Modeling the Diving Behavior of Whales: A Latent-Variable Approach with Feedback and Semi-Markovian Components     

Roland Langrock  Tiago A. Marques  Robin W. Baird  Len Thomas 《Journal of Agricultural, Biological & Environmental Statistics》2014,19(1):82-100

Recent years have seen a fast-growing body of literature concerned with the statistical modeling of animal movement in the two horizontal dimensions. On the other hand, there is very little statistical work that deals with animal movement in the vertical dimension. We present an approach that provides an important step in analyzing such data. In particular, we introduce a hidden Markov-type modeling approach for time series comprising the depths of a diving marine mammal, thus modeling movement in the water column. We first develop a baseline Markov-switching model, which is then extended to incorporate feedback and semi-Markovian components, motivated by the observations made for a particular species, Blainville’s beaked whale (Mesoplodon densirostris). The application of the proposed model to the beaked whale data reveals both strengths and weaknesses of the suggested modeling framework. The framework is general enough that we anticipate that it can be used for many other species given minor changes in the model structure.  相似文献   

Comparison of total tract digestibility,development of visceral organs and digestive tract of Mong cai and Yorkshire × Landrace piglets fed diets with different fibre sources     

N. T. Len  T. T. T. Hong  B. Ogle  J. E. Lindberg 《Journal of animal physiology and animal nutrition》2009,93(2):181-191

The aim of the study was to evaluate the effects of piglet age and dietary fibre source on the development of visceral organs and the gastrointestinal tract (GIT), and on growth performance and total tract apparent digestibility (TTAD) in local [pure‐breed Mong cai (MC)] and exotic [Landrace × Yorkshire (LY)] piglets. The experimental diets contained different fibre sources: C (basal diet), RB (basal diet + rice bran), SPVM (basal diet + sweet potato vine meal) and CReM (basal diet + cassava residue meal). The neutral detergent fibre (NDF) content in diet C and the fibrous diets was 8.8% and 17.1%–17.7% respectively (dry matter basis). Collection of faecal samples to determine TTAD was carried out for five consecutive days before the experiment was finished (63 days). The piglets were killed at the age of 10 days (before being given the same solid feed), 30 days (weaning, 20 days after solid feed introduced) and 63 days (33 days after being given the different fibrous diets) when the length of intestinal segments, weight of organs (liver, heart, kidneys) and empty weight of the GIT (stomach, small intestine, caecum and colon + rectum) were measured. As the age of animals increased, the relative weight of organs and the length of intestines (expressed on a mass‐specific basis) decreased (p < 0.05), and the weight of GIT increased (p < 0.001). The piglets fed fibrous diets had heavier GIT than those fed diet C with the highest values in CReM (p < 0.05). The colon + rectum length was not significantly different among C, RB and SPVM, but was shorter than in CReM (p < 0.05). Coefficient of total tract apparent digestibility (CTTAD) of nutrients in the fibrous diets was lower than in C (p < 0.01). Average daily gain (ADG) and feed conversion ratio (FCR) in C, RB and CReM were not different and were better than in SPVM (p < 0.01). There were no significant differences in the weights of organs between the two breeds at day 10, 30 and 63 (p > 0.05). The weight and length of GIT were not significantly different between the two breeds at day 10 and day 30, but were greater for MC at day 63. The caecum and colon + rectum at 10 and 30 days were longer in MC than in LY (p < 0.001). The relative development of GIT post‐weaning was higher than pre‐weaning, the difference being most apparent in MC. As a result at 63 days, MC had heavier visceral organs and GIT, and longer intestines on fibrous diets than LY (p < 0.05). The MC at 63 days had higher CTTAD of organic matter, gross energy, crude fibre and NDF (p < 0.001) and ether extract and crude protein (p < 0.05), but lower ADG and poorer FCR than LY (p < 0.001). It can be concluded that the GIT of the MC piglets developed more rapidly than LY when they were introduced to solid feed, and that the difference was more marked on the fibrous diets and after weaning, which resulted in higher total tract digestibility of nutrients in MC compared with LY. Cassava residue meal was better digested than RB and SPVM, and supported higher live weight gains.  相似文献   

