Wk Of Growth Research Articles

PSVI-18 Low and high feed efficiency grower-finisher pigs fed three different levels of dietary crude protein showed no immediate difference in blood metabolomics profile

Abstract Improving feed efficiency (FE) of grower-finisher pigs is of great importance considering its impact on production economy, nutrient excretions as well as carbon-footprint. The biological background describing variation in FE between pen mates, is difficult to establish as feed intake (FI) and FE are not estimated on an individual level. In this study advanced feeding stations were used to estimate FI and further calculate feed conversion ratio (FCR) on individual level. The study aimed to investigate the possible difference in the blood metabolic profile between low and high FE grower-finisher pigs fed three different levels of dietary crude protein (CP). The study included 60 newly weaned gilts divided in two series, housed as 10 pigs/pen. The 30 pigs per series were distributed between three pens (10 pigs/pen) and were balanced by body weight and litter. Throughout the entire weaner period all pigs had ad libitum access to the same diet. Pigs were redistributed among the grower-finisher pens to balance FCR levels between dietary treatments (CP levels) and to reduce any carry over effect from the weaner to the grower-finisher pens. From 30-115 kg body weight (BW), pigs were fed either a low (L; 14.8% CP), standard (15.2% CP) or high (H; 15.8% CP) CP diet equal in energy, where BW, average weekly gain (AWG), and FCR were determined on weekly basis, while FI was estimated on daily basis. Three low FE (20% least) and three high FE (20% greatest) pigs were selected based on the final 4 wk of growth within station and CP level. On the final day of the experimental period all low-FE and high-FE pigs within each dietary treatment were euthanized and blood plasma was sampled and subjected to a nontargeted LC-MS metabolomics analysis. Growth performance and metabolite data were, respectively, analyzed in R and MetaboAnalyst 5.0 with FE and CP as fixed effects. High-FE and H-CP pigs continuously displayed numerically greater BW, while AWG and FCR were, respectively, numerically greater, and less in L-CP than H-CP group during last 2 wk of the experimental period. Principal Component Analysis (PCA) showed no grouping (P > 0.05) of metabolites and no specific pattern of the metabolic profile from either the two FE categories or the three dietary CP levels. Furthermore, no correlation (P >0.05) of metabolites to any other observation was found, and only little variation, measured by distance to model showing deviation of each pig to overall model, was observed. In conclusion, at first glance the metabolomics profile did not appear to present any specific pattern between low and high feed efficiency grower-finisher pigs or between pigs exposed to different levels of dietary CP in the grower finisher period.

PSVI-19 No apparent association between the microbiome in the distal part of the small intestine and feed efficiency in grower-finisher pigs fed three different levels of dietary crude protein

Abstract Improving feed efficiency (FE) of grower-finisher pigs is important considering its production, environmental and climate impact. The biological background describing variation in FE between pen mates, is difficult to establish as feed intake (FI) and FE is not estimated on an individual level. In this study advanced feeding stations were used to estimate FI and further calculate feed conversion ratio (FCR) on individual level. The study aimed to investigate the possible association between FCR and microbiome (alpha and beta diversity; observed features and Shannon index, and Bray-Curtis dissimilarity and Jaccard Distance) in the distal part of the small intestine (SI) in grower-finisher pigs fed three different levels of dietary crude protein (CP). The study included 60 newly weaned gilts divided in two series, housed as 10 pigs/pen. The 30 pigs per series were distributed between three pens (10 pigs/pen) and were balanced by body weight (BW) and litter with ad libitum access to the same diet. Pigs were redistributed among the grower-finisher pens to balance FCR levels between dietary treatments (CP levels) and to reduce any carry over effect from the weaner to the grower-finisher pens. From 30-115 kg BW, pigs were fed either a low (L; 14.8% CP), standard (Std; 15.2% CP) or high (H; 15.8% CP) CP diet equal in energy, where BW, average weekly gain (AWG), and FCR were determined on weekly basis, while FI was estimated on daily basis. Three low FE (20% least) and three high FE (20% greatest) pigs were selected based on the final 4 wk of growth within station and CP level. All low-FE and high-FE pigs within each dietary treatment were euthanized around 115 kg BW and content and mucosa scrabe from the distal part of the SI was sampled and subjected to 16S rRNA gene amplicon sequencing. Data were analyzed in R using a generalized linear mixed-effects model with FE, CP, and their interaction as explanatory variables, start BW of weaner and grower phase as covariables, and series as random effect. High-FE and H-CP pigs continuously displayed numerically greater BW, while AWG and FCR were, respectively, numerically greater, and less in L-CP than H-CP group during last 2 wk of the experimental period. While FE and CP individually had no significant impact [Pr(> Chisq] > 0.05), their interaction could be important in explaining the variation (Chisq = 6.42, Df = 2, Pr(>Chisq) = 0.04) as expressed by observed features. But a pairwise comparison with a Benjamini–Hochberg correction showed no difference between groups. Concerning the Shannon index, no significance was found between groups, and no difference with respect to beta diversity was observed. In conclusion, the microbiome as expressed by alpha and beta diversity did not explain the variation between low and high FE in grower-finisher pigs.

