The generation and persistence of genetic variation in foot-and-mouth disease virus

Genetic variation in foot-and-mouth disease virus (FMDV) is of interest for at least two reasons. First, changes to the genes encoding capsid proteins results in antigenic variation, and affects vaccine efficiency and effectiveness of vaccination programs; second, genetic changes can lead to important insights into the transport of virus between countries, regions, herds, and even possibly individuals. Current estimates of RNA virus mutation rates suggest that an average of about one base mis-incorporation is likely to occur each time a single FMDV genome replicates. This should result in the introduction of every possible 1-step mutation from the progenitor genotype into the viraemia of a single infected animal many times a day. In the absence of purifying selection, a single infected animal should therefore generate a genetically very diverse population of virus.Viral-capsid sequences obtained from infected animals sampled over long-term FMDV epidemics suggest that these genetic changes accrue in a remarkably linear 'clock-like' fashion and at rates of around 1% change per year. While such a rate is generally regarded as quite high, it is actually somewhat lower than one might expect based on the rate at which viral diversity could be generated within a single animal. The difference might be explained in a variety of possible ways: (1) the mutation rate has been overestimated; (2) purifying selection is stronger than predicted; (3) only a restricted subset of excreted virus is actually infectious; (4) infected animals only excrete virus from a small partitioned subset of amplified virus, and that most of the generated viral diversity is unable to exit the animal; or (5) only a small fraction of all infected animals participate in the actual disease-transmission process.     

Nutrient digestibilities of soft winter wheat, improved triticale cultivars, and pearl millet for finishing pigs

A replicated 4 x 4 Latin square digestion trial was conducted to determine apparent nutrient digestibilities and N and energy balances for soft red winter wheat, Beagle 82 triticale, Florico triticale, and pearl millet using finishing pigs fitted with ileal T-cannulas. Fortified experimental diets contained 97.5% of each respective grain. Nitrogen and amino acid digestibilities of soft winter wheat and triticale were similar (P greater than .13) when measured near the end of the small intestine and over the total digestive tract. Ileal digestibilities of alanine, isoleucine, leucine, threonine, tryptophan, and valine were higher (P less than .05) for pearl millet than for the other grains. Total tract N and amino acid digestibilities were all higher than ileal digestibilities. Gross energy and DM digestibilities determined at the small intestine were higher (P less than .05) for wheat and pearl millet than for Beagle 82 triticale, with the Florico variety being intermediate in energy digestibility. Total tract digestible and ME concentrations followed essentially the same pattern as ileal GE digestibility and were 2 to 3% higher (P less than .05) for wheat and pearl millet than Beagle 82 triticale. Florico triticale had similar (P greater than .05) DE but was 1.3% lower (P less than .05) in ME content than wheat.     

Harvest residue management and fertilisation effects on soil carbon and nitrogen in a 15-year-old Pinus radiata plantation forest

Growing interest in the use of planted forests for bioenergy production could lead to an increase in the quantities of harvest residues extracted. We analysed the change in C and N stocks in the forest floor (LFH horizon) and C and N concentrations in the mineral soil (to a depth of 0.3 m) between pre-harvest and mid-rotation (stand age 15 years) measurements at a trial site situated in a Pinus radiata plantation forest in the central North Island, New Zealand. The impacts of three harvest residue management treatments: residue plus forest floor removal (FF), residue removal (whole-tree harvesting; WT), and residue retention (stem-only harvesting; SO) were investigated with and without the mean annual application of 190 kg N ha⁻¹ year⁻¹ of urea-N fertiliser (plus minor additions of P, B and Mg). Stocks of C and N in the forest floor were significantly decreased under FF and WT treatments whereas C stocks and mass of the forest floor were significantly increased under the SO treatment over the 15-year period. Averaged across all harvesting treatments, fertilisation prevented the significant declines in mass and C and N stocks of the forest floor which occurred in unfertilised plots. The C:N ratio of the top 0.1 m of mineral soil was significantly increased under the FF treatment corresponding to a significant reduction in N concentration over the period. However, averaged across all harvesting treatments, fertilisation prevented the significant increase in C:N ratio of the top 0.1 m of mineral soil and significantly decreased the C:N ratio of the 0-0.3 m depth range. Results indicate that residue extraction for bioenergy production is likely to reduce C and N stocks in the forest floor through to mid-rotation and possibly beyond unless fertiliser is applied. Forest floors should be retained to avoid adverse impacts on topsoil fertility (i.e., increased C:N ratio). Based on the rate of recovery of the forest floor under the FF treatment, stocks of C and N in the forest floor were projected to reach pre-harvest levels at stand age 18-20. While adverse effects of residue extraction may be mitigated by the application of urea-N fertiliser, it should be noted that, in this experiment, fertiliser was applied at a high rate. Assessment of the sustainability of harvest residue extraction over multiple rotations will require long-term monitoring.     

Serotonin selectively inhibits growth cone motility and synaptogenesis of specific identified neurons

The motile activity of growth cones of specific identified neurons is inhibited by the neurotransmitter serotonin, although other identified neurons are unaffected. As a consequence, affected neurons are unable to form electrical synapses, whereas other neurons whose growth is unaffected can still interconnect. This result demonstrates that neurotransmitters can play a prominent role in regulating neuronal architecture and connectivity in addition to their classical role in neurotransmission.     

