Temporal and compositional differences of arbuscular mycorrhizal fungal communities in conventional monocropping and tree-based intercropping systems

Previous research has found that conventional agricultural systems adversely affect arbuscular mycorrhizal (AM) fungi. However, there is little information on how more ecologically sustainable agricultural practices such as tree-based intercropping (TBI) influence AM fungal communities. In this study, we investigated whether TBI promotes a more abundant and diverse AM fungal community compared to conventional monocropping (CM). Abundance was estimated by measuring spore abundance and hyphal length in soil, and AM fungal colonization of corn (Zea mays) roots. Overall, AM fungal abundance was similar in both systems as corn roots from the CM and TBI systems were heavily colonized (>50%) by AM fungi throughout the growing season. Additionally, soil samples from the CM and TBI systems contained similar spore densities and hyphal length. Molecular analysis of the AM fungal community was assessed using terminal restriction fragment length polymorphism (T-RFLP) analysis of large subunit rRNA genes amplified from roots in the two cropping systems. A total of fourteen AM fungal phylotypes that belonged to the Glomeraceae were found in the two cropping systems. The TBI system had a higher AM fungal richness and contained several taxa not found in the CM system. Molecular analysis of AM fungal communities also revealed significant temporal and compositional differences between the TBI and CM systems. Within the TBI system, tree species differentially influenced the AM fungal community composition in the alley cropping regions. Future research should focus on determining whether compositional differences among AM fungal communities in CM and TBI systems have a functional effect on crop growth and productivity.     

Post-fire tree stress and growth following smoldering duff fires

Understanding the proximate causes of post-fire conifer mortality due to smoldering duff fires is essential to the restoration and management of coniferous forests throughout North America. To better understand duff fire-caused mortality, we investigated tree stress and radial growth following experimental fires in a long-unburned forest on deep sands in northern Florida, USA. We burned basal fuels surrounding 80 mature Pinus palustris Mill. in a randomized experiment comparing the effects of basal burning treatments on stem vascular meristems; surficial roots; root and stem combinations; and a non-smoldering control. We examined the effects of duration of lethal temperatures (>60 °C) on subsequent pine radial growth and root non-structural carbohydrates (starch and sugar). Duff and mineral soil temperatures in the experimental fires consistently exceeded 60 °C for over an hour following ignition, with lethal temperatures of shorter duration recorded 20 cm below the mineral soil surface. Duff heating was best explained by day-of-burn Oe horizon moisture (P = 0.01), although little variation was explained (R² = 0.24). Post-fire changes in latewood radial increment in the year following fires was related to duration of temperatures >60 °C 10 cm deep in the mineral soil (P = 0.07), but explained little variability in post-fire growth (R² = 0.17). In contrast, changes in non-structural carbohydrate content in coarse roots (2–5 mm diameter) 120 days following burning were more strongly correlated with the duration of lethal heating 5 cm below the mineral soil surface (P = 0.02; R² = 0.53). Results from this study implicate the role of mineral soil heating in the post-fire decline of mature longleaf pine following restoration fires in sandy soils.     

Automated detection and tracking of marine mammals: A novel sonar tool for monitoring effects of marine industry

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A single IGF1 allele is a major determinant of small size in dogs

The domestic dog exhibits greater diversity in body size than any other terrestrial vertebrate. We used a strategy that exploits the breed structure of dogs to investigate the genetic basis of size. First, through a genome-wide scan, we identified a major quantitative trait locus (QTL) on chromosome 15 influencing size variation within a single breed. Second, we examined genetic variation in the 15-megabase interval surrounding the QTL in small and giant breeds and found marked evidence for a selective sweep spanning a single gene (IGF1), encoding insulin-like growth factor 1. A single IGF1 single-nucleotide polymorphism haplotype is common to all small breeds and nearly absent from giant breeds, suggesting that the same causal sequence variant is a major contributor to body size in all small dogs.     

The Effects of Feed Form on Consumption Time and Glucose and Insulin Response to a Concentrate Meal in Equine

This study tested the hypothesis that feeding an identically formulated, low sugar and starch concentrate in three forms (5-mm extruded [E], 4-mm pellet [P], and 19-mm oval [O]) would affect consumption rate and glucose or insulin responses, or both. Horses received 1.8 kg treatment feed in a randomized, crossover design, with samples taken every 30 minutes for 6 hours for blood glucose and insulin response. Pearson's correlation compared consumption time, insulin and glucose peak, and time to peak insulin and glucose. The pellet (P) elicited a lower (P = .01) glucose concentration at 2.5 hours than O. The pellet also elicited a lower (P = .03) insulin concentration at 5.5 hours than E and O. There were no differences (P > .05) in area under the curve (AUC) insulin, peak insulin, and time to peak insulin for the three treatments. Average insulin concentration was lower (P = .01) for P versus O. There were no differences (P > .05) in average insulin between P and E, nor between O and E. There were no differences (P > .05) in AUC and peak glucose concentration. Time to peak glucose was longer (P = .04) for P versus E. Average glucose concentration was lower (P = .02) for P versus O. Consumption time was longer (P = .03) for O versus P. There was a positive correlation between consumption time and time to peak insulin (r = 0.46, P = .029). Further research on feeding practices, feed forms, and consumption times that affect glycemic response is necessary.     

Pharmacokinetics of subcutaneously administered doramectin in alpacas

The objective of this research was to evaluate comparative pharmacokinetics of doramectin in alpacas, after subcutaneous administration of 0.2 mg/kg dose. Six healthy adult alpacas, mean age of 5 years ± 1, (three female and three gelded males) of mean bodyweight of 62 kg ± 16 kg with an average body condition scored 2.8 ± 1 out of five, were used in this study. Serial blood samples were collected from the jugular vein before the administration until day 21 afterwards to establish the pharmacokinetics of doramectin after its subcutaneous administration at 0.2 mg/kg dose. The blood samples were analysed using high-performance liquid chromatography (HPLC), fluorescence detection method with precolumn derivatisation, validated for alpacas. The pharmacokinetic parameters were calculated using a noncompartmental model, and results showed Cmax (6.05 ± 5.34 ng/ml), Tmax (3.83 ± 2.48 days), AUC (62.12 ± 18.86 ng/ml × d), terminal half-life (6.2 ± 4.9 days) and MRT (11.56 ± 4.43 days). The results of this study showed that the Cmax and AUC were much lower than in cattle and sheep at the same dosage. Tmax remained similar to cattle and sheep. This study presents valuable information about pharmacokinetics of doramectin in alpacas, which can be utilised in its future efficacy studies.