Supplemental lighting spectrum impact on sweet potato cutting production and rooting

AbstractLight is an important factor in plant growth and morphology of sweet potato (Ipomoea batatas L. Lam). This study explored the impact of supplemental lighting provided by three commercially available units on a stock plant cutting production and cutting rooting of two sweet potato cultivars ‘Covington’ and ‘Beauregard’. In experiment one, stock plants were grown under one of four lighting conditions, no supplemental light, high blue light emitting diode (LED), low blue LED, or halogen. Cuttings were collected twice a week for 5 wk and the total weekly cutting number and cutting caliper per plant were recorded. During this experiment plants grown under supplemental lighting exhibited significantly greater weekly total cutting numbers after 2 wk of growth when compared with those that were not exposed to supplemental lighting. In experiment two, cuttings were rooted under the same four light treatments and sampled on Days 7, 14, and 21 in which the cutting height, root weight, and shoot weight were recorded. On Day 21 Covington plants grown under low blue and halogen supplemental lighting exhibited significantly greater root dry weight when compared with those that did not receive supplemental lighting. However, no differences in rooting were observed for Beauregard. These results demonstrate that supplemental light increases stock plant growth regardless of the three commercially available light spectrums examined when compared with no supplemental light. This suggests that increasing the daily light integral (DLI) has a larger impact on plant growth than the spectrum of the commercially available lights that were examined.

Effects of Hatch Window and Nutrient Access in the Hatcher on Performance and Processing Yields of Broilers Reared with Equal Hatch Window Representation.

Simple SummaryIn commercial hatcheries, hatched broiler chicks remain in the hatcher without feed or water until all chicks are pulled from the hatching cabinet. Subsequent hatchery holding and transport periods can further delay nutrient access, potentially causing dehydration and limiting the bird’s growth potential. This can possibly be mitigated by providing feed and water in the hatching cabinet to promote immediate nutrient access to chicks after hatching. In the current experiment, chicks hatched in baskets modified to supply feed and water were compared with those hatched in standard baskets in regards to their organ weights, growth performance to 42 d, and processing yields. Additionally, chicks were identified according to moment of hatch within the hatch window to evaluate this factor and its potential interaction with nutrient access. Chicks from hatching baskets with nutrient and water access had heavier body weights during the first 4 wk of growth, but were otherwise similar to chicks from standard baskets in growth performance and meat yield, regardless of the timing of their hatch. This indicates that broilers may be able to compensate for some degree of delayed feed and water access associated with their timing of hatch and subsequent holding and transport.The objective of this experiment was to investigate the effects of feed and water availability in hatching baskets on broiler performance, processing yield, and organ weights while considering the influence of hatch window. Cobb 500 eggs were transferred into illuminated hatchers with two hatching basket types [control (CTL) hatching baskets with no nutrients provided or baskets containing feed and water (FAW)]. Chicks were pulled sequentially to establish four hatch window periods (HWP): early, pre-peak, post-peak, or late. Chicks were then held for 4 h at the hatchery without nutrient access and subsequently reared in 26 floor pens designated as CTL (n = 13) or FAW (n = 13), with 13 chicks from each of the 4 HWP per pen (52 chicks per pen). At 43 d, 16 males from each pen were processed. Chicks from FAW baskets were 1 g heavier (p < 0.001) than those from CTL baskets at placement and were heavier through 28 d (p = 0.003) but similar (p > 0.05) in body weight (BW) for the remainder of the 42 d. No differences (p > 0.05) in feed conversion ratio, mortality, or processing data were observed between CTL and FAW groups. Early-hatching chicks were lighter (p < 0.001) than those from all other HWP at placement, but were only lighter (p < 0.001) than the post-peak group by 42 d. In summary, it was found that hatching basket nutrient access increased the BW of broilers during the first 4 wk of growth, with no other effects on performance or yield. Also, earlier-hatching chicks were generally able to compensate for a lighter placement BW.

