crowding coefficient of P. maximum and D. intortum mixed forage showed significance differences (P<0.05). However, the value of seed proportion on crowding coefficient of panicum maximum and desmodium intortium were more than one. The LER has significant differences (P<0.05) due to ratio of P.maximum and D.intortium mixture and its value at T2, T3, and T4 showed as to be (LER>1) that revealed the yield advantages. Cobined mean results showed that there is significance difference (P<0.05) of CP, Ash, ADF, NDF and ADL due to different seed proportion mixture. In addition the CP of panicum incurred from 8.24% to 18.55% by mixing different seed proportion of D.intortium. An integration of legume forage with grasses improves the feed quality and quantity. Thus, based on the dry matter, yield advantage and nutritive values the integration of 75% and 50% desmodium is recommended for use in the study areas and similar agro-ecologies.

Sheep performance and forage quality in grass-legume pastures with different canopy heights

Sheep performance and forage quality in grass-legume pastures with different canopy heights

216 Alternative Trace Mineral Supplementation Strategies for Beef Cattle

Abstract This study evaluated an injectable trace mineral (ITM) source containing Cu, Mn, Se, and Zn (Multimin90) administered to gestating beef cows receiving a free-choice 2:1 mineral supplementation. Two hundred and eight multiparous and primiparous cross-bred cows (BW = 621 kg ± 96.6 kg; avg. 4 yr. old) were randomly allotted into one of two treatments and received either i) ITM + inorganic, granular 2:1 trace mineral free-choice; or ii) inorganic, granular 2:1 trace mineral free-choice alone (CON). A cross-over design was used for the study and cows in year 2 (n = 202) were allocated to the other treatment group. The ITM was administered at 4 weeks pre-calving and 4 weeks pre-breeding. Body weight and body condition score (BCS) were evaluated at injection times and pregnancy diagnosis using a weigh scale and a 5-point BCS scale (Lowman et al., 1976). Mineral status was determined from blood serum mineral concentration at 4 weeks pre-calving, 4 weeks pre-breeding, and at pregnancy diagnosis. Cows grazed grass-legume pastures in the summer and had access to dugout and well water sources. Cows were managed as two groups during spring and while on summer pasture during a 63-day breeding season until weaning. Serum blood mineral concentrations at 4 weeks pre-calving, 4 weeks pre-breeding, and pregnancy diagnosis did not differ (P > 0.05) between treatment groups. Copper conetrations at pregnancy diagnosis tended (P = 0.09) to be greater for the ITM cows compared with CON cows. At 4 weeks pre-calving and pregnancy diagnosis, Cu and Mn concentrations were numerically greater in the ITM group compared with the CON group. There were no significant results (P > 0.05) for cow BW, BCS, and days pregnant. Over 2-yr, pregnancy rates were 93.6% and 88.6% for the ITM and CON cows, respectively. Calves born to ITM and CON cows did not differ (P > 0.05) for birth weight, Julian birth date, age at weaning, average daily gain, or adjusted 205 d wean weight. However, CON calves tended (P = 0.07) to be heavier at weaning. Study findings suggest that administering an ITM source to beef cows does not improve cow and calf performance, which suggests that more research in this area is required. Additionally, pregnancy rates in beef cattle may be improved with the use of an injectable trace mineral.

Light competition is the key factor determining spatio-temporal variability in legume proportion within Marandu palisadegrass–forage peanut mixed pastures

Context Understanding ecology in grass–legume pastures can help support strategies aimed at maintaining canopy stability in terms of botanical composition. Aims This 2-year study evaluated spatial variability, focusing on plant structural characteristics in a Marandu palisadegrass [Urochloa brizantha (Hochst. Ex A. Rich.) R.D. Webster cv. Marandu]–forage peanut (Arachis pintoi Krapov. and W.C. Greg. cv. BRS Mandobi) mixed canopy under grazing in continuous stocking management. Methods The pasture was managed with canopy height of 20–25 cm. The experimental area had a permanent sample grid containing 50 pre-established and georeferenced plots. Principal component analysis was performed, and spatial dependence structure of the first principal component and structural variables were separately characterised by geostatistical analysis. Key results There was spatial dependence of the structural characteristics, with marked spatial heterogeneity in the distribution of all variables. Taller grass canopies caused competition for light between species, reducing legume contribution and inducing more erect forage peanut growth habit. Conversely, in areas with lower grass canopy height, forage peanut botanical composition increased to up to 70%, as it propagated more effectively by stoloniferous propagation. Conclusions The canopy structure spatial variability of a Marandu palisadegrass–forage peanut mixed pasture determines the overall average pasture grass/legume proportion. In regions with taller canopies, Marandu palisadegrass was favoured, while in areas with shorter canopy, forage peanut proportion was promoted. Satisfactory legume proportions can be reached in the canopy despite areas with reduced legume contribution. Implications Our findings using geostatistical techniques facilitate the development of useful and innovative tools allowing better comprehension for the management of mixed pastures.

