Assessment of Dothistroma Needle Blight of Pinus radiata Using Airborne Hyperspectral Imagery

ABSTRACT Dothistroma needle blight is a serious foliar disease in Australian Pinus radiata plantations causing defoliation, decreased productivity and, in extreme cases, tree death. Conventional methods of monitoring forest health such as aerial survey and ground assessments are labor intensive, time consuming, and subjective. Remote sensing provides a synoptic view of the canopy and can indicate areas affected by damaging agents such as pests and pathogens. Hyperspectral airborne remote sensing imagery (CASI-2) was acquired over pine stands in southern New South Wales, Australia which had been ground assessed and ranked on an individual tree basis, according to the extent of Dothistroma needle blight. A series of spectral indices were tested using two different approaches for extracting crown-scale reflectance measurements and relating these to ground-based estimates of severity. Dothistroma needle blight is most severe in the lower crown and statistically significant relationships were found between crown reflectance values and ground estimates using a 'halo' approach (which ignored each tree crown's brightest central pixels). Independent accuracy assessment of the method indicated that the technique could successfully detect three levels of Dothistroma needle blight infection with an accuracy of over 70%.     

Effect of dietary melengestrol acetate on the incidence of acute interstitial pneumonia in feedlot heifers

Over a 3-y period, 906,000 cattle were monitored in 23 feedlots in southern Alberta for symptoms of acute interstitial pneumonia (AIP). Plasma, urine, and lung tissue were collected at slaughter from 299 animals clinically diagnosed with AIP and from 156 healthy penmates and analyzed for 3-methylindole (3MI) derivatives and reduced glutathione concentration. From each animal, the left lung was subsampled for histologic examination. Concentrations of glutathione in lung tissue were reduced (P < 0.001) in animals showing clinical symptoms of AIP as compared with their asymptomatic penmates. Animals histologically confirmed as having AIP had higher levels of 3MI protein adducts in blood and lung tissue (P < 0.05) than did emergency-slaughtered animals without AIP. Within feedlots, where pens of heifers were fed either a standard dosage of melengestrol acetate (MGA) or none, the rate of death attributable to AIP was similar between treatment groups, but emergency slaughter after clinical diagnosis of AIP was done 3.2 times more often (P < 0.001) in the MGA-fed heifers than in the group not fed MGA. Use of MGA did not influence glutathione concentration. As growth performance of heifers given steroidal implants may not be improved by feeding MGA, the most cost-effective method of reducing the incidence of AIP-related emergency slaughter in feedlot heifers may be to eliminate MGA from the diet.     

Can heat‐killed Gordonia bronchialis enhance growth and immunity in rainbow trout (Oncorhynchus mykiss)?

In this study, the efficacy of heat‐killed Gordonia bronchialis on growth performance, immune system and gastrointestinal structure in rainbow trout (Oncorhynchus mykiss) was evaluated. Fish (mean weight 30 g) were fed basal diet (control), or treatment diets containing 2.48 × 10⁸ (low dose) or 1.24 × 10⁹ (high dose) cells kg^?1 feed of heat‐killed G. bronchialis on a pulse basis (5 days on treatment diet; 10 days on basal diet) for 95 days. On days 95 and 105, some of the fish were sampled for analysis of mentioned parameters. On days 110 and 120, the remaining fish were injected intraperitoneally with a 20 mL L^?1 suspension of chicken red blood cells. Results showed that growth performance was significantly enhanced in both treatment groups compared with the control group. Serum complement and lysozyme activities and hemagglutination antibody titre were higher in both treatment groups compared with the control group. The length of the intestinal and pyloric caeca folds was increased in the high‐dose group. Meanwhile, the number of goblet cells was increased in both treatment groups. This study suggests that heat‐killed G. bronchialis has the potential to enhance growth, immunological parameters and the gastrointestinal structure in rainbow trout.     

Chitosan-alginate microcapsules for oral delivery of egg yolk immunoglobulin (IgY)

Chitosan-alginate microcapsules were evaluated as a method of oral delivery of IgY antibodies. Physical characteristics, encapsulation efficiency (EE%), the loading capacity for IgY (IgY loading percentage, %, w/w of microcapsules), gastro-resistance, and release characteristics of these microcapsules in vitro under varying pH were investigated. Optimum physical factors were established for preparation of homogeneous, spherical, and smooth microcapsules. IgY loading% was not significantly altered by pH of the encapsulation medium. Encapsulation efficiency was highest (73.93%) at a pH of 3.5, above which EE% decreased significantly (p < 0.05). IgY was released from microcapsules upon exposure to simulated intestinal fluid (SIF, pH 6.8), and decreasing pH increased significantly IgY release (p < 0.05). The stability of IgY in simulated gastric fluid (SGF, pH 1.2) was greatly improved by encapsulation in chitosan-alginate microcapsules, and the residual activity was not affected by pH of the encapsulation medium. Moreover, microencapsulated IgY was significantly resistant to pepsin hydrolysis. This approach may enable intact IgY to reach target microorganisms within the lower digestive tract.     