Detection and quantification of Fusarium oxysporum f. sp. cucumerinum in environmental samples using a specific quantitative PCR assay     

Kelly Scarlett  Len Tesoriero  Rosalie Daniel  David Guest 《European journal of plant pathology / European Foundation for Plant Pathology》2013,137(2):315-324

The rapid and reliable identification and quantification of pathogens is essential for the management of economically important plant diseases. Fusarium oxysporum f. sp. cucumerinum is the soil borne fungus responsible for Fusarium vascular wilt of cucumber. In this study, we report the development of a specific and reliable real-time quantitative PCR assay and the development of an ultra-sensitive diagnostic pseudo-nested PCR assay. The capacity of the PCR assays to accurately identify and quantify Fusarium oxysporum f. sp. cucumerinum was experimentally tested by the development of standard curves from serial dilutions of copy numbers in a range of complex environmental DNA samples. The amplification efficiency, sensitivity and reproducibility of the qPCR assays were not significantly affected by the presence of any of the non-target background DNA tested. In quantitative real-time PCR, as few as 100 copies could be reliably quantified, and in simple and pseudo-nested PCR as little as 10 pg and 10 fg, respectively, could be detected. This rapid and sensitive qPCR method can be used to facilitate investigations into plant–pathogen interactions, epidemiology, and disease management practices.  相似文献   

The effect of feeding rumen contents on glutamate dehydrogenase activity in some organs of broilers]     

K Holovská  V Lenártová  J Várady 《Veterinární medicína》1979,24(7):443-448

The effect of the replacement of 50, 60 and 80% of proteins in diet by dried rumen contents on glutamate dehydrogeanse activity (EC 1.4.1.3) in the kidneys, liver, and caecum tissue and contents was studied in broilers. The liver and caecum tissue did not show any significant changes in the activity of glutamate dehydrogenase (GLDH) in dependence on the concentration of rumen contents in the diet. A statistically significant drop of GLDH activity was ascertained in the kidneys, the drop being the most marked at a 65% concentration of rumen contents in the diet. Similarly, a statistically significant decrease of GLDH activity, caused by rumen contents feeding in comparison with the control, was observed in caecum contents, in which the activity of GLDH was the highest.  相似文献   

柑桔炭疽病潜伏带菌的普遍性及侵染动态     

王卫芳  冷怀琼 《四川农业大学学报》1990,8(2):147-151

研究表明柑桔炭疽病菌(Colletotrichum gloeosporioides Penz,)潜伏于柑桔复芽的苞片、叶、花、果皮及枝、主干皮层中,品种问带菌率存在差异。病原菌对温州蜜柑的集中侵染期为5—6月及9月。  相似文献   

Genetic diversity of Afrikaner cattle in southern Africa     

Lené Pienaar  J. Paul Grobler  Michiel M. Scholtz  Hannelize Swart  Karen Ehlers  Munro Marx  Michael D. MacNeil  Frederick W. C. Neser 《Tropical animal health and production》2018,50(2):399-404

The Afrikaner is an indigenous South African breed of “Sanga” type beef cattle along with breeds such as the Drakensberger and Nguni. Six composite breeds have been developed from crosses with the Afrikaner. Additionally, Afrikaner has been the base from which exotic breeds were established in South Africa through backcrossing. The study examined genetic diversity of Afrikaner cattle by genotyping 1257 animals from 27 herds in different geographic areas of South Africa and Namibia using 11 microsatellite markers. Multiple-locus assignment, performed using the Bayesian clustering algorithm of STRUCTURE, revealed three underlying genotypic groups. These groups were not geographically localized. Across herds and markers, the proportion of unbiased heterozygosity ranged from 0.49 to 0.72 averaging 0.57; mean number of alleles per locus ranged from 3.18 to 7.09, averaging 4.81; and allelic richness ranged from 2.35 to 3.38, averaging 2.67. It is concluded that a low inbreeding level of 2.7% and a moderate to high degree of variation still persists within the Afrikaner cattle breed, despite the recent decline in numbers of animals.  相似文献   

Using allele-specific oligonucleotide probes to characterize benzimidazole resistance in Rhynchosporium secalis     

