Transcriptome-Wide Gene Expression Plasticity in Stipa grandis in Response to Grazing Intensity Differences

Organisms have evolved effective and distinct adaptive strategies to survive. Stipa grandis is a representative species for studying the grazing effect on typical steppe plants in the Inner Mongolia Plateau. Although phenotypic (morphological and physiological) variations in S. grandis in response to long-term grazing have been identified, the molecular mechanisms underlying adaptations and plastic responses remain largely unknown. Here, we performed a transcriptomic analysis to investigate changes in gene expression of S. grandis under four different grazing intensities. As a result, a total of 2357 differentially expressed genes (DEGs) were identified among the tested grazing intensities, suggesting long-term grazing resulted in gene expression plasticity that affected diverse biological processes and metabolic pathways in S. grandis. DEGs were identified in RNA-Seq and qRT-PCR analyses that indicated the modulation of the Calvin–Benson cycle and photorespiration metabolic pathways. The key gene expression profiles encoding various proteins (e.g., ribulose-1,5-bisphosphate carboxylase/oxygenase, fructose-1,6-bisphosphate aldolase, glycolate oxidase, etc.) involved in these pathways suggest that they may synergistically respond to grazing to increase the resilience and stress tolerance of S. grandis. Our findings provide scientific clues for improving grassland use and protection and identifying important questions to address in future transcriptome studies.

Changes in Antibiotic-Resistance Genes Induced by the Grazing Effect in Three Cladoceran Species

The acquisition of Antibiotic-Resistance Genes (ARGs) by natural bacteria caused by antibiotic abuse is causing serious problems for human and animal welfare. Here, we evaluated the influence of three cladoceran species on Antibiotic-Resistant Bacteria (ARB) and tetracycline-resistance gene (tet(A)) copies, and discussed the effect of these biological interactions on the distribution and diffusion of ARGs in freshwater ecosystems. Bacterial community and tet(A) abundances in water samples collected from wetlands were strongly influenced by cladoceran presence. The presence of Daphnia obtusa dramatically decreased ARB and tet(A) abundance compared to that with other cladoceran species (Chydorus sphaericus and Simocephalus vetulus). Interestingly, we found a high abundance of Flavobacteriales in the microbiomes of cladoceran species. Considering that Flavobacteriales species are potential carriers of the tet(A) gene, their adsorption and assimilation with cladocerans could significantly impact the reduction of tet(A) in water. Field surveys also showed that tet(A) abundance could be low if the dominance of D. obtusa in each wetland was high. This study highlighted the need for ecological interactions and a broad range of niches in the food web when discussing the fate of ARGs in freshwater ecosystems.

DETERMINATION OF ANIMAL LOAD AND GRAZING SYSTEM IN THE WEIGHT GAIN OF BOVINES WITH SECONDARY VEGETATION FEEDING

The present study was to evaluate the weight gain of bovinesin three animal loads with two grazing systems and three levels of grazing, furthermore to evaluate the botanic composition of secondary vegetation areas. The study was carried out during two years, in the first year, the animal loads used were 0.25, 0.50 and 0.75 animal unit per hectare (AU/ha).The vegetation which animals were evaluated was secondary vegetation of 8 years old. Botanic composition was determined by transects at the beginning of experiment. The two systems used were rotational and alternate grazing with three animals per each load and system.The initial average weights were 175 kg and evaluation were carried out each 56 days. The experimental design used was random totally with factorial arrange of 3X2, the first factor was the animal load and the second was the grazing system. Results indicated changes in botanic composition caused by grazing effect (P≤0.05), furthermore, grazing system and animal loads showed significative statistical differences between treatments and interaction. The best weight gain was 520 g of weight gain average per day detected in 0.50AU/ha with rotational grazing system (P≤0.05).

Disturbance and the (surprising?) role of ecosystem engineering in explaining spatial patterns of non-native plant establishment

The Intermediate Disturbance Hypothesis is widely considered to be wrong but is rarely tested against alternative hypotheses. It predicts that soil disturbances and herbivory have identical impacts on species richness via identical mechanisms (reduction in biomass and in competition). An alternative hypothesis is that the specific traits of disturbance agents (small mammals) and plants differentially affects richness or abundance of different plant groups. We tested these hypotheses on a degu (Octodon degus) colony in central Chile. We ask whether native and non-native forbs respond differently to degu bioturbation on runways vs. herbivory on grazing lawns. We ask whether this can explain the increase in non-native plants on degu colonies. We found that biopedturbation did not explain the locations of non-native plants. We did not find direct evidence of grazing increasing non-native herbs either, but a grazing effect appears to be mediated by grass, which is the dominant cover. Further, we provide supplementary evidence to support our interpretation that a key mechanism of non-native spread is the formation of dry soil conditions on grazing lawns. Thus ecosystem engineering (alteration of soil qualities) may be an outcome of disturbances, which each interact with specific plant traits, to create the observed pattern of non-native spread in the colony. Based on these results we propose to extend Jentsch & White’s (2019) concept of combined pulse/ disturbance events to the long-term process duality of ecosystem engineering/ disturbance.