Effects of wheat or corn distillers dried grains with solubles on feedlot performance, fecal shedding, and persistence of Escherichia coli O157:H7

Distillers dried grains with solubles (DDGS) are a coproduct of the ethanol industry and are often used as a replacement for grain in livestock production. Feeding corn DDGS to cattle has been linked to increased fecal shedding of Escherichia coli O157:H7, although in Canada, DDGS are often produced from wheat. This study assessed the effects of including 22.5% wheat or corn DDGS (DM basis) into barley-based diets on performance, carcass characteristics, animal health, and fecal E. coli O157:H7 shedding of commercial feedlot cattle. Cattle (n = 6,817) were randomly allocated to 10 pens per treatment group: WDDGS (diets including 22.5% wheat DDGS), CDDGS (diets including 22.5% corn DDGS), or CTRL (barley substituted for DDGS). Freshly voided fecal pats (n = 588) were collected and pooled monthly for fecal pH measurement and screened for naturally occurring E. coli O157:H7 by immunomagnetic separation (IMS) and direct plating (DP). Hide swabs (n = 367) were collected from randomly selected cattle from each pen before slaughter. Pen-floor fecal samples (n = 18) were collected from treatment groups at entry to the feedlot (<14 d on the finishing diet) and after adapting to the finishing diet for ≥14 d, inoculated (10(9) cfu of a 5 strain naldixic acid-resistant E. coli O157:H7 mixture), incubated (20°C) and evaluated weekly (IMS and DP) to assess fecal E. coli O157:H7 persistence. The WDDGS group had 3.0% poorer ADG (P = 0.007), 5.3% poorer G:F (P < 0.001), and a decreased proportion of Canada Quality Grade AAA carcasses (P = 0.022) compared with CTRL cattle. The CDDGS group had a similar ADG (P = 0.06), a decreased proportion of Canada Yield Grade (YG) 1 (P < 0.001), and greater proportions of Canada YG 2 (P = 0.003) and YG 3 (P < 0.001) carcasses compared with the CTRL group. There were no differences among groups in any of the animal health parameters assessed. Inclusion of DDGS in cattle finishing diets had no effect on fecal shedding (P = 0.650) or persistence (P = 0.953) of E. coli O157:H7. However, feces from cattle on starter diets <14 d had longer persistence of E. coli O157:H7 (week) than cattle on finishing diets ≥14 d (P < 0.003). Inclusion of DDGS in feedlot diets depends on commodity pricing relative to that of barley and for WDDGS must also include the risk of feedlot performance and carcass grading disadvantages. Feeding cattle barley based-diets with 22.5% corn or wheat DDGS did not affect fecal shedding of E. coli O157:H7.     

Biomass and compositional changes in the periphytic community of an artificial stream in response to lowered pH

Two artificial streams simulating low-order, softwater streams of the Upper Peninsula of Michigan were employed to examine the effects of lowered pH on periphytic algae. The control stream contained water with a circumneutral pH whereas the pH of the water in the acidified stream was decreased to pH 4 with H₂SO₄. Chlorophyll a concentrations and cell densities in the periphytic algal communities were used to measure differences in biomass accumulations between the 2 streams over a 42-d, spring colonization period. Relative abundances of algal genera and Stander's similarity index (SIMI) were used to examine compositional differences between the control and acidified periphytic algal communities. These algal communities exhibited pronounced differences in their total biomasses and compositions indicating periphytic algal communities inhabiting low-order, softwater streams, such as those of the Upper Peninsula of Michigan, are vulnerable to acidic deposition. Decreased biomass accumulation under acidified conditions was believed to result primarily from decreased nutrient availability, and possibly secondarily from elevated aluminum and/or iron concentrations. The shift in community compositions was interpreted to be a more direct response to the lowered pH as acidophils and acid tolerant genera became favored, and thus more abundant.     

Open-Air Windrows for Winter Disposal of Frozen Cattle Mortalities: Effects of Ambient Temperature and Mortality Layering

After imposition of fees for disposal of cattle carcasses by the rendering industry, on-farm methods of mortality disposal are being investigated. Three open-air mortality compost windrows were constructed in January (JAN) and February (FEB) of 2004 in the cold, semiarid climate of southern Alberta, Canada. Windrow A included a base of barley straw a minimum of 46 cm thick, a layer of cattle mortalities (n=12) and a layer of stockpiled manure (minimum of 46 cm) covering the mortalities. Windrows B and C also had a bottom layer of barley straw, with windrow B containing 9 mortalities in 2 layers and windrow C containing 12 mortalities in 3 layers. Due to ambient temperatures > 0°C, carcasses (range 236 to 673 kg) were frozen at the time of windrow construction. Type ‘T’ thermocouples were embedded at the base of B and C windrows and temperatures within 120 cm of the surface were measured using a stainless steel dial probe. Windrows were turned 3 times at 3 mo intervals. Samples were collected from initial compost amendments and prior to each turning for determination of dry matter (DM), organic matter (OM), N, C and coliform bacteria. Ambient temperature was 13°C higher (P < 0.05) for the initial heating of FEB as compared to JAN compost, although the rate of compost temperature decline did not differ between replicates in this period. Days at maximum temperature did not differ between replicates and maximum temperatures in all windrows exceeded 55°C. After 3 heating periods and 9 mo, flesh was not evident and only fragments of bones (max wt. 740 g) were found. Results of this study demonstrate that ambient temperatures < 0°C and frozen mortalities provide no barrier to the use of open-air windrows for disposal of cattle mortalities. As well, stacking up to 3 layers of full-sized cattle mortalities in a windrow did not affect temperature profiles, residual flesh or bone, or analyses of the finished compost. Under the climatic conditions of southern Alberta, layering mortalities would reduce space requirements for large-animal mortality composting in a feedlot setting.