Feeding value of pastures for ruminants     

GC Waghorn  DA Clark 《New Zealand veterinary journal》2013,61(6):320-331

Perennial ryegrass is the primary forage component of ruminant diets in New Zealand. It is persistent and palatable, and immature ryegrass has a high nutritive value (NV). However, seed-head development substantially lowers its feeding value (FV) as fibre concentration increases, the rate and extent of digestibility decreases, and voluntary intake declines. Ryegrass pastures are susceptible to accumulation of endophytic and saprophytic fungi in dead material at the base of the sward, especially when mature and laxly grazed. Feeding forage legumes to ruminants grazing grass-dominant pastures will improve animal performance and lessen the reliance on a single species to meet all nutritional requirements.

The FV of forage is a function of intake and NV, measured by chemical analyses and animal feeding trials. Performance of individual animals grazing forages is usually limited by energy intake because structural fibre can slow digestion and clearance from the rumen and because of competition between individuals for available feed. The use of metabolisable energy (ME) content of forage to signify FV can give a reasonable indication of animal performance, but it should be used in conjunction with chemical analyses to improve the accuracy of predictions.

The relationship between FV, pasture production, animal performance and profitability is complex. The importance of skilled management to maintain pasture quality and optimise animal performance under inconsistent climatic conditions should not be underestimated. Acceptable animal performance with minimal veterinary intervention requires good nutrition, but the genetic potential of livestock in New Zealand cannot be met solely by grazing pasture, especially when a high utilisation of pasture is required to maintain quality and profitability.

Producers are responding to industry demands to reduce the seasonality in supply of milk and meat by changing lambing and calving dates, and extending lactation length in dairy cows. Social changes include adoption of once-daily milking in the dairy industry. Some changes have necessitated increased use of supplements and others can be met by feeding forages with a higher FV than ryegrass, all of which require an improved knowledge of feed quality. This information is available through rapid and inexpensive near infrared spectroscopy (NIRS) analysis, enabling animal nutritional needs to be balanced by appropriate nutrient supply. It is essential that producers continue to improve animal welfare, limit excessive use of fertilisers and meet the demands of overseas consumers. Good nutrition, with an increased use of legumes and other forages to complement ryegrass pastures, will enable these objectives to be achieved.  相似文献   

Aural plaques in two imported horses in New Zealand     

RA Fairley  CM Morley  SD Williams  DA Senior  MA Neill 《New Zealand veterinary journal》2013,61(4):232-233

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西藏原始林芝云杉林空间结构参数分布特征     

韩艳英    盛基峰  李垚  大布穷  叶彦辉   《西北林学院学报》2023,38(1):146-152

以藏东南波密岗乡自然保护区原始林芝云杉林为研究对象,应用空间结构参数角尺度、混交度和大小比数,建立空间结构参数的三元分布,揭示林分的空间结构特征。结果表明,从一元分布看,林木整体属于随机分布,林分强度混交,树种的优劣程度参差不齐,整体处于中庸状态;在混交度和角尺度分布中,以随机分布和强度混交林木株数最多,大小比-角尺度组合中,均以随机分布轴线和中庸轴线两侧基本对称;三元结构参数组合为强度混交、随机分布、亚优势状态林木分布较多。主要树种的混交程度较高,呈现强度和极强度混交状态;其中林芝云杉和华山松为该群落的优势树种随机分布,其他主要树种都为轻度聚集分布;树种间大小比数差异明显,其中林芝云杉最低,<0.252,处于亚优势状态。全面分析原始林芝云杉林的空间结构,为林芝云杉林结构优化调整提供重要参考,为藏东南天然林可持续发展提供科学依据。  相似文献   

浅析阿拉善左旗林业有害生物防治现状及应对措施   总被引：1，自引：0，他引：1  

姚艳芳  杨芹  巴依尔  王晓勤  常桂霞  郝淑香  达来夫 《内蒙古林业调查设计》2019,(4):54-56

文章对阿拉善左旗林业有害生物防治现状进行了调查,分析了林业有害生物监测防治工作存在的问题,提出做好林业有害生物防治社会化服务工作应对的措施,对于建立起适应当前林业改革和发展形势需要的林业有害生物防治公共服务保障体系提供了理论依据。  相似文献   

Host–strain mediated selection for an effective nitrogen-fixing symbiosis between Trifolium spp. and Rhizobium leguminosarum biovar trifolii     

R.J. Yates  J.G. Howieson  W.G. Reeve  L. Brau  J. Speijers  K. Nandasena  D. Real  E. Sezmis  G.W. O’Hara 《Soil biology & biochemistry》2008,40(3):822-833

We have previously reported significant strain–host incompatibility between the microsymbiont Rhizobium leguminosarum biovar trifolii and Trifolium spp. related to geographic and phenological barriers. Additionally, we have shown that an effective symbiosis between strains of R. l. trifolii and clover was established despite the soil harbouring ineffective R. l. trifolii capable of nodulating the host. We termed this “selection” for effective symbiosis. This paper reports glasshouse-based experiments to validate and further explore this in situ selection phenomenon. The effect of cell density and strain ratio at the time of inoculation, as well as soil pH, were investigated on two hosts (Trifolium purpureum and Trifolium polymorphum) that were each exposed to one microsymbiont capable and one incapable of N₂ fixation. In co-inoculation experiments at a cell density of 10⁴ cells/mL, each host nodulated solely with its effective strain, even when this strain was outnumbered 100-fold by the ineffective strain. However, the selection process ceased when the effective strain was outnumbered 1000-fold. At higher basal cell concentrations of 10⁵–10⁸ cells/mL, selection for WSM1325 to form effective nodulation on T. purpureum was evident, but was significantly reduced as the ratio of ineffective cells in the inoculum increased above 4-fold. The results indicate that the selection mechanism is highly dependent on the basal rhizobial cell density. Soil pH did not significantly alter the process, and both strains grew at similar rates and formed nodules at similar rates. A preliminary investigation into the genetic backgrounds of WSM1325 and WSM2304 revealed that although their 16S rRNA sequences were identical, they have considerable differences in their symbiotic and chromosomal replicons through examination of atpD, GSII and nodD sequences.  相似文献   

