Water relations and growth of loblolly pine seedlings planted under a shelterwood and in a clear-cut

We investigated the influence of shelterwood conditions on water relations and growth of loblolly pine (Pinus taeda L.) seedlings on two harsh sites in eastern Texas. Site I was harvested to provide four overstory density treatments (0, 2.3, 4.6 and 9.2 m(2) of residual basal area per ha). To quantify the effects of overstory competition, trenched and nontrenched subplots, each containing 25 one-year-old seedlings, were established within each overstory treatment plot, and predawn and midday water potentials (Psi(w)), seedling growth and survival were measured during the growing season. Leaf area and seedling biomass partitioning were measured at the end of the growing season. Site II was harvested to provide two overstory density treatments (0 and 6.9 m(2) ha(-1)) and planted with one-year-old loblolly pine seedlings. Seedling Psi(w), stomatal conductance (g(wv)), transpiration flux density (E), leaf area, height and survival were determined. On Site I, seedling Psi(w) increased with increasing overstory basal area, whereas trenching only substantially affected Psi(w) of seedlings in the 9.2 m(2) ha(-1) overstory treatment. Growth was not affected by overstory treatment or trenching. On Site II, Psi(w) and g(wv) were highest during the morning hours and lowest in the afternoon, whereas E peaked in the afternoon. Vapor pressure deficits and photosynthetic photon flux density were major factors in determining g(wv) differences between treatments. On individual days, the presence of an overstory increased Psi(w) and reduced both g(wv) and E. On Site II, leaf area was affected by overstory treatment throughout most of the study. We conclude that the presence of an overstory can have ameliorative effects on harsh sites at the western fringe of the loblolly pine natural range.     

Direct seeding of native trees and shrubs in low rainfall areas and on non-wetting sands in South Australia

Seeds of common endemic species of Acacia, Callitris, Eucalyptus and Melaleuca were sown at 12 sites in Southern Australia in 1994 and 1995 to determine the role of soil stabilisers, fertilisers, time of seeding, herbicides, ripping and soil preparation with a V-blade or a disc in improving the reliability of direct seeding in Mediterranean type climates with low rainfall. Rainfall in 1994 was below average with 140 mm at the northern sites (55% of the average) and 300 mm at the southern sites (74% of the average) and only Acacia was successful with at least 3 plants/10 m present at the end of spring at eight sites and a survival rate after the first summer of 43%. In 1995 at least 3 plants/10 m of Acacia and Eucalyptus spp. were present at the end of spring at eight sites, with at least 3 plants/10 m of Melaleuca at six sites and at least 3 plants/10 m of Callitris at only three sites. Melaleuca had the highest overall survival rate at the end of summer with 52% compared to Acacia 42%, Eucalyptus 41% and Callitris 29%. Sowing two to three weeks after the opening rains (May at most sites) with good weed control gave the best results. Plant survival over the summer was reduced by 40% where weeds were not controlled by a herbicide. Ripping or fertiliser did not improve success. Ground preparation with an 80 cm wide V-blade generally produced better results than using a 25 cm wide disc except for Melaleuca. The effect of bitumen was variable in the trials, but appeared to be beneficial on wind eroded sites. The results indicate that direct seeding of trees and shrubs can be carried out in Mediterranean type climates with 250 to 425 mm average annual rainfall including on soils that are water repellent. This technology could be used for large scale revegetation in areas of the world with low rainfall Mediterranean type climates that have been largely denuded of trees and shrubs. This revised version was published online in August 2006 with corrections to the Cover Date.     

Comparison of techniques for estimation of resting spores of Plasmodiophora brassicae in soil

Clubroot (Plasmodiophora brassicae) is an important disease of canola (Brassica napus) and other brassica crops. Accurate estimation of inoculum load in soil is important for evaluating producer risk in planting a susceptible crop, but also for evaluation of management practices such as crop rotation. This study compared five molecular techniques for estimating P. brassicae resting spores in soil: quantitative polymerase chain reaction (qPCR), competitive positive internal control PCR (CPIC-PCR), propidium monoazide PCR (PMA-PCR), droplet digital PCR (ddPCR) and loop-mediated isothermal DNA amplification (LAMP). For ddPCR and LAMP, calibrations were developed using spiked soil samples. The comparison was carried out using soil samples collected from a long-term rotation study at Normandin, Québec, with replicated plots representing 0-, 1-, 2-, 3-, 5- and 6-year breaks following susceptible canola infested with clubroot. CPIC-PCR and ddPCR provided repeatable estimates of resting spore numbers in soil compared with estimates from qPCR or LAMP alone. CPIC-PCR provided the most robust measurement of spore concentration, especially in the 2 years following a crop of susceptible canola, because it corrected for effects of PCR inhibitors. PMA-PCR demonstrated that a large proportion of the DNA of P. brassicae detected in soil after the susceptible canola crop was derived from spores that were immature or otherwise not viable. Each assay provided a similar pattern of spore concentration in soil, which supported the conclusion of a previous study at this site that resting spore numbers declined rapidly in the first 2 years after a susceptible crop, but much more slowly subsequently.     

Immune responses of cattle to experimental anti-Fasciola hepatica vaccines.