New species of Tulasnella associated with Australian terrestrial orchids in the Cryptostylidinae and Drakaeinae

ABSTRACT Many orchids have an obligate relationship with Tulasnella mycorrhizal fungi for seed germination and support into adulthood. Despite the importance of Tulasnella as mycorrhizal partners, many species remain undescribed. Here, we use multiple sequence locus phylogenetic analyses to delimit and describe six new Tulasnella species associated with Australian terrestrial orchids from the subtribes Cryptostylidinae and Drakaeinae. Five of the new species, Tulasnella australiensis, T. occidentalis, T. punctata, T. densa, and T. concentrica, all associate with Cryptostylis (Cryptostylidinae), whereas T. rosea associates with Spiculaea ciliata (Drakaeinae). Isolates representing T. australiensis were previously also reported in association with Arthrochilus (Drakaeinae). All newly described Tulasnella species were delimited by phylogenetic analyses of four loci (nuc rDNA internal transcribed spacer region ITS1-5.8S-ITS2 [ITS], C14436 [ATP synthase], C4102 [glutamate synthase], and mt 16S rDNA [mtLSU]). The pairwise sequence divergence between species for the ITS region ranged from 5.6% to 25.2%, and the maximum sequence divergence within the newly described species ranged from 1.64% to 4.97%. There was a gap in the distribution of within- and between-species pairwise divergences in the region of 4–6%, with only one within-species value of 4.97% (for two T. australiensis isolates) and one between-species value of 5.6% (involving an isolate of T. occidentalis) falling within this region. Based on fluorescence staining, all six new Tulasnella species are binucleate and have septate, cylindrical hyphae. There was some subtle variation in culture morphology, but colony diameter as measured on 3MN+vitamin medium after 6 wk of growth did not differ among species. However, T. australiensis grew significantly (P < 0.02) slower than others on ½ FIM and ¼ potato dextrose agar (PDA) media. Formal description of these Tulasnella species contributes significantly to documentation of Tulasnella diversity and provides names and delimitations to underpin further research on the fungi and their relationships with orchids.

Characterization of Caecal Microbiota in Broilers that Differ in Genetic Strain, Nutrition, and Development of Woody Breast

ObjectivesWoody breast (WB) meat from broilers has undesirable textural characteristics, including, crunchiness and stickiness. Genetic, nutritional, and environmental factors are associated with the mechanism of WB development. A diverse microbiota plays an important role on the growth performance and health of the host, and greater than 900 species of bacteria have been isolated in the gastrointestinal tract of chicken. However, minimal information is known about the microbiota in the guts of broilers that yield WB meat. Therefore, the objective of this research was to characterize and compare the bacterial diversity of caecal microbiota in broilers with normal and woody breast fillets.Materials and MethodsThe Institutional Animal Care and Use Committee of Mississippi State University (IACUC-16–542) reviewed and approved all protocols. One-day-old mixed sex broilers from two strains (A2 and B2) were raised in 32 pens in a chicken house. Birds of each strain were randomly assigned to 16 pens (15 birds per pen) and 8 pens were fed a control diet and 8 pens were fed an amino acid reduced diet (digestible lysine, total sulfur amino acids, and threonine reduced by 20% as compared to the control diet). After 8 wk of growth, 4 male broilers with normal breast (1 chick per pen) and 4 male broilers with WB (1 chick per pen) determined by palpation were selected for each treatment (breed × diet). The cecum samples were collected after birds were euthanized and bled. DNA was extracted and amplified using universal primers that target the V3∼4 regions of bacterial 16S rRNA for sequencing in Illumina MiSeq. Raw sequences were processed, and the quality was filtered using the default parameters of Quantitative Insights into Microbial Ecology (QIIME 2). Differences between species were assessed using the unpaired two-tailed Student t test assuming unequal variance at α = 0.05.ResultsData suggested that the most abundant phyla in all samples were Firmicutes, followed by Bacteroidetes and Proteobacteria. Accounting for both abundance and evenness of the species present in each sample (α diversity), results indicated that there was no difference (P &gt; 0.05, pairwise Kruskal–Wallis test) in the diversity of gut microbiota between two phenotypes (normal vs. woody), two strains (A2 vs. B2) or two diets (control vs. reduced). However, principal coordinate analysis plots (β diversity) revealed that the samples were clustered based on the phenotype rather than by the strain or diet. These results revealed that the microbiota of each bird with normal breast was more similar to each other than the microbiota of birds with WB. Among all species (300–400) identified, no difference (P &lt; 0.05) existed in bacterial abundance between the two genetic strains. However, 16 and 13 species were differentially abundant (P &lt; 0.05) between normal and woody breast and between control and reduced diet treatments, respectively. In the ceca of WB birds Selenomonas bovis (12.6%) and Bacteroides plebeius (12.3%) were the top two predominant bacteria; however, the relative abundances of these two bacteria were only 5.1% and 1.2% in normal birds, respectively.ConclusionDifferences in the microbiome may be associated with the development of WB. Further studies are needed to investigate the potential mechanism and how to reduce broiler WB incidence by regulating their gut microbiota.

