Grassland Science最新文献

Aridity, edaphic variables and livestock grazing are major drivers of plant community composition across arid rangelands. Accumulated knowledge exists on the impact of each driver on community composition. Although previous studies have demonstrated changes in direct grazing impacts on ecosystem functions and community composition at different aridity levels, ranging from mesic to arid grasslands, whether a regional-scale and continuous spatial pattern of plant compositional change along a gradient of aridity or edaphic variables is altered by grazing remains controversial. We compared the determinants and patterns of compositional changes with/without highly intensive grazing in the semi-arid/arid regions of Mongolia. The compositional changes based on Bray–Curtis dissimilarity were investigated using generalized dissimilarity modeling, including geographic distance, aridity, soil pH and soil texture as independent variables. Aridity consistently had a significant impact on community composition, regardless of the region and presence/absence of grazing. However, a difference in response patterns was observed between the regions. The compositional change was steeper at the upper (drier) limit of aridity than at the lower limit in the arid region. This pattern indicates the vulnerability of plant communities to aridity shifts owing to future climate change, especially in the desert steppe of Mongolia, although the predictions of shifts in aridity are not accurate. In addition, regardless of the region, the effects of soil pH on the community composition were eliminated by the presence of grazing. Grazing may homogenize community composition by not reflecting the spatial heterogeneity of soil pH or nutrient availability via selective herbivory. Despite the potential indirect impacts of climate change on community composition via soil pH, the observations for only plant communities under intensive grazing might overlook regional biodiversity changes caused by global change drivers.

The effects of feeding corn silage (CS) instead of oat hay on nutrient intakes, growth performance and digestive organ weight in the raising of Japanese Black steers were studied. In a feeding trial, 5.5-month-old Japanese Black steers (n = 15) received one of three dietary treatments with the same formula feed and different roughage (oat hay only, CS only and an equal mixture of oat hay and CS) until they reached 10.1 months old. At the feeding trial's conclusion, we observed that the three forms of roughage had no effect on the intakes of nutrients such as crude protein, non-fibrous carbohydrate, fibers and total digestible nutrients except for ether extract, and no significant difference was observed in body weight, body measurements, average daily gain, or feed efficiency among the roughage groups. Steers fed the different roughage had identical weights of carcass, digestive organs and visceral fat immediately after the feeding trial. These findings suggest that corn silage can be used as a substitute for oat hay fed to Japanese Black steers during the raising period.

The introduction of legumes such as alfalfa (Medicago sativa L.) into forage systems is a sustainable alternative to pasture restoration by adding biologically fixed N and contributing to the biodiversity of the system. Also, crabgrass (Digitaria sanguinalis L.; [CG]) is known as a grass weed but has the potential to maintain forage mass (FM) during the summer contributing to restoration. Different experiments were carried out in Spring Hill, TN for 2 years each in tall fescue (Schedonorus arundinaceus [Schreb.] Dumort; [TF]) or orchardgrass (Dactylis glomerata L. [OG]), with the addition of alfalfa and CG. For each grass sward, two separate pastures were selected, and treatments were established in different years, totaling four different experiments [two Establishments (EST 1 and EST 2) for TF and OG]. The treatments imposed were (1) control (C), (2) synthetic N fertilization (SNF), (3) fall seeding of alfalfa (FA), (4) spring seeding of alfalfa (SA), (5) fall seeding of alfalfa + CG (FA + CG) and (6) spring seeding of alfalfa + CG (SA + CG). Each experiment had four replications totaling 24 plots each, and measurements included botanical composition and FM. In the TF pastures, there was no presence of alfalfa documented (0%), and little CG was detected, due to its high competitiveness; meanwhile, FM was only increased when N fertilization was used in EST 2, 3391 kg DM/ha. The average FM for all treatments in EST 1 was 2476 kg DM/ha. The OG pastures showed the presence of both alfalfa and CG in their botanical composition, with N fertilization also showing higher FM (EST 1, 2705 kg DM/ha; EST 2, 2390 kg DM/ha). Thus, alfalfa and CG have the potential to improve OG swards, but more research is needed to assess different establishment methods of alfalfa into TF swards.

