Functional heterogeneity in resources within landscapes and herbivore population dynamics

Large mammalian herbivores are notorious for their propensity towards population irruptions and crashes, yet many herbivore populations remain relatively stable. I explore how resource heterogeneity within landscapes dampens population instability, using a metaphysiological modelling approach considering patch state distributions. Resource heterogeneity is functionally stabilizing through spreading consumption away from preferred resources before these become critically depleted. Lower-quality resources act as a buffer against starvation during critical periods of the seasonal cycle. Enriching resource quality is destabilizing, even if patch diversity is maintained, because food quantity then becomes the limitation. The potential consequences of landscape fragmentation are explored using the Serengeti ecosystem, characterised by broadscale resource gradients, as a hypothetical example. Further insights provided by the model are illustrated with specific examples concerning the effects of patch scales and waterpoint distribution. A metaphysiological modelling approach enables the basic consequences of landscape heterogeneity to be distinguished from further effects that may arise from specific patch scales and configurations, without the distracting detail of spatially explicit models.     

Validation of the specificity and sensitivity of species-specific primers that provide a reliable molecular diagnostic for <Emphasis Type="Italic">Xiphinema diversicaudatum</Emphasis>, <Emphasis Type="Italic">X. index</Emphasis> and <Emphasis Type="Italic">X. vuittenezi</Emphasis>

Xiphinema diversicaudatum and X. index are vector nematode species of economic importance in viticulture regions as they can transmit Arabis Mosaic, Grapevine Fanleaf and Strawberry Latent Ringspot viruses to grapevine. Wang et al. (2003) designed species-specific diagnostic primers from ribosomal genes for both these vector species as well as a vector and a non-vector species X. italiae and X. vuittenezi, respectively. Our study aimed to confirm the specificity and determine the sensitivity and reliability of the primers for the two vector species, X. diversicaudatumand X. indexwhen challenged with closely related longidorid species and general nematode communities typical of vineyard soil. With one exception, no PCR product was observed when the primers were tested against six Longidorus, one Paralongidorus and one Xiphinema non-target species. Occasionally (three out of eight replicate PCR reactions) a weak PCR product was noted when primers for X. index were tested with L. elongatus. Furthermore, when challenged with a range of non-target nematode species comprising the nematode community typical of viticulture soil, no PCR product was amplified. An experimental dilution series of extracted DNA rigorously demonstrated that DNA from an equivalent single specimen of the target virus-vector species, X. diversicaudatum and/or X. index, could be detected amongst 1000 equivalent non-targetX. vuittenezi. Also, extracted DNA from an equivalent single target specimen was detected when added to DNA extracted from the overall soil nematode community. The primers were assessed further by using serial mixtures of actual nematodes rather than extracted DNA to simulate field soil. Using this method, a single target nematode could be detected amongst 200 non-target specimens. Given their specificity, sensitivity and reliability, it appears that these diagnostic primers will be of great benefit to phytosanitary/quarantine services related to the viticulture industry.     

生长肥育猪骨骼肌注射表达pGRF基因质粒的效应研究

将猪的GRF基因表达质粒注射于猪的骨骼肌后,研究其促生长效应与机理。选用始重6.3kg的44头去势长白×太湖仔猪,分6组,采用2×3因子安排的完全随机区组设计,按6～10kg、10～20kg、20～50kg、50～100kg4个阶段饲养。4个饲养阶段的饲粮低蛋白水平分别是20.70%,17.90%,15.03%,13.00%;高蛋白水平分别是23.70%,20.90%,18.02%,16.00%。pGRF基因质粒注射剂量设0mg、0.5mg、1.0mg3个水平,于试验开始与试验猪体重达60kg时共注射基因质粒2次。测定各阶段日增重,饲料消耗量,耗料增重比以及30、70、100kg时血液中GH、GRF、IGF-I的浓度。100kg时屠宰进行胴体品质测定。结果表明:饲粮蛋白水平对各阶段及全期试验猪日增重均有显著影响(P<0.05或P<0.01),对50～100kg阶段与全期日采食量和耗料增重比有显著影响(P<0.05或P<0.01)。注射pGRF基因质粒对各阶段及全期日增重均有显著影响(P<0.05),对6～10kg、10～20kg、50～100kg3阶段及全期日采食量有显著影响(P<0.05),对6～10kg阶段、50～100kg阶段及全期耗料增重比有显著影响(P<0.05)。注射pGRF基因质粒对30kg及70kg体重时猪血液中GRF、GH、IGF-I浓度均有显著影响(P<0.05)。提高饲粮蛋白水平与注射pGRF基因质粒均可明显降低超声波测膘厚及屠宰测膘厚、增大眼肌面积(P<0.05)。     

