Anthelmintic resistance impact on tropical beef cattle productivity: effect on weight gain of weaned calves

The performance of grazing cattle in tropical areas is deeply influenced by parasitism, and the increasing reports of resistance are a threat to effective nematode control. The present study aimed to evaluate the effect of avermectins on the performance of weaned calves naturally infected by ivermectin-resistant gastrointestinal nematodes. The effect of four commercial endectocides (ivermectin 2.25 % + abamectin 1.25 %, ivermectin 3.15 %, doramectin 3.15 %, and doramectin 1 %) on parasitism and performance of a hundred weaned Nellore calves were evaluated during 112 days. The most effective anthelmintic showed efficacy of 84 % and resulted in an increase (P?<?0.05) of live weight gain of 11.85 kg, compared to untreated group, 9.05 and 9.41 kg compared to those treated with more ineffective avermectins which showed efficacy of 0 and 48.2 %, respectively. A significant (P?<?0.05) and weak negative correlation (r?=??0.22) between the eggs per gram (EPG) and body weight was observed, indicating that even the low mean EPG (175?±?150) observed at day 0 in the control group, with predominance of Haemonchus sp., was responsible for production losses. These results indicate that control of nematode parasites in beef cattle in the weaning phase may not result in increased productivity when carried out without technical criteria.     

Status of insecticide resistance in Culex pipiens field populations from north-eastern areas of Italy before the withdrawal of OP compounds

BACKGROUND: Heavy and constant use of organophosphorus (OP) larvicides selected Culex pipiens L. resistant populations through two main mechanisms of genetic resistance, the increased activity of detoxifying esterase and the production of alterate acetylcholinesterase‐1 (AChE1) by G119S mutation. The aim of this study was the assessment of the distribution of Cx. pipiens populations resistant to temephos and chlorpyrifos in the north‐eastern regions of Italy and the occurrence of the insensitive AChE in these populations. Data describe the situation in the last years before European legislation prohibited the use of OP larvicides in mosquito control, up until 2007. RESULTS: For the first time a high level of OP resistance in the samples from Ravenna (182‐fold, 80% A4/B4 or A5/B5 esterases and 38.3% Ester⁵), Emilia Romagna region, was detected; therefore, new data from the Veneto and Friuli Venezia Giulia regions were obtained and reinforced existing knowledge about resistance previously studied along the Adriatic coast. Nearby, in the Villa Verucchio locality, the highest (87.5%) AChE1R was found. CONCLUSION: Cx. pipiens resistance esterases A5/B5 and A4/B4 spread southward along the Adriatic coastal plain while OPs were being used in mosquito control, as confirmed by the first molecular screening of the AChE1 gene in these populations. Copyright © 2010 Society of Chemical Industry     

Influence of porosity of low-density polyethylene media on the maturation process of biofilters used in recirculating aquaculture systems

The effect of pores with different diameters in polyethylene media on the process of ammonia nitrification during the maturation of biofilters is evaluated. Four types of media were produced: M1 without pores, M2 with 40–112 μm in diameter pores, M3 with 125–187 μm diameter pores, and M4 with 312–437 μm diameter pores. Ammonia concentrations were statistically equal among media. On the majority of days, nitrite concentrations were lowest for M1 and M2, intermediate for M3, and highest for M4. Increased pore diameter favored the formation of biofilm in the interior, but the pores obtained in the expansion process were not interconnected, which may have caused low oxygenation of the water in the internal area. It was concluded that porosity did not reduce biofiltration time and did not increase the efficiency of nitrification of ammonia.     