Fertilizing Corn With Manure Decreases Caterpillar Performance but Increases Slug Damage.

Many farmers use manure as an alternative to inorganic fertilizer. Previous research has shown that manure can decrease plant susceptibility to herbivores, but the mechanisms remain unclear. To determine how manure affects herbivore performance in a greenhouse setting, we fertilized corn with stacked cow manure or an equivalent amount of NPK fertilizer and measured caterpillar development, plant nutritional content, and defenses. After 4 wk of growth, we allowed fall armyworm (Spodoptera frugiperda) or black cutworm (Agrotis ipsilon) caterpillars to feed on these plants for 6 d. Compared to inorganic fertilizer, manure reduced mass-gain of black cutworm caterpillars and smaller fall armyworms. We paired this greenhouse experiment with a 3-yr field experiment, which incorporated a wheat cover-crop treatment crossed with the two fertilizer treatments in a 2 × 2 factorial design. We measured plant damage early in the season from naturally occurring herbivores and measured neonate fall armyworm performance on field-collected leaf tissue. In 2017, corn in manure-fertilized plots sustained more herbivore damage, primarily driven by a higher incidence of slug damage. Fall armyworm performance, however, was lower on leaves collected from manure-fertilized plants. In contrast to previous studies, we did not find increased micronutrients or enhanced defenses in manure treated plants. While manure can offer resistance to some herbivores, our results suggest that this resistance can be overshadowed by habitat conditions.

Best-fitting growth curves of the von Bertalanffy-Pütter type.

ABSTRACTIntroduction: A large body of literature aims at identifying growth models that fit best to given mass-at-age data. The von Bertalanffy-Pütter differential equation is a unifying framework for the study of growth models.Problem: The most common growth models used in poultry science literature fit into this framework, as these models correspond to different exponent-pairs (e.g., Brody, Gompertz, logistic, Richards, and von Bertalanffy models). Here, we search for the optimal exponent-pairs (a and b) amongst all possible exponent-pairs and expect a significantly better fit of the growth curve to concrete mass-at-age data.Method: Data fitting becomes more difficult, as there is a large region of nearly optimal exponent-pairs. We therefore develop a fully automated optimization method, with computation time of about 1 to 2 wk per data-set. For the proof of principle, we applied it to literature data about 217 male meat-type chickens, Athens Canadian Random Bred, that were reared under controlled conditions and weighed 28 times during a time span of 170 D.Results: We compared 2 methods of data fitting, least squares using the sum of squared errors (SSE), which is common in literature, and a variant using the sum of squared log-errors SSElog. For these data, the optimal exponent-pairs were (0.43, 4.06) for SSE = 2,208.6 (31% improvement over literature values for the residual standard deviation) and (0.89, 0.93) for SSElog = 0.04599. Both optimal exponents were clearly distinct from the exponent-pairs of the common models in literature. This finding was reinforced by considering the region of nearly optimal exponents.Discussion: We explain, why we recommend using SSElog for data fitting and we discuss prognosis, where data from the first 8 wk of growth would not be enough.

Soil‐Test Biological Activity with the Flush of CO2: II. Greenhouse Growth Bioassay from Soils in Corn Production

Core Ideas Grass growth in the greenhouse was dependent on soil nitrogen mineralization. Soil‐test biological activity was a valuable indicator of nitrogen mineralization. Biological activity, residual inorganic nitrogen, and total nitrogen were most important. Soil nitrogen (N) mineralization is variably affected by management and edaphic conditions. A routine soil test that reflects both soil biological activity and N mineralization could improve predictions for N fertilizer recommendations to cereal grains on different soil types and landscape settings. We collected soils from 47 corn production fields in North Carolina and Virginia at depths of 0 to 10, 10 to 20, and 20 to 30 cm and evaluated soil C and N characteristics in association with sorghum‐sudangrass [Sorghum bicolor (L.) Moench ssp. Drummondii] dry matter production and N uptake during 6 to 8 wk of growth in the greenhouse. Plant dry matter and N uptake were strongly associated, as expected. Plant available N (sum of net N mineralization during 24 d of aerobic incubation + residual inorganic N) had the strongest association with plant dry matter production (r2 = 0.76) and N uptake (r2 = 0.85). However, the flush of CO2 during a 0‐ to 3‐d period following rewetting of dried soil was nearly equally effective at r2 = 0.74 and r2 = 0.76, respectively. Multiple regression models with 4 ± 2 additional variables led to r2 = 0.88 ± 0.10 among different separations of data based on depth, region, and soil textural class. We suggest the optimum combination of variables to predict soil N availability would be the flush of CO2, residual inorganic N, and total soil N concentration, as they balance relevant scientific information with limited soil‐testing resources (time and labor). We demonstrated that the flush of CO2 was a rapid and reliable indicator of soil N availability.

