PSX-33 Effect of supplementing different proportions of sericea lespedeza with alfalfa silage on intake, digestibility, and nitrogen balance in sheep

Dietary manipulations to include tannins can change the proportion and amounts of N excreted in the urine and feces as well as improve N-use efficiency in ruminants. This study was conducted to investigate effects on animal digestion parameters of adding different proportions of sericea lespedeza hay (SL) to alfalfa silage. Alfalfa was harvested in June 2018 at 75% bloom, chopped, and then packed at 55% moisture into plastic-lined bins and allowed to ensile for 3 months. Alfalfa silage was either offered alone or mixed with 9, 18, or 27% SL on a DM basis. These diets were offered randomly for ad libitum consumption to 16 ewes (41.8 ± 4.61 kg BW) in a randomized complete block design experiment with 2 periods to provide 4 observations per treatment per experimental period, each consisting of a 14-d dietary adaptation period followed by 5 d of total fecal and urine collection. Data were analyzed using PROC MIXED of SAS and orthogonal linear and quadratic trend analyses were tested. Digestibility (%) of DM and OM and digestible DM and OM intake (g/kg BW) decreased linearly (P < 0.05) with increasing SL addition to the diet. Digestibility of NDF and ADF decreased linearly (P < 0.01) with increasing SL, and apparent absorption (%) of N decreased linearly (P < 0.05) with increasing SL in the diet. Urinary N excretions (g/d) tended (P = 0.10) to decrease linearly while fecal N (g/day) tended to increase (P = 0.10) linearly with increasing SL proportion in the diet. In this study, supplementation with sericea lespedeza as a tannin source to alfalfa silage decreased forage digestibility and digestible organic matter intake and did not positively influence nitrogen use. The study was supported in part by USDA-ARS specific cooperative agreement 58-3655-4-052 and by USDA NIFA grant 2018-67019-27804.

Ecology and management of earthworm casting on sports turf

Earthworm activity is beneficial in most natural and agricultural systems, but excessive earthworm casting is a problem on sports fields worldwide. Expulsion of soil-rich earthworm fecal matter, or casts, as mounds of soil on the turf canopy can muddy the surface, reduce photosynthesis, and lead to thinning, weed invasion and surface softening. Casts affect ball roll on sports fields, cause fouling of maintenance equipment, and dull mower blades. Build-up of cast material on reel mower units can affect height and quality of cut. Casting activity is dependent on environmental conditions such as soil texture, temperature, moisture, pH, and organic matter. Response to environmental conditions varies by species. Management options are limited, because no pesticides are specifically labeled for earthworm control at this time, and cultural control methods such as soil modification, turfgrass clipping removal, and sand topdressing have limited and inconsistent efficacy. Products containing plant-derived saponins and irritants show promise for earthworm management. Pest management practices to mitigate excessive earthworm casting will likely need to be species-specific, but limited knowledge of earthworm identification by end-users further inhibits the efficacy of control measures. © 2019 Society of Chemical Industry.

Reducing Phosphorus Runoff and Leaching from Poultry Litter with Alum: Twenty-Year Small Plot and Paired-Watershed Studies

Treating poultry litter with alum has been shown to lower ammonia (NH) emissions and phosphorus (P) runoff losses. Two long-term studies were conducted to assess the effects of alum-treated poultry litter on P availability, leaching, and runoff under pasture conditions. From 1995 to 2015, litter was applied annually in a paired watershed study comparing alum-treated and untreated litter and in a small plot study comparing 13 treatments (an unfertilized control, four rates of alum-treated litter, four rates of untreated litter, and four rates of NHNO). In the paired watershed study, total P loads in runoff were 231% higher from pasture receiving untreated litter (1.96 kg P ha) than from that receiving alum-treated litter (0.85 kg P ha). In both studies, alum-treated litter resulted in significantly higher Mehlich III P (M3-P) and lower water-extractable P at the soil surface, reflecting greater retention of applied P and lesser availability of that P to runoff or leaching. In soils fertilized with alum-treated litter, M3-P was much higher when analyzed by inductively coupled argon plasma emission spectrometry than by colorimetry, possibly due to the formation of aluminum phytate. Indeed, alum-treated poultry litter leached less P over the 20-yr study: M3-P at 10 to 50 cm was 266% greater in plots fertilized with untreated litter (331 kg M3-P ha) than with alum-treated litter (124 kg M3-P ha). This research provides compelling evidence that treating poultry litter with alum provides short-term and long-term benefits to P conservation and water quality.