The purpose of the current experiment was to determine the effects of ruminal fermentation parameters of the additions of canola or soybean oils at different rates (4, 8 and 12%) to beef cattle total mix rations (TMR), based on corn silage and barley grain. The addition of 4% soybean oil to TMR positively affected in vitro gas production, net energy lactation (NE_L), metabolic energy (ME), and organic matter digestion (OMd). The additions of 8% and 12% of soybean oil to TMR linearly decreased ME, NE_L and OMd (p < 0.05). The additions of 4, 8 and 12% canola oil to the TMR linearly decreased the in vitro gas production and estimated fermentation values (ME, NE_L and OMd) (p < 0.05). All doses of soybean or canola oils in TMR reduced the molarities of total short-chain fatty acids (tSFCA), acetic (AA), butyric (BA), propionic (PA), valeric (VA), iso-valeric (IVA) and iso-butyric acids (IBA) for in vitro fermentation fluid (p < 0.05). There was a negative correlation between the increasing dietary stearic, oleic and linoleic acid and the end-products of in vitro rumen fermentation. However, increasing dietary α-linolenic acids had no adverse effect on in vitro ruminal fermentation end-products. As a result, 4% addition of the soybean oil, which included a higher rate of α-linolenic acid and saturated fatty acids and a lower rate of oleic, linoleic acids according to those of canola oil, to the TMR positively affected in vitro ruminal fermentation. In addition, the ≥8% addition of canola or soybean oil adversely affected the in vitro fermentation values.

Large areas of tropical grass pastures are not grazed by lambs because of the difficulties in managing high growth rate swards with high selective animals. The objective of this study was to evaluate the physical and biochemical characteristics of tropical pastures offered to lambs in continuous grazing. An upright grass and a shrub legume were set out in three pasture types and grazed by lambs: (1) aruana grass monoculture (AG—Panicum maximum Jacq. cv. IZ-5), (2) pigeon pea monoculture (PP—Cajanus cajan [L.] Millsp. cv. Anão) and (3) contiguous swards (CS), half of the paddock with AG (CSAG) and half with PP (CSPP). The pastures were evaluated for structural characteristics, production, nutritional composition and antioxidant concentrations in four periods over 92 days of continuous grazing by lambs. Hand plucking samples, similar to animal diet, were collected for chemical analysis. Regarding height, the PP legume monoculture after 42 days of grazing had uncontrollable growth by the lambs, reaching 1.2 m in height. This same legume but as a CS beside AG (CSPP) was maintained at a lower and similar height throughout the experimental periods. In general, the leaf:stem ratio of the different pastures decreased over the experimental periods from 0.7 to 0.2. In most periods, the CS showed intermediary nutritional quality compared to AG and PP. The alpha-tocopherol content was similar among swards, with an average of 137.2 ± 13.67 mg/kg of green matter (p > .05). Pigeon pea showed the highest levels of total tannin and condensed tannin at 63 and 92 days (p < .05). The use of tropical grass together with a legume provides a better physical structure of the pigeon pea for grazing lambs than when monoculture of this species.

Livestock excretions are crucial for nutrient cycling in pasture ecosystems. However, conventional methods based on field observations require significant human power and are time-consuming. This study developed a model, ‘Dung Detector (DD)’, for detecting cattle dung in pastures from drone images using the You Only Look Once (YOLO) v5 algorithm. The DD model was trained using our custom dataset including 1,504 split images from drone orthomosaic images in five paddocks: Obihiro (OBH), Shintoku (STK), Minokamo (MNO), Miyota (MYT), and Yatsugatake (YGK). The detection accuracy was evaluated using ground-truth data acquired in two quadrats within paddocks. The DD model performed well for OBH and STK (F-score = 0.861 and 0.835) paddocks with simple grass species and low surface sward height (SSH). Although the MNO and MYT, with complex vegetation and high SSH, showed few false positives (precision >0.9), some cattle dung pats were undetectable, presumably due to grass height (Recall = 0.500 and 0.276).

The objective of this study was to evaluate the effects of different potassium (K) fertilization levels and defoliation intensities on performance of “BRS Zuri” guineagrass Megathyrsus maximus (Jacq.) B.K. Simon & S.W.L Jacobs (syn. Panicum maximum Jacq.). Treatments were the factorial arrangement of three K fertilization levels: 0 (control), 40, 80 kg K₂O/ha/harvest) and two defoliation intensities (10- and 20-cm stubble heights), distributed in a completely randomized design with five replications. The experiment was conducted in Araguaina, TO, Brazil, from October to January, 2020–2021 and 2021–2022. Plots were harvested four times per year with 21-day regrowth interval. The 40 and 80 kg K₂O/ha/harvest fertilization levels had greater HA than the control (5490 vs. 3,440 kg DM/ha, respectively). There was a K fertilization level × stubble height interaction on tiller population. There was greater tiller population at 20- than 10-cm stubble height at 40 kg K₂O/ha/harvest; however, no effect of stubble height was detected at 0 and 80 kg K₂O/ha/harvest. Plots fertilized with 80 kg K₂O/ha/harvest had greater tiller population than 40 kg K₂O/ha/harvest, which was greater than control. Forage harvested at 10 cm had greater crude protein (CP) than 20-cm stubble height (mean = 11.4% vs. 10.8%). Tissue K concentration increased from control to 40 kg K₂O/ha/harvest, but there was no difference between 40 and 80 kg K₂O/ha/harvest (mean = 1.1% vs. 3.5%). The combination of 40 kg K₂O/ha/harvest and 20-cm stubble height may be a desirable management strategy to promote Zuri guineagrass productivity in tropical regions.