Near-infrared–conjugated humanized anti-carcinoembryonic antigen antibody targets colon cancer in an orthotopic nude-mouse model

BackgroundThe success of a curative surgery for cancer is dependent on the complete removal of all cancer cells. Tumor visualization by the surgeon can be enhanced through fluorescent-antibody targeting. To further develop such technology, we selected humanized anti-carcinoembryonic antigen (CEA) conjugated to a near-infrared dye to target orthotopically-implanted human colon cancer in nude mice. Materials and methodsThe HT-29 human colon cancer cell line was grown in culture and subcutaneously injected in mice. After 3 wk of growth, tumors were resected and cut into 2 mm3 fragments that were sutured to the cecum of five additional nude mice for orthotopic implantation. The tumors were allowed to grow for 4 wk at which point 3 had successful orthotopic tumor growth and were selected for injection of the humanized anti-CEA antibody conjugated to the near-infrared dye IRDye800CW (anti-CEA-IRDye800CW). The antibody-dye conjugate (75 μg) was administered via tail vein injection. Images were obtained with the Pearl Trilogy Small Animal Imaging System with both 700 and 800 nm channels and evaluated using Image Studio. ResultsLaparotomy was performed 24 h after labeling the tumors. When imaged through the 800 nm channel, the tumors were observed to be strongly labeled with anti-CEA-IRDye800. At 48 h, laparotomy was repeated which again demonstrated strong labeling of the tumors through the 800 nm channel, but with a lower absolute intensity (in relative units), than at 24 h. ConclusionsHumanized anti-CEA-IRDye800CW can rapidly and effectively label CEA-expressing human colon cancer in an orthotopic nude mouse model. Given the ability of this technology to target and label tumors with great specificity, the anti-CEA-IRDye800CW is currently being developed for clinical use in fluorescence-guided surgery.

Effect of age on the occurrence of muscle fiber degeneration associated with myopathies in broiler chickens submitted to feed restriction

To evaluate muscle fiber degeneration (MFD) associated with white striping and wooden breast, pectoralis major of 192 broilers differing for genotype (standard vs. high breast yield), gender, and feeding regime (ad libitum vs. restricted rate 80% from 13 to 21 d of age) were sampled at 14, 21, 28, 35, and 46 d of age for histological analyses by hematoxylin and eosin (H&E) staining to evaluate tissue morphology, Masson's trichrome to identify collagen presence, and Oil red and Nile blue for lipid presence. Microvessels (diameter ≤15 μm), nuclei positive to anti-cleaved lamin A and monoclonal proliferating cell nuclear antigen (PCNA) antisera were counted to assess apoptotic and regenerative processes, respectively. Significant differences were found according to feeding system, age, and their interactions. The frequency of chickens with MFD was higher with ad libitum than restricted feeding (75.0% vs. 62.5%; P = 0.01) and increased with age (18.8%, 28.1%, 75.1%, 96.9%, and 96.9% at 14, 21, 28, 35, and 46 d). However, at 14 d a similar frequency (18.8%) was found in all broilers; at 21 d, MFD occurred more in broilers fed ad libitum than in those under restriction (50.0% vs. 6.3%; P < 0.01); at 28 d differences were reduced (87.5% vs. 62.5%; P = 0.10) to disappear by 35 (100% and 93.8%) and 46 d (96.9% and 96.9%). The number of microvessels decreased with age (20.7 to 9.46; P < 0.001) and the number of nuclei positive to the anti-cleaved lamin A antibody increased. At histology, MFD at 46 d corresponded to loss of typical cross striations, massive necrotic process, degenerating fibers surrounded by inflammatory cells, scattered fibers in an abundant collagen-rich connective tissue, numerous adipose cells; necrotic fibers showed a high percentage of apoptotic nuclei, and regenerating fibers appeared positive to anti-PCNA antibody. In conclusion, MFD soon occurred after 2 wk of growth and increased dramatically within 28 d. Early feed restriction reduced MFD as long as animals were restricted, but no residual effect was recorded after re-alimentation.

