A review of visual soil evaluation techniques for soil structure

Soil structure forms a key component of soil quality, and its assessment by semi‐quantitative visual soil evaluation (VSE) techniques can help scientists, advisors and farmers make decisions regarding sampling and soil management. VSE techniques require inexpensive equipment and generate immediate results that correlate well with quantitative measurements of physical and biochemical properties, highlighting their potential utility. We reviewed published VSE techniques and found that soils of certain textures present problems and a lack of research into the influence of soil moisture content on VSE criteria. Generally, profile methods evaluate process interactions at specific locations within a field, exploring both intrinsic aspects and anthropogenic impacts. Spade methods focus on anthropogenic characteristics, providing rapid synopses of soil structure over wider areas. Despite a focus on structural form, some methods include criteria related to stability and resiliency. Further work is needed to improve existing methods regarding texture influences, on‐farm sampling procedures and more holistic assessments of soil structure.     

Nutrient availability and corn growth in a poultry litter biochar‐amended loam soil in a greenhouse experiment

Nutrient‐rich biochar produced from animal wastes, such as poultry litter, may increase plant growth and nutrient uptake although the role of direct and indirect mechanisms, such as stimulation of the activity of mycorrhizal fungi and plant infection, remains unclear. The effects of poultry litter biochar in combination with fertilizer on mycorrhizal infection, soil nutrient availability and corn (Zea mays L.) growth were investigated by growing corn in a loam soil in a greenhouse with biochar (0, 5 and 10 Mg/ha) and nitrogen (N) and phosphorus (P) fertilizer (0, half and full rates). Biochar did not affect microbial biomass C or N, mycorrhizal infection, or alkaline phosphomonoesterase activities, but acid phosphomonoesterase activities, water‐soluble P, Mehlich‐3 Mg, plant height, aboveground and root biomass, and root diameter were greater with 10 Mg/ha than with no biochar. Root length, volume, root tips and surface area were greatest in the fully fertilized soil receiving 10 Mg/ha biochar compared to all other treatments. The 10 Mg/ha biochar application may have improved plant access to soil nutrients by promoting plant growth and root structural features, rather than by enhancing mycorrhizal infection rates.     

Use of Porcine Meal in Plant‐based Practical Diets for Pacific White Shrimp,Litopenaeus vannamei

Two growth trials were conducted to evaluate and confirm the efficacy of a porcine meal (PM) with high protein content (>90%) as an alternative feed ingredient in commercial‐type feed formulation for Pacific white shrimp, Litopenaeus vannamei. Six experimental diets were formulated for the two growth trials. The first five diets contained increasing levels (0, 1, 2, 4, and 6%) of PM as a replacement for soybean meal in a plant‐based diet with low inclusion level (6%) of fish meal (FM). The last experimental diet was produced utilizing 4.2% PM to completely replace FM. In Trial 1, shrimp (1.5 g initial mean weight, 20 shrimp/tank, n = 4) were offered test diets for 6 wk in a semirecirculation system. At the end of Trial 1, shrimp fed with the diet containing 6% PM exhibited significantly enhanced weight gain (WG), feed conversion ratio (FCR), and survival compared to those fed with the diet devoid of FM. As survival was poor across all treatments and different densities could mask growth results the trial was repeated. In Trial 2, shrimp (0.85 g, 15 shrimp/tank, n = 4) were offered diets for 6 wk. Dietary supplementation of PM at 6% significantly improved WG, FCR, and apparent net protein retention in contrast with the treatment devoid of FM, confirming the same trends in Trial 1. No significant difference was detected in protein, lipid, moisture, and mineral profiles of whole‐body shrimp as well as survival across all the treatments. Results of this study indicate that PM is a good high protein source in shrimp feeds, which can be included up to 6% in the low FM‐based diet without compromising the growth of shrimp.     

