Chitin synthesis inhibitor effect on Aedes aegypti populations susceptible and resistant to organophosphate temephos

BACKGROUND: In Brazil, dengue vector control is hampered by the resistance of Aedes aegypti L. populations to organophosphates (OPs). Insect growth regulators (IGRs) are a promising alternative, as their mechanisms of action are different from those of conventional insecticides. The authors analysed the effect of the IGR triflumuron, a chitin synthesis inhibitor, on the Ae. aegypti insecticide-susceptible strain Rockefeller, as well as on field populations both susceptible (TemS) and resistant (TemR) to the OP temephos. RESULTS: Triflumuron arrested development and inhibited adult emergence of the Rockefeller strain in a dose-dependent way (EI(50) and EI(90) of 0.8 and 1.8 microg L(-1) respectively). A direct relationship between triflumuron concentration and the precocity of its effects was evident. TemS and TemR temephos resistance ratios (RR(90)) were 4.5 and 13.8, triflumuron RR(90) being 1.0 and 1.3 respectively. CONCLUSION: The IGR triflumuron exhibited a dose-dependent effect against the reference Ae. aegypti Rockefeller strain. It was also effective against two field populations, regardless of their OP resistance status. The present results are discussed in the context of utilization of chitin synthesis inhibitors as potential alternatives in the control of Ae. aegypti in Brazil.     

P and Ca requirements for Japanese quail

Four experiments were conducted to estimate the phosphorus and calcium requirements for weight maintenance and weight gain in Japanese quails during their growth phase from 16 to 36 days. Japanese quails aged 16 days were used for estimating the phosphorous and calcium requirements for weight maintenance or weight gain, with these quails composing each reference slaughter group and the others distributed in a completely randomized design, housed in cages of galvanized wire (33 × 33 × 16 cm) that were stored in acclimatized chambers with specific environmental temperatures. The light programme used during the 20‐day experimental period was 24 h of artificial light. Analysis of the data showed that the prediction equations for estimating the phosphorus and calcium requirements for weight maintenance and weight gain of Japanese quails between 16 and 36 days of age were P (g/quail/day) = P^0.75*(9.3695 + 7.7397*T) + 9.70*WG, in which P is the phosphorus requirement, and Ca (g/quail/day) = P^0.75*(363.99 – 8.0262*T) + 28.15*WG, in which Ca is the calcium requirement, P is BW (kg), T is temperature (°C) and WG (g/quail/day).     

Estimate of choline nutritional requirements for chicks from 1 to 21 days of age

Choline is an essential nutrient in poultry diets because it performs various important metabolic functions. The objective of this study was to re‐evaluate the choline requirements of male broiler chickens from 1 to 21 days of age at two levels of methionine. Two assays using 2,160 Cobb^® chickens (1,080 in each assay) were conducted. The study design was completely randomized and consisted of six treatments and six replicates, with 30 animals per experimental unit. The semipurified basal diet was formulated with corn, soya bean meal, soya protein concentrate, starch and sugar, providing 390 mg/kg choline and 0.593% digestible methionine (requirement level) in Assay 1 and a reduction of about one‐quarter in the requirement level of digestible methionine (0.440%) in Assay 2. Choline chloride (62.5%) was added by a supplementation technique to both basal diets to compose crescent levels of choline supplementation (715, 1,040, 1,365, 1,690 and 2,015 mg/kg). The weight gain responses were fitted using quadratic polynomial (QP) and broken‐line (BL) models. The ideal intake of choline (mg/bird.day) was estimated from the first intercept of the QP with the BL plateau (BL + QP). The results showed that the diet with the 25% reduction in digestible methionine limited the maximum weight gain by approximately 10%. The choline requirements of broilers from 1 to 7, 1 to 14 and 1 to 21 days of age were 27,013, 44,458 and 62,535 mg/bird.day, respectively, for the requirement level of digestible methionine and 26,796, 41,820 and 56,578 mg/bird.day for the broilers receiving the diet with the 25% reduction in digestible methionine.     

Role of new bacterial surfactins in the antifungal interaction between Bacillus amyloliquefaciens and Fusarium oxysporum

The aim of this work was to investigate the major mechanisms involved in antagonism of BO7, a novel strain of Bacillus amyloliquefaciens isolated from orchard soil, against the vascular wilt fungus Fusarium oxysporum f. sp. lycopersici (Fol). BO7 markedly reduced the incidence of Fol vascular wilt on tomato plants and displayed strong in vitro inhibitory activity against Fol. Scanning electron microscopy demonstrated the ability of BO7 cells to adhere to fungal hyphae and to efficiently colonize tomato roots. The low molecular weight fraction of BO7 culture filtrate displayed high antifungal activity against Fol, resulting in growth inhibition and dramatic alterations of hyphal morphology. Three structurally related surfactin lipopeptides, identified as the major components of the bioactive fraction, were assayed for their inhibitory activity against Fol. One of these compounds exerted a strong and uncommon antifungal activity for lipopeptides of the surfactin family, accounting for most of the inhibitory activity of the BO7 culture filtrate. Among a collection of Fol knockout isolates tested, mutants altered in cell wall structure showed increased sensitivity to the bacterial compounds. These results suggest that the fungal cell wall might have a key role in the sensitivity of Fol towards bacterial surfactins from B. amyloliquefaciens.     