Purple Nutsedge (Cyperus rotundus) Tuber Production and Viability Are Reduced by Imazapic

Weeds exploit underutilized space, causing economic losses in cropping systems. Weed management tactics alter that underutilized space until the crop can mature and efficiently use that space. One tactic is to reduce the weed propagules (e.g., seeds and tubers) that persist quiescently in the soil, which includes minimizing production and addition of new propagules to the soil. Purple nutsedge is a problematic weed around the globe, persisting between growing seasons as tubers in the soil. Imazapic is a peanut herbicide often used in Georgia for control of purple nutsedge. The objective of the experiment was to evaluate the effect of various rates of imazapic on purple nutsedge tuber production. Single presprouted purple nutsedge tubers were transplanted into outdoor microplots and treated after 6 wk of growth with six rates of imazapic (5 to 140 g ai ha−1) POST. A nontreated control was included. All emerged shoots at the time of application were marked with plastic rings; this allowed for classification of tubers at exhumation as (1) tubers attached to shoots that were emerged at time of application, (2) tubers attached to shoots that emerged after application, and (3) tubers without an aerial shoot during the study. At 7 wk after application, the tubers in the microplots were exhumed, classified, and quantified, and their ability to sprout was evaluated. In the nontreated control, there were 544 total tubers, with a log-logistic regression model describing the declining tuber population with increasing imazapic rate. The rate of imazapic that reduced total tuber population 50% (I50) was 36 g ha−1. In the nontreated control, there were 161 tubers attached to shoots that emerged, as when compared with plots that received an imazapic application that had an I50=60 g ha−1. Viability of purple nutsedge tubers was 44% at 70 g ha−1imazapic, suggesting the action of the herbicide may have rendered the tubers nonviable after new shoots were produced. The final classification of tubers included those that did not have an aerial shoot during the study. These were tubers in which apical dominance suppressed shoot development or were likely the most recent tubers to develop. Of the three classes, the tubers without shoots were the most prevalent in the nontreated control, with 358 tubers and an I50=18 g ha−1. Imazapic controls purple nutsedge foliage but also reduces the number of new tubers produced, and overall tuber viability and is a valuable tool in management of the long-term population density of this weed.

Enhanced Fire-Related Traits May Contribute to the Invasiveness of Downy Brome (Bromus tectorum)

Although several invasive species have induced changes to the fire regime of invaded communities, potential intraspecific shifts in fire-related traits that might enhance the invasion success of these species have never been addressed. We assumed that traits conferring persistence and competitiveness in postfire conditions to downy brome, a quintessential invasive species of the Great Basin (North America), might be under selection in areas with recurrent fires. Therefore, we hypothesized that populations from frequently burned regions of the Great Basin would have (1) greater tolerance to fire at seed level, (2) higher relative seedling performance in postfire environments, and (3) greater flammability than unburned Central European populations that evolved without fire. Seeds were collected from three introduced populations from frequently burned regions in North America and three introduced populations of rarely or never burned sites from Central Europe. We performed (1) germination experiments with seeds subjected to the effect of different fire components (heat shocks, smoke, flame, ash), (2) pot experiments analyzing the effect of postfire conditions on the early growth of the seedlings, and (3) a series of flammability tests on dry biomass of plants reared in a common garden. All seeds tolerated the low-temperature treatments (40 to 100 C), but were destroyed at high heat shocks (140 and 160 C). Only the 100 C heat treatment caused a difference in reaction of seeds from different continents, as the European seeds were less tolerant to this heat shock. We found significantly increased seedling height and biomass after 4 wk of growth under postfire conditions in American populations, but not in European ones. American populations had enhanced flammability in three out of five measured parameters compared to European populations. In summary, these intraspecific differences in fire-related traits might contribute to the persistence and perhaps invasiveness of the frequently burned North American downy brome populations.

Halosulfuron Reduced Purple Nutsedge (Cyperus rotundus) Tuber Production and Viability

Weeds persist and cause economic losses in agricultural systems because they exploit underused portions of that system. Reducing the effect of weeds on agroecosystems begins with minimizing the number of propagules (e.g., seeds and tubers) that are produced and returned to the soil. Purple nutsedge is a problematic weed around the globe, persisting between growing seasons as tubers in the soil. Halosulfuron is an effective herbicide for controlling purple nutsedge foliage and is used in corn and several vegetable crops. Studies were conducted to evaluate the effect of various rates of halosulfuron on purple nutsedge tuber production. Single, presprouted purple nutsedge tubers were transplanted into outdoor microplots and treated after 6 wk of growth with six rates of halosulfuron (7 to 208 g ai ha−1) POST with a nontreated control (NTC). All shoots that had emerged at the time of application were marked with plastic rings; this allowed for classification of tubers at exhumation of (1) tubers attached to shoots that had emerged by the time of application, (2) tubers attached to shoots that emerged after application, and (3) tubers without an aerial shoot during the study. Seven weeks after application, the tubers in the microplots were exhumed and tubers were classified, quantified, and their ability to sprout was evaluated. In the NTC, there were 530 total tubers, with a log-logistic regression model describing the tuber population with increasing halosulfuron rate. The rate of halosulfuron that reduced total tuber population 50% (I50) was 8 g ha−1. In the NTC, 200 tubers were attached to shoots that emerged following halosulfuron application, and this class of tubers had anI50of 19 g ha−1. Viability of tubers with shoots that emerged following halosulfuron application was 28% at the 52 g ha−1halosulfuron, suggesting the action of the herbicide may have rendered the tuber nonviable after new shoots were produced. The final classification of tubers was those that did not have an aerial shoot during the study. These were tubers in which apical dominance suppressed shoot development or were likely the most-recent tubers to develop. Of the three classes, the tubers without shoots were the most numerous in the NTC, with 294 tubers and anI50of 1 g ha−1. Halosulfuron is an effective herbicide that not only controls purple nutsedge foliage but also reduces the number of new tubers produced and overall tuber viability. This could be an important component to reduce the long-term population density of the weed.