Plant size is a critical component of agricultural productivity as larger plants produce more biomass. To identify genes related to plant size, we grouped C₄ grasses into small and large and used OrthoFinder to find orthologous genes present in large but absent in small grasses. Three such genes were identified from sorghum (Sorghum bicolor [L.] Moench) by phylogenomic approach, and they encode nitrate transporter (Sobic.007G213200), oxysterol binding protein (SbRio.01G578800) and thioredoxin reductase (SbRio.05G168300), respectively. Overexpression of all three genes driven by the maize ubiquitin promoter in Setaria viridis (L.) Beauv. indicates that they all affected plant size as measured by plant height and tiller number. Both nitrate transporter and oxysterol binding protein increased plant height and tiller number, and thioredoxin reductase significantly decreased tiller number but had minimal effect on plant height. In rice (Oryza sativa L.), all three constructs reduced plant height significantly. The only commonality between the transgenic species was that nitrate transporter and oxysterol binding protein increased tiller number in both S. viridis and rice. Overall, we have demonstrated that phytogenomic approach can be used to identify genes responsible for large plant size in the grasses.

Sainfoin (Onobrychis viciaefolia) is an important legume forage. This study aims to explore the response mechanisms of sainfoin germplasm resource accessions to drought stress, which provides the theoretical basis for tolerant breeding of sainfoin. In this study, 20 sainfoin germplasm resource accessions were used as the test materials, and the effects of drought stress on morphological and physiological characteristics were determined under simulated levels of drought (−0.5, −1.0, −1.5 and −2.0 MPa) × exposure times (7 days) in pots. The results showed that leaf area, leaf relative water content, root-shoot ratio, root length, root surface area, root volume, root diameter, root tip number, chlorophyll a content, chlorophyll b content and catalase activity decreased with increasing drought stress. In contrast, proline, soluble sugar, soluble protein and malondialdehyde contents increased in response to drought. Root activity, superoxide dismutase and peroxidase activities increased first and then decreased and reached the maximum at −1.0 MPa. Cluster analysis showed that 20 sainfoin germplasm resources could be divided into three categories, of which four accessions were high tolerance types, and three accessions were low tolerance type. These findings will help provide some theoretical basis for cultivating new varieties.

Integrated production systems have been an alternative for diversifying agricultural production, and therefore, it is necessary to study tropical forage grasses that can impact both straw production and soil organic matter, as well as benefit animal production. The objective of this work was to evaluate the productive characteristics and accumulation of nutrients in the biomass of grasses of the genus Panicum grown in the off-season, in Cerrado biome soil as cover plants for use in integrated production systems. It evaluated different grasses of Panicum maximum: Aruana, Tamani, and Massai guinea grasses, distributed in a randomized block design with four replications of each grass. The productive characteristics, mineral accumulation, and carbon/nitrogen (C/N) ratio in the biomass of the cultivars were evaluated. No cultivar effect was observed for forage mass (3997.4 kg/ha DM). However, the largest (p = 0.0077) leaf blade masses were observed in the Massai and Tamani guinea grasses. On the contrary, the Aruana guinea grass exhibited the highest value (p = 0.0001) for stem mass, reflected in a higher (p = 0.0001) leaf/stalk ratio in the Massai and Tamani guinea grasses. No effect (p > 0.05) of the cultivar on micronutrients, magnesium, and phosphorus concentrations was observed. However, the Aruana guinea grass presented higher concentrations of calcium and sulfur; on the other hand, potassium values were higher in the Massai and Tamani guinea grasses. The Massai guinea grass exhibited a higher (p = 0.0214) C/N ratio, while the Aruana guinea grass recorded lower values, with no significant differences between these cultivars and Tamani guinea grass. The Tamani and Massai guinea grasses stand out as recommended choices for cultivation during the off-season in Cerrado biome soils as cover crops in integrated production systems.