Brucella-associated cervical bursitis in cattle

Bovine brucellosis poses a risk to human health and causes serious economic losses for the animal industry. This report describes the use of different diagnostic methods for the diagnosis of brucellosis in cattle affected by cervical bursitis from a slaughterhouse located in São Luís, Maranhão, Brazil. Serum samples from a total of 47 cattle with bursitis were collected and submitted to the Rose Bengal Test (RBT), and RBT-positive samples were further confirmed by the 2-mercaptoethanol (2-ME) assay. RBT indicated 85.1% (40/47) of positive samples, from which 78.7% (37/47) were confirmed by 2-ME. Immunohistochemistry detected Brucella spp. in 34.0% (16/47) of tissues with bursitis. PCR and/or bacterial isolation demonstrated that 63.8% (30/47) of samples were positive and morphologically compatible with Brucella sp. All colonies suggestive of Brucella sp. were confirmed by PCR. Isolates were further characterized by PCR Multiplex AMOS-ENHANCED, which indicated that the isolates corresponded to biovar 1, 2, 4 (43.33%). This study evidences an association between cervical bursitis and Brucella spp. infection in cattle, and that different biovars of Brucella circulate in bovine herds in Maranhão.

     

Interactions Among Different Devices and Electrical Stimulus on the Electroejaculation of Captive Agoutis (Dasyprocta leporina)

The interactions among different electroejaculation devices associated with serial or continuous stimuli were investigated to improve the efficiency of the electroejaculation for semen collection in agoutis. Ten sexually matured male Dasyprocta leporina were restrained by the intramuscular administration of xylazine–ketamine association. Each individual was randomly subjected to four electroejaculation protocols, by combining two devices (one presenting longitudinal electrodes emitting square waves and other presenting ring electrodes emitting sine waves) and two electrical stimuli protocols (serial or continuous). A total of 40 attempts for electroejaculation were conducted in agoutis, being 10 per treatment. The most efficient treatment in providing ejaculates containing sperm (p < 0.05) was that using and electroejaculator connected to a probe with ring electrodes and associated with serial stimuli (4/7; 57%). In spite of semen parameters obtained by sine waves were adequate for using the samples for assisted reproduction, higher values for sperm motility and functional membrane integrity were obtained in the use of the square wave, independently of the electric stimulation protocol used (p < 0.05). In conclusion, we verified that the use of a device presenting a probe with ring electrodes and emitting sine waves, associated with a serial stimuli protocol, improves the efficiency for semen obtaining by electroejaculation in adults D. leporina.     

Efficiency of microbial phytase supplementation in diets formulated with different calcium:phosphorus ratios,supplied to broilers from 22 to 33 days old

An experiment was conducted with broilers from 22 to 33 days of age to evaluate the efficiency of six microbial phytases supplemented in diets (1500 FTU/kg) that were formulated with three different calcium:available phosphorus (Ca:P_avail) ratios (4.5:1.0, 6.0:1.0 and 7.5:1.0). A positive control diet without phytase was formulated with a Ca:P_avail ratio of 7.5:3.4 to meet the nutritional requirements of the broilers. The P and ash contents of the tibia, magnesium in the plasma, performance, balance and retention of phytate phosphorus (P_phyt), intake of total P and nitrogen (N), nitrogen‐corrected apparent metabolizable energy and apparent digestibility of dry matter of the diets were not influenced (p > 0.05) by the type of phytase or the dietary Ca:P_avail ratio. However, there was an interaction (p < 0.05) between the phytase type and the Ca:P_avail ratio for the retention coefficients of total P, Ca and N. Phytase B resulted in the highest Ca deposition in the tibia (p < 0.01). Phytases D, E and F reduced the Ca concentrations in the tibia (p < 0.01) and plasma (p < 0.05). Phytase D increased the P level in the plasma and decreased the total P excretion (p < 0.01). Phytases E and F increased Ca excretion, while phytase A reduced it (p < 0.01). Regardless of the phytase type, increasing the dietary Ca:P_avail ratio reduced (p < 0.05) the plasma P concentration and the excretion of total P and N and, conversely, increased (p < 0.05) the plasma concentration, intake and excretion of Ca. For the rearing period evaluated, it is possible to reduce the P_avail of the diet to 1.0 g/kg when Ca is maintained at 7.5 g/kg, and the diet is supplemented with 1500 FTU of phytase A, C, D or E/kg. This diet allows the maintenance of performance and adequate bone mineralization, and it improves the Ca, total P and P_phyt utilization in addition to reducing the excretion of N and P into the environment.     

Acute Toxicity of Ammonia and Nitrite to Painted River Prawn,Macrobrachium carcinus,Larvae

This study evaluated the toxicity of ammonia and nitrite to different larval stages of Macrobrachium carcinus. Three replicated groups of larvae in the zoea stages II, V, and VIII (hence named Z₂, Z_5, and Z₈, respectively) were exposed separately to five ammonia (5, 10, 20, 40, and 80 mg total ammonia nitrogen [TAN]/L) and six nitrite concentrations (5, 10, 20, 40, 80, and 160 mg NO₂‐N/L), plus a control treatment with no addition of ammonia and nitrite, at a salinity of 20 g/L. The ammonia LC₅₀ values at 96 h for Z₂, Z₅, and Z₈ were 8.34, 13.84, and 15.03 mg TAN/L (0.50, 0.71, and 0.92 mg NH₃‐N/L), respectively, and the nitrite LC₅₀ values at 96 h for Z₂, Z₅, and Z₈ were 3.28, 9.73, and 34.00 mg NO₂‐N/L, respectively. The estimated LC₅₀ values for NO₂‐N were lower than those for TAN in most of the stages evaluated. This observation suggests that M. carcinus larvae are more tolerant to ammonia, except at Z₈, in which larvae had a higher tolerance to nitrite. Based on the lethal concentrations at 96 h, it may be concluded that the tolerance of M. carcinus to ammonia and nitrite increases with larval development. Safe levels were estimated to be 0.834 mg TAN/L (0.05 mg NH₃‐N/L) and 0.328 mg NO₂‐N/L; therefore, efforts should be made to maintain lower concentrations of these compounds throughout the larval rearing of M. carcinus.