Evaluation of the productivity and feed value of Wondergraze and Redlands leucaena cultivars under grazing

Context Leucaena leucocephala (leucaena) is a leguminous shrub used for beef grazing in low-rainfall regions (<600–700 mm). Newer cultivars have the potential to extend adoption of the species to higher rainfall (>600–700 mm), frost-free areas of Australia. Aim We compared productivity, nutritional value and animal performance of two leucaena cultivars, new psyllid-resistant Redlands and the 2010-released Wondergraze, under continuous grazing management in a higher rainfall environment. Methods Growing steers were allocated to replicated established stands of Wondergraze or Redlands with inter-row mixed grass–legume pasture from January to July 2021. Pasture and leucaena were characterised for biomass and nutritive characteristics. Botanical composition was measured. Liveweight gain, rumen fermentation, and leucaena mimosine breakdown products were measured in grazing steers. Key results At the beginning of the study, leucaena edible biomass was similar for both cultivars (P > 0.05), but at subsequent samplings, biomass of Redlands was lower than of Wondergraze (P < 0.01). Biomass of both cultivars declined rapidly over the grazing period. Pasture biomass increased between February and July and was significantly higher in Wondergraze paddocks (P < 0.05). Animal performance was not significantly different between cultivar treatments, averaging 0.8 kg/day, but declined over time. Patterns of mimosine conversion to DHP isomers and their conjugation were similar for the two cultivars, suggesting that effectiveness of detoxification did not differ between them. Conclusion The results demonstrate that leucaena can sustain high levels of animal performance when included in tropical grass pastures in a higher rainfall environment if present in a sufficient quantity (>2 t leucaena edible dry matter/ha established leucaena). Implications Grazing leucaena–grass pastures is an effective means of increasing animal productivity in parts of subtropical Australia. However, managing grass and/or leucaena growth to match animal requirements can be challenging.

FORAGE YIELD AND COMPOSITION OF BLACK OAT IN MONOCULTURE AND IN ASSOCIATION WITH WINTER VETCH

Associated grass-legume pastures have advantages over grass monoculture; in order to evaluate them the association of black oat (Avena strigosa Schreb) with winter vetch (Vicia villosa Roth) was analysed. The objective of the study was to evaluate forage yield, the botanical, morphological, and chemical composition of black oat in monoculture and in association with winter vetch, at different crop heights and residual stubble heights. Eighteen treatments were evaluated in randomized complete blocks with divided plots. In large plots, the culture type (monoculture or association); and in small plots, nine harvest management options (combinations) of three crop heights (Ch: 40, 50 and 60 cm) and three residual stubble heights (Rsh: 8, 14 and 20 cm). Forage yield was higher (p ≤ 0.05) in Ch50-Rsh8, Ch60-Rsh8 and Ch60-Rsh14 during the second crop cycle, with an average 8555 kg DM ha-1. In monoculture and in association, more cuts were made (three to four) with Ch40-Rsh14 and Ch40-Rsh20 and fewer cuts (one to two) with Ch60-Rsh8, Ch60-Rsh14 and Ch60-Rsh20. Crude protein concentration was 19 % higher (p ≤ 0.05) in monoculture than in association (19.2 and 16.2 %); the highest concentrations (p ≤ 0.05) of crude protein were obtained in Ch40-Rsh8, Ch40-Rsh14 and Ch40-Rsh20 (average 20.5 %), and the lowest was recorded in Ch60-Rsh8 (13.2 %). The forage with the least neutral detergent fibre (p ≤ 0.05) was harvested in Ch40-Rsh8, Ch40-Rsh14 and Ch50-Rsh14 (average 43.4 %), and the highest (49.3 %) was obtained in Ch60-Rsh20. In monoculture and in association, a greater amount of forage was harvested, distributed in at least two harvests, with Ch of 50 and 60 cm in combination with 8 and 14 cm of Rsh. However, the forage did not have the best composition, due to higher concentrations of neutral detergent fibre and lower crude protein concentration.