Effects of selective logging on the mating system and pollen dispersal of Hymenaea courbaril L. (Leguminosae) in the Eastern Brazilian Amazon as revealed by microsatellite analysis

Using nine microsatellite loci, we studied the effects of selective logging on genetic diversity, mating system and pollen dispersal in a population of the tree species Hymenaea courbaril, located in a 546 ha plot in the Tapajós National Forest, Pará State, Brazil. We analyzed 250 offspring (nursery reared seedlings) collected after a logging episode from 14 open-pollinated seed trees. These were compared to 367 seedlings from 20 open-pollinated seed trees previously collected from the pre-logging primary forest. The genetic diversity was significantly lower in the post-logging seed cohort. In contrast to the pre-logging population, significant levels of selfing were detected in the post-logging population (t_m = 0.962, P < 0.05). However, correlated matings were reduced and the effective number of pollen donors almost doubled after harvesting (3.8 against 7.2). Logging also reduced pollen immigration into the plot (from 55% to 38%) and we found no significant correlation between the size of the pollen donors and the number of seeds fathered. Inside the plot, pollen dispersal distance was shorter before logging than after (827 and 952 m, respectively) and the reproductive pollination neighbor area (A_ep) was larger (average of 178 ha). The individual and average variance effective population size within families (ranged from 1.80 to 3.21, average of 2.47) was lower than expected in panmictic populations (N_e = 4). The results indicate that while logging greatly reduced the levels of genetic diversity after logging, it also increased genetic recombination within the population and constrained crossing among related individuals. The results show that low-density tropical tree species such as H. courbaril, when harvested in moderate levels may be resilient to a reduction in the reproductive population and may maintain similar levels of outcrossing and pollen dispersal after logging.     

Detection of rubber tree orchards infested by Meloidogyne exigua using vegetation indexes obtained from satellite images

New Forests - Hevea brasiliensis natural rubber production is strategic for the world economy. Meloidogyne exigua causes the main root disease in this crop in Brazil. Its early diagnosis allows...     

Seasonal leaf dynamics in an Amazonian tropical forest

The ecological consequences of climate change for large tropical forests such as the Amazon are likely to be profound. Amazonian forests strongly influence regional and global climates and therefore any changes in forest structure, such as deforestation or die-back, may create positive feedback on externally forced climate change. Monitoring, modelling and managing the impacts of anthropogenic climate change on forest dynamics is therefore an important objective of forest researchers, and one that requires long-term data on changes at the level of community, populations and phenotypes. In this paper we provide the most comprehensive study yet on the seasonal dynamics of various leaf traits: leaf area index (LAI), leaf mortality (LM), leaf biomass (LB), leaf growth rate (LG), and leaf residence time (TR) from 50 experimental plots in a forest site at Belterra, Pará State, Brazil. From this study we estimate annual mean leaf area index (LAI) to be 5.07 m² m⁻² and annual mean leaf dry biomass to be 0.621 kg m⁻². The typical leaf grew at 0.049 kg m⁻² month⁻¹ and remained on the tree for 12.7 months. We compare these results to other similar studies and critically discuss the factors driving leaf demographics in Amazonia.     

Improvement in Brazilian wheat breeding: changes in developmental phases and ecophysiological traits

Understanding the processes responsible for genetic progress in grain yield and relating them to the growth and developmental phases of the wheat plant are essential for improving yield potential. This study aimed to evaluate the duration of developmental phases and eco-physiological traits associated to grain yield in Brazilian wheat cultivars released in different decades. Wheat cultivars released from 1940 to 2009 were evaluated during 2010 and 2011 in Pato Branco, Paraná, Brazil. The length of the following periods was compared: sowing-emergence (SW-EM), emergence-double ridge (EM-DR), double ridge-terminal spikelet (DR-TS), terminal spikelet-anthesis (TS-ANT), anthesis-physiological maturity (ANT-PM), sowing-anthesis (SW-ANT) and sowing-physiological maturity (SW-PM). Yield components were also measured. Breeding has reduced the days until anthesis by 14.2%, while it has extended the grain-filling period by 7.6%, compared to the first cultivars released in the country, thereby contributing to a significant increase in 1000-grain weight (12.4 and 9.0% in 2010 and 2011, respectively). The TS-ANT phase was the only phase prior to anthesis exhibiting an extension from old to modern cultivars; this phase increased 1.56 °Cd syear^?1. Spike fertility index (SFI) showed increases of 37.8 and 23.8% in 2010 and 2011, respectively. Shortening of the time to flowering, shifting of critical phases of wheat development to better environmental conditions (i.e., TS-ANT phase), and selection for shorter cultivars have been directly responsible for the increase in spike dry weight at anthesis (SDWa) and SFI [i.e., grain number (GN)].     

