Efficacy of ivermectin (22,23-dihydroavermectin B1) against gastrointestinal parasites in ponies

The controlled test method was used to evaluate the antiparasitic efficacy of IM inoculated 22,23-dihydroavermectin B1 (ivermectin) against gastrointestinal parasites of horses (ponies). Parasite infections were naturally acquired in southern Louisiana. Dose levels of the drug tested were 0.2 mg/kg, 0.3 mg/kg, and 0.5 mg/kg. Ivermectin at all dose levels tested had an efficacy greater than 97% (P less than 0.05) against Gasterophilus intestinalis larvae, Trichostrongylus axei, Oxyuris equi larvae, Strongylus vulgaris, S edentatus, 15 species of small strongyles, and small strongyle larvae. Ponies were less uniformly infected with Habronema sp larvae, G nasalis larvae, Parascaris equorum, O equi adults, Anoplocephala perfoliata, S equinus, and 11 small strongyle species, and statistical analysis was not possible to do. However, observations indicate that the drug was also highly effective against these species. There were no gross or clinical reactions observed in treated animals. Dissections of the injection sites revealed spindle-shaped lesions, 3 to 5 cm long, in a few ponies in all treatment groups, including those given the placebo injection.     

Carbon and nitrogen mineralization of non-composted and composted municipal solid waste in sandy soils

A sterilized, but undecomposed, organic by-product of municipal waste processing was incubated in sandy soils to compare C and N mineralization with mature municipal waste compost. Waste products were added to two soils at rates of 17.9, 35.8, 71.6, and dry weight and incubated at for 90 d. Every 30 d, nitrate and ammonium concentrations were analyzed and C mineralization was measured as total CO₂-C evolved and added total organic C. Carbon mineralization of the undecomposed waste decreased over time, was directly related to application rate and soil nutrient status, and was significantly higher than C mineralization of the compost, in which C evolution was relatively unaffected across time, soils, and application rates. Carbon mineralization, measured as percentage C added by the wastes, also indicated no differences between composted waste treatments. However, mineralization as a percentage of C added in the undecomposed waste treatments was inversely related to application rate in the more productive soil, and no rate differences were observed in the highly degraded soil. Total inorganic N concentrations were much higher in the compost- and un-amended soils than in undecomposed waste treatments. Significant N immobilization occurred in all undecomposed waste treatments. Because C mineralization of the undecomposed waste was dependant on soil nutrient status and led to significant immobilization of N, this material appears to be best suited for highly degraded soils low in organic matter where restoration of vegetation adapted to nutrient poor soils is desired.     

Efficacy of ivermectin in injectable and oral paste formulations against eight-week-old Strongylus vulgaris larvae in ponies

A controlled test method was used to evaluate the efficacy of injectable micelle and oral paste formulations of ivermectin (22,23-dihydroavermectin B1) against 8-week-old Strongylus vulgaris larvae in experimentally infected pony foals. The dosage level of the drug in both formulations tested was 0.2 mg/kg. Ponies were euthanatized and necropsied 5 weeks after treatment. Based on the recovery of live vs dead S vulgaris from mesenteric arteries, both formulations were greater than 99% effective. Increased weight gains and marked reductions in the severity of arterial lesions were observed in treated ponies.     

Effect of microbial‐based inoculants on nutrient concentrations and early root morphology of corn (Zea mays)

Microbial‐based inoculants have been reported to stimulate plant growth and nutrient uptake. However, their effect may vary depending on the growth stage when evaluated or fertilizer applied. Thus, the objective of this study was to test the hypothesis that microbial‐based inoculants known to promote root growth and nutrient uptake will promote plant growth, enhance early root development, and increase nutrient concentrations of corn (Zea mays L.). Plants were evaluated at four different growth stages and in the presence of three different nitrogen (N) fertilizers. The microbial‐based treatments evaluated were: SoilBuilder™ (SB), a filtered metabolite extract of SoilBuilder™ (SBF), a mixture of four strains of plant growth‐promoting Bacillus spp (BM), and a water‐inoculated control. The experiment also included four fertilizer treatments: urea (U), urea‐ammonium nitrate (UAN), calcium‐ammonium nitrate (CAN), and an unfertilized control. Corn plants were evaluated at growth stages V2, V4, V6, and VT. Plant growth parameters for biomass, height, and SPAD readings were enhanced by the three microbial‐based treatments. A greater effect of microbial‐based treatments was observed when plants were evaluated at V6 and VT stages. Parameters of early root development such as total root length (TRL), root surface area (RSA), and length of fine roots were enhanced when microbial‐based treatments were applied. Concentrations of N, P, and K were also increased by microbial‐based treatments compared to the non‐inoculated control. Increases in plant N concentration due to microbial‐based treatments were on average 72% for CAN, 61% for UAN, 72% for urea, and 54% for the unfertilized control. Phosphorus concentration was increased most (138%) when BM was applied with CAN. In the same way, when CAN was present, K concentration was increased by 95% with BM and 65% when SB and SBF were applied. Overall, the results demonstrate that microbial‐based inoculants evaluated in this study can positively impact corn growth and nutrient concentration, especially during the late vegetative stages. Furthermore, the results indicate that the enhancement of nutrient concentrations (N, P, and K) in this case was related to the capacity of microbial‐based treatments to impact root morphology at early stages of corn growth.     

Growth and magnesium uptake of tall fescue clones with varying root diameters

Abstract

A cool season perennial grass with a root system capable of penetrating hardpans and which can accumulate adequate Mg to prevent deficiencies in forage is needed in the Coastal Plain region. A greenhouse experiment was conducted to determine the effects of magnesium (Mg) concentration in nutrient solution and root diameter on Mg uptake and growth of tall fescue (Festuca arundinacea Schreb.). Propagules of two fescue clones with large root diameter (LDR >1 mm), two clones with small root diameter (SDR <0.8 mm), and a single clone from ‘Kentucky 31’ (Ky‐31) were transferred into 12‐liter tanks containing Mg concentrations of 3, 21, 42, 125, 250, and 500 μM as MgSO₄ and grown for 39 or 70 days. Leaf Mg concentration was increased linearly with Mg solution concentration in LDR clones for a 39‐day growth period (Harvest 1), but increased according to a cubic equation in the SDR clones and the Ky‐31. Predicted leaf Mg concentration as a function of solution Mg followed a cubic equation for a 70‐day growth period (Harvest 2) in all clones. Predicted root Mg concentration was linearly related to Mg solution concentration for the LDR clones and the Ky‐31, but followed a cubic equation for the SDR clones for the first growth period. For the second growth period, the root Mg concentration of the SDR clones and the Ky‐31 was increased linearly, while the LDR clones followed a quadratic equation. Magnesium uptake followed a cubic equation with Mg solution concentration for both growth periods on all tall fescue clones. This nonlinear variation of Mg uptake and plant Mg concentration with respect to solution Mg concentration strongly suggests that a dual uptake mechanism might have been present in tall fescue clones. Root volume was greater in the SDR than LDR clones or Ky‐31 for both growth periods. The Ky‐31 had the greatest leaf and root dry weight for both growth periods, while the LDR clones had the lowest.