Ian E. Wheeler  Sheila J. Kendall  Jenny Butters  Derek W. Hollomon  Len Hall 《Pest management science》1995,43(3):201-209

Benzimidazole fungicides are important mixture components in strategies to combat fungicide resistance in Rhynchosporium secalis Davis. To monitor the performance of these strategies, a rapid, accurate assay has been developed to detect point mutations in the β-tubulin gene which confers resistance of benzimidazoles. The β-tubulin gene of a benzimidazole-resistant strain of R. secalis has been cloned and sequenced. Except for the difference in the position of one of its six introns, this gene showed a strong homology with other β-tubulin genes from filamentous fungi. Resistance was related to a point mutation in codon 198 which caused a glutamic acid to glycine change in resistant field strains, but glutamic acid to lysine in a laboratory mutant. A DNA fragment surrounding codon 198 was amplified directly from diseased lesions using a ‘nested’ set of PCR primers. Combining PCR amplificiation of a target DNA sequence with hybridization of Allele-Specific Oligonucleotide probes (ASO_s, 15-mers) allowed accurate detection of benzimidazole resistance. Only two probes, one sensitive and one resistant, were sufficient to monitor current field populations. Detection was achieved using either ³²P-labelled probe, or non-radioactively using a biotin-labelled probe coupled to streptavidin/alkaline phosphatase. This rapid method using ASOS can detect benzimidazole resistance within 48 h compared with 6–8 weeks by conventional assay procedures.  相似文献   

Synthesis of a new class of pyridine herbicide     

Len F. Lee  Gina L. Stikes  Larry Y. L. Sing  Maria L. Miller  Mark G. Dolson  Jean E. Normansell  Susan M. Auinbauh 《Pest management science》1991,31(4):555-568

A new class of fluoroalkylated pyridine herbicides has been discovered. The 3,5-pyridinedicarboxylates are prepared either from ethyl 4,4,4-trifluoroacetoacetate via Hantzsch dihydropyridine synthesis or from trifluoroacetonitrile via cyclocondensation and carboxylation. Hydrolysis of the ester groups, followed by derivatization of the resulting acids yields a variety of herbicidally active analogs including ester, thioester, amide, halogen, amino, alkoxy and alkylthio derivatives.  相似文献   

Exploring Reasons for Varying Support for the Status Quo among Ontario’s Moose Hunters     

Len M. Hunt  Peter Davis 《Human Dimensions of Wildlife》2017,22(1):83-90

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Population‐level consequences of seismic surveys on fishes: An interdisciplinary challenge     

Hans Slabbekoorn  John Dalen  Dick de Haan  Hendrik V. Winter  Craig Radford  Michael A. Ainslie  Kevin D. Heaney  Tobias van Kooten  Len Thomas  John Harwood 《Fish and Fisheries》2019,20(4):653-685

Offshore activities elevate ambient sound levels at sea, which may affect marine fauna. We reviewed the literature about impact of airgun acoustic exposure on fish in terms of damage, disturbance and detection and explored the nature of impact assessment at population level. We provided a conceptual framework for how to address this interdisciplinary challenge, and we listed potential tools for investigation. We focused on limitations in data currently available, and we stressed the potential benefits from cross‐species comparisons. Well‐replicated and controlled studies do not exist for hearing thresholds and dose–response curves for airgun acoustic exposure. We especially lack insight into behavioural changes for free‐ranging fish to actual seismic surveys and on lasting effects of behavioural changes in terms of time and energy budgets, missed feeding or mating opportunities, decreased performance in predator‐prey interactions, and chronic stress effects on growth, development and reproduction. We also lack insight into whether any of these effects could have population‐level consequences. General “population consequences of acoustic disturbance” (PCAD) models have been developed for marine mammals, but there has been little progress so far in other taxa. The acoustic world of fishes is quite different from human perception and imagination as fish perceive particle motion and sound pressure. Progress is therefore also required in understanding the nature and extent to which fishes extract acoustic information from their environment. We addressed the challenges and opportunities for upscaling individual impact to the population, community and ecosystem level and provided a guide to critical gaps in our knowledge.  相似文献