Nematodes as bioindicators of ecosystem recovery during phytoremediation of crude oil contaminated soil

Restoration of a weathered crude oil contaminated site undergoing phytoremediation was evaluated using nematodes as bioindicators. Samples were collected twice per year equating to spring and fall/winter. Mean annual total abundances ranged from 18-130 in the non-fertilized non-vegetated control (CTR) to 69-728 in tall fescue-ryegrass (FES) to 147-749 (100 g(-1)) in the fertilized bermudagrass-fescue (BER) treatment. Proportions of plant-parasitic (PP) and free-living (FL) nematodes were significantly impacted by treatment, but not year, with PP nematodes accounting for 27, 59, and 68% of CTR, FES, and BER communities, respectively. There was no significant year by season by treatment or treatment by year effect for total, PP, or FL nematode abundances. Diversity did not increase over time. The BER and FES treatments had more mature communities as indicated by higher plant-parasitic index (PPI) values. Phytoremediation accelerates petroleum degradation and alters the soil habitat which is reflected in the nematode community. However, low numbers and inconsistent presence of persister strategist omnivores and predators, and the lack in improvement over time in treatment effects for total and PP nematode abundances, PP and FL proportions, or PPI indicate the system is being rehabilitated but has not been restored after 69 months of phytoremediation.

Performance by spring and fall-calving cows grazing with full, limited, or no access to toxic Neotyphodium coenophialum-infected tall fescue

Replacing toxic, wild-type Neotyphodium coenophialum-infected tall fescue (E+) with nontoxic, N. coenophialum-infected tall fescue (NE+) has improved cow performance, but producer acceptance of NE+ has been slow. The objective was to compare performance by spring- and fall-calving cows grazing either E+ or NE+ at different percentages of the total pasture area. Gelbvieh×Angus crossbred cows (n=178) were stratified by BW and age within calving season and allocated randomly to 1 of 14 groups representing 5 treatments for a 3-yr study: i) Fall-calving on 100% E+ (F100); ii) Spring-calving on 100% E+ (S100); iii) Fall-calving on 75% E+ and 25% NE+ (F75); iv) Spring-calving on 75% E+ and 25% NE+ (S75); and v) Spring-calving on 100% NE+ (SNE100). Groups allocated to F75 and S75 grazed E+ until approximately 28 d before breeding and weaning, then were then moved to their respective NE+ pasture area for 4 to 6 wk; those allocated to F100, S100, and SNE100 grazed their pastures throughout the entire year. Samples of tall fescue were gathered from specific cells within each pasture at the time cows were moved into that particular cell (∼1 sample/mo). Blood samples were collected from the cows at the start and end of the breeding season. Stocking rate for each treatment was 1 cow/ha. Forage IVDMD, CP, and total ergot alkaloid concentrations were affected (P<0.05) by the treatment×sampling date interaction. Hay offered, cow BW, and BCS at breeding, end of breeding, and at weaning were greater (P<0.05) from fall-calving vs. spring-calving. Cow BW at weaning was greater (P<0.05) from F75 and S75 vs. F100 and S100. The calving season×NE+ % interaction affected (P<0.05) calving rates. Preweaning calf BW gain, actual and adjusted weaning BW, ADG, sale price, and calf value at weaning were greater (P<0.05) from fall-calving vs. spring-calving and from SNE100 vs. S75 except for sale price which was greater (P<0.05) from S75 vs. SNE100. Cow concentrations of serum prolactin at breeding and serum NEFA at the end of breeding were affected (P<0.05) by the calving season×NE+ % interaction. Serum Zn and Cu concentrations from cows were affected (P<0.05) by calving season. A fall-calving season may be more desirable for cows grazing E+, resulting in greater calving rates, cow performance, and calf BW at weaning, whereas limited access to NE+ may increase calving rates, serum prolactin, and NEFA concentrations during certain times in the production cycle, particularly in spring-calving cows.

Dead-end hollow-fiber ultrafiltration for concentration and enumeration of Escherichia coli and broad-host-range plasmid DNA from wastewater

Broad-host-range plasmids can facilitate dissemination of antibiotic resistance determinants among diverse bacterial populations. We evaluated hollow-fiber ultrafiltration for increases in detection efficiency of broad-host-range plasmids and Escherichia coli DNA in wastewater. Ultrafiltration followed by PCR showed limited increases in DNA detection and quantification in effluent compared with membrane filtration alone.