Effects of Aboveground Community Structure and Belowground Root Morphological Characteristics on Nitrogen Use Efficiency of Mixed-Perennial Legume-Grass Pastures

Nitrogen use efficiency (NUE) in plants is dependent on various factors including nitrogen availability and root morphology. This study investigated changes in root morphological and growth features in response to plant community structures in legume-grass mixed pastures. Three types of legume forage and three gramineous forage were selected, including Bromus. innermis, Onobrychis. viciaefolia, Phleum pretense, Trifolium. pretense, Dactylis glomerata, and Medicago sativa. The effects of different community structures on changes in the land equivalent ratio, crowding, aggressivity, and competition, as well as the NUE, N yield, and root morphologies, were investigated. It was found that mixed seeding combinations increased the forage yield significantly but increasing the number of mixed seeding species did not further affect the herbage yield. Both the root lengths and root specific areas of the forage grass increased with increasing spatial distance, indicating that while the root morphology of the grass was controlled by genetic factors, the phenotypic characteristics of forage grass were changed by the balance between aboveground and underground growth. Root morphology was found to play a significant role in the NUE and the relation between specific root area of legume and LN(WN), specific root length of grass, and LN (WNt) can be expressed by the binomial function model.

364 Blood Profile of Kiko Does Raised on Grass-legume-mixed Pastures vs. Sole-grass Pastures During Fall

Abstract Goats raised in pastures dominated with perennial grasses in the southeast United States commonly show poor health and performance. Addition of legumes to grass pastures may improve nutrient content and enhance animal performance. However, how legume addition to pastures would impact blood profile in goats has not been documented well. The objective of the study was to evaluate the impact of legume-grass mixed pastures on the blood profile of Kiko does. The study was conducted in fall 2020 using 10 fenced plots (average plot size: 0.44 ha). Five plots were sown to southern peas (Vigna unguiculata (L.) Walp.)-browntop millet (Urochloa ramosa L. Nguyen) 50:50 mix) and remaining five plots to sole browntop millet. Nineteen Kiko does (initial age 15–16 months and live weight - 34 ± 1.4 kg) were divided into two uniform groups: Group 1 and Group 2. Does in Group 1 were allocated to legume-grass plots and Group 2 to sole grass plots; they were rotationally stocked in their respective plots for 87 days. Blood samples were collected on Day 1 before allowing them to their respective plots, Day 47, and Day 87. Samples were analyzed for different cellular and metabolic parameters. GLM procedure in SAS 9.4. was used to analyze the data. Group-1 does had higher level of basophil, glucose, and blood urea nitrogen, but lower level of globulin concentration was significantly higher in compared to Group 2 (P < 0.05). Interaction effect of group and sampling date occurred for 21 variables (P < 0.05). Results indicated that addition of legume forage in pastures can alter blood profile of grazing goats. Further investigation on the impact of mixing legumes with grass pastures on animal performance, economics, and soil health will be helpful to understand the holistic effect of legumes on animal agriculture.

Nitrogen cycling in tropical grass-legume pastures managed under canopy light interception

Nitrogen cycling in tropical grass-legume pastures managed under canopy light interception

Nutrient excretion from cattle grazing nitrogen‐fertilized grass or grass–legume pastures