The effect of protease, amylase, and nonstarch polysaccharide-degrading enzyme supplementation on nutrient utilization and growth performance of broiler chickens fed corn-soybean meal-based diets

A study was conducted to determine if amylase and protease addition would improve nutrient digestion during the first 2 wk of growth. The experimental treatments included a control corn-soybean meal-based diet and diets supplemented with either amylase or amylase plus protease. No effect of enzyme supplementation was observed on BW gain and feed conversion ratio. This was corroborated by similar ileal starch and protein digestibility values, which averaged 96.8, 96.8, and 96.9% and 83.9, 80.1, and 79.6%, respectively, for the control and for the amylase or amylase plus protease supplemented diets. Total tract digestibility of starch averaged 97.8, 97.7 and 97.7% for the 3 diets and was followed by a similar diet with AMEn values of 3,129, 3,129, and 3,106 kcal/kg. In another study, a 23 factorial arrangement of 8 dietary treatments was used to evaluate the effect of corn particle size (conventional or coarse vs. fine) and the addition of a nonstarch polysaccharide enzyme, amylase, or both on growth performance and nutrient utilization of broiler chickens from 1 to 21 d of age. Chickens fed a diet containing a conventionally ground corn (geometric mean diameter of 736 µm) showed higher (P < 0.001) BW gain (808 vs. 750 g/bird) and lower feed conversion ratio (1.27 vs. 1.32) than those consuming a fine corn-containing diet (geometric mean diameter of 482 µm). This was further substantiated by a lower AMEn content (2,852 vs. 2,972 kcal/kg). Addition of amylase had no effect on growth performance of chickens fed a conventional corn-containing diet, but improved BW gain, feed conversion ratio, and diet AMEn in those fed the finely ground corn, possibly due to increased starch digestion in the upper gut. Addition of nonstarch polysaccharide enzymes was effective for both diets, with the most pronounced effects observed in feed converstion ratio for the conventional corn-containing diet (1.27 vs. 1.23) and BW gain (750 vs. 789 g/bird) for the fine corn-containing diet. This was followed by the same magnitude of difference in diet AMEn content, which increased from 2,972 to 3,042 and 2,852 to 3,009 kcal/kg following enzyme addition.

Effect of different day and night nutrient solution concentrations on growth, photosynthesis, and leaf NO3- content of aeroponically grown lettuce

Nitrate content in leafy green vegetables has raised concerns among consumers and policy makers worldwide. Several cultural practices have been evaluated to manipulate NO3- content in fresh leaves with varying degrees of success. The present study was conducted to evaluate different concentrations of the nutrient solution applied during the day (D) and night (N) to aeroponically grown lettuce (Lactuca sativa L.) in Davis, California, USA, in the spring of 2012 with the objective of assessing the effect on growth, leaf photosynthesis, and nitrate accumulation in leaves. Two different treatments in the nighttime solution concentration (D25/N75, EC: 1.8 dS m-1; and D25/N50, EC: 1.2 dS m-1), a day nutrient solution of EC 0.6 dS m-1, plus a day and night treatment with constant EC (D50/N50, EC: 1.2 dS m-1) were applied. Plant growth, leaf photosynthesis, and leaf nutrient content were evaluated after 3 wk of growth. Mean shoot weight was 106.3 g with no differences among treatments. Root biomass was lower with D25/N75 (0.14 vs. 0.85 g in the other treatments). The maximum rate of leaf photosynthesis was 66% lower with D25/N75 than in the other treatments. Nitrogen, P, K, Ca, and Mg were lower in leaf tissue in the treatments with different solution concentrations where leaf NO3- content was reduced by approximately 75%. Switching nutrient solution concentration between day and night is a viable practice to reduce NO3- in lettuce leaves with no detriment to leaf production.