Flow alteration and thermal pollution depress modelled growth rates of an iconic riverine fish,the Murray cod Maccullochella peelii

The serial discontinuity concept (SDC) proposes that hypolimnetic‐releasing impoundments cause major disruptions to the naturally occurring physical, chemical and biological gradients of rivers but that this impact diminishes with distance downstream. Such a gradient in discharge, flow velocity and temperature regime occurs below a large hypolimnetic‐releasing impoundment, the Hume Dam, on the River Murray in south‐eastern Australia. To examine the effects of this disturbance gradient on a warm‐water large‐bodied freshwater fish, the Murray cod (Maccullochella peelii), a bioenergetics model was developed and calibrated to explore energy expended under differing water velocities and temperature regimes. Model simulations predicted negative growth of juveniles directly downstream of the impoundment, due largely to the energetic costs associated with active and, to a lesser extent, standard metabolism outweighing the achievable energetic gains through food consumption. As flow velocity and temperature regimes became more favourable downstream, so did the simulated growth of the species. It was not until +239 km downstream of the impoundment that the model predicted that flow velocity and temperature regimes were suitable for greater weight gains. The modelled growth responses of juvenile Murray cod are consistent with the predictions of the SDC, emphasising that changes in the bioenergetics of individuals are likely to be reflected in reduced growth rates under the changed flow velocity and temperature regimes imposed by disturbance gradients. This research represents a valuable step in the biological understanding of Murray cod within variable riverine environments and emphasises the urgency required to mitigate impacts associated with hypolimnetic impoundments.     

Evaluation of Heterotrophic Algae Meal as a Diet Ingredient for Channel Catfish,Ictalurus punctatus

Most microalgae evaluated in aquaculture diets have been produced autotrophically. In order to produce a cost‐efficient biomass at greater magnitudes for biofuel feedstock, heterotrophic production may be warranted. However, the chemical/nutritional attributes of these microalgae could differ from those grown autotrophically. An 8‐wk feeding trial was conducted to evaluate Chlorella spp. algae meal (AM) that had been cultured heterotrophically. The oil (lipid) was extracted to simulate biofuel production. Juvenile channel catfish, Ictalurus punctatus (5.7 ± 1.4 g; 8.9 ± 0.8 cm), were stocked at 10 fish/tank into fifteen 37.7‐L aquaria in a closed recirculating system and fed one of the five experimental diets to apparent satiation twice daily. Diets contained either 0 (control, CTL), 10, 20, or 40% AM and an additional diet containing 40% AM was supplemented with 2% lysine (40% AM+LYS). After 8 wk, there were no statistically significant differences in terms of survival, dressout percentages, whole‐body proximate composition, or fatty acid composition of the fillets among fish fed the diets containing varying levels of AM without added lysine. Feed consumption and weight gain for fish fed the 10, 40, and 40% AM+LYS diets were significantly greater than those fed the CTL diet. Feed conversion ratio was significantly lower for fish fed the 40% AM+LYS diet compared to those fed all other diets, which did not differ significantly from each other. These data indicate that channel catfish readily accept and can efficiently utilize heterotrophically produced AM at levels up to at least 40% of the total diet and that AM may enhance diet palatability.     

Effect of Caffeine Added to the Activating Solution on Sperm Motility of Fresh and Thawed Semen of Pacu,Piaractus mesopotamicus,and Curimba,Prochilodus lineatus

The aim was to evaluate the effect of different concentrations of caffeine added in activating solution over sperm motility in fresh and thawed semen of pacu, Piaractus mesopotamicus, and curimba, Prochilodus lineatus. The activating solutions were prepared with sodium bicarbonate solution of 0.76% (NaHCO₃) and caffeine was added at concentrations of 2.5, 5.0, 10.0, and 20.0 mM. As control, a solution of NaHCO₃ 0.76 without caffeine was used. Eight males of pacu and 20 males of curimba were used. Aliquots of 200 μL of semen were diluted in 800 μL extender solution (DMSO 10% and BTS 5%), placed in 0.5 mL straws and cryopreserved for 7 d in a liquid nitrogen tank. There was a linear increase in sperm motility for fresh semen of pacu, and for curimba fresh and thawed semen (P < 0.05), due to the increase in the concentration of caffeine. There was a quadratic response for duration of motility for thawed semen of pacu and for fresh semen of curimba (P < 0.05), respectively. These results indicate that addition of caffeine in the activator solution can improve sperm motility parameters, however, is dependent on the species and concentration used.     

Transient bilateral blindness associated with presumptive idiopathic pachymeningitis in a 22-year-old Irish Sport Horse

A 22-year-old Irish Sport Horse presented following a period of bilateral blindness with subsequent spontaneous resolution. Brain magnetic resonance imaging (MRI) demonstrated features consistent with pachymeningitis. Cerebrospinal fluid (CSF) analysis revealed increased numbers of basophils, suggestive of an immunologic or neoplastic aetiology. It was suspected that the enlarged meninges led to compression of the optic nerves in the optic canals, causing bilateral blindness. Initial spontaneous remission, as seen in this case, has been reported in human patients with this condition. Pachymeningitis should be considered as a possible cause of cranial nerve deficits, including bilateral and unilateral blindness, in horses.     