AbstractNutrient cycling via livestock excreta is an important grassland ecosystem service. This study was conducted in 2016 and 2017 and determined nutrient excretion from cattle grazing three systems: (a) N‐fertilized bahiagrass (Paspalum notatum Flüggé) overseeded with rye (Secale cereale L.) and oat (Avena sativa L.) during winter (Grass+N), (b) unfertilized bahiagrass overseeded with rye–oat–clover (Trifolium sp.) mixture (Grass+clover), and (c) rhizoma peanut (Arachis glabrata Benth.)–bahiagrass mixture overseeded with a rye–oat–clover mixture (Grass+CL+RP). Urinary volume excreted in the warm season ranged from 122 to 182 L ha−1d−1, more than double that in the cool season (56–70 L ha−1 d−1). Urinary N concentration during the warm season was greater in Grass+CL+RP compared with Grass+N (4.4 vs. 3.1 g kg−1, respectively). In addition, fecal dry matter and organic matter output was greater for Grass+N than for steers grazing Grass+CL+RP during the warm season (3.8 and 3.2 vs. 2.8 and 2.2 kg hd−1 d−1, respectively). Total annual feces excretion concentrations of P, K, Mg, and N were greater in the Grass+N than in Grass+CL+RP system. The introduction of legumes increased the proportion of N returning via urine. However, when summed across seasons, total N excretion (feces and urine) was greater in Grass+N than in Grass+CL+RP (89 vs. 71 kg ha−1 yr−1), mainly due to the greater stocking rate in the former. Grass–legume systems receiving 34 kg N ha−1 yr−1 recycled 80% of the N recycled in the grass system receiving 224 kg N ha−1 yr−1, indicating the potential of forage legumes to add N to grasslands.

Foraging behaviour of gestating sows on pasture and damages to vegetation cover are influenced by restriction of concentrate feed

One of the main challenges of outdoor pig production systems is their potential environmental impact due to direct deposition of pigs’ excreta on the land that can lead to nitrate leaching. However, plants can recycle nutrients, and a sufficient vegetation cover can mitigate adverse environmental impacts of outdoor pigs. The aim of this study was to investigate the impact of concentrate feed restriction on gestating sows foraging behaviour and ensuing damages caused to vegetation cover in a pasture-based system. Ten groups of three sows were randomly assigned to two concentrate feed levels, supplying either 90 % (P90) or 40 % (P40) of metabolizable energy requirements, from week 5 of gestation until farrowing. All groups of sows were housed at a density of 8 sows/ha in a rotational pasture system including a permanent area and three 25 × 50-m legume-grass pasture plots, which could be accessed in rotation for periods of 2–3 weeks. Posture and location of sows were assessed at weeks 8–9, 12–13 and 15 of gestation using data loggers. During the same weeks, video recordings were made when the sows were at pasture, in order to determine their time spent foraging. Vegetation cover of pasture plots was determined at the beginning and end of the grazing periods using a method based on Unmanned Aerial Vehicle-acquired image processing. In the second half of gestation, P40 sows spent 60 % more time active on pasture than P90 sows during the daytime (P < 0.01). The feeding level did not influence the number of daily visits to pasture plots, but P40 sows spent more time on pasture and travelled longer distances per visit than P90 sows. While at pasture, P90 sows spent more time rooting (P < 0.001) and less time grazing (P = 0.002) than P40 sows. In pasture plots with P90 sows, an increasing proportion of bare soil was observed over time, whereas in P40 plots, a greater proportion of high vegetation was replaced by medium vegetation. These results indicate that a higher concentrate restriction promoted grazing behaviour in pregnant sows, leading to greater disappearance of high vegetation but not to greater vegetation cover destruction. In contrast, the lower concentrate restriction increased the proportion of rooting activity, leading to greater damage to vegetation cover. In conclusion, this study has shown that concentrate feeding level of gestating sows on pasture can be reduced without adverse effects on pasture vegetation cover.

Management Practices of Pasture, Range and Grazing Reserves for Livestock Production in the Tropics: A Review

The objective of the paper was to review management practices of pasture, range and grazing reserves in order to ensure steady supply of feed and promote sustainable livestock productivity in the tropics. Grazing management deals with such questions as how long should animals stay in one area and how long they should stay off it; which animals should graze what pasture; how many animals should graze together and what other activities should be integrated with grazing. Grazing management and stocking rate are the two most important variables affecting herbage production, seasonal pattern of production, herbage quality and botanical composition. Farm animals require nutrients to support body maintenance, reproduction, lactation, and growth. The nutritional needs of livestock vary according to breed, age, sex, class, stage of production, performance level and weight. Physiological and environmental stressors, such as sickness and weather, can also influence nutritional requirements. Ruminant animals, especially cattle, sheep and goats are natural grazers and possess remarkable ability to digest plant carbohydrates that is generally indigestible by most other mammals. It is natural then to assume that, grazing is the best way to supply a nutrient-dense diet to ruminant animals. Pasture land with high quality grass-legume can meet energy requirements of growing or lactating ruminants in the wet season. Energy supplementation on pasture helps in maintaining high grains and milk production. High quality forages have the ability to supply all the energy needed to maintain highly-productive ruminants throughout the growing season, but only when managed intensively. Legume-grass pastures have protein content greater than 18% during the vegetative stage. Feed resources that contain minerals include; range or pasture plants, harvested forages, concentrates and mineral supplements. The levels of minerals in plants are a function of interaction between several factors which include soil type, plant species, stage of maturity, dry matter yield, grazing management and climate. Forage conservation and preservation should be highly encouraged among farmers especially during the wet season where the feed resources are in abundant supply.