Prediction of chemical composition and peroxide value in unground pet foods by near‐infrared spectroscopy

The massive development of the pet food industry in recent years has lead to the formulation of hundreds of canine and feline complete extruded foods with the objective of meeting both the needs of the animals and numerous demands from pet owners. In the meantime, highly variable raw material compositions and the industry's new production techniques oblige manufacturers to monitor all phases of the extrusion process closely in order to ensure the targeted composition and quality of the products. This study aimed at evaluating the potential of infrared technology (visible and near‐infrared spectrophotometer; 570–1842 nm) in predicting the chemical composition and peroxide value (PV) of unground commercial extruded dog foods. Six hundred and forty‐nine commercial extruded dog foods were collected. For each product, an unground aliquot was analysed by infrared instrument while a second aliquot was sent to a laboratory for proximate analysis and PV quantification. The wide range of extruded dog food typologies included in the study was responsible for the wide variability observed within each nutritional trait, especially crude fibre and ash. The mean value of the 208 pet foods sampled for PV quantification was 17.49 mEq O₂/kg fat (min 2.2 and max 94.10 mEq O₂/kg fat). The coefficients of determination in cross‐validation of NIRS prediction models were 0.77, 0.97, 0.83, 0.86, 0.78 and 0.94 for moisture, crude protein, crude fat, crude fibre, ash and nitrogen‐free extract (NFE) respectively. PV prediction was less precise, as demonstrated by the coefficient of determination in cross‐validation (0.66). The results demonstrated the potential of NIRS in predicting chemical composition in unground samples, with lower accuracy for moisture and ash, while PV prediction models suggest use for screening purposes only.     

豆科与禾本科牧草间作的生长互作效应及对氮、磷养分吸收的影响

为了解牧草间作对作物生长和养分吸收的影响,以及为不同牧草优化配置、豆科和禾本科牧草间作提高结氮量提供理论依据,本试验采用随机区组试验设计,研究了间作对柱花草、扭黄茅和孔颖草的生物量和氮磷吸收的影响。结果表明,由于柱花草生物固氮,对扭黄茅和孔颖草养分吸收和生长有促进作用,与柱花草间作后的扭黄茅和孔颖草与禾本科牧草单作模式相比,能获得高的养分吸收量和产量。与各自单作对比,间作体系中的禾本科牧草生物量高于单作0.06%和26.78%;与柱花草单作对比,两个间作体系中的柱花草生物量低于单作9.70%和12.83%。扭黄茅与柱花草间作后,对氮磷的吸收量高于单作扭黄茅24.26%和35.18%,对氮磷的吸收量高于单作孔颖草40.64%和47.50%。相对于单作而言,柱花草分别与扭黄茅和孔颖草间作,对氮吸收量分别降低8.31%和28.94%,磷吸收量分别降低3.56%和20.58%。而且两种间作模式当量比均大于1,具有间作优势;柱花草/扭黄茅间作系统生产力、种间竞争能力高于柱花草/孔颖草,具有产量优势。在株行距为50 cm种植密度下,间作体系中禾本科牧草生长旺盛,柱花草的生长受到抑制,在与两个禾本科牧草间作中为弱竞争作物。结果表明,在合理的种植密度下,适合的牧草配置能够充分利用各种资源,促进种间有益作用,提高单位面积牧草产量和禾本科牧草氮磷的吸收,有利于改善牧草品质。     

Guanidinoacetic acid supplementation in broiler chickens fed on corn-soybean diets affects performance in the finisher period and energy metabolites in breast muscle independent of diet nutrient density

(1) Guanidinoacetic acid (GAA) is the single immediate endogenous precursor of creatine (Cr). It was hypothesised that dietary GAA would have different effects on performance and energy metabolites in breast muscle depending on the nutrient density (ND) of corn-soybean-based diets.