Grazing effects of sea urchin Diadema savignyi on algal abundance and coral recruitment processes

Herbivores control algae and promote coral dominance along coral reefs. However, the majority of previous studies have focused on herbivorous fish. Here we investigated grazing effects of the sea urchin Diadema savignyi on algal abundance and coral recruitment processes. We conducted an in situ cage experiment with three density conditions of D. savignyi (0, 8, 16 indiv. m−2) for three months during the main coral recruitment season in Taiwan. Results demonstrated a strong algal control by D. savignyi. At the end of the experiment, average algal cover was 95% for 0 indiv. m−2, compared to 47% for 8 indiv. m−2 and 16% for 16 indiv. m−2. Average algal biomass at 8 indiv. m−2 declined by one third compared to 0 indiv. m−2 and almost zero at 16 indiv. m−2. On the other hand, a negative grazing effect of D. savignyi was observed on coral recruitment processes. Notably, at 16 indiv. m−2, the density of coral recruits declined and mortality of small coral fragments (proxy of coral juveniles) increased. Our results confirm findings of previous studies and indicate the need to balance both positive (strong algal control) and negative (physical damage) influences of Diadema grazing to facilitate the coral recruitment process.

95 Multi-Specie cover crop bale grazing effect after annual forage grazing on yearling steer grazing and feedlot performance, muscling, carcass measurements and carcass value

Yearling crossbred steers (n = 144) were randomly assigned to native range (NR) or annual forage (ANN>: native range plus field pea-barley, corn, 13-species cover crop) to evaluate grazing season extension by feeding (“Grazing”) cover crop bales (field pea, forage barley, clover, sorghum sudan 12.8% CP, 54.4% NDF, 31.4% ADF, 59.0% TDN) before feedlot entry to measure the effect on steer grazing and subsequent feedlot performance and economics. Grazing was extended 43.6 days (177.9 to 221.5 days). ANN plus bale grazing ADG was 0.95 kg/day; NR was 0.77 kg/day (P = 0.01). Ending ANN grazing gain was 43.0 kg heavier (P = 0.001). Grazing muscling was measured using ultrasound. The ratio for REA:45.4 kg live weight did not differ (P = 0.53). End grazing ANN steer REA (P = 0.002) and percent intramuscular fat (IMF) were greater (P = 0.05) than NR steers. End grazing marbling score did not differ (489.0 vs. 470.0). In the feedlot, steers were fed 95.7 days. The ANN steer feedlot arrival weight was heavier (P = 0.04), but ending weight did not differ between ANN and NR treatments (717.6 vs. 684.0 kg; P = 0.19). ANN steer hot carcass weight (HCW) was 25.6 kg heavier (P = 0.03). The NR steer dressing percent was greater (P = 0.01) and muscling (REA:HCW) was greater for the NR steers (P = 0.007), resulting in improved USDA yield grade (P = 0.01). Quality grade did not differ (98.6% Choice or better; P = 1.00). ANN steer HCW resulted in $92.26 more per carcass (P = 0.031) than NR. Grazing medium forage quality cover crop bales is an effective method for increasing gain and live animal muscle and intramuscular fat quality before feedlot entry, and ANN steer weight advantage entering the feedlot carried over to greater ending HCW and subsequently, greater carcass value.

Grazing effect of flagellates on bacteria in response to phosphate addition in the oligotrophic Cretan Sea, NE Mediterranean

ABSTRACT The planktonic food web in the oligotrophic Mediterranean Sea is dominated by small-sized (<20 μm) microbes, with nanoflagellates being the major bacterial grazers and the main participants in nutrient cycling. Phosphate is a key nutrient in the P-limited Cretan Sea (NE Mediterranean) and P-availability can affect its trophic dynamics. Here, we examined the grazing potential of heterotrophic (HF) and pigmented (PF) nanoflagellates as a response mechanism to phosphate amendment. Flagellate grazing effect on bacteria was quantified in P-amended nutrient-depleted water from the Cretan Sea over the course of 4 days using microcosm experiments. P-addition positively affected HF abundance, while PF abundance remained unchanged. At the community level, P-addition had a negative effect on PF bacterial removal rates. In the control, PF-grazing rate was significantly higher than that of HF throughout the experiment. Pigment analysis showed no changes in phytoplankton community composition as a result of P-addition, indicating that PF grazing rate declined as a physiological response of the cells. The present study emphasizes the dominant grazing role of PF under P-depleted conditions and reveals that during the late stratified season PF respond to P-addition by lowering their grazing rates, enhancing the relative importance of bacterial removal by HF.

Impact of different stocking densities of sheep on establishing stands of Larix sibirica in Iceland

The present study was the first in Iceland to investigate the effects of different stocking densities of sheep on planted Siberian larch (Larix sibirica) trees. It covered two years and involved four stocking densities in enclosures with 0.1–3.0 m tall trees, as well as a grazed area on treeless commons. The grazing effect was followed for 75 days each summer. A significant grazing effect was found on the vegetation in both years. None of the sheep stocking densities had a measurable effect on the growth or the survival of the larch trees, however, and no damage was observed on their apical shoots. During the second summer, significant visual and measured browsing effects were recorded on side branches in enclosures with medium and high stocking densities. No trees <0.5 m were browsed, however. Siberian larch is generally not sought after by sheep and the results indicated that it may be generally safe to utilize established monoculture Siberian larch stands for sheep grazing during the summer months, if enough other vegetation is present.