Achieving drought resilience in the grazing lands of northern Australia: preparing, responding and recovering

Northern Australia is characterised by high rainfall variability and extended droughts that challenge sustainable and profitable management of grazing properties. To achieve drought resilience, emphasis must be placed on supporting livestock managers to prepare for drought as well as implementing appropriate drought response and recovery actions. Here we describe insights and learnings gained from working with scientists, industry development and extension officers, and property managers, to enable more profitable and drought resilient extensive livestock production systems across northern Australia. We provide examples from the modelling and analysis of hypothetical grazing properties representative of enterprises across northern Australia. To prepare for drought, we principally propose the application of the farm-management economics framework to identify investment strategies which can improve enterprise resilience through building wealth over the longer term. The critical first step in drought preparedness for beef businesses was the implementation of management strategies to achieve the optimal herd structure, steer sale age, and breeder body condition. Other key strategies to improve profitability across northern Australia were (1) addressing a phosphorus deficiency for cattle through effective supplementation and (2) establishing adapted perennial legume-grass pastures to improve steer nutrition. In addition, we identify the benefits of working closely with livestock managers and industry to gain adoption of proven technologies that effectively improve decision-making capacity and the drought preparedness of extensive livestock production systems. The usefulness of the farm-management economics approach to assess the relative value of alternative tactical destocking and restocking decisions during drought response and recovery is also discussed. These latter analyses can highlight important differences between options in terms of future profit and cash flow, as well as the ability to rapidly return the property to the most profitable herd structure and age of turnoff, with consideration of production and financial risk. Additionally, integrating pasture growth models with herd or flock economic models can provide insights into the effects, on profitability and sustainability, of alternative destocking and later restocking strategies over the longer term. Combined, the farm-management economics framework approach can support more informed decision-making by livestock producers and hence enable more profitable and drought resilient extensive livestock production systems. However, achieving drought resilience in the grazing lands of northern Australia will require emphasis on drought preparation, in addition to appropriate action in response and recovery phases of drought. Key to this approach is increasing the adoption of strategies that enhance drought preparedness.

110 Fecal pH, dry matter and volatile fatty acids of horses grazing legume-grass mixed pastures

Abstract Inclusion of legumes into grass pastures improves pasture quality while significantly decreasing the use of nitrogen (N) fertilizer. Changes in nutritive value of the pasture can affect gut microbiome and health. This study aimed to determine the effects of bahiagrass (Paspalum notatum) pasture intercropped with rhizoma peanut (RP, Arachis glabrata) on forage nutrient composition and fecal variables. Unfertilized bahiagrass (UNF) with no N fertilizer, bahiagrass with 120 kg N.ha-1 (FER), and bahiagrass intercropped with RP and 30 kg N.ha-1 (RP) pastures were evaluated using twelve mature Quarter Horses continuously stocked for 84 days in a randomized block design. Forage and fecal samples were collected every 28 days. Pasture samples were analyzed for nutrient composition by NIR, and fecal samples were analyzed for dry matter (DM), fecal fluid pH and volatile fatty acids (VFA). Data were analyzed using a repeated measure mixed model ANOVA and associations between variables were tested using Pearson’s correlations. Pasture starch was higher (P &amp;lt; 0.01) and non-fiber carbohydrates tended to be higher (P &amp;lt; 0.1) in RP. Hemicellulose and aNDF tended (P &amp;lt; 0.1) to be higher in UNF than in RP. Horses grazing RP tended (P &amp;lt; 0.1) to have greater fecal fluid propionic acid concentration and lower proportion of butyric acid. Proportion of acetic acid was lower (P &amp;lt; 0.05) in FER. Propionic acid concentration was negatively correlated with aNDF (r = -0.55) and ADF (r = -0.52), and positively correlated with ethanol-soluble carbohydrates (ESC, r = 0.55). Butyric acid proportion was negatively correlated with nonstructural carbohydrates (r = -0.70). Horses grazing FER pasture tended to have lower (P &amp;lt; 0.1) fecal DM when compared to RP. Fecal DM was negatively correlated with hemicellulose (r = -0.51), and positively correlated with water-soluble carbohydrates (r = 0.68) and ESC (r = 0.64). Intercropping RP provides pasture nutrient composition superior to UNF and similar to FER with decreased N fertilizer rate, and stimulates positive fermentation outcomes.