Populations of antibiotic-resistant coliform bacteria change rapidly in a wastewater effluent dominated stream

Incomplete elimination of bacteria and pharmaceutical drugs during wastewater treatment results in the entry of antibiotics and antibiotic-resistant bacteria into receiving streams with effluent inputs. In Mud Creek in Fayetteville, AR, ofloxacin, trimethoprim, and sulfamethoxazole have been detected in water and sediment, and tetracycline has been detected in sediment downstream of treated effluent input. These antibiotics have been measured repeatedly, but at low concentrations (<1μg/L) in the stream. To determine if effluent input results in detectable and stable changes in antibiotic resistances downstream of effluent input, antibiotic resistance in Escherichia coli and total coliform bacteria in Mud Creek stream water and sediment were determined using a culture-based method. Isolated E. coli colonies were characterized for multiple antibiotic resistance (MAR) patterns on solid media and to evaluate E. coli isolate richness by amplification of a partial uidA gene followed by denaturant gradient gel electrophoresis (DGGE). Despite temporal variability, proportions of antibiotic-resistant E. coli were generally high in effluent and 640m downstream. The MAR pattern ampicillin-trimethoprim-sulfamethoxazole was associated with a DGGE profile that was detected in effluent and downstream E. coli isolates, but not upstream. Percent resistance among coliform bacteria to trimethoprim and sulfamethoxazole was higher 640m downstream compared to upstream sediment and water (with one exception). Resistance to ofloxacin was too low to analyze statistically and tetracycline resistance was fairly constant across sites. Resistances changed from 640m to 2000m downstream, although dissolved nutrient concentrations within that stream stretch resembled effluent. Antibiotic resistant bacteria are entering the stream, but resistances change within a short distance of effluent inputs, more quickly than indicated based on chemical water properties. Results illustrate the difficulty in tracking the input and fate of antibiotic resistance and in relating the presence of low antibiotic concentrations to selection or persistence of antibiotic resistances.

Broad-host-range plasmids in treated wastewater effluent and receiving streams

The occurrence of broad-host-range (BHR) plasmid amplicons belonging to incompatibility (Inc) groups IncA/C, IncN, IncP, and IncW in two wastewater treatment plant (WWTP) effluents and effluent-receiving streams in Northwest Arkansas, Mud Creek and Spring Creek, was determined. Community DNA captured on filter membranes and plasmid DNA extracted from antibiotic-resistant Escherichia coli isolated from Mud Creek was used for polymerase chain reaction at amplification of partial gene sequences specific to BHR plasmids. IncP plasmid amplicons were detected in effluent and downstream sites in both streams, while IncN and IncW plasmid amplicons were detected in Spring Creek in effluent and downstream but not upstream. IncA/C plasmid amplicons, in contrast, were detected at all sites, including upstream in most samples in Spring Creek and in one sample from Mud Creek. One IncP and two IncN were the only BHR plasmid amplicons found in 85 screened antibiotic-resistant E. coli isolates, and were detected only in isolates from effluent and downstream samples. Broad-host-range plasmids frequently carry antibiotic-resistance genes and can facilitate horizontal transfer of those genes. While BHR plasmids have been detected in WWTPs, WWTPs do not target these genetic elements for destruction. This study indicates that BHR plasmids are in WWTP effluent and are introducing BHR plasmids into streams. Additionally, species other than E. coli may be better targets as indicator bacteria for future studies of the impact of treated effluent on environmental dissemination of BHR plasmids.

Mesocosm-scale evaluation of faunal and microbial communities of aerated and unaerated leachfield soil

Aeration improves the capacity of leachfields to decontaminate and reduce the nutrient load of wastewater. To gain a better understanding of the effects of aeration, we examined the faunal and microbial communities of septic system leachfield soil (0-4 and 4-13 cm) using replicated (n = 3) mesocosms that were actively aerated (AIR) or unaerated (LEACH). Protozoa were 40 to 140 times more abundant in AIR than in LEACH soil. No nematodes were found in LEACH soil, whereas AIR soil contained 5 to 14 x 10(3) nematodes (all bacteriovores) kg(-1). Active microbial biomass was four to five times higher in AIR than LEACH soil. Proteobacteria and actinomycetes/sulfate-reducing bacteria constituted a higher proportion of the community in AIR soil, whereas anaerobic Gram-negative bacteria/firmicutes were more prominent in LEACH soil. Ratios of prokaryotic to eukaryotic phospholipid fatty acids (PLFAs) were higher in LEACH soil, as were membrane stress index values, whereas the starvation index was higher in AIR soil. Community-level physiological profiles showed that 29 and 30 different substrates were used for growth by LEACH and AIR soil microorganisms, respectively. The AIR soil had more microorganisms capable of growing on 10 substrates, whereas growth on two substrates was higher in LEACH soil. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis of 16S rRNA gene fragments revealed greater diversity of dominant phylotypes in AIR than LEACH soil, with communities separated by treatment. Aerated leachfield soil had a larger and more diverse faunal and microbial community than unaerated soil, possibly due to differences in the type and availability of electron acceptors.