Serum immunoglobulin G concentration in Southern elephant seal, Mirounga leonina (Linnaeus, 1758), from Elephant Island (Antarctica): sexual and adrenal steroid hormones effects

Serum immunoglobulin G (IgG; indirect enzyme-linked immunosorbent assay), as well as sexual and adrenal steroid hormones' concentrations (radioimmunoassay) were determined in 63 (male and female) Southern elephant seals (Mirounga leonine) at different developmental stages (weaned pups, juveniles and adults). In females, IgG values (mean+/-S.D.) were higher (P<0.05) in adults (15.9+/-6.5mg ml(-1)) than in juveniles (7.9+/-4.0mg ml(-1)), but similar to weaned pups (12.0+/-5.0mg ml(-1)). Estrogen concentration was higher (P<0.05) in adults than in the weaned pups. In females, a significant (P<0.05) correlation (R=0.4) between serum IgG level and progesterone concentration was observed. In males, testosterone concentration was higher (P<0.05) in adults than in the juveniles and weaned pups. Aldosterone and cortisol concentrations were higher (P<0.05) in weaned pups (1056.0+/-643.1pmol 1(-1) and 272.7+/-110.0 nmol 1(-1), respectively) than in the juveniles (638.6+/-579.7pmol1(-1) and 152.9+/-97.3nmol 1(-1), respectively) and adults (386.5+/-209.1pmol (-1) and 145.7+/-67.3nmol 1(-1), respectively). These findings indicate that weaned pups are subjected to a higher natural stressful condition in the field. Despite this, humoral immunity, measured through IgG concentration, is not impaired in weaned pups.     

Organo‐mineral associations in temperate soils: Integrating biology,mineralogy, and organic matter chemistry

We summarize progress with respect to (1) different approaches to isolate, extract, and quantify organo‐mineral compounds from soils, (2) types of mineral surfaces and associated interactions, (3) the distribution and function of soil biota at organo‐mineral surfaces, (4) the distribution and content of organo‐mineral associations, and (5) the factors controlling the turnover of organic matter (OM) in organo‐mineral associations from temperate soils. Physical fractionation achieves a rough separation between plant residues and mineral‐associated OM, which makes density or particle‐size fractionation a useful pretreatment for further differentiation of functional fractions. A part of the OM in organo‐mineral associations resists different chemical treatments, but the data obtained cannot readily be compared among each other, and more research is necessary on the processes underlying resistance to treatments for certain OM components. Studies using physical‐fractionation procedures followed by soil‐microbiological analyses revealed that organo‐mineral associations spatially isolate C sources from soil biota, making quantity and quality of OM in microhabitats an important factor controlling community composition. The distribution and activity of soil microorganisms at organo‐mineral surfaces can additionally be modified by faunal activities. Composition of OM in organo‐mineral associations is highly variable, with loamy soils having generally a higher contribution of polysaccharides, whereas mineral‐associated OM in sandy soils is often more aliphatic. Though highly reactive towards Fe oxide surfaces, lignin and phenolic components are usually depleted in organo‐mineral associations. Charred OM associated with the mineral surface contributes to a higher aromaticity in heavy fractions. The relative proportion of OC bound in organo‐mineral fractions increases with soil depth. Likewise does the strength of the bonding. Organic molecules sorbed to the mineral surfaces or precipitated by Al are effectively stabilized, indicated by reduced susceptibility towards oxidative attack, higher thermal stability, and lower bioavailability. At higher surface loading, organic C is much better bioavailable, also indicated by little ¹⁴C age. In the subsurface horizons of the soils investigated in this study, Fe oxides seem to be the most important sorbents, whereas phyllosilicate surfaces may be comparatively more important in topsoils. Specific surface area of soil minerals is not always a good predictor for C‐stabilization potentials because surface coverage is discontinuous. Recalcitrance and accessibility/aggregation seem to determine the turnover dynamics in fast and intermediate cycling OM pools, but for long‐term OC preservation the interactions with mineral surfaces, and especially with Fe oxide surfaces, are a major control in all soils investigated here.