Influence of isoxaflutole on colonization of corn (Zea mays L.) roots with arbuscular mycorrhizal fungus Glomus intraradices

Stokłosa, A., Nandanavanam, R., Puczel, U. and Upadhyaya, M. K. 2011. Influence of isoxaflutole on colonization of corn (Zea mays L.) roots with arbuscular mycorrhizal fungus Glomus intraradices. Can. J. Plant Sci. 91: 143–145. In a greenhouse pot culture study, corn plants were grown in sterilized soil containing mycorrhizal fungus Glomus intraradices and different concentrations of Converge Pro® herbicide (19.8, 39.6, 79.2, and 158.4 µg a.i. isoxaflutole L−1 soil). Mycorrhizal colonization of corn roots was observed to be 10 to 20% at 6 wk (exp. I) and 50 to 60% at 8 wk (exps. II and III) of plant growth. Isoxaflutole did not inhibit mycorrhizal colonization in any of the three experiments. These results show that the use of isoxaflutole does not affect corn plants by influencing mycorrhizal colonization for up to 8 wk of growth.

Influence of isoxaflutole on colonization of corn (Zea mays L.) roots with arbuscular mycorrhizal fungus Glomus intraradices

Stoklosa, A., Nandanavanam, R., Puczel, U. and Upadhyaya, M. K. 2011. Influence of isoxaflutole on colonization of corn (Zea mays L.) roots with arbuscular mycorrhizal fungus Glomus intraradices. Can. J. Plant Sci. 91: 143-145. In a greenhouse pot culture study, corn plants were grown in sterilized soil containing mycorrhizal fungus Glomus intraradices and different concentrations of Converge Pro® herbicide (19.8, 39.6, 79.2, and 158.4 µg a.i. isoxaflutole L-1 soil). Mycorrhizal colonization of corn roots was observed to be 10 to 20% at 6 wk (exp. I) and 50 to 60% at 8 wk (exps. II and III) of plant growth. Isoxaflutole did not inhibit mycorrhizal colonization in any of the three experiments. These results show that the use of isoxaflutole does not affect corn plants by influencing mycorrhizal colonization for up to 8 wk of growth.

Growth and Reproduction of Benghal Dayflower (Commelina benghalensis) in Response to Drought Stress

Greenhouse experiments were conducted to evaluate growth and reproduction of Benghal dayflower in response to daily (nondrought stress) and weekly (drought stress) irrigation. With daily irrigation, Benghal dayflower plants added one leaf per plant each week during the initial 6 wk of growth and then increased leaf number eightfold between the intervals of 6 and 10 wk after planting (WAP) and 10 and 15 WAP. By 15 WAP each plant had in excess of 400 leaves. Benghal dayflower plant height increased 2.4 cm wk−1 between 5 and 14 WAP, increasing eightfold during this interval, while plant width increased 20-fold. Aerial spathe formation began between 7 and 8 WAP, with 26 spathes maturing (containing seeds ready for dispersal) each week beginning at 11 WAP. In another study, the influence of duration of drought stress at intervals between 7 and 56 d on early growth and development of cotton and Benghal dayflower was evaluated. Benghal dayflower aboveground biomass was 3.5 times greater than cotton. There was an inverse linear relationship between aboveground biomass and duration of drought stress for cotton and Benghal dayflower, though there was a more rapid decline for Benghal dayflower. A final study evaluated Benghal dayflower response to weekly moisture regimes that approximated 13, 25, 50, and 100% of soil field capacity. Benghal dayflower aerial spathes were 4.6 times more numerous than subterranean spathes. Rate of seed production decreased in a linear manner with decreasing water volume, however, rate of subterranean seed production was less affected by water volume than was aerial seed production. These data indicate that Benghal dayflower thrives under high soil moisture regimes, but that drought stress inhibits growth and reproduction. Cotton appears to be more drought tolerant than Benghal dayflower. Judicious water use in cotton cropping systems in the southeastern United States could be an important component of multiple-tactic Benghal dayflower management program.

Phytoextraction of Arsenic from Soil by Leersia Oryzoides

The potential of Leersia oryzoides (rice-cut grass) to remediate arsenic-contaminated soil was studied in greenhouse pot experiments. Leersia oryzoides grown in soil amended with arsenic to a concentration of 110 mg kg−1, extracted up to 305 mg kg−1 and 272 mg kg−1 arsenic into its shoots and roots, respectively, giving a shoot:root quotient of 1.12 and phytoextraction coefficients up to 2.8. Plants in the arsenic-amended soil showed visible signs of stress in the first 8 wk of growth, but then recovered. Based on the 132 plants that were grown in a surface area of approximately 180 cm2, the calculated total arsenic taken up by shoots is 120, 130, and 130 g ha−1 at 6, 10, and 16 wk, respectively, suggesting that additional arsenic could be removed by periodic mowing over a growing season. Extraction with a mixture of nitric acid and hydrogen peroxide indicated that the available arsenic was constant after the first 6 wk. Uptake is comparable to that reported for duckweed (Lemna gibba L.) and overlaps the low end of the values reported for Chinese brake fern (Pteris Vittata L.)