Links between phytoplankton and bacterial community dynamics in a coastal marine environment

Bacteria and phytoplankton dynamics are thought to be closely linked in coastal marine environments, with correlations frequently observed between bacterial and phytoplankton biomass. In contrast, little is known about how these communities interact with each other at the species composition level. The purpose of the current study was to analyze bacterial community dynamics in a productive, coastal ecosystem and to determine whether they were related to phytoplankton community dynamics. Near-surface seawater samples were collected in February, May, July, and September 2000 from several stations in the Bay of Fundy. Savin et al. (M.C. Savin et al., Microb Ecol 48: 51-65) analyzed the phytoplankton community in simultaneously collected samples. The attached and free-living bacterial communities were collected by successive filtration onto 5 microm and 0.22 microm pore-size filters, respectively. DNA was extracted from filters and bacterial 16S rRNA gene fragments were amplified and analyzed by denaturing gradient gel electrophoresis (DGGE). DGGE revealed that diversity and temporal variability were lower in the free-living than the attached bacterial community. Both attached and free-living communities were dominated by members of the Roseobacter and Cytophaga groups. Correspondence analysis (CA) ordination diagrams showed similar patterns for the phytoplankton and attached bacterial communities, indicating that shifts in the species composition of these communities were linked. Similarly, canonical CA revealed that the diversity, abundance, and percentage of diatoms in the phytoplankton community accounted for a significant amount of the variability in the attached bacterial community composition. In contrast, ordination analyses did not reveal an association between free-living bacteria and phytoplankton. These results suggest that there are specific interactions between phytoplankton and the bacteria attached to them, and that these interactions influence the composition of both communities.

Plankton diversity in the Bay of Fundy as measured by morphological and molecular methods

Phytoplankton have traditionally been identified based on morphological characteristics. However, identifications based on morphology are time-consuming, require expertise in taxonomy, and often fail to distinguish differences among the multitudes of minute, nondescript planktonic organisms. Molecular techniques, which have revealed new insights into bacterial and picoplankton communities, may also enhance our knowledge of the diversity among communities of larger plankton. We compared plankton identifications and community assessments based on the two types of techniques (morphological vs molecular) for surface seawater samples collected on 2 May, 31 July and 25 September 2000 from several sampling stations in the Bay of Fundy. Phytoplankton captured in surface bucket samples were quantified and identified based on morphology. DNA was extracted from plankton communities (5-100 microm in diameter) collected by filtration, and 18S rRNA gene fragments were amplified with primers specific for eukaryotes. Denaturing gradient gel electrophoresis (DGGE) was used to develop DNA profiles of eukaryotic phylogenetic diversity and to select cloned 18S rDNA fragments for sequencing. Both morphological and molecular methods showed great community diversity. However, the communities identified with the two different types of techniques were starkly different. Morphological abundances and taxon richness were lowest in the May samples, whereas the number of DGGE bands was highest in May and July. Morphological identifications showed a succession of dominant organisms through time. Whereas neither diatoms nor dinoflagellates were dominant in May, diatoms and a few dinoflagellates were dominant in July and September. In contrast, few 18S rDNA sequences were related to rDNA sequences of known identity, and furthermore, few diatoms were identified in the molecular analyses. Molecular phylogenetic analysis indicated the presence of many novel organisms, several of which were most closely related to other unidentified sequences from diverse marine environments representing new lineages. Our results support the ideas that we are just beginning to uncover the diversity of eukaryotic marine organisms and that there may be many more ubiquitous, microeukaryotic plankton than previously realized. Our results suggest that both types of methods capture only a portion of the community. Morphological methods may be more adept at capturing the phototrophic organisms within the community. However, just as for bacteria and picoplankton, molecular techniques can enhance our understanding of plankton diversity, particularly by detecting previously unidentified organisms.