Inter-observer agreement between two observers for bovine digital dermatitis identification in New Zealand using digital photographs     

DA Yang  RA Laven 《New Zealand veterinary journal》2019,67(3):143-147

Aims: To assess the inter-observer agreement for detecting bovine digital dermatitis (BDD) lesions in digital colour photographs of the hind feet of cows, which had been taken while the animals were standing to be milked, between two trained observers.

Methods: Thirty-six photographs were selected from a total of 184 photographs held by the first author (R1), who had classified them as negative (n=11) or positive (n=25) for BDD. They were delivered to a technician (R2) who had previously visually inspected cattle for BDD lesions, and who then recorded the photographs as being either BDD-positive or BDD-negative. The percentage agreement between R1 and R2, and two other inter-observer agreement statistics, Cohen’s κ and Gwet’s first-order chance correction agreement coefficient (AC1), were calculated. The cumulative membership probabilities of Cohen’s κ and Gwet’s AC1 were then calculated for different benchmark ranges of κ.

Results: The percentage agreement between R1 and R2 was 33/36 (92%), Cohen’s κ was 0.80 (95% CI=0.57–1.0) and Gwet’s AC1 was 0.86 (95% CI=0.69–1.0). Based on the cumulative membership probabilities for Gwet’s AC1, there was 75% probability that the two observers had almost perfect agreement (κ≥0.81). For both Cohen’s κ and Gwet’s AC1, there was >95% probability that the two observers had at least substantial agreement (κ≥0.61).

Conclusions: The two trained observers had at least substantial agreement in identifying from a digital photograph as to whether BDD lesions were present or absent. Therefore results from the two could be used interchangeably.

Clinical Relevance: Visual assessment for BDD lesions in the milking parlour can be subjective. However a high agreement between these two trained BDD inspectors means BDD prevalence reported from different regions in New Zealand by these two can be directly compared.  相似文献   

Effects of hydroxyurea on replication of infectious bovine rhinotracheitis virus in bovine kidney cells: an electron microscopic study     

V Jasty  P W Chang  V J Yates  C C Goertemiller  J M Cece 《American journal of veterinary research》1972,33(9):1759-1766

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Scale-specific land cover thresholds for conservation of stream invertebrate communities in agricultural landscapes     

Jeremy P. Grimstead  Edward M. Krynak  Adam G. Yates 《Landscape Ecology》2018,33(12):2239-2252

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Impact of a catastrophic hurricane on island populations     

DA Spiller  JB Losos  TW Schoener 《Science (New York, N.Y.)》1998,281(5377):695-697

Lizard and spider populations were censused immediately before and after Hurricane Lili on islands differentially affected by the storm surge. The results support three general propositions. First, the larger organisms, lizards, are more resistant to the immediate impact of moderate disturbance, whereas the more prolific spiders recover faster. Second, extinction risk is related to population size when disturbance is moderate but not when it is catastrophic. Third, after catastrophic disturbance, the recovery rate among different types of organisms is related to dispersal ability. The absence of the poorer dispersers, lizards, from many suitable islands is probably the result of long-lasting effects of catastrophes.  相似文献   

Persistence of maternal antibodies against Mycoplasma agassizii in desert tortoise hatchlings.     

I M Schumacher  D C Rostal  R A Yates  D R Brown  E R Jacobson  P A Klein 《American journal of veterinary research》1999,60(7):826-831

OBJECTIVE: To investigate Mycoplasma agassizii-specific maternal antibodies in desert tortoise (Gopherus agassizii) hatchlings. SAMPLE POPULATION: Plasma from 43 captive-reared desert tortoise hatchlings. PROCEDURE: ELISA for M agassizii-specific antibodies was performed. Four hatchlings from 4 clutches of 3 M agassizii-seropositive females with chronic upper respiratory tract disease (URTD) were tested on the day of hatching (set 1), and 20 hatchlings from 4 clutches of 4 M agassizii-seropositive females with URTD and 19 hatchlings from 4 M agassizii-seronegative healthy females were tested at 4, 8, 12, and 29 months old (set 2). Immunoblot analysis was performed to determine immunoglobulin classes in yolk and plasma of hatchlings. To determine infection status of hatchlings, yolk, egg shell membranes (set 1), and nasal lavage fluid (sets 1 and 2) were examined for M agassizii by use of polymerase chain reaction. RESULTS: Yolk and hatchling plasma had significantly lower amounts of specific antibodies than did plasma from adult females. The IgG and IgM antibodies were transferred, but M agassizii-specific antibodies were of the IgG class. Hatchlings were not infected with mycoplasmas. Offspring of sick females had significantly higher specific antibody titers than did offspring of healthy females. Titers were still significantly different in 1-year-old hatchlings. CONCLUSIONS: Desert tortoise females transfer specific IgG and IgM antibodies to their offspring that are still detectable after 1 year. CLINICAL RELEVANCE: Infection with M agassizii may be misdiagnosed in hatchlings with persistent maternal antibodies. Passively acquired antibodies may have a role in pathogenesis of mycoplasma-induced respiratory tract disease and other diseases.  相似文献