111 Grazing behavior of horses managed on legume-grass mixed pastures

Abstract Intercropping legume into grass pastures improves pasture quality and decreases the need for nitrogen (N) fertilizer, while providing a more heterogenic grazing environment. This study aimed to evaluate the effect of rhizoma peanut (RP, Arachis glabrata) intercropped into bahiagrass (Paspalum notatum) pasture on horse grazing performance. Unfertilized bahiagrass (UNF) with no N fertilizer, bahiagrass with 120 kg N ha-1 (FER), and bahiagrass with RP and 30 kg N ha-1 (RP) pastures were evaluated using twelve mature Quarter Horses continuously stocked for 84 days in a randomized block design with two blocks. Grazing, activity and leisure behaviors were recorded every 10 minutes for 24 hours on day 35 and 70 using scan sampling. Chew (CR, chew/min) and bite (BR, bite/min) rates were counted for five consecutive 1-min intervals on days 36 and 71. Data were analyzed using a repeated measure mixed model ANOVA. Pasture did not affect (P &amp;gt; 0.05) total time spent on grazing (13.57 ± 1.81 h, mean ± SD), leisure (9.64 ± 1.64 h), and activity (0.79 ± 0.60 h). Pasture x time of day interaction (P &amp;lt; 0.05) was significant for grazing, leisure and activity. Horses grazing FER spent more time grazing between 1100 and 1700 h, whereas horses grazing RP spent more time grazing between 2300 and 500 h when compared to horses grazing FER. Horses grazing FER spent more time in leisure between 2300 and 700 h. No day or pasture effects were observed for BR (30.8 ± 6.3 bites/min, mean ± SD), but a pasture x day interaction was observed for CR. On day 36, CR of horses grazing FER was similar to RP (50.8 and 53.8 chews/min), but lower than RP on day 71 (41.4 and 61.3 chews/min). Intercropping RP into bahiagrass pastures does not affect total grazing, leisure and activity time of horses.

Pasture rejuvenation using sainfoin and cicer milkvetch in western Canada

AbstractSod‐seeding of depleted pastures with non‐bloating legumes can be a low‐cost pasture rejuvenation strategy for ranchers in the North American prairies. A study was conducted to determine if sainfoin (Onobrychis vicifolia subsp. vicifolia) or cicer milkvetch (CMV) (Astragalus cicer L.) populations or cultivars (hereinafter populations) can be used to rejuvenate alfalfa (Medicago sativa L.) or grass pastures. The study included sainfoin populations with increased fitness to grow with alfalfa and CMV cultivars that were selected for early emergence and rapid seedling growth. These populations were seeded using three seeding methods: traditional re‐seeding, drilling seed with Great Plains drill, or Pan drill, using split‐plot randomization at three locations in Alberta in 2015 or 2016. Lethbridge had pre‐existing alfalfa while Ponoka and Red Deer were predominantly grass pastures. The sod‐seeded rejuvenation, as indicated by percentage dry matter (DM) contributed by newly planted species succeeded at Lethbridge (≥15), failed at Ponoka (∼1), and partially succeeded at Red Deer (≥9). Successful establishment of new plants did not increase the total forage mass of the rejuvenated pasture. Sainfoin populations established better and contributed greater forage mass compared to CMV cultivars when sod‐seeded on alfalfa pasture, but the improvement was not consistent on grass pasture. Forage nutritive values were not different among populations within species, but pasture seeded with CMV cultivars had greater crude protein than unseeded plots. Sod‐seeded grass–legume pasture had greater crude protein than unseeded plots at Red Deer. Sod‐seeding alfalfa pasture with sainfoin populations can be an efficient pasture rejuvenation strategy.