Fasciola hepatica infection of cattle and sheep is an important cause of clinical disease and production losses, and is controlled at present by a combination of chemotherapy and management measures. However, the prospects for the control of F. hepatica infection by vaccination are good, and we have previously shown substantial protection of cattle against experimental challenge infection following immunisation with a combination of the purified fluke-derived enzymes cathepsin L1 (CATL 1), cathepsin L2 (CATL 2) and fluke-derived Hb fraction (FHB). This and other recent studies have also demonstrated fundamental differences between protective and non-protective immune responses to liver fluke infection. In this present study we have further analysed the response of animals to liver fluke challenge following experimental vaccination. Calves were vaccinated with either CATL 2 plus FHB, or CATL 1 plus CATL 2. Partial protection against challenge infection was achieved in both vaccinated groups, with the greatest level of protection (55 per cent reduction in fluke burdens) recorded in the group vaccinated with CATL 1 plus CATL 2. This latter group also showed the greater level of lymphocyte proliferation and the greater production of gamma-INF in response to stimulation with fluke antigen in vitro following challenge. These results are significant in our attempts to characterise the elements within the immune response to vaccination which are protective.     

寄生虫疫苗的现状与未来

在过去的十年间,驱虫药市场是18万亿美元动物药品市场中增长最快的部分。尽管治疗家畜寄生虫的药物仍然统治这一领域,并将继续开发或重新配制,由于消费者对不含化学药品食物的需求以及关心重视环境和动物福利,研制安全有效的疫苗逐渐受到关注。在盈利超过3万亿美元的宠物市场,对疫苗也有需求。对疫苗的这些需求将给在过去十五年已取得巨大进步的领域增加一个较大的动力。许多驱虫疫苗已经研制出来,如基因重组的45W和EG95六钩蚴蛋白分别预防绵羊带绦虫和细粒棘球绦虫,Bm86疫苗预防微小牛蜱。此外,预防肝片形吸虫的组织蛋白酶L疫苗和预防捻转血矛线虫的H11疫苗的研制进展顺利,还有许多其它的候选疫苗用于预防捻转血矛线虫和其它线虫如奥斯特线虫和毛圆线虫,这些疫苗可能最终成为广谱的消化道寄生虫疫苗。尽管预防原虫的分子疫苗仍让人感到难以捉摸,活苗和致弱活苗可以用来控制禽球虫病、绵羊弓形虫病和牛边虫病。已经掌握的大量的基因组学、蛋白组学和免疫学的知识将为疫苗研制提供新的方法,在不久的将来可以看到许多新的疫苗投入市场。     

Acid and Fermented Silage Characterization and Determination of Apparent Digestibility Coefficient of Crude Protein for Pacu Piaractus mesopotamicus

Three types of raw materials including commercial waste from saltwater (SW), freshwater fish (FW) and tilapia fillet residue (FR) were used to produce fish silage by either acid digestion (2% formic acid and 2% sulfuric acid) or anaerobic fermentation (5% of Lactobacillus plantarum and 15% sugar cane molasses). Six test diets were used in digestibility trials prepared with 70% reference diet and 30% of each experimental silage. These diets were fed to juvenile pacu Piaractus mesopotamicus (146 g average weight) in triplicate. Fish were kept in 500-L tanks and feces collected by manual extrusion. It was observed for both processes that SW waste always had the highest moisture content and lowest fat and ash. Highest crude protein levels were found in silages from commercial fish waste (SW and FW) made from whole fish unfit for human consumption. However, apparent digestibility coefficients did not vary among diets ( P > 0.05). Although values did not differ statistically, fermented silage consistently displayed higher digestibility coefficients compared to acid silage. The silages exhibited relatively high protein digestibility (72.5–80.0%), thus suggesting the feasibility of using fish industry by-products in aquaculture feeds.     

Growth and metabolism of pacu (Piaractus mesopotamicus Holmberg 1887) juveniles fed diets containing different protein, lipid and carbohydrate levels

To verify the potential of lipids and carbohydrates to spare dietary protein and to understand the intermediary metabolism of interaction of these nutrients in pacu juveniles, an experiment was carried out to evaluate pacu physiological and performance parameters. The experimental design was completely randomized with 12 treatments in a 2 × 2 × 3 factorial arrangement, consisting of diets containing two digestible protein levels (200 and 230 g kg⁻¹ PD), two lipid levels (40 and 80 g kg⁻¹) and three carbohydrate levels (410, 460 and 500 g kg⁻¹). Fish‐fed 230 g kg⁻¹ digestable protein (DP) showed increased glycaemia, decreased hepatic glycogen, as well as a smaller intake index and better feed conversion ratio. The higher dietary lipid level (80 g kg⁻¹) reduced protein intake and serum protein concentration, increased liver and body fat content, but did not affect growth. At a lipid level of 80 g kg⁻¹, the increase in dietary carbohydrate levels promoted greater weight gain (WG), crude protein intake (CPI) and better feed conversion ratio (FCR). For fish fed diets containing 40 g kg⁻¹ lipid, the best energy‐productive values (EPV) were obtained at 460 g kg⁻¹ carbohydrate. Increased levels of the main nutrients in the diets reduced the levels of serum triglycerides, while the increase in energy concentration increased the hepatosomatic (HSI) and glycaemia index values. Pacu used lipids as effectively as carbohydrates in the maximization of protein usage, as long as dietary protein was at a level of 230 g kg⁻¹ DP. The physiological parameters indicated that the best balance between the DP, dietary lipid and carbohydrate levels within the ranged this trial was obtained at 230, 40 and 460 g kg⁻¹, respectively, without lower growth.