(2) A total of 540 one-day-old male Ross 308 broilers were allocated to 9 dietary treatments with 6 replicates (10 birds each) in a 3 × 3 factorial arrangement with three levels of ND (low, 2800; medium, 2950 and high, 3100 kcal metabolizable energy (ME)/kg; and with the other nutrients being constant relative to ME) and supplemented with three levels of GAA (0, 0.6 and 1.2 g/kg) in a 42-d feeding trial.

(3) In the starter and grower periods, increasing levels of ND improved body weight (BW), average daily gain (ADG), average daily feed intake (ADFI) and feed conversion ratio (FCR), with the exception of ADFI in the starter period. GAA supplementation did not affect performance characteristics. All performance indicators responded markedly to increasing ND in the finisher period, whereas the highest GAA level reduced ADFI compared to the unsupplemented control (156 vs. 162 g/d) and concomitantly FCR (1.81 vs. 1.93). No interactive effects were noted for any performance trait. The high ND diet resulted in more breast meat yield on d42, associated with higher fat content and darker colour compared to the other ND levels. The GAA supplementation did not affect carcass and breast traits. At the end of the experiment, Cr was elevated when feeding GAA at 1.2 g/kg (5455 vs. 4338 mg/kg fresh muscle).

(4) To conclude, ND had a substantial effect on performance and carcass traits, whereas any effect of GAA was limited to FCR in the finisher period and independent of diet ND level.     

A review on breeding and genetic strategies in Iranian buffaloes (<Emphasis Type="Italic">Bubalus bubalis</Emphasis>)

The aim of current study was to review breeding progress and update information on genetic strategies in Iranian buffaloes. Iranian buffalo is one of the vital domestic animals throughout north, north-west, south and south-west of Iran with measurable characteristics both in milk and meat production. The species plays an important role in rural economy of the country due to its unique characteristics such as resistance to diseases and parasites, having long productive lifespan and showing higher capability of consuming low-quality forage. In Iran, total production of milk and meat devoted to buffaloes are 293,000 and 24,700 tons, respectively. Selection activities and milk yield recording are carrying out by the central government through the Animal Breeding Centre of Iran. The main breeding activities of Iranian buffaloes included the estimation of genetic parameters and genetic trends for performance traits using different models and methods, estimation of economic values and selection criteria and analysis of population structure. Incorporating different aspects of dairy buffalo management together with improved housing, nutrition, breeding and milking, is known to produce significant improvements in buffalo production. Therefore, identifying genetic potential of Iranian buffaloes, selection of superior breeds, improving nutritional management and reproduction and developing the education and increasing the skills of practical breeders can be useful in order to enhance the performance and profitability of Iranian buffaloes.     

Prevalence of <Emphasis Type="Italic">Haemonchus contortus</Emphasis> infection in sheep slaughtered at Jimma town municipal abattoir,Ethiopia

Haemonchus contortus is a parasite of major economic importance of most sheep-rearing areas of the world. A cross-sectional study was conducted from November 2015 to March 2016 with objectives of determining the prevalence and associated risk factors of Haemonchus contortus infection in sheep slaughtered at Jimma town municipal abattoir, Ethiopia. Of the total 7000 sheep slaughtered during the study time period, 384 sheep were randomly selected and examined for parasites. The overall prevalence of Haemonchus contortus infection was 264 (68.75%). Infection rate of poor body condition animals was significantly (P?=?0.000) higher than good body conditioned animals. The mean packed cell volume (PCV) values (%) of parasitemic and aparasitemic sheep were 23.73?±?3.7 SD and 37.66?±?4.736 SD, respectively. The prevalence in adult sheep (>?1 year) was insignificantly (P?=?0.653) higher than that of young sheep (≤?1 year). The highest prevalence was recorded in sheep that originated from Seka district (73.3%) and the lowest in Kersa district (63.4%) with non-significant variation (P?=?0.691). The highest monthly mean worm burdens and prevalence of Haemonchus contortus infection were recorded in November and lowest in March. The current study revealed that Haemonchus contortus infection is an important and common parasitic disease and requires special attention to its control.