Vaccination strategies to conserve the endangered African wild dog (Lycaon pictus)

Pathogens such as rabies virus and canine distemper virus present a significant risk to the long-term survival of some endangered African wild dog (Lycaon pictus) populations. Vaccination of wild dogs is one approach that might reduce population extinction risks; however clear guidelines for how best to do this are lacking. Hence, we developed a mathematical model of wild dog population dynamics that integrates a pathogen transmission model and a vaccination process. Simulations indicated that the most effective vaccination strategy includes all age classes (when pups are 2-months old), prioritizes the breeding pair, and vaccinates at least 4 animals per pack included in the vaccination effort. In addition, populations for which an Allee effect, high rates of pathogen introduction, or low rates of recovery and immunity were simulated, required greater vaccination coverage (dogs/pack), to protect an equivalent number of packs compared to populations for which no Allee effect, low rates of pathogen introduction, or high rates of recovery and immunity were simulated. For populations in which some packs (high-risk) have a greater risk of pathogen exposure than others (low-risk), vaccinating both high- and low-risk packs, or only low-risk packs, is more effective than vaccinating only high-risk packs when pathogen introduction rates are high. Finally, model results suggest that vaccination of wild dog populations against pathogens, such as canine distemper virus, that do not cause 100% mortality and against which some wild dogs develop acquired immunity, may be unnecessary.     

Effect of lasalocid on reproductive performance and subsequent lactation in the sow

The effect of lasalocid (140 mg . head-1 . d-1) on sow reproductive performance and subsequent piglet performance during lactation were examined in a trial that involved 114 sows. Treatments consisted of 1) control diet with no lasalocid during gestation and lactation; 2) lasalocid diet during gestation, control diet during lactation; 3) control diet during gestation and lasalocid diet during lactation; and 4) lasalocid diet during gestation and lactation. The addition of lasalocid either to gestation or lactation diets had no effect (P greater than .10) on sow weight gains or days to return to estrus postweaning. Milk protein percentages were similar (P greater than .10) for sows in all treatment groups for samples taken at 3, 7 and 14 d postfarrowing. Milk fat percentages were higher (P less than .05) in fall-bred sows at d 3 for Treatments 1, 3 and 4 than for Treatment 2 No significant differences (P less than .10) were observed for litter size at birth, 21 d postfarrowing or at weaning. Piglet weights at birth, 21 d and weaning were similar (P less than .10) among treatment groups. However, litter size and litter weight gains tended to be heavier at 21 d postfarrowing and at weaning for fall-bred sows fed lasalocid in either gestation and (or) lactation compared with those fed the control diet.     

酶混合物添加剂对生长猪养分回肠和粪便消化率的影响

试验旨在测定β-葡聚糖酶和蛋白酶的混合物（EBP）对生长猪粪消化率（FD）、表观回肠消化率（AID）、标准回肠消化率和后肠消化率的影响。12头安装回肠瘘管的生长阉公猪,体重为（38．2±0．5）kg,单独饲养在代谢箱中,按照先前的饲料摄入量编号到3个组中,每组4头。试验采用4×4拉丁方设计,试猪随机分配到每组（方）3个重复的4个处理中。处理分别为基础饲粮（基础）,基础＋0．05％EBP（0．05％EBP）,基础＋0．10％EBP（0．10％EBP）及水解酪蛋白,水解酪蛋白用以测定内源氨基酸。基础饲粮含玉米和豆粕,其营养水平计算值分别为代谢能3．36Meal·kg^-1,总赖氨酸1．1％。在第一阶段,拉丁方的每个重复的饲粮采食量是预试阶段4头试猪最小饲料采食量的85％,且每组相等。每个继发阶段饲养水平提高100g·d^-1。每个试验阶段14d,其中饲粮适应期4d,粪便收集期5d、过渡期3d和回肠收集期2d。每天间隔12h连续收集回肠流出物。与栗食基础饲粮的猪相比。采食EBP的猪干物质（DM）、有机物（OM）、能量、粗蛋白（CP）、非纤维性碳水化合物、总饲粮纤维、不溶饲粮纤维、酸水解脂肪、灰分、钙（Ca）和磷（P）的FD显著升高（P〈0．05）。饲粮中添加EBP0．05％或0．10％,试猪中性洗荆纤维（NDF）和半纤维素的AID显著升高（P〈0．05）,但是DM和能量的AID没有增加。与采食基础饲粮的试猪相比,采食EBP的试猪酸水解脂肪的AID趋向于升高（P〈O．051）。各处理间多数氨基酸的回肠消化率没有显著差异,但是EBP显著降低蛋氨酸、丙氨酸和丝氨酸的表观、标准消化率（P〈0．05））。与采食基础饲粮的试猪相比,采食EBP的试猪半纤维素的FD与AID的差异显著减小（P〈0．05）。结果显示,生长猪采食EBP能改善DM、OM、能量、CP、非纤维碳水化合物、总饲粮纤维?