Digestibility of nutrients and amino acids of different protein sources in practical diets by largemouth bass Micropterus salmoides (Lacepéde, 1802)

This study evaluated the apparent digestibility coefficients (ADCs) of dry matter, protein, lipid, energy, calcium, phosphorus, and essential and non‐essential amino acid availability of animal and plant protein sources in practical diets for the carnivorous fish, largemouth bass Micropterus salmoides (8.0±0.5 g; 10.0±0.3 cm). Fish were conditioned to accept artificial feed and those stocked in plastic cages were fed pelleted test diets. Diets contained 30% of the ingredient tested mixed with 70% of a reference ration (RD) containing 40 g 100 g^?1 of crude protein, 19.85 kJ g^?1 crude energy, and 0.5% of chromic oxide. Cages were then transferred to cylindrical, conical‐bottomed aquaria (200 L) where the faeces were collected by sedimentation in a refrigerated container. All the tested ingredients had high ADCs for protein and lipid; ADCs of amino acids of varying protein sources showed significant differences (P<0.01). Plant protein sources did not significantly influence the ADCs of diets. The results allow the inference that the availability of amino acids in plant and animal protein sources varies considerably.     

Growth, nutrient utilization and parameters of mineral metabolism in Nile tilapia Oreochromis niloticus (Linnaeus, 1758) fed plant-based diets with graded levels of microbial phytase

Diets with graded levels of the experimental microbial phytase SP1002 (0, 500, 1000, 2000 and 4000 FTU/kg) were fed to juvenile Nile tilapia (average BW = 68.8 g) for 60 days (n = 4). A digestibility trial ran parallel to the growth trial using 0.3 g TiO2/100 g as an indigestible marker. The efficiency of phytase supplementation was evaluated by parameters of growth response, crude protein and mineral utilization (using body composition data), apparent nutrient digestibility, mineral content in scale and vertebra and inorganic phosphorus in blood plasma. Data were submitted to ANOVA and Tukey-test using SAS-program. Significant improvements (p < 0.01) were found for growth, FCR and SGR, mainly for diets with 1000 and 2000 FTU/kg phytase supplementation. Protein utilization was significantly increased and maximized between 1000 and 2000 FTU/kg. Phosphorus utilization increased significantly up to 4000 FTU/kg. Digestibility of protein and phosphorus was also significantly improved. Phosphorus concentration in the blood, vertebra and scale increased significantly after phytase addition. Similarly, calcium and magnesium concentration in vertebra and scale were increased. Generally, phytase supplementation between 1000 and 2000 FTU/kg resulted in growth rates and mineralization parameters similar to a control diet with inorganic phosphorus.     

Use of White Fat as a Replacement for Squid Liver Oil in Practical Diets for Surubim Pseudoplatystoma coruscans

The effect of dietary lipid on culture performance, fatty acid composition of carcass, and the liver polar lipid of surubim fingerlings Pseudoplatystoma coruscans was investigated. Five isonitrogenous (46.5% crude protein) and isolipidic (19% crude lipid) diets were formulated with squid liver oil (SLO) and white fat (pig lard-PL) as lipid sources. Diet 1 was supplemented with 12% SLO, diet 2 with 8% SLO and 4% PL, diet 3 with 6% SLO and 6% PL, diet 4 with 4% SLO and 8% PL, and diet 5 with 12% PL. Fish were fed to apparent satiation over a 64-d feeding trial. No statistically significant difference ( P >0.05) was observed in growth performance of fish. In contrast, fatty acid profile of fish carcass and liver polar lipid fraction was affected ( P 0.05) by dietary fatty acid composition. Palmitic (16:O) and the oleic (18:1n-9) acids were the major saturated and monoene fatty acids respectively found in fish carcass, independent of the lipid source in the diets. The total amount of saturated and monoene fatty acids was significantly higher ( P 0.05) in the carcass of the fish fed diets 4 and 5, than in the other fish. The concentration ( P 0.05) of eicosapentaenoic and docosahexaenoic acids and the n-3/n-6 ratio in fish carcass and in polar lipid fraction of liver increased in direct proportion to the level of squid liver oil in diet. Results of this experiment clearly demonstrated that both squid liver oil and pig lard have a positive nutritive value for surubim and that it is possible to increase the n-3 to n-6 ratio in favor of n-3, without loss in the growth performance, feeding fish with a diet containing a lipid source rich in this fatty acid.     

Active crop sensor to detect variability of nitrogen supply and biomass on sugarcane fields

Nitrogen management has been intensively studied on several crops and recently associated with variable rate on-the-go application based on crop sensors. Such studies are scarce for sugarcane and as a biofuel crop the energy input matters, seeking high positive energy balance production and low carbon emission on the whole production system. This article presents the procedure and shows the first results obtained using a nitrogen and biomass sensor (N-Sensor^™ ALS, Yara International ASA) to indicate the nitrogen application demands of commercial sugarcane fields. Eight commercial fields from one sugar mill in the state of S?o Paulo, Brazil, varying from 15 to 25 ha in size, were monitored. Conditions varied from sandy to heavy soils and the previous harvesting occurred in May and October 2009, including first, second, and third ratoon stages. Each field was scanned with the sensor three times during the season (at 0.2, 0.4, and 0.6 m stem height), followed by tissue sampling for biomass and nitrogen uptake at ten spots inside the area, guided by the different values shown by the sensor. The results showed a high correlation between sensor values and sugarcane biomass and nitrogen uptake, thereby supporting the potential use of this technology to develop algorithms to manage variable rate application of nitrogen for sugarcane.     