Urochloa Grasses Swap Nitrogen Source When Grown in Association with Legumes in Tropical Pastures

The degradation of tropical pastures sown with introduced grasses (e.g., Urochloa spp.) has dramatic environmental and economic consequences in Latin America. Nitrogen (N) limitation to plant growth contributes to pasture degradation. The introduction of legumes in association with grasses has been proposed as a strategy to improve N supply via symbiotic N2 fixation, but the fixed N input and N benefits for associated grasses have hardly been determined in farmers’ pastures. We have carried out on-farm research in ten paired plots of grass-alone (GA) vs. grass-legume (GL) pastures. Measurements included soil properties, pasture productivity, and sources of plant N uptake using 15N isotope natural abundance methods. The integration of legumes increased pasture biomass production by about 74%, while N uptake was improved by two-fold. The legumes derived about 80% of their N via symbiotic N2 fixation. The isotopic signature of N of grasses in GA vs. GL pastures suggested that sources of grass N are affected by sward composition. Low values of δ15N found in some grasses in GA pastures indicate that they depend, to some extent, on N from non-symbiotic N2 fixation, while δ15N signatures of grasses in GL pastures pointed to N transfer to grass from the associated legume. The role of different soil–plant processes such as biological nitrification inhibition (BNI), non-symbiotic N2 fixation by GA pastures and legume–N transfer to grasses in GL pastures need to be further studied to provide a more comprehensive understanding of N sources supporting the growth of grasses in tropical pastures.

Benefits of mixed grass–legume pastures and pasture rejuvenation using bloat-free legumes in western Canada: a review

Forage mixtures containing legume out-yield monocultures, fix atmospheric nitrogen, and have lower carbon footprints. However, evidence-based information on creating forage mixtures by direct seeding legumes into existing pastures is limited, and information on bloat-free legumes is nonexistent. Traditionally, pastures requiring improvement in western Canada were fully replaced by breaking up the old stand and reseeding. With new and improved forage cultivars, better seeding equipment, and increased knowledge about pasture management, there is a growing interest among producers in rejuvenating pastures instead of replacing them. Pasture rejuvenation refers to the improvement in biomass productivity and (or) nutritional quality of existing pasture without removing the existing vegetation. This can be done through fertilizer application, which is generally expensive and causes negative environmental impacts. Amelioration of compacted pastureland via mechanical aeration is short-lived and can lead to weed problems. As an alternative, direct seeding of productive, nutritive and bloat-free legume species into existing pasture is an attractive option for pasture rejuvenation. For high performance grazing systems, identification of suitable bloat-free legumes and methods for direct seeding into old grass and legume stands will be essential strategies. This review includes information on the benefits of mixed pastures and seeks possible methods of introducing bloat-free forage legumes into existing pastures in western Canada for rapid improvement in productivity and quality while positively influencing animal, soil, and environmental health.

Nitrogen Fixation and Resource Partitioning in Alfalfa (Medicago sativa L.), Cicer Milkvetch (Astragalus cicer L.) and Sainfoin (Onobrychis viciifolia Scop.) Using 15N Enrichment under Controlled Environment Conditions

Availability of nitrogen (N) limits pasture production. Inclusion of legumes into grass pastures can provide an alternative N source through biological N2 fixation (BNF), and enhance retention and cycling of soil C and N. Despite the use of alfalfa (Medicago sativa L.), cicer milkvetch (Astragalus cicer L.) and sainfoin (Onobrychis viciifolia Scop.) in grass-legume pastures to improve forage quality, relative BNF potentials and resource partitioning are unknown. We quantified BNF using 15N isotope dilution and estimated resource partitioning in alfalfa, two cultivars of cicer milkvetch and two cultivars of sainfoin under controlled conditions. Percentage of nitrogen derived from atmosphere followed the order alfalfa (92%) &gt; cicer milkvetch (87%) &gt; sainfoin (81%); corresponding to estimated N contributions of 200, 128 and 65 kg N ha−1 yr−1, respectively, based on total herbage. Root dry matter was 24% to 36% greater than shoot dry matter in all of the legumes, providing substantial below-ground C and N. Cultivars of the same species did not differ in any measured parameter (p &gt; 0.05). Despite the lower BNF in cicer milkvetch and sainfoin compared to alfalfa, their use may not negatively affect stand productivity and C storage.