Major ascaroside pheromone component asc-C5 influences reproductive plasticity among isolates of the invasive species pinewood nematode

Pheromones are communication chemicals and regulatory signals used by animals and represent unique tools for organisms to mediate behaviors and make “decisions” to maximize their fitness. Phenotypic plasticity refers to the innate capacity of a species to tolerate a greater breadth of environmental conditions across which it adapts to improve its survival, reproduction, and fitness. The pinewood nematode, Bursaphelenchus xylophilus, an invasive nematode species, was accidentally introduced from North America into Japan, China, and Europe; however, few studies have investigated its pheromones and phenotypic plasticity as a natural model. Here, we demonstrated a novel phenomenon, in which nematodes under the condition of pheromone presence triggered increased reproduction in invasive strains (JP1, JP2, CN1, CN2, EU1, and EU2), while it simultaneously decreased reproduction in native strains (US1 and US2). The bidirectional effect on fecundity, mediated by presence/absence of pheromones, is henceforth termed pheromone-regulative reproductive plasticity (PRRP). We further found that synthetic ascaroside asc-C5 (ascr#9), the major pheromone component, plays a leading role in PRRP and identified 2 candidate receptor genes, Bxydaf-38 and Bxysrd-10, involved in perceiving asc-C5. These results suggest that plasticity of reproductive responses to pheromones in pinewood nematode may increase its fitness in novel environments following introduction. This opens up a new perspective for invasion biology and presents a novel strategy of invasion, suggesting that pheromones, in addition to their traditional roles in chemical signaling, can influence the reproductive phenotype among native and invasive isolates. In addition, this novel mechanism could broadly explain, through comparative studies of native and invasive populations of animals, a potential underlying factor behind of the success of other biological invasions.     

Death of a neonatal lamb due to Clostridium perfringens type B in New Zealand

ABSTRACT

Case history and clinical findings: A flock of 20 sheep was kept within three paddocks on a single property. None of the animals in the flock had been vaccinated against any disease for at least three years. Abdominal bloating and haemorrhagic diarrhoea were observed in Lamb 1 at 24 hours-of-age. The lamb subsequently died within an hour of the onset of clinical signs. Lamb 2 was 3-days-old when observed to be recumbent with opisthotonus. The lamb was treated with dextrose, vitamins B1 and B12, and penicillin G, but died 4 hours later.

Pathological findings: Examination of Lamb 1 revealed markedly increased gas within the peritoneum and within dilated loops of intestine. The intestines were dark red and contained large quantities of haemorrhagic fluid. Histology of the intestines revealed peracute mucosal necrosis with minimal accompanying inflammation. The intestinal lumen contained cell debris, haemorrhage, and myriad large Gram-positive bacilli. The intestines of Lamb 2 did not appear bloated or reddened. However, multiple fibrin clots were visible within the pericardial sac. Histopathological examination revealed small foci of necrosis within the mucosa of the distal intestine. The necrotic foci were often associated with large numbers of large Gram-positive bacilli.

Immunohistochemsitry and molecular biology: Intestinal samples from Lamb 1 were processed for Clostridium perfringens immunohistochemistry, which revealed large numbers of intralesional, positively immunostained rods. Fragments corresponding to the expected sizes for genes encoding alpha, beta, and epsilon C. perfringens typing toxins were amplified by PCR from DNA extracted from formalin-fixed sections of intestine.

Diagnosis: Lamb dysentery due to C. perfringens type B.

Clinical relevance: C. perfringens bacteria have a worldwide distribution, but disease due to C. perfringens type B has only been diagnosed in a small number of countries and has never been reported in New Zealand or Australia. C. perfringens type B produce both beta toxin and epsilon toxins, therefore both haemorrhagic enteritis and systemic vascular damage can develop. As many animals are exposed to C. perfringens without developing disease, there must be additional unknown factors that resulted in disease in these particular sheep. Vaccines that specifically protect against C. perfringens type B are available and may be recommended for use in smaller non-commercial flocks, as in the present case.