Wheat blast caused by Magnaporthe oryzae pathovar Triticum is efficiently controlled by the plant defence inducer isotianil

Journal of Plant Diseases and Protection - Wheat blast caused by Magnaporthe oryzae pv. Triticum is an upcoming threat to wheat cultivation worldwide. The disease crossing over to wheat first...     

Control of plant diseases by natural products: Allicin from garlic as a case study

This review aims to increase awareness of the potential for developing plant protection strategies based on natural products. Selected examples of commercial successes are given and recent data from our own laboratory using allicin from garlic are presented. The volatile antimicrobial substance allicin (diallylthiosulphinate) is produced in garlic when the tissues are damaged and the substrate alliin (S-allyl-l-cysteine sulphoxide) mixes with the enzyme alliin-lyase (E.C.4.4.1.4). Allicin is readily membrane-permeable and undergoes thiol-disulphide exchange reactions with free thiol groups in proteins. It is thought that these properties are the basis of its antimicrobial action. We tested the effectiveness of garlic juice against a range of plant pathogenic bacteria, fungi and oomycetes in vitro. Allicin effectively controlled seed-borne Alternaria spp. in carrot, Phytophthora leaf blight of tomato and tuber blight of potato as well as Magnaporthe on rice and downy mildew of Arabidopsis. In Arabidopsis the reduction in disease was apparently due to a direct action against the pathogen since no accumulation of salicylic acid (a marker for systemic acquired resistance, SAR) was observed after treatment with garlic extract. We see a potential for developing preparations from garlic for use in organic farming, e.g. for reducing the pathogen inoculum potential in planting material such as seeds and tubers. We have tested various encapsulation formulations in comparison to direct treatment. Note added in proof: The complete chemical synthesis of azadirachtin has now been achieved. Nature (2007) 448: 630–631     

Growth and body composition of juvenile largemouth bass Micropterus salmoides in response to dietary protein and energy levels

To determine the dietary protein and energy requirements of juvenile largemouth bass, 1350 feed‐conditioned fishes (average weight 14.46 ± 0.81 g) were stocked in ninety 60‐L cages, set up in 1000‐L tanks at three cages/tank, and fed for 64 days with a dry, extruded feed containing six levels of crude protein (CP) (340–540 g kg^–1, with increases of 40 g kg^–1) and five levels of energy (150.7–171.7 kJ g^–1 feed, with increases of 5.2 kJ). The trial was set up in a 6 × 5 factorial, completely randomized design (n=3). Weight gain (WG), daily feed consumption (DFC), feed conversion rate (FCR), protein efficiency ratio (PER), specific growth rate (SGR), protein and energy retention were recorded and evaluated. There was no interaction between feed energy and protein levels with all parameters evaluated. Data analysis by the broken line method showed that the minimum dietary requirement for maximum daily weight gain of 8.0 g kg^–1 is 435.9 g kg^–1 CP; the best feed conversion ratio (1.04:1) was attained with a minimum of 448.2 g kg^–1 CP; a minimum of 162.1 kJ g^–1; DFC was reduced as dietary protein and energy levels increased; dietary levels of 460–500 g kg^–1 CP led to best PER (1.665); best values for protein (33.14 g 100 g^–1) and energy (26.87 g 100 g^–1) retention were observed for fish feeding on the 420 g kg^–1 CP ration. Limits of energy to protein ratio to feed largemouth bass are 25.01 and 26.89 mg protein kJ^–1, enabling feed conversion ratios of 0.96–1.10.     

Effects of garlic (<Emphasis Type="Italic">Allium sativum</Emphasis>) juice containing allicin on <Emphasis Type="Italic">Phytophthora infestans</Emphasis> and downy mildew of cucumber caused by <Emphasis Type="Italic">Pseudoperonospora cubensis</Emphasis>

The volatile antimicrobial substance allicin (diallylthiosulphinate) is produced in garlic when the tissues are damaged and the substrate allicin (S-allyl-l-cysteine sulphoxide) mixes with the enzyme alliin-lyase (E.C.4.4.1.4). Allicin undergoes thiol-disulphide exchange reactions with free thiol groups in proteins and it is thought that this is the basis of its antimicrobial action. At 50 μg ml^-1, allicin in garlic juice inhibited the germination of sporangia and cysts and subsequent germ tube growth by Phytophthora infestans both in vitro and in vivo on the leaf surface. Disease severity in P. infestans-infected tomato seedlings was also reduced by spraying leaves with garlic juice containing allicin over the range tested (55–110 μg ml⁻¹) with an effectiveness ranging from approximately 45–100%. Similarly, in growth room experiments at concentrations from 50–1,000 μg ml⁻¹, allicin in garlic juice reduced the severity of cucumber downy mildew caused by Pseudoperonospora cubensis by approximately 50–100%. These results suggest a potential for developing preparations from garlic for use in specialised aspects of organic farming, e.g. for reducing pathogen inoculum potential and perhaps for use under glass in horticulture.